Agilent Innovative Applications for an RF/microwave USB Power Meter or Sensor and Power Analysis Manager Software Application Note
Introduction Every once in a while, a new product concept comes along which offers engineers a novel way to use their measurement creativity in order to devise their own application setups. In the case of RF and microwave power measurements, Agilent’s traditional sensor and meter combination has served since World War II in the 1940s. With the new USB-based power sensor, measurement engineer can now remove the power meter instrument from the conventional measurement process.
A New USB Power Sensor Series and Power Analysis Manager Software The Universal Serial Bus (USB) is no longer a stranger to many and is increasingly gaining favor as an alternative interface in the world of testing and measurements. USB provides easy and wideband data connections to peripheral devices.
Most importantly, the N1918A Power Panel software leverages power measurement data available from the data outputs of other power meter instruments like the Agilent P-Series N1911/12A and Agilent N8262A meters. Since those meters and associated peak and average sensors characterize complex power signals, including pulsed, spread spectrum and wireless communications formats, the optional N1918A-100 Power Analysis Manager delivers statistical measurement results with such data like PDF, CDF, and CCDF.
U2000 Series Product Concepts and Capabilities The U2000 Series is based on the powerful RF/icrowave diode sensing technologies which have been exploited by Agilent for over 30 years. Introduced as the HP 8484A sensor in 1975, it utilized the then-new LBS diode technology, which featured metal to semiconductor junctions. Such diode junctions are rugged, highly consistent and repeatable from diode to diode, and reliable in long term measurement. [Ref: 1.
In brief, the input RF/microwave power drives two measurement channels, one for the lower level signals and the other through a resistive 30 dB attenuator for the high level channel. At the transition power point, approximately –10 dBm, the internal circuitry determines which channel will provide the output data. Amplification and signal conditioning assure that drift and gain stability are not compromised before hitting the high performance 14-bit analog-to-digital converter modules.
N1918A Power Analysis Manager Product Concept and Capabilities Once the data is digitized, power measurement data which is derived from the U2000 Series power sensors or P-Series power meter can be processed in different ways. The N1918A Power Analysis Manager provides powerful analysis tools for a variety of purposes, which are summarized here. The N1918A is available in two configurations: • Power Panel, Basic: Bundled with the purchase of the U2000 Series USB Power Sensor.
In Figure 11, the Power Analyzer provides four display formats; Digital Softpanel, Strip Chart, Analog Gauge and Trace Graph. The Power Analyzer supports and manages more than ten sensors and displays up to four data results in a single tab. Furthermore, users can also create multiple tabs to support multiple measurements. Users can save and restore their instrument settings. The Power Analyzer can be programmed in order to record specific measurements using a specific setup at a specific or repetitive time.
Measurement Applications Remote Power Measurements of the U2000 Series USB One of the serious limiting factors of the traditional power meter and sensor Power Sensor instrumentation is that the connection cable between them carried ultra-lowWith the performance capabilities and data flexibility of the new U2000 Series and the Power Analysis Manager, measurement engineers have the ready-to-use solutions at hand for the power measurement requirements of their applications.
Portable Power Measurement – Mobile Power Acquisition and Data Logging While previous power meters have been available in battery-operated configurations, they only permitted simple local measurement functions. The U2000 Series allows mobile operation using a laptop operating with a minimum power, fed through the USB data cable from the laptop’s battery. Thus, measurements can be easily made at remote sites, such as wireless base stations.
Multiple-Channel Power Measurements Many power measurement applications do not allow engineers to sense multiple power points simultaneously and rather require them to move single sensors from point to point. This is where the USB signal multiplexer can be used because it can sequence data from as many as ten channels of USB data from ten U2000 Series sensors.
Obtaining Absolute Power Measurements on Associated Measuring Instruments Many modern test instruments have powerful signal processing and displays of a variety of important parameters. Spectrum analyzers provide many different signal characteristics versus frequency, including nominal power levels of unknown signals. Network analyzers, with their multi-band signal sources are great for measuring S-parameters of all sorts of passive and active components.
Measurement Data Gathering Function Applications of the N1918A The N1918A Power Analysis Manager is a multi-faceted software application, Power Analysis Manager running on Windows operating systems, which multiplies the measurement and The N1918A Power Analysis Manager is a suite of application toos that comprises a basic version which comes with the purchase of the U2000 Series, and an advanced version, Option 100, which is an optional, licensed software.
Table 1 Overview of the software capabilities for the two versions of the N1918A Power Analysis Manager.
Providing Comprehensive Pulsed Signal Characterization with all Pulse Parameters The Agilent 8990A Peak Power Analyzer pioneered the comprehensive signal characterization of pulsed microwave signals approximately in 1990. It has become obsolete some years ago. When you combine the N1918A Power Analysis Manager with a P-Series power meter, including its peak and average sensors, the complete 15 pulse parameters’ real-time and computed data are immediately shown on the screen.
Measuring and Computing PDF, CDF, and CCDF Statistical Parameters Figure 20 The computed CCDF function is an important system performance parameter for wireless system engineers. The statistical measurements can be easily provided by the Power Analyzer. It can display statistical parameters in both tabular and graphical display formats. Control Tower Monitoring of Types of Power Functions Figure 21 shows four different monitoring and computed power functions on one screen at the same time.
Record and Load Function The record and load function allows you to store data of up to seven days based on preprogrammed measurement schedules. Thus, data can be archived and loaded for later viewing or use. The data is stored in a comma-separated value file (CSV), which is compatible with Microsoft Excel. This function can be used to troubleshoot equipment which exhibits random and and unwanted changes in the power output.
Measurement Tips, Calibration, Traceability, and Measurement Uncertainties 5.1 Measurement Tips There are four important steps that are necessary to achieve better power measurement results: • • • • Understanding the modulation formats of the signal under test, Understanding the power sensor technology and operating principles, Understanding the principles of power measurement traceability, and Selecting the right sensor and PC, power meter or display for the signals under test.
Signal Formats The wide-dynamic square-law range of the U2000 Series sensors makes them ideally suited to measure signal formats with complex modulation formats which cause high crest factors. The principle is that the peaks of the crest factor spikes do not exceed the square-law detection range. Crest factors of ten are easily handled by assuring that the measurement range of the sensor is dialed down in such a way that the peak power does not exceed +20 dBm.
Traceability and Uncertainty All the previous technology history and knowledge acquired in using Agilent’s power measurement equipment is preserved in the U2000 Series. Agilent follows international standards and processes for assuring traceability to NMIs (National Measurement Institutes) such as NIST in the U.S. Agilent’s Application Note 1449–3, which provides exhaustive documentation on the subject. [Ref: 3].
References Related Literatures Related Web Resources [1] Zurakowski, M, et al, Nov, 1986, Diode Integrated Circuits for MM Applications, Hewlett-Packard Journal. [1] Agilent Fundamentals of RF and Microwave Power Measurements (Part 1), Introduction to Power, History, Definitions, International Standards and Tracebility, Literature Number 5988-9213EN For SCPI standards, refer to the following URL: [2] Anderson, Alan B.
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