ZXC10 BTSB (V1.0) cdma2000 Base Transceiver Station Installation Manual
12-4
Depending on the input cross choice for the TSM and the output cross choice for the
BLPA backplane, seven LPAs are configured for 6+1 backup.
The CDMA system adopts the QPSK modulation mode, a linear modulation mode. To
reduce the spectral expansion of signals, some linear features are required from the PA.
In addition, the PA shall also provide constant gain and precisely controllable output
power. In the CDMA system, the ratio of peak power to average power of a signal is
usually around 10 dB. To ensure the inter-modulation index, the PA shall provide a
peak output power around 10 dB. Thus, the efficiency of the PA is reduced due to its
great back off. To improve the efficiency of the PA, a technology in trend provides
linear pre-distortion. In this solution, interfaces for linear distortion are reserved for
forward compatibility with the subsequent R&D achievements.
Excellent performance is expected from the LPA in an environment with appropriate
temperature and power drift. A thorough alarming system is thus required. At present
six types of alarms are to be provided: Over-heat alarms, over-power alarms, VSWR
alarms, loop 1 failure alarms, loop 2 failure alarms and power alarms.
Fully distributed power supply is adopted, and the centralized power shelf is removed.
–48V direct power supply requires support from the LPA. As the power supply is
converted to 27V by the internal power module, the heat consumption caused by the
power conversion should be taken into account during the heat design of LPA.
12.2.3 Transceiver (TRX)
The TRX is to convert the forward/reverse link signals, such as the conversion from
forward/reverse digital baseband signals to analog RF signals. The digital intermediate
frequency (software radio) and the multi-carrier technologies enhance the performance
and the integration of the system.
The working principles and functions of the TRX are as follows:
A TRX can transmit forward/reverse 4-carriers.
Process forward link signals: Receive forward baseband signals from the RMM;
perform digital filtering, digital up-conversion, digital quadrature modulation, and
digital intermediate frequency combination through the processing of the forward
digital intermediate frequency; D/A convert, amplify and filter the signals through the
intermediate frequency; simulate the up-frequency to the RF; control the forward
power attenuation, amplify the RF; output the RF filter; switch TSM and then deliver
Summary of Contents for ZXC10 BTSB I1
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