RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) 3. TTY Nonvolatile Setups (draft) The RVP8 provides an interactive setup menu that can be accessed either from a serial TTY, or from the host computer interface. Most of the RVP8’s operating parameters can be viewed and modified with this menu, and the settings can be saved in non-volatile RAM so that they take effect immediately on power-up. This permits custom trigger patterns, pulsewidth control, matched FIR filter specs, PRF, etc.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) From the command prompt, typing “help” or “?” gives the following list of available commands.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) number (if it is not zero) in the printout of the ”V” command. Likewise, the minor release number of the code that last saved the nonvolatile RAM is also shown. This is an improvement over having to check the date of the code to determine which minor release was running.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Values were last saved using ROM version V14 This line tells which version of RVP8 code was the last to write into the non-volatile RAM. It is printed only if that last version was different from the ROM version that is currently running. The information is included so that a “smart upgrade” can often be done, i.e., values that did not exist in the prior release can be filled in with a guess that is better than merely taking the factory default.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) 0x00400000 : Internal tests failed on some slave 0x00800000 : Trigger Generator RAM and addressing 0x01000000 : Excessive coax/fiber round trip jitter 0x02000000 : No sync found in round trip test 0x04000000 : Internal error in compile/link Coax/Fiber/Pipeline Delay: 0.624 usec (Stdev: 0.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) RVP8> ~ IFD Burst/IF Inputs are: SWAPPED RVP8> ~ IFD Burst/IF Inputs are: NORMAL The selection remains in effect for the duration of the setup session, but then returns to NORMAL upon exiting the TTY monitor. The “~” command is very handy because it allows the Pb, Pr, and Ps plotting commands to easily run with one input or the other. Here are two examples of how this might be useful.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) 3.2 Host Computer I/O Debugging The RVP8 supports two very powerful monitoring functions that are helpful in debugging the I/O interface to the host computer. One examines the physical layer of the interface, i.e., the electrical handshake and data lines themselves. The other examines the application layer, i.e., the 16-bit opcodes and data that define the RVP8’s application programming interface. 3.2.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) generated by this option, all other RTM selections are disabled whenever host computer I/O is being monitored. Also, those other RTM selections would interfere with the multi-line formatting of the I/O text. The TTY printout shows incoming opcodes called out by name, and subsequent input and output words formatted into a table. The data are printed in Hex, twelve words per line, and include a word offset (origin zero) at the start of each line.
RVP8 User’s Manual April 2003 Opcode 0x0010 (SETPWF) Input Words 0: 2EE0 Opcode 0x0001 (LRMSK) Input Words 0: 0001 0000 0000 0000 12: ... 504: 0000 0000 0000 0000 TTY Nonvolatile Setups (draft) 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 This RTM option to monitor computer I/O is automatically disabled at powerup, and therefore can not be saved permanently.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) 3.3 View/Modify Dialogs The M command may be used to view, and optionally to modify, all of the current settings. The current value of each parameter is printed on the screen, and the TTY pauses for input at the end of the line. Pressing Return advances to the next parameter, leaving the present one unchanged. You may also type U to move back up in the list, and Q to exit from the list at any time.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Dual–LNA/Rcvr single–channel switched mode: NO For dual-polarization single-receiver systems, this question decides whether you have a single LNA and IF-Amplifier that switches between H&V (the typical case); or two separate receivers, each hard wired to H and V, with switching performed after the IF amplifiers. The question affects how noise levels are measured and applied to the data. Synthesize LOG video output waveform: YES Upper 100.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) three available slave DSPs would be reduced to two; whereas on a dual-board system, the 13 available DSPs would be reduced to 12. Obviously, the percentage penalty is less in a larger system. The second question decides how the overall dynamic range of the receiver will fit into the 12-bit unipolar output voltage span of the DAC that produces the LOG Video waveform.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) unique to the RVP8 can be handled by the local TTY and Scope setups, thus making no demands on the user’s system code for support. Answer this question “YES” for maximum compatibility with old driver software. However, if you are running IRIS version 6.11 or higher, then answer “NO” to enable using new RVP8 features as they are developed. The RVP8 returns a version number of 35 when the processor is running in RVP7 compatibility mode.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Unfold Velocity (Vh–Vl) – 0:Never, 1:User, 2:Always : 0 This question allows you to choose whether the RVP8 will unfold velocities using a simple (Vhigh – Vlow ) algorithm, rather than the standard algorithm described in Section 5.6. Bit-11 of SOPPRM word #10 is the host computer’s interface to this function when the “1:User” case is selected (See Section 6.3). Note: This setup question is included for research customers only.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Limits: 10 to 500 pulses IFD built–in noise dither source: –57.0dBm This question will only appear if the processor is attached to a Rev.D RVP8/IFD that includes an out-of-band noise generator to supply dither power for the A/D converters. The available power levels are { Off, –57dBm, –37dBm, –32dBm, –27dBm, –22dBm, –19dBm }. The closest available level to your typed-in value will be used.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Polarization Params – Filtered:YES NoiseCorrected:YES PhiDP – Negate: NO , Offset:0.0 deg KDP – Length: 5.00 km T/Z/V/W computed from: H–Xmt:YES V–Xmt:YES T/Z/V/W computed from: Co–Rcv:YES Cx–Rcv:NO The first question decides whether all polarization parameters will be computed from filtered or unfiltered data, and whether noise correction will be applied to the power measurements.
RVP8 User’s Manual April 2003 Spectral Clutter Filters –––––––––––––––––––––––– Filter #1 – Type:0(Fixed) Filter #2 – Type:0(Fixed) Filter #3 – Type:0(Fixed) Filter #4 – Type:0(Fixed) Filter #5 – Type:1(Variable) Filter #6 – Type:1(Variable) Filter #7 – Type:1(Variable) TTY Nonvolatile Setups (draft) Width:1 Width:2 Width:3 Width:4 Width:1 Width:2 Width:3 EdgePts:2 EdgePts:2 EdgePts:3 EdgePts:3 EdgePts:2 EdgePts:2 EdgePts:3 Hunt:2 Hunt:2 Hunt:3 These questions define the heuristic clutter filters that
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) For example, if we observe 20dB of total power above receiver noise, and then apply a clutter correction of 19dB, we are left with an apparent weather signal power of +1dB above noise. However, the uncertainty of this +1dB residual signal is much greater than that of a pure weather target at the same +1dB signal level. The “Residual Clutter LOG Noise Margin” allows you to increase the LOG noise threshold in response to increasing clutter power.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Answer the second sub-question according to whether the radar transmitter is directly fired by the the external pretrigger, rather than by one of the RVP8’s trigger outputs. In other words, answer “YES” if the transmitter would continue running fine even if the RVP8 TRIGIN signal were removed. This information is used by the ”L” and ”R” subcommands of the ”Pb” plotting command, i.e.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) This question permits the state of the triggers during noise measurements to be consistent and known, regardless of whether the antenna happens to be within a blanked sector; and you have the additional flexibility of choosing blanked noise triggers all the time.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Merge triggers to create composite waveforms: Merge Trigger #1 into : #1: #2: #3: #4: Merge Trigger #2 into : #1: #2: #3: #4: Merge Trigger #3 into : #1:Y #2: #3: #4: Merge Trigger #4 into : #1: #2:Y #3: #4: Merge Trigger #5 into : #1: #2:Y #3: #4: Merge Trigger #6 into : #1: #2: #3: #4: YES #5: #5: #5: #5: #5: #5: #6: #6: #6: #6: #6: #6: These questions allow you to merge the six user triggers together; resulting in trigger patterns that can
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) between every pair of transmitted pulses, and remains correctly positioned regardless of changes in the PRF Enter this multiplier as “0” if you do not wish to use this term, and it will be omitted entirely from the printout.. In the above example, Trigger #2 is a 10.0 msec active-high pulse whose leading edge occurs precisely halfway between the zero-range of every pair of pulses. Likewise, Trigger #6 is a 2.
