Novel FIR filter designs for digital quadrature demodulation

Finite impulse response (FIR) filters can provide ideal group delay characteristics. This makes them attractive for implementing quadrature demodulators based on quadrature mixing and lowpass filtering concepts. This paper describes novel quadrature demodulators based on third-band FIR filters in which nearly a third of the filter coefficients are zero valued. The proposed designs can achieve high accuracy while retaining stop bands which are useful for suppressing undesired signals.