Service Manual

GSM-205-323
CTU
31st Oct 01
Technical Description: Horizon macro indoor
68P02902W07-B
CONTROLLED INTRODUCTION
Tech. 5–13
CTU Tx
connector
The CTU Tx connector is a short SMA to SMA link to the base of the
appropriate Tx block or feedthrough plate.
NOTE
The Tx cable has a 90° SMA connector at one end and a
straight SMA connector at the other end. The 90° end is
designed for connection to the Tx port of a CTU.
CTU Rx
function
The receiver part of the CTU accepts two amplified and filtered receive antenna
signals from the SURF module. These two signals are applied to inputs (branch
A and branch B) of the CTU transceiver board. Figure 5-5 shows a CTU
receiver functional diagram for one branch.
The input from the SURF module is filtered, amplified and down converted to
ensure the signal level and frequency range are correct for the next stage.
RSSI data (applicable only to GPRS and RACH bursts) is used for automatic
gain control (AGC) to ensure signal strength is correct for the intermediate
frequency (IF) stage.
Figure 5-5 CTU receiver functional diagram for one branch
The primary function of the IF is to filter and amplify the incoming signal.
The path is demodulated into quadrature signals and filtered by baseband
analogue filters. These signals are then digitized (I1/I2 data and Q1/Q2 data)
and made available to the equalizer for the purposes of receive synchronization
and data recovery.