Performance of improved tangent type FM demodulator using digital signal processing

FM demodulators using DSP techniques include the DPLL type, the quadrature type, the tangent type, etc. Compared to their analog counterparts, they are more useful with respect to stability, reliability and convenience of adjustment. However, since the detection characteristics for DPLL or quadrature‐type demodulators are sinusoidal, the introduction of distortion cannot be avoided. In particular, if the input signal is wideband FM, there is a marked deterioration in the characteristics caused by distortion. This paper investigates the tangent‐type FM demodulator whose circuit construction only has in the past been shown and whose characteristics have not been studied at all. It is made clear that the parameter‐setting condition is strictly limited. Next, the detection condition is described and an improved tangent‐type FM demodulator, whose detection characteristics are largely elevated, is represented and its better characteristics are shown. Moreover, comparison is made between this and other types of demodulators by means of simulation, and the effectiveness of this type is shown.