Motorola MTR2000 T5544 Instruction / Field Service Manual page 169

1
DESCRIPTION
The Models CLN1226, CLN1227 Power Amplifier Modules are described in this section. A general description,
identification of inputs/outputs, functional block diagram, and functional theory of operation are provided. The
information provided is sufficient to give service personnel a functional understanding of the module, allowing
maintenance and troubleshooting to the module level. (Refer also to the Troubleshooting section of this manual
for detailed troubleshooting procedures for all modules in the station.)
General Description
Overview of Circuitry
Motorola Inc., 2005
All Rights Reserved
Printed in U.S.A.
The Power Amplifier Module (PA) accepts a low-level modulated RF sig-
nal from the Exciter Module and amplifies the signal for transmission via
the site transmit antenna. The output power is continually monitored and
regulated by a feedback and control loop, with a power output control
voltage being generated by the transmitter control circuitry located on the
PA Input/Output boards.
The PA contains the following circuitry:
• Intermediate Power Amplifier (IPA) – hybrid substrate amplifier
stage which accepts low-level input from Exciter Module, amplifies
the signal, and outputs a 0 W to 10 W RF signal
• Butterfly Module – hybrid substrate amplifier stage which accepts
output from IPA Hybrid and provides final amplification to 50 W
(maximum)
• Directional Coupler/Power Detector/Low Pass Filter – couples am-
plified RF signal to transmit antenna connector; also generates dc
voltages proportional to forward and reflected power for use in TX
power control loop; provides harmonic suppression for the station
• Dual Circulator – provides isolation between Power Amplifier out-
put and transmit antenna
• Temperature Sense Circuitry – provides variable resistance signal
proportional to heat sink temperature; signal is monitored by the PA
power control circuitry
Government & Enterprise Mobility Solutions
1301 E. Algonquin Road, Schaumburg, IL 60196
POWER AMPLIFIER
MODEL CLN1226, 40 W
MODEL CLN1227, 30 W
MODULE
132 to 174 MHz
68P81096E26-B
09/30/05-UP