RVP8 User’s Manual April 2003 Maximum number of Pulses/Sec: Maximum instantaneous ’PRF’ : TTY Nonvolatile Setups (draft) 2000.0 2000.0 (/Sec) These are the PRF protection limits for this pulsewidth. The wording of the “Maximum number of Pulses/Sec” question serves as a reminder that the number shown is not only an upper bound on the PRF, but also a duty cycle limit when DPRT mode is enabled.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) S It should be at least as long as the transmitted pulsewidth. If it were shorter, then some of the returned energy would be thrown away when “I” and “Q” are computed at each bin. The SNR would be reduced as a result. S It should be at least as long as the range bin spacing. The goal here is to choose the longest filter that retains statistical independence among successive bins.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Output control 4–bit pattern: 0001 These are the hardware control bits for this pulsewidth. The bits are the 4-bit binary pattern that is output on PWBW0:3 Bit Limits: 0 to 15 (input must be typed in decimal) Current noise level: –75.00 dBm Powerup noise level: –75.00 dBm –or– Current noise levels – PriRx: –75.00 dBm, SecRx: –75.00 dBm Powerup noise levels – PriRx: –75.00 dBm, SecRx: –75.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) safety zones on either side of integer multiples of half the RVP8/IFD’s 36MHz sampling frequency. The value entered here implicitly defines the band, and hence, the boundaries of the 18MHz window in which the IF is assumed to fall. Limits: 22 to 68 MHz. Primary Receiver Intermediate Frequency: 30.0000 MHz Secondary Receiver Intermediate Frequency: 24.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) choice. The Blackman window is useful if you are trying to see plotted spectral components that are more than 40dB below the strongest signal present. It is especially useful in the “Pr” plot when a long span of data are available. FIR filters designed with the Blackman window will have greater stopband attenuation than those designed with the Hamming window, but the wider main lobe may be undesirable.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) The following rather long list of questions will appear only if AFC and MFC functions have been enabled. AFC Servo– 0:DC Coupled, 1:Motor/Integrator : 0 The AFC servo loop can be configured to operate with an external Motor/Integrator frequency controller, rather than the usual direct-coupled FM control.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) arbitrary units ranging from –100 to +100 corresponding to the complete span of the D/A converter. Since the D–Unit corresponds in a natural way to a percentage scale, the shorter “%” symbol is sometimes used. AFC feedback will be applied in proportion to the frequency error that the algorithm is attempting to correct.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) backpanel RS232 outputs, or sent on the uplink as a value to be received by the RVP8/IFD and converted to an analog voltage. Yet another option is for the bits to be sent on the uplink and received by the RVP8/DAFC board, which supports arbitrary remapping of its output pins.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) The voltage range of the “I” and “Q” outputs is approximately 1 Volt, and is not adjustable. When AFC/MFC is mirrored on these lines, you will probably need to add an external Op-Amp circuit to adjust the voltage span and offset to match your RF components. We also recommend that you add significant low-pass filtering (cutoff at 3Hz) to remove any power line noise or crosstalk that may be originating within the RVP8/Main chassis.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) The automatic hunt for the burst pulse will always run at least once whenever the feature is enabled. The automatic hunting ceases, however, as soon as any activity is detected from the host computer. Only use this feature on radars with a serious drift problem in their burst pulse timing. Simulate burst pulse samples: NO The RVP8 can simulate a one microsecond envelope of burst samples.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) S A zero D-Unit output will always be produced whenever AFC is locked. S When AFC is tracking, the output drive will always be at least 15 D-Units. This minimum non-zero drive should be set to the sustaining drive level of the motor actuator, i.e., the minimum drive that actually keeps the motor turning. S When AFC is tracking, the output drive will never exceed 90 D-Units.
RVP8 User’s Manual April 2003 TTY Nonvolatile Setups (draft) Noise level for simulated data: –50.0 dB This is the noise level that is assumed when simulated “I” and “Q” data are injected into the RVP8 via the LSIMUL command. The noise level is measured relative to the power of a full-scale complex (I,Q) sinusoid, and matches the levels shown on the slide pots of the ASCOPE digital signal simulator.
RVP8 User’s Manual April 2003 10–1F: 20–2F: 30–3F: 40–4F: 50–5F: 60–6F: 70–7F: 80–8F: 90–9F: A0–AF: B0–BF: C0–CF: D0–DF: E0–EF: F0–FF: – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – TTY Nonvolatile Setups (draft) – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4. Plot-Assisted Setups The RVP8/IFD receiver module replaces virtually all of the IF components in a traditional analog receiver. The alignment procedures for those analog components are usually very tedious, and require continued maintenance even after they are first performed. Subtle drifts in component specifications often go unnoticed until they become so severe that the radar’s data are compromised.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.1 Oscilloscope Connections All that is required to view the graphical displays is an oscilloscope with a single vertical input channel. Setup the scope as follows: Vertical Input BNC cable to “Q” output of RVP8, terminated in 50W or 75W according to cable type. Vertical Channel Variable gain, approximately 1V full–scale deflection.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.2 P+ — Plot Test Pattern The RVP8 can produce a simple test pattern that is useful when the oscilloscope is attached for the first time. From the TTY monitor enter the “P+” command. This will print the message “Plotting Test Pattern...” on the TTY and then produce the plot shown in Figure 4–1.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.3 General Conventions Within the Plot Commands The “Pb”, “Ps”, and “Pr” commands all have a similar structure to their TTY user interface. Each command begins by printing a list of subcommands that are valid in that context. These subcommands are single keystrokes that are executed immediately by the RVP8 as they are typed. The “ENTER” key is not required.
RVP8 User’s Manual April 2003 Plot–Assisted Setups The “Pb”, “Ps”, and “Pr” commands are intended to be used together for the combined purpose of configuring the RVP8’s digital front end. You may, of course, run any of the commands at any time; but the following procedure may be used as a guideline for first time setups. The full procedure must be repeated for each individual pulsewidth that the radar supports. 1. Use Mb to set the system’s intermediate frequency (See Section 3.3.6). 2.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.4 Pb — Plot Burst Pulse Timing For magnetron radars the RVP8 relies on samples of the transmit pulse to lock the phase of its synthesized “I” and “Q” data, and to run the AFC feedback loop. The “Pb” command is used to adjust the trigger timing and A/D sampling window so that the burst pulse is correctly measured. 4.4.
RVP8 User’s Manual April 2003 Plot–Assisted Setups actual transmitted pulse, and thus, the samples contributing to the frequency estimate will include the leading and trailing edges of the pulse. These edges tend to have severe chirps and sidebands, compared to the more pure center portion of the pulse. The AFC frequency estimate (which is power weighted) could be mislead by these edges and might not tune to the optimum center frequency if they were included.
RVP8 User’s Manual April 2003 T/t Z/z B/b + Plot–Assisted Setups 0.025 msec steps, and the uppercase commands shift in 1.000 msec steps (approximately). The reason for shifting all six triggers at once is that the relative timing among the triggers remains preserved. However, the absolute timing (relative to range zero) will vary, and this will cause the burst pulse A/D samples to move within the sample window. The “T” command increments or decrements the overall time span of the plot.
RVP8 User’s Manual April 2003 Pwr DC Trig#1 BPT Plot–Assisted Setups Indicates the mean power within the full window of burst samples. DC offsets in the A/D converter do not affect the computation of the power, i.e., the value shown truly represents the waveform’s (Signal+Noise) energy. Indicates the nominal DC offset of the burst pulse A/D converter. This is of interest only as a check on the integrity of the front end analog components. The value should be in the range 2.0%.
RVP8 User’s Manual April 2003 Plot–Assisted Setups AFC. However, if the signal is too weak, then the upper bits of the A/D converter are wasted and noise is unnecessarily introduced. We recommend a peak signal level between –6dBm and +1dBm, i.e., a signal that might be viewed at x2 or x4 zoom. Take note of the burst energy level reported on the TTY; it will help decide the minimum energy threshold for a valid burst pulse, which is needed in Section 3.3.6.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.5 Ps — Plot Burst Spectra and AFC Once the transmit burst pulse has been captured the next step is to analyze its frequency content and to design a bandpass filter that is matched to the pulse. In a traditional analog receiver the matched filters use discrete components that can not be adjusted, and the transmit spectrum can not be viewed unless a spectrum analyzer is on hand.
