Patent ID: 7088790

Claim:
A circuit for detecting a center level of a frequency shift keying (FSK) demodulated signal to correct same comprising: control means for holding a sample peak value of a demodulated base band signal of a FSK signal and a second sample value thereof having a polarity opposite to the first sample value in a first or a second sample hold circuit respectively in response to data information of said FSK signal; average calculation means for calculating a center level value of the demodulated FSK signal by averaging said first and second sample values; shift width calculation means for calculating a shift width value by taking ½ of difference between the first sample value and the second sample value; third sample means holding said shift width value in response to said data information; adder means for adding said shift width value to said first sample value to calculate a center level value; subtraction means for subtracting said shift width value from said second sample value to calculate a center level value; selection means for selecting the center level value calculated by said average calculation means, adder means or subtraction means in response to said data information; and judgement means for judging whether a received information data of said FSK signal is “1” or “0” on a basis of a selected center level value.