User's Manual

68P80801H45-1 1/20/2002 15

EBTS System Manual - Vol 2 Base Radio

QUAD Channel 900 MHz Base Radio Overview

The BR uses diversity reception for increased coverage area and improved

quality. The Receiver modules within the QUAD Channel 900 MHz BR contain

three receiver paths. Two-branch diversity sites use two Receiver paths, and

three-branch diversity sites use three Receiver paths.

All Receiver paths within a given Receiver module are programmed to the same

receive frequency. Signals from each receiver arrive at the EX / CNTL module.

This module performs a diversity combining algorithm on the signals. The

resultant signal undergoes an error-correction process. Then, via Ethernet, the site

controller acquires the signal, along with control information about signal

destination.

Two separate FRUs comprise the transmit section of the QUAD Channel 900 MHz

BR. These are the Exciter portion of the EX / CNTL and the Power Ampliﬁer (PA).

The Exciter processes commands from the CNTL, assuring transmission in the

proper modulation format. Then the low-level signal enters the PA. The PA

ampliﬁes this signal to the desired output power level. The PA is a continuously

keyed linear ampliﬁer. A power control routine monitors the output power of the

BR. The routine adjusts the power as necessary to maintain the proper output

level.