RVP8 User’s Manual April 2003 Plot–Assisted Setups The vertical axis of the spectrum plot is logarithmic and is marked with faint horizontal lines in 10-dB increments. An overall dynamic range of 70 dB can be viewed at once. The horizontal lines also contain major and minor tick marks to help calibrate the frequency axis. Major marks are small downward triangles that represent integer multiples of 5MHz; minor marks are in between and represent 1-MHz steps.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.5.2 Available Subcommands Within “Ps” The list of subcommands is printed on the TTY: Frequency span of the plot is 18.0 MHz to 36.0 MHz.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 2 4 – O 2 3 – N 2 2 – M 2 1 – L 2 0 – K 1 9 – J 1 8 – I 1 7 – H 1 6 – G 1 5 – F 1 4 – E 1 3 – D 1 2 – C 1 1 – B 1 0 9 8 7 6 5 4 3 2 1 0 – – – – – – – – – – – A 9 8 7 6 5 4 3 2 1 0 The Ps command continues to run normally during the AFC test mode. The customary AFC information will be replaced with a hexadecimal readout of the present 25-bit value. Your live display may look something like: Navg:3, FIR:1.33 usec (48 Taps), BW:1.
RVP8 User’s Manual April 2003 V/v Z/z % Plot–Assisted Setups “W/wN/n” subcommands to manually move to that starting point. Typing “$” would then print a dialog line in which the search span length and width are chosen. You may keep the indicated values or type in new ones, just as for all RVP8 setup questions. The search begins when the spans are accepted. The search procedure may require a few seconds to a few minutes, depending on the length and width spans that are being scanned.
RVP8 User’s Manual April 2003 FIR BW DC-Gain Freq Pwr Loss AFC Plot–Assisted Setups Indicates the length of the impulse response of the matched FIR filter. See description on Page 4–8. Indicates the actual 3dB bandwidth of the matched filter. This is the complete width of the passband from the lower frequency edge to upper frequency edge. Note that the filter’s center frequency is fixed at the radar’s intermediate frequency, as chosen in the “Mb” setup command.
RVP8 User’s Manual April 2003 Plot–Assisted Setups (NoBurst) (Wait) (Track) (Locked) The energy in the burst is below the minimum energy threshold for a valid pulse (See Page 3–26). The AFC loop remains idle. The burst pulse has become valid just recently, but the AFC loop is idle until the transmitter stabilizes (See Page 3–27) The burst pulse is valid, and the AFC loop is tracking in order to bring the burst frequency within the inner hysteresis limits.
RVP8 User’s Manual April 2003 Plot–Assisted Setups We can now examine what the filter loss (dB loss ) would be if this pulse were applied to a bandpass filter. The filter loss is simply the ratio of the power that is passed by the filter, divided by the total input power (1.0 in this case).
RVP8 User’s Manual April 2003 Plot–Assisted Setups power spectrum estimate that is derived in an identical manner using the same number of ^ samples, but of a pure sine wave at the radar’s IF. The RVP8 determines B(f) according to its ^ sampled measurement of the transmitted waveform; however it can calculate C(f) internally based on an idealized sinusoid.
RVP8 User’s Manual April 2003 Plot–Assisted Setups 21–27MHz and 27–33MHz respectively. This is necessary to avoid picking up energy from the other receiver and interpreting it as out-of-band input power. A consequence, however, is that the real out-of-band power is underestimated, i.e., the filter loss itself is underestimated. We recommend temporarily switching dual-receiver systems back to single-receiver mode when the filter loss is being measured.
RVP8 User’s Manual April 2003 Plot–Assisted Setups S The filter width should be no greater than the burst spectral width. A wider passband will reduce the SNR of the received signal because out-of-band noise would be allowed to pass. S The DC gain should be as small as possible, preferably less than –64dB (See discussion below). S If there are conspicuous interference spikes at particular frequencies, try to adjust the location of the filter’s zeros so that the interference is maximally attenuated.
RVP8 User’s Manual April 2003 Plot–Assisted Setups Figure 4–5: Example of a Filter With Poor DC Rejection 4–22
RVP8 User’s Manual April 2003 Plot–Assisted Setups 4.6 Pr — Plot Receiver Waveforms The “Pb” and “Ps” commands described in the previous sections have been used to analyze the signal that is applied to the “Burst-In” connector of the RVP8/IFD receiver module. The task that remains is to checkout the actual received signal that is connected to “IF-In”. The goal is to verify that the received signal is clean and appropriately scaled, and that nearby targets can be seen clearly.
RVP8 User’s Manual April 2003 Plot–Assisted Setups the two equal-power targets just to the left of center are approximately 18dB down from the top. The amplitude of the samples is thus 10 (*18ń20) + 0.13 , i.e., 13% of full scale. This correspondence between the LOG scale and the amplitude scale applies regardless of the plot’s zoom level. As the IF samples are zoomed up and down by factors of two, the LOG plot will shift up and down in 6dB steps.
RVP8 User’s Manual April 2003 Plot–Assisted Setups Figure 4–7: Example of a Noisy High Resolution “Pr” Spectrum 4.6.2 Available Subcommands Within “Pr” The list of subcommands is printed on the TTY: Available Subcommands within ’Pr’: L/l & R/r Start range Left/Right T/t Plot time span Up/Dn V/v Number of spectra averaged Z/z Amplitude zoom Alternate Plots % Toggle between dual receivers .
RVP8 User’s Manual April 2003 Plot–Assisted Setups V/v The “V” command increments or decrements the number of power spectra that are averaged together to create the plot. The count ranges from one (no averaging) to 25, and is reported on the TTY as “Navg”. Z/z The “Z” command zooms the amplitude of the IF samples by factors of two from one to 128. The LOG plots are shifted in corresponding 6dB increments as the amplitude is zoomed up and down.
RVP8 User’s Manual April 2003 MidSamp Plot–Assisted Setups Also indicates the RMS power within the passband of the FIR filter, but using only the raw IF samples in the exact center of the chosen interval. The computation of “Total Power” is performed using the same subset of central IF samples that are used to compute “Filtered Power”.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5. Processing Algorithms (draft) This draft chapter is based on the legacy RVP7 algorithms. The RVP8 will have some additional features and may not contain some of the legacy features. This chapter describes the real-time data processing algorithms implemented within the RVP8 signal processor. The discussion is confined to the mathematical description of these algorithms.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) The signed (CCW positive) angle made between the positive real axis and the above vector is: {s } ƪImag ƫ Real{s } ë + Arg{s } + arctan where this angle lies between * p and ) p and the signs of Real{s} and Imag {s} determine the proper quadrant. Note that this angle is real, and is uniquely defined as long as |s| is non-zero. When |s| is equal to zero, Arg{s} is undefined.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Figure 5–1: Flow Diagram of RVP8 Processing dBT dBZ VW Speckle Remover SIGTH LOGTH SQITH CCORTH FLAGS Thresholding dBZ N l dBZ 0 V W SQI SIG CCOR dBT Calibrate Calculate Output Data Moments a K–bins Range Averaging CCORTH Micro Clutter Suppression R0 R1 (R2) Correlate M Correlate D/A si FFT Compute Frequency FIR Decimate in Time A/D 36 MHz Burst IF 5–3 M This step difĆ fers for FFT and Pulse Pair Modes Filter AFC A/D
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.1 IF Signal Processing The starting point for all computations within the RVP8 are the instantaneous IF-receiver samples p n and, the instantaneous burst-pulse or COHO reference samples b n . These data are available at a very high sampling rate (typically 36MHz), which makes possible the digital implementation of functions that are traditionally performed by discrete components in an analog receiver.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) where f IF is the radar intermediate frequency, f SAMP is the RVP8/IFD crystal sampling frequency, and l n are the coefficients of an N-point symmetric low-pass FIR filter that is matched to the bandwidth of the transmitted pulse. The multiplication of the l n terms by the sin() terms effectively converts to the low-pass filter to a band-pass filter centered at the radar IF.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.1.3 Burst Pulse Tracking The RVP8 has the ability to track the power-weighted center-of-mass of the burst pulse, and to automatically shift the trigger timing so that the pulse remains in the center of the burst analysis window of the Pb plot. This means that external sources of drift in the timing of the transmitted pulse (temperature, aging, etc.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.1.4 Interference Filter The interference filter is an optional processing step that can be applied to the raw (I,Q) samples that emerge from the FIR filter chips. The intention of the filter is to remove strong but sporadic interfering signals that are occasionally received from nearby man-made sources. The technique relies on the statistics of such interference being noticeably different from that of weather.