Digital frequency synthesis circuit

The invention provides a digital frequency synthesis circuit comprising a DDS circuit, a modulator, a clock signal generating circuit, and a pulse signal generating circuit. The DDS circuit is used for receiving a frequency control word and outputting an analog voltage signal according to the frequency control word; the modulator is used for modulating the analog voltage signal outputted by the DDS circuit and using the modulated signal as the output of the digital frequency synthesis circuit; the clock signal generating circuit is used for generating a reference clock signal and outputting the reference clock signal to the DDS circuit as a clock signal for component synchronization work in the DDS circuit; and the pulse signal generating circuit is used for generating a first pulse signal and outputting the first pulse signal to the modulator and the DDS, wherein the first pulse signal is coherent with the reference clock signal and the first pulse signal is used for modulating the analog voltage signal outp