Harmonic Filter; Antenna Matching Network; Power Control Integrated Circuit (Pcic); Temperature Cut Back Circuit - Motorola PRO3150 Service Manual

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2.5.3 Harmonic Filter

The harmonic filter consists of C104, L102, C143, C103, L101, C142 and C102. The harmonic filter
for UHF is a modified Zolotarev design optimized for efficiency of the power module. This type of filter
has the advantage that it can give a greater attenuation in the stop-band for a given ripple level. The
harmonic filter insertion loss is typically less than 1.2dB.

2.5.4 Antenna Matching Network

The matching network (L116 and C141) matches the antenna's impedance with the harmonic filter to
optimize the performance of the transmitter and receiver.

2.5.5 Power Control Integrated Circuit (PCIC)

The transmitter uses the PCIC (U102) to regulate the power output of the radio. The current to the
final stage of the power module is supplied through R102, which provides a voltage proportional to
the current drain. This voltage is then fed back to the Automatic Level Control (ALC) within the PCIC
to regulate the output power of the transmitter.
The PCIC contains internal digital to analog converters (DACs) that provide a programmable control
loop reference voltage. The reference voltage level is programmable through the SPI line of the PCIC.
The PCIC internal resistors, integrators, and external capacitors (C133, C134 and C135) control the
transmitter rise and fall times to reduce the power splatter into adjacent channels.

2.5.6 Temperature Cut Back Circuit

Diode CR105 and associated components are part of a temperature cut back circuit. This circuit
senses the printed circuit board temperature around the transmitter circuits and outputs a DC voltage
to the PCIC. If the DC voltage produced exceeds the set threshold in the PCIC, the transmitter output
power decreases to reduce the transmitter temperature.
UHF Transmitter