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) interference points that manage to get through the filtering process without being removed. The “False” (false alarm) rate is the percentage of non-interference points that are incorrectly modified when they should have been left alone. Table 5–2: Algorithm Results for +16dB Interference C1,C2 ––––– 6.0dB 8.0dB 9.0dB 10.0dB 11.0dB 12.0dB 13.0dB 14.0dB 16.0dB 20.0dB Alg.1 Missed/False –––––––––––– 17.8% 10.91% 10.5% 6.57% 8.5% 5.09% 7.3% 4.01% 8.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Table 5–3: Algorithm Results for +26dB Interference C1,C2 ––––– 6.0dB 8.0dB 9.0dB 10.0dB 11.0dB 12.0dB 13.0dB 14.0dB 16.0dB 20.0dB Alg.1 Missed/False –––––––––––– 17.8% 10.75% 9.9% 6.48% 7.4% 4.99% 5.9% 3.91% 4.8% 3.06% 3.2% 2.37% 2.6% 1.83% 1.9% 1.45% 1.3% 0.90% 3.1% 0.39% Alg.2 Missed/False –––––––––––– 17.8% 3.95% 9.9% 2.31% 7.4% 1.75% 5.9% 1.36% 4.8% 1.06% 3.2% 0.83% 2.6% 0.62% 1.9% 0.50% 1.3% 0.30% 3.1% 0.12% Alg.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 12 11 10 9 8 7 6 5 4 3 2 1 0 –1 –2 –3 –4 –4 –3 –2 –1 0 1 2 3 4 5 6 7 8 9 10 11 12 Figure 5–2: Linearization of Saturated Signals Above +4dBm corrected data are produced even when the RVP8 is alternating rapidly between different data acquisition tasks, e.g., in a multi-function ASCOPE display. The additional pipeline delay will not affect the high-speed performance when the RVP8 runs continuously in any single mode.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2 Video (“I” and “Q”) Signal Processing This section describes the processing of the video (“I” and “Q”) data to obtain the reduced parameters: reflectivity, total power, velocity, width, signal quality index, clutter power correction, and sometimes ZDR. The RVP8 employs two methods (selectable) for processing the I and Q signals: pulse-pair and FFT. The methods are similar except in regard to the procedures for clutter filtering.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2.4 Range averaging and Clutter Microsuppression The next step (optional) is to perform range averaging. Range averaging can be performed over 2, 3, ..., 16 bins. This is accomplished by simply averaging the T 0 , R 0 , R 1 and R 2 values. This reduces the number of bins in the final output to save processing both in the RVP8 and in the host computer.
RVP8 User’s Manual April 2003 Z + CSr 2 + Processing Algorithms (draft) ƪ ƫƪ ƫƪ Cr 20N g rg t r2 r 2o k To * k N k N ƫ Thus the k’s cancel to give us the same result for Z. This makes the approach robust to system gain fluctuations. Another way of saying this is that as long as the system sensitivity (noise figure) does not change, then the system does not require re-calibration. The individual terms in the dB form of the equation are summarized below.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2.6 Velocity For a Doppler power spectrum that is symmetric about its mean velocity, the velocity is obtained directly from the argument of the autocorrelation at the first lag, i.e., V + l q 4pt s 1 where q 1 + arg NJR 1Nj . l is the radar wavelength, t s is the sampling time (1/PRF). q 1 is constrained to be on the interval [* p, p] . When q 1 +" p , then V +" V u where the unambiguous velocity is , l .
RVP8 User’s Manual April 2003 Processing Algorithms (draft) where “ln” represents the natural logarithm. This can be compared to the expression in the preceding section for SQI to illustrate that this expression for the variance is only valid when: SNR [ 1 SNR ) 1 which occurs when the SNR is large. This variance estimator is normalized to the Nyquist interval in units of [* p, p] .
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2.9 Clutter Correction (CCOR threshold) In addition to calculating the R 0 , R 1 and optional R 2 autocorrelation terms, which are based on filtered time series data, the RVP8 also computes T 0 which is the total unfiltered power. By comparing the total filtered and unfiltered powers at each range bin, a clutter power, and hence a clutter correction, for that bin can be derived.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.2.10 Weather Signal Power (SIG threshold) A parameter called SIG is also calculated to provide an estimate of the weather signal-to-noise ratio in dB for thresholding. The SIG calculation is different depending on the whether the optional R 2 autocorrelation is computed. R 0, R 1 Calculation In this case the SIG is computed as follows: SIG + 10 log ƪT *N Nƫ ) CCOR 0 This term represents the SNR after the removal of clutter.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.3 Thresholding An important feature of the RVP8 is its ability to accept or reject incoming data based on derived properties of the signals themselves. Typically, “rejected” data are not displayed by the user’s software, thus making for very clean weather presentations. 5.3.1 Threshold Qualifiers For data quality control, each RVP8 output parameter can be qualified, i.e.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Parameter Description Threshold dBZ dBT V W ZDR Reflectivity with clutter correction Reflectivity without clutter correction Mean velocity Spectrum width Differential reflectivity LOG and CCOR LOG SQI and CCOR SQI and CCOR and SIG LOG 5.3.2 Adjusting Threshold Qualifiers The effect of the various threshold qualifiers for each output parameter are discussed in this section.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) is traditionally used to qualify LOG data only in the Random Phase processing mode. But the secondary SQI threshold is applied uniformly in all processing modes whenever reflectivity data are specified as being thresholded by SQI. This gives you more freedom in applying an SQI threshold to your LOG data, because the cutoff value for reflectivity can be chosen independently from the cutoff value for the other Doppler parameters.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 1D Speckle Filter A ray is the basic azimuth unit of the RVP8 (e.g., 1 degree) over which the samples are averaged to obtain the output base data (T, Z, V, W). For this filter, a speckle is defined as any single, valid bin (not thresholded), having thresholded bins on either side of it in range. Any such isolated bin in a ray is set to “threshold”. The algorithm is shown schematically below.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 2D 3x3 Filtering Concepts ÂÂÂ ÂÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ Threshold if center point is valid but there are no or only one valid neighbor. 1 Azimuth Z 00 0 Z 0*1 -1 Range -1 0 Z 1 output 00 + Threshold Fill thresholded center point with average if there 6 or more valid neighbors.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) makes it more likely that the algorithm will find the pairs of Low/High PRF data that are required for unfolding. S Step 2: The unfolded velocities are then subjected to the standard 3x3 filtering. Dual PRF, Random Phase Processing In random phase processing, the “seam” at the start of the second trip is always problematic since the transmitter main bang and nearby clutter will virtually always wipe–out the first few 2nd trip range bins.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.4 Reflectivity Calibration The calculation of reflectivity described in section 5.2.5 required the calibration reflectivity dBZ o . This section describes it’s derivation. Note that customers with the SIGMET IRIS system can use the zauto utility to perform the calibration. (See the IRIS Utilities Manual.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) avoid ground thermal noise. Also tune the frequency of the signal generator using the setup command “pr”, and displaying the received signal spectrum. Be sure to check the tuning at the end of the calibration to make sure the signal generator and IFD have not drifted apart.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Treatment of Losses in the Calibration In the calibration of the dBm level of the test signal, be sure to account for any losses that may occur between the antenna feed and the injection point, and in the cable and coupler that is used to connect the signal generator to the injection point. Figure 5–4 illustrates the nomenclature of the various losses that are involved in the calibration.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Figure 5–4: Illustration of Losses that Affect LOG Calibration dBm Feed Receive Path Feed Pt Feed L Feed:Coupler Transmit Path Coupler Lt Receiver RVP7 IFD L Coupler L Cable Transmitter Pt Sig Gen dBm siggen Determination of dBZ o The calibration reflectivity is determined from the radar equation as follows: dBZ o + 10 log ƪCr 2oIoƫ where I o is in mW (corrected for receive losses), the reference range r o is 1 km, and the radar const
RVP8 User’s Manual April 2003 Processing Algorithms (draft) The radar constant is determined from the characteristics of your radar (check with the manufacturer if you are unsure of the values). Note that transmit losses are accounted for in the radar constant, while receiver loss is usually included in the calculation of I o .
