Service Manual

GSM-204-323
SURF module
31st Oct 01
Technical Description: Horizon macro outdoor
68P02902W02-A
CONTROLLED INTRODUCTION
Tech. 5–29
Functional
description of
dual band SURF
modules
The dual band SURF modules provide front end filtering, amplification, and
matrix control of the RF receive signal between the antenna and the CTU. The
dual band SURFs each have three antenna pair connections providing main
frequency reception, and one antenna pair providing reception on a second
frequency. The two types of dual band (DB) SURF enable 900 CTUs to be
mixed with 1800 CTUs in any combination, up to the maximum total of six CTUs
per cabinet.
The dual band SURF functional sections (see Figure 5-16) consist of loopback,
filtering, amplification, splitting, digital processing and power selection.
Each section is duplicated for the second diversity path, except for the digital
and dc power section, which is shared by the two diversity paths. There are four
antenna pair inputs (ANT 0, ANT 1, ANT 2 and ANT DB) for each of the two
diversity branches (branch A and branch B). There are six outputs to the CTU
for each of the two diversity branches, as well as one input from the CTU for the
loopback (LPBK) signal. There is also an output for an expansion cabinet for
ANT 0 on each branch.
The software database has to be configured at the OMC-R to accept 1800
CTUs and 900 CTUs in the appropriate cabinet locations.
Digital codes are transmitted from the 900 CTUs and 1800 CTUs to the digital
section. The digital codes are different, so that 900 or 1800 CTUs can be
recognized and appropriate switching can be made to the required antenna for
transmission and reception.
The digital and power supply section is also responsible for loopback switch
control, manual overrides, alarms and dc voltages.
The RF loopback test function is described in RF overview and RF test
function in this chapter.