Synthesizer-modulator for SCPC satellite Earth station

The study, design, and practical implementation of a frequency synthesizer in the 52.020 MHz to 87.990 MHz band, with step of 30 kHz is comprised. A PLL (phase-locked loop) synthesis technique consists basically in using a PLL with a programmable divisor in the feedback loop. The output frequency is a function of the value of this divisor. This synthesizer has also the function of a FM modulator and is being used to generate 1200 different channels of a SCPC (single channel per carrier) Earth station. In the transmitter of this station, the carrier will be present in the output only when there is voice signal in the modulator input; so that it may occur, a carrier suppressor circuit is used.