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.5 Dual PRT Processing Mode The RVP8 supports two major modes for Dual PRT processing, i.e., algorithms using triggers that consist of alternate short and long periods. Most of the Doppler parameters are available in each of these modes. You may also request time series data in both cases; the samples will be organized so that the first pulse of a short PRT pair always comes first. 5.5.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.5.2 DPRT-2 Mode The trigger consists of alternating short and long period pulses, where the ratio of the periods is determined by the velocity unfolding ratio that has been selected. Doppler data are extracted from both the short and long pulse pairs (hence the “-2” suffix), and unfolded velocities are made available on each ray based on the combined PRT data from that ray alone.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.6 Dual PRF Velocity Unfolding For a radar of wavelength l operating at a fixed sampling period t s + 1ńPRF , the unambiguous velocity and range intervals are given by: Vu + l 4t s Ru + c and ts 2 where “c” is the speed of light. Often these intervals do not fully cover the span of velocity and range that one would like to measure.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Now if t l and t h are in a 3:2 ratio, then: tl * th + and thus Vu unfold tl t + h 3 2 + 3V ul + 2V uh The angle f represents a velocity phase angle in [* p, p] , but with respect to an enlarged unambiguous interval. Thus, by simply differencing the folded angles from the high and low PRFs, we obtain an angle that is unfolded to a larger velocity span.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) nearest the difference angle, we conclude that this is the correct unfolding. Likewise, on the left diagram we unfold the low-PRF angle by dividing the plane into thirds centered on the difference angle. The result angle is either ql , 3 q l 2p ) 3 3 or q l 4p ) 3 3 depending on which one falls into the acceptance Region 1. Note that the resultant angle is the same in each case.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) points. However, there is a useful work-around in the RVP8 to minimize their impact — turning the clutter filter off at far ranges where little clutter is expected and using a narrow clutter filter minimizes the effects of the clutter filter on weather targets. The 4:3 PRF unfolding ratio is more susceptible to unfolding errors in cases where the spectrum width is large and/or the SNR is low.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7 Optional Dual Polarization- ZDR, PHIDP, KDP, LDR, ... 5.7.1 Overview of Dual Polarization Polarization measurements can provide additional information that can be used to determine more accurate measurements of rainfall or, in some cases, infer particle type such as hail or graupel.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) LDR: Linear Depolarization Ratio Some advanced polarization radars can transmit at one polarization and receive simultaneously in two channels, usually the co–polarized and cross–polarized components. For example, when transmitting horizontal, both horizontal (co–polarized) and vertical (cross–polarized) are received by two separate channels.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.2 Radar System Considerations A polarization radar is characterized by how it transmits and how it receives. For simplicity we will assume that the radar uses horizontal and/or vertical polarization. However, other polarization pairs could be used (e.g., right and left circular polarization). Transmit Modes S Fixed (horizontal or vertical)- this can be controlled by a switch or the radar can be simply fixed to transmit a single polarization.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) (e.g., RHOH and PHIH). The simultaneous H+V transmission and dual-channel reception is sometimes called the STAR mode (simultaneous transmit and receive). This allows the co–pol measurements to be made (ZDR, RHOHV, PHIDP and KDP). The alternating transmission dual-channel receiver allows both the co–pol and the cross-pol measurements to be made, i.e., it is the most complete.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.3 RVP8 Dual-Channel Receiver Approach Dual-Channel Multiplexing for the IFD The RVP8 uses an innovative technique for implementing the dual-channel receiver approach, i.e., dual-channel multiplexing. Just as a single wire can carry multiple telephone conversations, two polarization channels can be put on the same wire at different IF frequencies, digitized by the IF Digitizer and then separated by digital filtering.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) anti–aliasing filters usually installed on the IFD are removed and replaced by separate filters that are placed ahead of the point where the signals are combined. Note that these filters are centered at the appropriate IF frequency and are typically 6 MHz wide for a 6 MHz IF separation.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.4 Overview of Processing Algorithms Polarization Modes and Outputs Supported by RVP8 The RVP8 supports four polarization modes summarized in the table below. For each case, the standard moments (T, Z, V and W) are calculated as well. The notation for the outputs used here is similar to that in standard usage (e.g., Doviak and Zrnic). However, for LDR we use the notation LDRH to indicate that this is the LDR for horizontal transmission.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Notation and Model for Correlations The pulse pair processing mode is used for all of the polarization calculations, except that ZDR-only processing for the STAR case can be done in either FFT or random phase as well as pulse pair. As with the standard moments, the autocorrelations form the basis for the processing of the polarization variables. The autocorrelations are computed in a manner identical to the standard moments, e.g.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Noise Bias of Channel Power and Optional Correction The average noise powers Nv and Nh are assumed to be receiver noise only. These bias the autocorrelations at lag zero, i.e., the channel power measurements. Autocorrelations at lags 1 and 2 are not biased by noise. Cross channel correlations are also not biased by noise, assuming that the noise in the two channels is independent (a good assumption).
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.5 Case 1: Fixed Transmit: Dual-Channel Receiver Input Receiver Samples In fixed mode the radar is configured (either permanently or by means of a switch) to transmit either vertical or horizontal polarization with dual-channel reception of both the co- and cross–channel polarizations, e.g., transmit horizontal and receive both horizontal (co) and vertical (cross) polarizations.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.6 Case 2: Simultaneous Dual Transmit and Receive (STAR mode) Input Receiver Samples In this mode there is simultaneous transmit and receive of both vertical and horizontal polarization. For each pulse there is a measurement of the complex amplitude in each channel, i.e., ƪs 1hh : s 1vvƫĄƪs 2hh : s 2vvƫĄƪs 3hh : s 3vvƫĄ.Ą.Ą.Ąƪs Mhh : s Mvvƫ We will assume that M samples are collected for processing, i.e.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.7 Case 3: Alternating H/V Transmit: Single-Channel Receiver Input Receiver Samples This is the traditional ZDR radar with a high-power fast switch that alternates between horizontal and vertical on each pulse. The switch is made just prior to the transmit pulse so that the transmitter radiates and then receives at a single polarization for each pulse. Thus the samples are: s 1hh s 2vv s 3hh ...
