Ddu; Overview; Structure And Principle - Huawei Airbridge BTS3612A-1900 Technical Manual

Technical Manual
Airbridge BTS3612A CDMA Base Station

3.7 DDU

3.7.1 Overview

The Dual Duplexer Unit (DDU) implements the following functions:
Isolation and low-pass filtering of two receiving and transmitting signals.
Providing two DC feeds to T-type Tower Mounted Amplifier (TMA).
Voltage Standing Wave Ratio (VSWR) test on transmit channels in both forward
and backward directions.
Coupling test of transmitting and receiving signals.
Key components within DDU include low-pass filter, duplexer, directional coupler, and
BIAS T (DC supply unit for TMA) which is optional.

3.7.2 Structure and Principle

There are two types of DDU, type A with the BIAS T, type B without the BIAS T. Type A
can be selected to feeder DC to the TMA which may be used when the BTS operates at
1900MHz band.
The DDU (with the BIAS T) structure is shown in Figure 3-7.
Pr1-OUT
Pf1-OUT
TX1
RXM-OUT
Pr2-OUT
Pf2-OUT
TX2
RXD-OUT
LPF: Low-pass Filter
Figure 3-7 Structure of DDU
D
D
LPF
D
LPF
BIAS T
D
D
D
LPF
D
LPF
BIAS T
D
D
N
D-SUB N-Type
Chapter 3 Radio Frequency Subsystem
DUPLEXER
COUPLER
DUPLEXER
COUPLER
S
SMA-Type
3-14
System Principle
TX1-TEST
S
BIAS T
TX/RXM-ANT
N
RXM-TEST
S
TX2-TEST
S
BIAS T
TX/RXD-ANT
N
RXD-TEST
S