Chapter 4 MTR3000 Power Amplifier
4.1 Description
The Power Amplifier (PA) is described in this section. A general description, identification of inputs
and outputs, a 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.
4.1.1 General Description
The Power Amplifier (PA) is a forced convection-cooled RF power amplifier. It accepts a low-level
modulated RF signal from the Exciter Module, and amplifies it for transmission via the site transmit
antenna port. The PA is non-linear, and is therefore used for continuous wave (CW) applications
only. 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.
4.1.1.1 Overview of Circuitry
The Power Amplifier contains the following sub-circuits:
• DC Distribution Board – Main interface for the PA to the Station Control Module (SCM) and
Power Supply (PS). This board contains PA SPI circuits including Analog to Digital Converter
(ADC), Digital to Analog Converter (DAC), and Non-Volatile Memory (NVM) devices, and
hardware (HW) metering circuitry
• RF Board – Provides RF signal amplification from the Exciter Module low-level signal to the
MTR3000 Base Station/Repeater (BR) output power level
• Isolator – Protects the PA from damage when poor RF load conditions exist. Also assists with
intermodulation attenuation performance
• Output Board – Performs harmonic filtering and RF power detection functions, and routes the
RF signal to the antenna port
Note
If the station is an upgraded MTR2000, refer to MTR2000 Basic Service Manual (included
with the original MTR2000 station) for all PA information.
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