Generalized structure for designing odd-order variable fractional-delay filters

We have shown that coefficient-symmetry can be exploited for designing high-accuracy and low-complexity even- order variable fractional-delay (VFD) finite-impulse-response (FIR) filters. This paper first reveals the coefficient-symmetry for odd-order case, and then proposes a generalized weighted- least-squares (WLS) method for designing odd-order VFD filters using different-order subfilters. Compared with the WLS method using same-order subfilters, this generalized one can further reduce the VFD filter complexity. Consequently, the generalized WLS method using both coefficient-symmetry and different- order subfilters can reduce the number of independent VFD filter coefficients by more than 50%, and thus reduce the hardware cost and the number of multipliers by more than 50%, which facilitates high-speed VFD filtering.