Motorola DIMETRA MTS 2 Installation, Configuration And Basic Service Manual page 340

Base Radio - Theory of Operation
Upon power-up, the BR performs self-diagnostic tests to ensure the integrity of the unit. These tests
are primarily confined to the BRC and include memory and Ethernet verification routines.
After the self-diagnostic tests are complete, the BR reports any alarm conditions present on any of its modules.
All alarms are reported to the Site Controller through the Ethernet LAN. Alarm conditions may also be verified
locally through the Service Access port on the front panel of the Base Radio and linked to a service computer.
The software resident in FLASH memory on the BRC registers the BR with the Site Controller through
the Ethernet LAN. Once registered, the Base Radio software is downloaded through the Ethernet
LAN and is executed from SDRAM. Operating parameters for the Base Radio are included in this
download. This software allows the Base Radio to perform call processing functions.
The Base Radio operates in a TDMA (Time Division Multiple Access) mode. This mode, combined with
voice compression techniques, provides an increased channel capacity ratio of as much as 4 to 1. Both the
receive and transmit signals of the Base Radio are divided into four individual time slots. Each receive
slot has a corresponding transmit slot; this pair of slots comprises a logical RF channel.
The Base Radio uses single, dual, and triple diversity reception for increased talkback coverage
area and improved quality. The Transceiver contains a three-branch receiver section in which
all receivers are used for triple diversity reception.
All receivers within a given Base Radio are programmed to the same receive frequency. The signals
from each receiver are fed to the BRC where a diversity combining algorithm is performed on the
signals. The resultant signal is processed for error correction and then sent to the Site Controller through
the Ethernet LAN with the appropriate control information regarding its destination.
The transmit section of the Base Radio is comprised of the Exciter (EXC) and Power Amplifier (PA).
The EXC processes the information to transmit from the BRC in the proper modulation format. This
low level signal is sent to the Power Amplifier where it is amplified to the desired output power level.
The PA is a continuous-keyed linear amplifier. A power control routine monitors the output power
of the Base Radio and adjusts it as necessary to maintain the proper output level.
For information on the performance specifications, see
10-4
The Base Radio is prepared for TEDS.
Chapter 14, "Technical Specifications".
Chapter 10: Base Radio
6802800U74-N September 2009