Filtering tricks for FSK demodulation

An efficient comb filter can be used to both remove the dc offset from signals and reduce the complexity of follow-on filtering. The advantages of the comb filter are its implementation simplicity and its ability to combat the problem of dc offset for both IF and baseband signals. Through examples, it is shown that the duty cycle for signals at the IF can be easily corrected to a 50% duty cycle. This corrected signal is amenable to additional processing at its IF frequency or may be down-converted to a baseband frequency for further processing.