SIN type FM demodulator using digital signal processing

FM demodulators using digital signal processing (DSP) technology are advantageous over analog type FM demodulators becasuse they have stable behavior, high reliability, compactness by LSI, and no need for adjustment. In this paper, we propose a new FM demodulator called SIN type FM demodulator which uses DSP technology. It reduces hardware complexity compared with TAN type FM demodulator which has the best characteristic among many FM demodulators using DSP. For example, SIN type needs only one A/D converter, while TAN type needs two. As for ROM, SIN type needs one‐third of ROM which TAN type requires. The circuit of SIN type required for phase detector is substantially simplified. First, the circuit configuration and operation principle of SIN type will be described and SIN type circuit is shown to be significantly simplified compared with TAN type circuit. Then, through computer simulation the performance of SIN type is shown to be much better than the Digital Quadrature type, which has the simplest structure of all the FM demodulators using DSP.