Andrew NBPCS-9002W User Manual

AE02B-A3659 Rev -- FUNCTIONAL DESCRIPTION

CHAPTER 3

FUNCTIONAL DESCRIPTION

3.1 OVERVIEW

The SelectAmp Channe l ized Paging Rep eat er accepts inputs i n t he 928 – 9 42 pag ing ba nd, and se lec ti v el y
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 fo r th e pa ge r t o bas e station si gnal. The forwar d pa t h inc lu de s a di pl exer, low no is e am pl i fi er an d
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 filter s tuned to the appropriate frequenci es.

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 t o the opposite band.

3.2.2 BROADBAND MODULE

The broadband mo dule conta in s thr ee boar ds , each mount ed in it s ow n comp art men t. The forw ar d chan nel
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 devi ces in the forward channel pat h. It consis ts 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.

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

AE02B-A3659 Rev -- FUNCTIONAL DESCRIPTION

REV CHANNEL PA (A10)

CHANNELIZERS (A4,A5,A6)

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 ch annel modul e prov ides four gain st ages, fi l t eri ng, and gai n adj ustm ent v ia t he front
panel.

3.2.3 CHANNELIZER

The channelizer module contains three boards, each mounted in their own compartment. These three
boards, which are described below, provide the channel selectivity. The channelizer module gain is
approximately 40 dB.

CONTROL/DISTRIBUTION (A1)

Document use is restricted to that described on cover 3-2

DIPLEXER (A9)

POWER SUPPLY (A2)