Motorola MTM700, Подробное руководство по обслуживанию

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4.2 - 8 MTM700 Mobile Radio / Detailed Service Manual THEORY OF OPERATION (800 MHz)
The reference oscillator –TCXO is a temperature compensated crystal oscillator producing an accu-
rate and stable 16.8 MHz master clock, from which all other clocks in the radio are derived. It pro-
vides the reference frequency for the following components:
• the main frequency synthesizer,
• the IF Digitizing Subsystem,
• the ADDAG, and
• the microcontroller
Its operating frequency is fine tuned by means of a warp voltage signal generated by the LVFRACN
IC.
Main Synthesizer
The Main Synthesizer consists of the main VCO and LVFRACN PLL IC. The main synthesizer pro-
vides the LO signal to the first mixer for down-converting the received signal to the 73.35 MHz first
IF frequency and in transmit mode provides the reference frequency for the ESCORT frequency
translation loop.
Transmit frequency translation loop
The transmitter frequency translation loop consists of the transmit VCO and ESCORT near unity
divider PLL IC. This subsystem generates the carrier frequency injection signal for the LNODCT.