Pll Frequency Synthesizer - Motorola EVX S24 Service Manual

MN006437A01-AB
Chapter 4: Circuit Description
4.3

PLL Frequency Synthesizer

The frequency synthesizer consists of VCO, TCXO X1001, and the custom IC Q1046 (RODINIA). The
output frequency from TCXO X1001 is 19.2 MHz and the tolerance is ±1.5 ppm in the temperature
range –22 °F to +140 °F (–30 °C to +60 °C).
VCO (Voltage Controlled Oscillator)
The VCO Q1036 (BFR460L3) generates a between 806-940 MHz. The output from VCO Q1036
(BFR460L3) is amplified by buffer amplifier Q1041 (2SC5010) and then is supplied to the custom IC
Q1046 (RODINIA). The VCO frequency is divided into two by the dividing section of the custom IC
Q1046 (RODINIA) in order to become a true receiving or transmitting frequency. In the reception, the
RF signal convert a Base Band signal by mixing with the divided VCO signal, and then supplied to the
demodulator section of the custom IC Q1046 (RODINIA), described previously. In the transmission, the
divide VCO frequency is modulated to the FM (or digital) in the custom IC Q1046 (RODINIA), and then
is supplied to the transmitter section described previously.
Varactor Control Voltage
The tuning voltage (VCV) of the VCO establishes the lock range of VCO by controlling the cathode of
varactor diode D1029, D1030, D1031 and D1032 (all 1SV279) from the custom IC Q1046 (RODINIA).
PLL
The main constitution product of the PLL is equipped all with in the custom IC Q1046 (RODINIA), so
that all pro- cessing regarding the frequency control is performed in the custom IC Q1046 (RODINIA).
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