User Manual
Airbridge cBTS3612 CDMA Base Station
System Description
2 Hardware Architecture
2-36
N
D-SUB
S
D
N-Type
SMA-Type
LPF
DUPLEXER
COUPLER
N
S
S
D
D
D
D
TX2-TEST
TX/RXD-ANT
RXD-TEST
Pf2-OUT
Pr2-OUT
TX2
RXD-OUT
LPF
LPF
DUPLEXER
COUPLER
N
S
S
D
D
D
D
TX1-TEST
TX/RXM-ANT
RXM-TEST
Pf1-OUT
Pr1-OUT
TX1
RXM-OUT
LPF
BIAS T
BIAS T
BIAS T
BIAS T
Figure 2-19
Structure of DDU
l
Low-pass filter
The low-pass filter is used to suppress the high-order harmonic wave. The low-pass
filter on receive channel also functions to suppress the interference from the
transmit channel.
l
Duplexer
The duplexer is used to isolate transmitting signals and receiving signals, suppress
transmission spurious and reduce antenna quantity.
l
Bi-directional coupler
The bi-directional coupler couples forward/reverse power for RLDU, and monitors
the antenna VSWR.
l
T-type feed connector
This connector receives the RF signals and divides/combines DC feeds, so that the
RF signals and DC go through different channels, realizing the DC supply to the
tower-top amplifier.
III. Interface
DDU is a module shared by the transmitting and receiving paths of the BTS. It has
interfaces with other modules both in the transmitting and receiving paths. Its
external interfaces include a set of 8W8 DB combination blind mate connectors on
the backside, and a set of N-connectors and SMA connectors on the front. The
interface signals include: