Digital T/2 Nyquist filtering using recursive all-pass two-stage resampling filters for a wide range of selectable signalling rates

The design and implementation of a cost effective polyphase recursive resampling filter which affords very high resolution adjustable sample rate as required in high performacne modems are described. The filters perform the addressed tasks of root-raised-cos matched filtering and half bandwidth 2:1 resample filtering, as well as spectral phase equalization. The computational burden required to implement these filters is extremely low. Using the filters with a sampler which can be varied over an octave results in a modem with versatile variable bandwidth and sample rate options