6-1
Chapter 6 VHF Theory of Operation
6.1 Transmitter
Figure 6-1. Transmitter Block Diagram
6.1.1 General
(Refer to Figure 6-1.)
The VHF transmitter contains five basic circuits:
• Power amplifier
• Antenna switch
• Harmonic filter
• Antenna matching network
• Power control integrated circuit (PCIC)
6.1.2 Power Amplifier
The power amplifier consists of two devices:
• 9Z67 LDMOS driver IC (U3501)
• PRF1507 LDMOS PA (Q3501)
The 9Z67 LDMOS driver IC contains a two-stage amplification with a supply voltage of 7.3 V.
This RF power amplifier is capable of supplying an output power of 0.3 W (pin 6 and 7) with an input
signal of 2 mW (3 dBm) (pin16). The current drain would typically be 130 mA while operating in the
frequency range of 136-174 MHz.
The PRF1507 LDMOS PA is capable of supplying an output power of 7 W with an input signal of
0.3W. The current drain would typically be 1800 mA while operating in the frequency range of
136-174 MHz. The power output can be varied by changing the biasing voltage.
PCIC
Antenna
PA
Driver
Vcontrol
Vcontrol
From VCO
Jack
Antenna Switch/
Harmonic Filter/
Matching Network
PA
Final Stage
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