Audio/Signaling; Uhf Transmitter; Figure 2-5:Uhf Transmitter Block Diagram; Power Amplifier (Pa) - Motorola Professional Radio Service Manual

2.4.1

Audio/Signaling

The audio/signalling/filter/companding IC (ASFIC) and the audio power amplifier (Figure 2-3) form the
main components of the audio/signalling section of the controller board. Inputs include a 16.8 MHz
clock from the synthesizer, recovered audio and squelch, MCU control signals, and external or
internal microphones. Outputs include a microprocessor clock (CLK), modulator output to the
synthesizer, and amplified audio signals to an internal or external speaker.
2.5

UHF Transmitter

The UHF transmitter consists of the following basic circuits as shown in Figure 2-5.
•

Power amplifier (PA).

• Antenna switch/harmonic filter.
• Antenna matching network.
• Power control integrated circuit (PCIC).
From VCO
2.5.1 Power Amplifier (PA)
The PA consists of two LDMOS devices:
• 9Z67 LDMOS driver IC (U101)
• PRF1507 LDMOS PA (Q110)
The 9Z67 LDMOS driver (U101) provides 2-stage amplification using a supply voltage of 7.3V. The
amplifier is capable of supplying an output power of 0.3W (U101pins 6 & 7) with an input signal of
2mW(3dBm) at U101 (pin 16). The current drain is typically 160mA while operating in the frequency
range of 403-470MHz.
The LDMOS PA is capable of supplying an output power of 7W with an input signal of 0.3W. The
current drain is typically 1300mA while operating in the frequency range of 403-470MHz. The power
output can be varied by changing the bias voltage.
PCIC
Vcontrol
Power Amplifier (PA)
PA
Driver
Figure 2-5: UHF Transmitter Block Diagram
Vcontrol
Antenna Switch/
PA Final
Harmonic Filter
Stage
Antenna
Matching
Network
2-5