User Manual
Airbridge cBTS3612 CDMA Base Station
System Description
2 Hardware Architecture
2-25
&
Note:
The above figure illustrates the RF configuration for 450MHz band. For 800MHz band, the duplexer
would be CDU. For 1900MHz band, the duplexer would be DDU.
In forward link, it performs power adjustable up-conversion and linear power
amplification to the modulated transmission signals, filtering the transmission signals
to meet the corresponding air interface standard.
In reverse link, it filters the signals received by the BTS antenna to suppress
out-band interference, and then performs low-noise amplification, noise factor
adjustable frequency down -conversion, and channel selective filtering.
2.3.2 BTS Transceiver Module (BTRM)
BTRM is in charge of modulating/demodulating of baseband signal, Analog/Digital
and Digital/Analog (AD/DA) conversion, digital up/down conversion and radio
up/down conversion.
I. Structure and principle
BTRM consists of BTS Intermediate Frequency Unit (BIFU) and BTS Radio up-down
Converter Unit (BRCU). Its structure is shown in Figure 2-14.
FIR
&
DAGC
FIR
DAC
Demultiplexer/multiplexer
ADC
Power
CPU
Clock
Optical interface
Down
converter
ADC
Filter
BHPA
Local oscillator
BRCU
RLDU
BIFU
RLDU
BTRM
+27V
Main receiver
Diversity receiver
Transmitter
BHPA
PSU
PSU
BHPA
Filter
Filter
Down
converter
Up
converter
Figure 2-14
Structure of BTRM