AE04B-A0279 Rev -- OVERVIEW
Document use is restricted to that described on cover 2-1
CHAPTER 2
OPERATIONAL OVERVIEW
2.1 OVERVIEW
Refer to Figure 2-1. The SelectAmp CDMA 800 bi-directional channelized amplifier provides selective
frequency amplification of user specified frequencies in the SMR, Cellular, and ESMR bands. This unit will
selectively filter for one 1.25 MHz or 5 MHz channel, depending on the part number ordered, in the Uplink
and Downlink band as determined by the operator. This is accomplished by downconverting the desired
signals to a 70 MHz intermediate frequency and using narrowband SAW filters to provide adjacent channel
rejection
2.2 RF DISTRIBUTION
The amplifier contains two paths; forward, or downlink, from the base station to the mobile, and reverse, or
uplink, from the mobile to the base station. Each path includes a diplexer, low noise amplifier, channelizer,
and power amplifier. The diplexers and channelizers determine the frequencies to be amplified.
2.3 POWER DISTRIBUTION
Main power for the amplifier is provided by a 14 amp power supply operating at +15 VDC. The power supply
accepts 90 - 260 VAC inputs. The interconnect board distr15 volts, +5 volts, and -5 volts to the
various modules.
2.4 CONTROL DISTRIBUTION
The operator has control over the gain and operating frequency of each path. Computer inputs for gain and
channel settings are routed to each low noise amplifier and channelizer. The gain setting is a four bit word
that sets downlink gain from 65 dB to 95 dB, and uplink gain from 55 to 85 dB. The channel setting is a
three wire serial input to a synthesizer in each channelizer. Each module outputs a status message to
indicate the overall condition of the active devices. If an active device fails, the module reports a fault.
