User Guide

PAMS
System Module DB6
NHB–3
Technical Documentation
Original 26/97
Page 4–45
and the control voltage (TXC) and controls voltage controlled amplifier (in
CRFRT) and the power amplifier. The control circuit is a part of CRFRT.
SYNTHESIZER
Reference Oscillator
The reference oscillator is a discrete VCXO and the frequency is 26 MHz.
The oscillator signal is used for a reference frequency of the synthesizers and
the clock frequency for the base band circuits.
VHF PLL
The VHF PLL consists of the VHF VCO, PLL integrated circuit and loop filter.
The output signal is used for the 3rd mixer of the receiver and for the I/Q modu-
lator of the transmitter.
VHF VCO + Buffer
The VHF VCO uses a bipolar transistor as a active element and a combination
of a chip coil and varactor diode as a resonance circuit. The buffer is combined
into the VCO circuit so, that they use same collector current.
UHF PLL
The UHF PLL consists of a UHF VCO, divider, PLL circuit and a loop filter. The
output signal is used for the 1st mixer of the receiver and the upconversion mix-
er of the transmitter. In PCN the VCO change the frequency according to the
RX/TX mode change.
UHF VCO + Buffer
The UHF VCO uses a bipolar transistor as a active element and a combination
of a microstripline and a varactor diode as a resonance circuit.
UHF VCO Buffers
The buffers amplifies the UHF VCO signal. The output signal is divided into the
1st mixer of the receiver and the upconversion mixer of the transmitter. There is
one buffer for TX and one for RX.
PLL Circuit
The PLL is NATIONAL LMX2331ATM. The circuit is a dual frequency synthesiz-
er including both the UHF and VHF synthesizers.