Improvement of error performance of digital modulation in the mobile radios using a novel multi-level FSK-QTFSK (quaternary-phase transition FSK)

A modulation scheme, named QTFSK (quaternary-phase transition FSK) is proposed for digital mobile radio applications, especially when severe power saving is required. As QTFSK is essentially a continuous phase FSK modulation scheme, it is preferable for satellite-mobile systems. It is clarified theoretically and experimentally that the error performance is almost the same as that of QPSK in the Rayleigh fading channel. The main lobe of the signal spectrum is a little narrower than QPSK.