Coherent Demodulation of Frequency-Shift Keying with Low Deviation Ratio

A coherent binary FSK modulation system is discussed, that has the following properties: 1) it is phase coherent; 2) it has a low deviation ratio, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h = \frac{1}{2}; 3</tex> ) it occupies a small RF bandwidth, typically only 0.75 times the bit rate, without need for intersymbol interference correction; 4) it uses as receiver a self-synchronizing circuit and a phase detector, which together achieve optimal decisions; and 5) its error performance is about S dB better than that of conventional FSK.