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RF
5.3 RX SYNTHESIZER
5.3.1 General
The RX synthesizer generates an upper side injection frequency for the receiver.
The injection frequency is fed to the receiver's first mixer.
Operating voltage
Current consumption
Output level to the receiver
Frequency range
5.3.2 Functional Description
The RX injection frequency is generated with a phase locked loop. The Voltage Con-
trolled Oscillator (VCO) produces the injection frequency determined by the control
voltage. After the VCO stage comes the amplifier stage Q430. After the amplifier
stage, part of the signal is fed to the synthesizer circuits I400 pre-scaller Fin1. The
synthesizer circuit contains a pre-scaler, programmable divider, reference frequency
divider, and a phase detector.
The synthesizer circuit produces current pulses at output DO1 as controlled by the
phase detector. The current pulses either charge or discharge the loop filter. The
VCO control voltage is derived from the loop filter output.
The synthesizer 12.5kHz reference frequency is made by dividing the 13.00 MHz
signal from the temperature compensated oscillator (TCXO). The series-form signal
which controls the channel frequency comes from the processor. SDATA, SCLK and
SLE signals are common to both TX- and RX-synthesizers. A positive pulse in the
SLE line loads the division ratio (corresponding to the frequency of the channel) fed
to the SDATA line, to the synthesizer circuit I400.
5.3.3 Control- and Output-Signals
VRX
SCLK
SDATA
SLE
RXINJ
RX_REG
4Z2700GB.fm
RX synthesizer operating voltage
Clock signal for the synthesizer control data
Synthesizer control data
ENABLE pulse to the synthesizer
RX synthesizer output to the receiver
Control line for VRX-regulator
Product: TDP80DN /
9.2.2001
3.0 VDC
14 mA
+1 dBm
540.950...545.925 MHz
OC2720 Processor/Audio/RF
3.0 V
+1 dBm
11
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