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.8 Case 4: Alternating H/V Transmit: Dual-Channel Receiver Input Receiver Samples This is the most comprehensive case of polarization operation since it permits calculation of all of the polarization measurands. In this case the transmitter alternates pulse-to-pulse between horizontal and vertical polarization and the dual-channel receiver provides measurement of both the co- and the cross-polarized return, i.e.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.10 KDP Calculation In all modes that compute PHIDP, the signal processor can also be configured to compute KDPthe specific differential phase in units of degrees per km. This is the range derivative of PHIDP. There are two techniques that have been used to obtain this: S The smoothed range derivative. S The slope from a least squares fit. The RVP8 uses the least squares approach which is shown schematically in the figure below.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.11 Standard Moment Calculations (T, Z, V, W) Overview Standard moments are available for all four of the polarization cases. Since there can be up to four different channels of time series input, there are several choices for computing the standard moments.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Model for standard moment autocorrelations The model for the moment autocorrelation calculations is as follows (using Ro as an example): r t R hh 0 Ą +Ą g hĄg hĄS hh ) N h r t R vh 0 Ą +Ą g vĄg hĄS vh ) N v r t R vv 0 Ą +Ą g vĄg vĄS vv ) N v r t R hv 0 Ą +Ą g hĄg vĄS hv ) N h where: vh vv hv R hh 0 ,Ą R 0 ,Ą R 0 ,Ą R 0 Are the autocorrelations if the samples at lag zero.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Case 1H: Fixed Horizontal Transmit, Dual Channel ReceiveĆ (HH, VH) dBZo from HH Channel TTY Setup Question Responses Calculate T, Z, V, W from: H–Xmt V–Xmt Co–Rcv Cx–Rcv HH (co) (Recommended) ––– ––– YES NO VH (xdr–1 weighting) ––– ––– NO YES HH+VH (xdr–1 weighting) ––– ––– YES YES HH Channel (co–pol) This is the recommended channel for the case of linear polarization.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) HH+VH Channels This choice would be used for elliptic transmit polarizations that give comparable return signal in both the co- and cross-channels.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Case 1V: Fixed Vertical Transmit and Dual Channel ReceiveĆ (VV, HV) dBZo from VV Channel TTY Setup Question Responses Calculate T, Z, V, W from: H–Xmt V–Xmt Co–Rcv Cx–Rcv VV (co) ––– ––– YES NO HV (xdr weighting) ––– ––– NO YES VV+HV (xdr weighting) ––– ––– YES YES This is the only case for which the calibration constant dBZo for the VV channel should be downloaded to the signal processor.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) VV+HV Channels This choice would be used for elliptic transmit polarizations that give comparable return signal in both the co- and cross-channels.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Case 2: Simultaneous Transmit and ReceiveĆ STAR (HH, VV) Case 3: Alternating Transmit SingleĆChannel Receive (HH, VV) dBZo from HH Channel TTY Setup Question Responses Calculate T, Z, V, W from: H–Xmt V–Xmt Co–Rcv Cx–Rcv HH YES NO ––– ––– NO YES ––– ––– YES YES ––– ––– VV (gdr–1 weighting) HH+VV (gdr–1 weighting) A fundamental difference between these two cases is that for all standard moment processing choices, the STAR ca
RVP8 User’s Manual April 2003 Processing Algorithms (draft) HH+VV Channels This approach gives the benefit of doubling the number of samples used for the reflectivity calculation. T 0Ą +Ą *1ĄT vv Thh o ) gdr o 2 R 0Ą +Ą *1ĄR vv Rhh o ) gdr o 2 R 1Ą +Ą Rhh ) gdr*1ĄR vv 1 1 2 R 2Ą +Ą Rhh ) gdr*1ĄR vv 2 2 2 NĄ +Ą N h ) gdr *1ĄNv 2 These adjusted autocorrelations are then used as input to the standard moment processing algorithms with dBZo calibrated with respect to the HH channel.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Case 4: Alternating DualĆChannel (HH, VH, VV, HV) dBZo from HH Channel TTY Setup Question Responses Calculate T, Z, V, W from: H–Xmt V–Xmt Co–Rcv Cx–Rcv HH YES NO YES NO VH (xdr–1 weighting) YES NO NO YES VV (gdr–1 weighting) NO YES YES NO HV (xdr/gdr weighting) NO YES NO YES HH+VV (gdr–1 weighting) YES YES YES NO HV+VH (xdr & gdr weighting) YES YES NO YES HH Channel Since the HH channel is directly calibrated
RVP8 User’s Manual April 2003 Processing Algorithms (draft) HH + VV Channels Processing is identical to Cases 2&3: STAR and Single Channel Alternating HH+VV Processing. HV + VH Processing The weighting here has to correct for both transmitter and receiver effects in order to use the HH channel dBZo.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.12 Thresholding of Polarization Parameters The thresholding of polarization parameters by the processor eliminates bins with weak or uncertain signals. Note that the thresholding can be disabled if it is desired to see all of the data regardless of the data quality. All of the polarization parameters are based on power ratios. The RVP8 requires that each power term in a ratio pass a signal-to-noise test similar to the log power test.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.7.13 Calibration Considerations Polarization systems require additional calibration as compared to conventional systems. There are three aspects to the calibration: S dBZo measurement in both channels for dBZ and dBT calibration. S GDR measurement for ZDR calibration. S xdr measurement for LDR calibration. These are discussed below. dBZo Calibration for dBZ The RVP8 supports separate calibration of both polarization channels.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) S Collect ZDR data at vertical incidence while the antenna is rotating in azimuth. S Use a separate application program to average the ZDR values around a full 360 degrees at each range bin (height). Generate a plot of 360-average ZDR vs height. S You should observe that the average ZDR values in regions of strong signal (>20 dB SNR) below the bright band are approximately constant with height.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) In all cases it is recommended that for the calibration, XDR be set to 0 dB in the application user software and that the RVP8 TTY setups be configured as follows: S Noise correction enabled for LDR and noise sample taken prior to the measurements (with care not to sample with a test signal turned–on or while looking at the sun). S Clutter correction disabled for LDR.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.8 FFT Mode 5.8.1 Overview The RVP8 can perform FFT processing of the I and Q time series. This is indicated by the inset box in Figure 5–1. The major difference between FFT and pulse pair processing is the way in which clutter filtering is performed. The pulse pair mode uses a time domain IIR filter while the FFT mode uses a frequency domain filter.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.8.2 FFT Implementation Figure 5–9 shows a data flow diagram for the FFT processing. In the example, 50 pulses of I and Q are processed. Recall that the I and Q samples refer to a single range bin with an I and Q sample generated for each pulse. Sampling Division The first step of processing is to split the I and Q values into two groups. The FFT algorithm requires the number of samples to be a power of two.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Figure 5–9: FFT Processing — 50 pulse example Example of 50 pulse input time series where An = In + j Qn A1 32 FFT A2 A3 A4 A5 A45 A46 A47 A48 A49 A50 ... 1st.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Figure 5–10: Effect of Windowing on FFT Response to Ground Clutter dB Power 0 Rectangular Window -20 -40 -60 -80 dB Power 0 Hamming Window -20 -40 -60 -80 dB Power 0 Blackman Window -20 -40 -60 -80 -Vu 0 +Vu Velocity S Blackman Window — This is the most aggressive window for clutter cancelation and is appropriate only for Klystron systems that can achieve very low phase noise (~0.1 degree).
RVP8 User’s Manual April 2003 Processing Algorithms (draft) FFT Averaging The power spectrum from the first group of samples is averaged with the power spectrum from the last group of samples. Note that if the total number of samples is exactly a power of two, then this step is skipped. Averaging the two power spectra from the overlapping sample groups effectively captures the information from all of the samples. The result is a smoother power spectrum than weather of the individual spectra.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) This procedure preserves the noise level and/or overlapped weather targets. The result is that more accurate estimates of dBZ are obtained. In extreme cases when the weather spectrum is very narrow, there can still be some attenuation of weather of a broad filter is selected. Inverse Transform After clutter removal, an inverse DFT (Discrete Fourier Transform) is performed to obtain the autocorrelations R0, R1 and R2 (optional).
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.9 Random Phase 2nd Trip Processing 5.9.1 Overview Second trip echoes can be a serious problem for applications when the radar is operated at high PRF (e.g., >500 Hz). Second trip echoes are caused by the range aliasing of targets. They appear as false echoes on the display, usually elongated in the radial direction. On Klystron systems they will have valid Doppler velocities.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Another way to implement a magnetron system is to let the COHO free-run (rather than phase locking to the transmit pulse), measure the phase of each transmit pulse and digitally correcting for the transmit phase. Using this digital phase locking technique, the RVP8 can phase lock or “cohere” to either the first or the second trip.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) algorithms check whether the SQI of each recovered trip is less than the secondary SQI threshold, and if so, the LOG portion of the data are rejected. This SQI test is necessary for a clean LOG picture, but we need to use a more permissive (lower) threshold value than would usually be applied to the Doppler data alone.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Random Phase and Dual PRF The random phase processing works seamlessly with the dual PRF processing to provide advanced range and velocity ambiguity resolution. Both the first and 2nd trip echoes can be recovered and displayed to a maximum range of 2X the unambiguous range corresponding to the high PRF. For optimum performance, the 2D 3x3 speckle filter should be used to smooth the 2nd trip seams that occur for each ray.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) Figure 5–12: Random Phase Processing Algorithm Ideal 1st Trip Ideal 2nd Trip Raw 1st Trip with 2nd Trip Noise Contamination Raw 2nd Trip with 1st Trip Noise Contamination Filtered 1st Trip Filtered 2nd Trip Inverse Transfrom and ReĆCohere Recovered 1st Trip Recovered 2nd Trip 5–74
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.10 Signal Generator Testing of the Algorithms This section describes a variety of IF signal generator tests that can be used to verify correctness of the RVP8 processing algorithms. These tests are routinely performed at SIGMET whenever new algorithms and/or major modes are added to the processor.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) 5.10.2 Verifying PHIDP and KDP The PHIDP and KDP processing algorithms can be tested using CW signal sources at IF. In the alternating-transmitter single-receiver case, a single FM signal generator is modulated with an RVP8 polarization select line so that slightly different frequencies are generated for the H and V pulses. A maximum FM depth of several kilohertz is all that is required.
