Motorola ASTRO XTL 5000 Basic Service Manual page 53

Basic Theory of Operation: 700–800 MHz Frequency Generation Unit (FGU)
In TX mode, the transmitter VCO output is coupled to a three-stage buffer before being injected into
the power amplifier (see
on page 3-24). In RX mode, the receiver VCO output is buffered and amplified with a two-stage
transistor/microwave monolithic IC (MMIC) circuit. The output of the first-stage transistor is split into
two paths. One path feeds back to the synthesizer prescaler; the other path is injected into the
second-stage MMIC. The output of the MMIC provides the proper signal level for the LO port of the
RX front-end mixer (see
The super filter supplies the voltage to the first two stages of the TX buffer and to the first-stage
transistor of the RX buffer/amplifier. The voltage for the third stage of the TX buffer is supplied by a
keyed 9.1 V source to conserve current drain while the radio is receiving. The second-stage MMIC of
the RX buffer/amplifier is supplied by a 9.3 V regulator.
6871769L01-A
"3.10 Radio-Frequency Power Amplifier (RF PA) & Output Network (ON)"
"3.13 700–800 MHz Receiver Overview" on page
3-31
3-27).
October 30, 2006