The Implementation of In-band FM based on Fractional-N PLL

This paper studied the in-band frequency modulation technology based on fractional-N PLL, first elaborated the basic principle and transfer function analysis of FM PLL, and according to the fractional-N theory gives the realization principle and the concrete algorithm of the modulation signal frequency in the loop modulation loop bandwidth of PLL, gives the design of key circuit, and the result shows that the technology can realize the frequency of modulation signal low to the DC, and high precision modulation, good frequency stability.