RVP8 User’s Manual April 2003 Processing Algorithms (draft) If we solve this equation for SQI=0.5 we find that the individual S A terms must have twice the power of the individual S B terms. This can be checked by adjusting either signal generator until the minimum plotted SQI is 0.5, and then verifying that the average H and V powers are identical; or, equivalently, that ZDR, LDRH and LDRV are zero. The linear FM ramp described in Section 5.10.
RVP8 User’s Manual May 2003 Host Computer Commands 6. Host Computer Commands This chapter describes the digital commands that the host computer must use to set up and control the RVP8 processor for recording data. Each command is described in detailed in a separate section of this chapter. Note that a command mnemonic, or shorthand reference name, is given in each section heading. These names are frequently used to refer to particular commands.
RVP8 User’s Manual May 2003 Host Computer Commands The sequence of events described above is altered when the FIFO becomes completely full. Then, when the processor generates the next output word, it waits in an idle loop until the user makes room in the FIFO by reading out one or more words. Until this space becomes available, the RVP8 simply waits and does not proceed any further with its internal processing. This, of course, leads to a slowdown in performance, but it is not a disastrous one.
RVP8 User’s Manual May 2003 Host Computer Commands packed into 512 16-bit words. The least significant bit of each packed word represents the nearest range, and the most significant bit represents the furthest range in each group of 16. Because of memory constraints, the RVP8 uses only the first 5600 bits in the mask.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Range Avg. (See Text) | | 0 0 0 0 1 | |_______________________________|_______|___|___________________| Command 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Bits for ranges 0.000km to 1.875km | Input 1 |_______________________________________________________________| \_1.875 . \_0.000 . .
RVP8 User’s Manual May 2003 16B CMS R2 3x3 End Lsr Dsr Rnv Host Computer Commands Configures for 16-bit (rather than 8-bit) data output from the PROC command. This bit affects the single-parameter versions of Reflectivity, Velocity, Width, and Zdr data. However, the PROC command’s archive format always holds 8-bit data, regardless of the setting of 16B. This gives the option of extracting both 8-bit and 16-bit data simultaneously from each ray.
RVP8 User’s Manual May 2003 Host Computer Commands The Signal Quality Index (SQI) threshold is an unsigned binary fraction in the range 0 to 255/256. When the SQI for a range bin falls below the stated value it may result in thresholding of data.
RVP8 User’s Manual May 2003 ZER Window UVD PCT Host Computer Commands If set, then the clutter filter’s internal state variables are zeroed prior to waiting the delay time. For some signal conditions, this may give better results than allowing the filter to naturally flow into the new data. Selects the type of window that is applied to time series data prior to computing power spectra via a DFT. Choices are: 0:Rectangular, 1:Hamming, 2:Blackman.
RVP8 User’s Manual May 2003 Host Computer Commands A simple way to generate these values is to imagine four 16-bit quantities having the following names and values: LOG=AAAA, CSR=CCCC, SQI=F0F0, SIG=FF00. The flag value needed to represent a given logical combination of threshold outcomes is obtained as the result when that same logical combination is applied to these special numbers.
RVP8 User’s Manual May 2003 Host Computer Commands This format is backward compatible with the previous linear format for all values between 0.0 and 0.1dB/km; but it extends the upper range of values from 0.65535 up to 5.6535. These larger attenuation corrections are needed for very short wavelength radars.
RVP8 User’s Manual May 2003 Host Computer Commands Table 6–1: Default Values For Operating Parameters (cont.) Parameter Scientific Units Input Calibration Reflectivity –22.0 dBZ –352 Gas Attenuation 0.016 dB/km 1600 Zdr Offset (GDR) 0.0 dB 0 LDR Offset (XDR) 0.0 dB 0 AGC Integration Period 8 pulses 8 Radar Wavelength 5.3 cm. 5300 Dual PRF Filter Stabilization 10 pulses 10 UnCor Refl. Thresh. Control Flag LOG AAAA Hex Cor Refl. Thresh.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Arbitrary Data Word #1 Supplied by Host Controller | |_______________________________________________________________| . .
RVP8 User’s Manual May 2003 Host Computer Commands temporarily set to a special noise rate (usually much lower than the operating rate) during the process. It is ultimately the user’s responsibility to insure that no returned power is present within the 32km sampling interval. In some cases it may be necessary to raise the antenna during the noise measurement to avoid thermal noise pickup from the ground, or from weather targets.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Starting Range in km (Max 992km) of 32km Sampling Interval | |_______________________________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Internal Trigger Rate (6Mhz/N) to use During Noise Sampling | |_______________________________________________________________| Input 1 Input 2 6.
RVP8 User’s Manual May 2003 Host Computer Commands simultaneously, in which case the archive format is output first, followed by whichever individual display format values were also selected. The archive format is not recommended for use with new drivers because it can only handle four of the many possible output parameter types. When time series mode is selected there are three output data formats available.
RVP8 User’s Manual May 2003 Host Computer Commands High Byte Low Byte | | | | V | Z | |___________|___________| _______________________ | | | | W | T | |___________|___________| First Word Second Word The remaining data parameters are available in both 8-Bit and 16-bit formats, according to SOPRM Command input word #2 (See Section 6.3). The same SOPRM word configures the RVP8 for Single or Dual polarization. The later is required for KDP, PDP, and RHV to be computed properly.
RVP8 User’s Manual May 2003 Host Computer Commands The overall range is from 0.01m/sec to 655.34m/sec in one centimeter/second steps as follows: 0 : Indicates width data is not available at this range 1: 0.01 m/sec 65534 : 655.34 m/sec 65535 : Reserved Code Z Selects clutter corrected reflectivity data. 8-Bit deciBel Format — The level in decibels is computed from the unsigned byte N as: dBZ = (N–64)/2. The overall range is therefore from –31.5 dBZ to +95.
RVP8 User’s Manual May 2003 Host Computer Commands 16-Bit ZDR Format — Same as 16-bit deciBel format. KDP Selects dual polarization specific differential phase data. 8-Bit KDP Format — Values are coded into an unsigned byte using a logarithmic scale. The KDP angles are multiplied by the wavelength in cm. (to reduce dynamic range) and then converted to a log scale separately for both signs. The minimum value is 0.25 deg*cm/km, and the maximum value is 150.0 deg*cm/ km.
RVP8 User’s Manual May 2003 Host Computer Commands 254 : 1.0000 255 : Reserved Code 16-Bit HV Format — The correlation coefficient is computed on the interval 0.0 to 1.0 linearly from the unsigned word N as: HV = (N – 1) / 65533 0 : Indicates no HV data available at this range 1: 0.0 (dimensionless) 65534 : 1.0 65535 : Reserved Code SQI Selects Signal Quality Index data. This dimensionless parameter uses the same 8-bit and 16-bit data formats as RHV ( HV).
RVP8 User’s Manual May 2003 Host Computer Commands The Command word format for Time Series Mode is: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | TSOUT | Spec Type |Unfold | | 1 1 | 0 0 1 1 0 | |_______|_______________|_______|___|_______|___________________| TSOUT Command Selects type of data to be output.
RVP8 User’s Manual May 2003 Host Computer Commands The “Log of Power in Sample” is provided mainly for backwards compatibility. It can be calculated from the I and Q numbers. To convert to dBm it requires a slope and offset as follows: dBm P MAX Slope [Value 3584 ] Where: P MAX = +4.5dBm for 12-bit IFD, +6.0dBm for 14-bit IFD V MAX = 0.5309 Volts for 12-bit IFD, 0.6310 Volts for 14-bit IFD Slope = “Log Power Slope” word 3 of SOPRM command. 0.03 recommended.
RVP8 User’s Manual May 2003 Host Computer Commands spectrum-of-sum or sum-of-spectra according to whether the “Spectra from DSP” button is pressed in the Processing/Gen-Setup window. Answering “No” will still produce the usual (BxN) time series output samples, except that the first half of these samples will be the first half of the “H” data in their normal order. This will be followed by a zero sample if (BxN) is odd; followed by the first half of the “V” data, also in their normal order.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | | IQ #1 | |___________________________________________________|___________| . . 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | | IQ #512 | |___________________________________________________|___________| Input 1 Input 512 6.9 Get Processor Parameters (GPARM) This command is used to access status information from the RVP8 processor.
