Quaternary FSK receiver and method of judging signals in quaternary FSK receiver

摘要

There is provided a quaternary FSK receiver which calculates an average of demodulated signals when a received quaternary FSK signal is converted into a quaternary digital signal, and the digital signal is entirely gradually increased or decreased in level so that the average is equal to a second reference value. This reduces influence exerted by fluctuation in a central value of the demodulated signal. The first and third reference values are varied in accordance with levels of “10 ” and “00 ” of the digital signal. Thus, it is possible to reduce sign error which is caused by fluctuation in an amplitude of the demodulated signal.