Phase locked loop angle modulation system with large modulation index

摘要

An angle modulation system comprises a voltage controlled oscillator, and at least one frequency divider for dividing the frequency of the output of the voltage controlled oscillator. A phase comparator responds to the output of the frequency divider and to a reference signal supplied from a reference signal oscillator, through another frequency divider. A frequency selection circuit is provided in the path extending from the output side of the voltage controlled oscillator, through the frequency divider, to the phase comparator. This selection circuit eliminates an undesired side band component in the output of the voltage controlled oscillator and derives a required carrier component. An adder adds an input modulation signal and the output of the phase comparator, and applies the resulting signal to the voltage controlled oscillator. From the output of the voltage controlled oscillator, an angle-modulated wave signal is derived with a large signal to noise ratio and large modulation index.