RVP8 User’s Manual May 2003 Host Computer Commands Table 6–2: RVP8 Status Output Words (cont.) Word Description Word Description 23 Pulse Width 2 min. Trig. Period 55 Immediate Status Word #3 24 Pulse Width 3 min. Trig. Period 56 Burst Tracking Slew 25 Pulse Width Bit Patterns 57 Polarization Algorithm Choices 26 Current /Pulse Width 58 — Reserved — 27 Current Trigger Gen. Period 59 — Reserved — 28 Desired Trigger Gen.
RVP8 User’s Manual May 2003 Host Computer Commands This value is scaled 4 times higher than the time series format. See the discussion in Section 6.7.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Immediate Status Word #1 (Current State of Affairs) | |_______________________________________________________________| Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7 Bit 8 Bit 9 Bits 11,10 Bits 13,12 Bit 14 No trigger, or, more than 50ms. since last trigger. Error in loading trigger angle table (See LSYNC Command). PWINFO command is disabled.
RVP8 User’s Manual May 2003 Host Computer Commands The trigger count is a running tally of the number of triggers received by the RVP8 on the TRIGIN line. It is a full 24-bit counter. 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Number of Properly Acquired Bins for Current Range Mask & PRT | |_______________________________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | No.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Min Trig Period (0.16667usec Increments) for Pulse Width 0 | |_______________________________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Min Trig Period (0.
RVP8 User’s Manual May 2003 Host Computer Commands The PRTs from the start and end of the last ray are the actual measured values whenever possible, i.e., when non-simulated data are being processed, and we either have an external trigger, or an internal trigger that is not in any of the Dual-PRT modes. The units are the same as for the measured current trigger period in Output #3. Outputs 31 through 37 are the current processing and threshold parameters set by SOPRM. See Section 6.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Reserved (Zero) | |_______________________________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Header Configuration of PROC data (Copy of CFGHDR Input #1) | |_______________________________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Noise Sum of I Squared MS
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | | IFD Sat.Power | MinRev | Inter.F | |_______________|_______________|_______________|_______________| Output 52 Inter.F Specifies which interference filter is running. Zero means “none”; see Section 5.1.4 for a description of the interference filter algorithms. MinRev Minor revision level of the RVP8 code that is currently running. IFD Sat.
RVP8 User’s Manual May 2003 Bit 3 Bit 4 Bit 5 Bit 6 Host Computer Commands Use Cross–Pol reception for (T,Z,V,W) Correct all polar params for noise Use filtered data for all polar params Sign convention for PHIdp 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Reserved (Zero) | |_______________________________________________________________| . .
RVP8 User’s Manual May 2003 Host Computer Commands The receiver noise and offset levels which are internally maintained by the RVP8 are zeroed by this command. This is because the measured offsets are not relevant to the simulated data, and must not be used in the subsequent computations. Thus, it is important to issue the SNOISE command before resuming the acquisition and processing of live radar data. 2 Load one pulse of data samples.
RVP8 User’s Manual May 2003 Host Computer Commands 6.11 Reset (RESET) The RESET command permits resetting either the entire RVP8 processor, or selected portions thereof. Flags within the command word determine the action to be taken. 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | |Nv |Nse|Fif|Nv |Nv | 0 1 1 0 0 | |_______________________|___|___|___|___|___|___________________| Nv Nse Fif Command Reloads configuration from the saved nonvolatile settings.
RVP8 User’s Manual May 2003 Host Computer Commands command) corresponds exactly to the instant at which data at range zero are sampled by the RVP8. Note that the output rate can also be interpreted as a new bit coming every 1/48 km. In some cases this is a more useful view. As an example, suppose we wish to make the TGEN0 output be a 0.42 microsecond pretrigger pulse, with a rising edge exactly five microseconds prior to range zero.
RVP8 User’s Manual May 2003 Host Computer Commands code. This is done using word #1 following the command, which contains four codes packed into one 16-bit word. The power-up default is to drive output line N low for a code of N, keeping all other lines high (Input of 7BDE Hex). The flexibility in defining the output bits usually makes the radar hardware connections very simple.
RVP8 User’s Manual May 2003 Host Computer Commands 6.14 Set Pulse Width and PRF (SETPWF) This command selects the pulsewidth and trigger rate. A 2-bit pulse width code is passed in bits 8 and 9 of the command word, and selects one of four pulse widths as described under PWINFO. The new radar PRT is passed in word #1. For all processing modes that use a fixed trigger rate, this value defines the trigger period that is output at all times except during noise measurements.
RVP8 User’s Manual May 2003 Host Computer Commands 360-degrees of rotation. This gives considerable flexibility in the choice of angles. For example, if local obstructions cause shadows in the radar image, then those regions can be skipped merely by omitting table entries in their vicinity. Likewise, as the antenna rotates data can be acquired within one or more sectors by simply specifying the appropriate sets of contiguous bearings at whatever angular resolution is desired.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | |NoI|Ena|El |BCD|Ld | | 1 0 0 0 1 | |___________|___|___|___|___|___|___________|___________________| NoI Ena El BCD Ld Command Ordinarily, the potentially lengthy sync wait loop is terminated if the user writes additional words to the RVP8. Setting this bit prevents such interrupts.
RVP8 User’s Manual May 2003 Host Computer Commands TTY, one can also do via this command. The RVP8 sends all TTY output to whichever stream (TTY, or host computer) provided the most recent input character. This command is also used to monitor the graphical data from the special scope plotting modes.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | 1 0 0 1 | 0 0 0 0 | Int 3 | Int 2 | Int 1 | Int 0 | |_______________|_______________|_______|_______|_______|_______| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | 1 0 0 1 | 0 0 0 1 | Int 7 | Int 6 | Int 5 | Int 4 | |_______________|_______________|_______|_______|_______|_______| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | 1
RVP8 User’s Manual May 2003 Host Computer Commands The linear intervening gas attenuation correction (See SOPRM) is always added to the reflectivity data, regardless of whether default or custom range normalization is in effect. If this is undesirable, the intervening gas slope should be set to zero.
RVP8 User’s Manual May 2003 8 10 Host Computer Commands a. Azimuth (TAG bits 0 – 15) b. Elevation (TAG bits 16 – 31) Doppler clutter filter coefficients (Same format as for LFCOEFS command) Range mask spacing in cm for each pulsewidth 6.20 Pass Auxiliary Arguments to Opcodes (XARGS) This command provides a backward compatible mechanism for supplying additional (optional) arguments to other opcodes.
RVP8 User’s Manual May 2003 Host Computer Commands to include, as indicated by the bit mask following the command. Setting a bit requests that those words be included in the header, and be placed in the order implied by the sequence of the bits. Leaving all bits clear will suppress the header entirely; though this can also be done without changing the configuration via the NHD (No-Headers) bit in SOPRM Input #2.
RVP8 User’s Manual May 2003 Host Computer Commands If the XARGS are not supplied, then the filter parameters will simply retain their previous values. Thus, CFGINTF with no XARGS can be used to turn the interference filters On/Off without making any other changes to their threshold constants. Likewise, if only XARG 1 is supplied, then that single threshold value will be used for both C1 and C2.
RVP8 User’s Manual May 2003 Host Computer Commands 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | | 0 0 0 0 1 1 0 1 1 1 1 1 | |_______________|_______________________________________________| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 | | | | | | | | | | | | | | | | | | Signed trigger slew in hundredths of microseconds | |_______________________________________________________________| Command Input 1 6.
RVP8 User’s Manual May 2003 Host Computer Commands choice is independent of any previous state. No XARG words accompany this command. PhSeq=2 Selects a User Defined sequence. If no XARGS have been supplied, then the RVP8 outputs the default idle phase that is defined in Mz. If XARGS are supplied, then they are interpreted as a sequence of 16-bit binary angles. The RVP8 will make the best match between each desired angle and the closest realizable angle that the phase modulation hardware can produce.
RVP8 User’s Manual May 2003 Host Computer Commands 6.28 Custom User Opcode (USRINTR and USRCONT) These opcodes are part of the open software extensions to the RVP8, which allow custom opcodes to be defined for each major mode of operation. Arguments may be passed into a custom opcode handler as an XARG list. Likewise, an optional array of words returned from that handler will appear after the command executes.
