| 摘要 |
The output of a fixed frequency local oscillator is multiplied in frequency by a frequency multiplier and used in the mixer of the first down-conversion stage of a heterodyne receiver. Receiver channel selection and tuning takes place at IF by means of a PLL, the phase detector for the receiver PLL being used also as the phase detected for the transmitter tracking loop PLL. The multiplied local oscillator output is also used in the mixer of the transmitter tracking loop.
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