Product Drawings Chapter 3

ManualsBrandsAndrew ManualsElectronicsChannelized Paging Repeater

AE02B-A3659 Rev -- FUNCTIONAL DESCRIPTION

Document use is restricted to that described on cover 3-1

CHAPTER 3

FUNCTIONAL DESCRIPTION

3.1 OVERVIEW

The SelectAmp Channelized Paging Repeater accepts inputs in the 928 – 942 paging band, and selectively

passes one discrete channel in each band while rejecting the others. In the forward channels this is

accomplished by downconverting the desired signals to a 45 MHz intermediate frequency and using

narrowband crystal filters to provide adjacent channel rejection. The reverse path is not channelized,

passing all frequencies in the 897 – 903 MHz band.

3.2 FUNCTIONAL DESCRIPTION

Refer to Figure 3-1. The amplifier contains two paths; forward for the base station to pager signal and

reverse for the pager to base station signal. The forward path includes a diplexer, low noise amplifier and

splitter, channelizer, combiner, and power amplifier. The channelizers determine the frequencies to be

amplified and provide the gain control. The reverse path includes a diplexer, broadband module (amplifier

and filters), and a power amplifier. Diplexing of the forward and reverse channels is accomplished by

diplexer filters tuned to the appropriate frequencies.

3.2.1 DIPLEXER

The diplexer module consists of dual filters with a common port on one end and two separate ports on the

other. One side of the diplexer is tuned for the forward channel, the other side for the reverse channel.

Insertion loss of each filter is 2 dB maximum and 65 dB minimum rejection to the opposite band.

3.2.2 BROADBAND MODULE

The broadband module contains three boards, each mounted in its own compartment. The forward channel

signals are routed through the LNA/Splitter and Combiner boards. The reverse channel signal is routed

through the 901 MHz board. Each board is described in more detail below.

3.2.2.1 LNA/SPLITTER

The LNA/Splitter module contains the first active devices in the forward channel path. It consists of a low

noise amplifier, 3-way power splitter, and a gain stage and filter per path. The amplifiers bias voltages are

monitored for a fault condition and reported to the control/distribution module.

3.2.2.2 COMBINER

The Combiner module consists of a 3-way power combiner, a gain stage and filter, and a level detector

circuit.

Summary of content (5 pages)

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AE02B-A3659 Rev -- FUNCTIONAL DESCRIPTION CHAPTER 3 FUNCTIONAL DESCRIPTION 3.1 OVERVIEW The SelectAmp Channelized Paging Repeater accepts inputs in the 928 – 942 paging band, and selectively passes one discrete channel in each band while rejecting the others. In the forward channels this is accomplished by downconverting the desired signals to a 45 MHz intermediate frequency and using narrowband crystal filters to provide adjacent channel rejection.
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AE02B-A3659 Rev -- CHANNELIZERS (A4,A5,A6) FUNCTIONAL DESCRIPTION REV CHANNEL PA (A10) FWD CHANNEL PA (A12) DIPLEXER (A8) BROADBAND (A7) FRONT PANEL (A13) Figure 3-1. SelectAmp NBPCS-900-3 Outline Drawing, front view. 3.2.2.3 901 MHZ REVERSE CHANNEL The 901 MHz reverse channel module provides four gain stages, filtering, and gain adjustment via the front panel. 3.2.3 CHANNELIZER The channelizer module contains three boards, each mounted in their own compartment.
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AE02B-A3659 Rev -- FUNCTIONAL DESCRIPTION Figure 3-2. SelectAmp NBPCS-900-3 Outline Drawing, rear view. 3.2.3.1 DOWNCONVERTER The downconverter board consists of a mixer driven by a synthesizer, a crystal filter centered at 45 MHz with either a 12.5 KHz (930 MHz channelizer), a 50 KHz (940 MHz ReFlex50 channelizer), or a 25 KHz (940 MHz ReFlex25 channelizer) 1 dB bandwidth. It has one fixed gain stage, and a variable gain stage to provide overall gain adjustment.
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AE02B-A3659 Rev -- 3.2.3.2 FUNCTIONAL DESCRIPTION UPCONVERTER The upconverter board mixes the filtered 45 MHz IF with a signal from the synthesizer and outputs the same frequency that was input to the downconverter. The upconverter consists of a mixer, gain stage, and filter. The DC current draw of each gain stage is monitored by a window comparator. The window comparator indicates a fault, if the gain stage has an open or short condition. 3.2.3.
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AE02B-A3659 Rev -- 3.3 FUNCTIONAL DESCRIPTION PROGRAMMING The amplifier forward channels are set by connecting a laptop computer with the supplied cable to the front panel connector. Details on setting the channels and software operation are provided in Appendix B.