An arctangent type wideband PM/FM demodulator with improved performances

It is shown that in PM (phase modulation) and FM (frequency modulated) communication systems a real baseband message is transformed into a complex baseband signal which is a rolled up version of that message on a unity radius cylinder. PM and FM signals could therefore be seen as QAM (quadrature amplitude modulation) signals and demodulated as such with a QAM demodulator. Various methods are presented which permit one to unroll the complex received signal in order to give back the original real baseband message. Among them, a modified version of the 'ranged extended tangent type FM demodulator' is studied in more detail and found to give excellent results. Special attention is given to digital signal processing.<>