Periodically Time-Varying Realizations of Multirate Converters for Hardware Reduction
Sachin Ghanekar, S. Tantaratana · 2004
Realizations of multirate FIR filters are proposed using periodically time-varying (PTV) structures. By exploiting the computational redundancy of the fil-tering operation in a multirate filter, it is possible to implement the filter with much less hardware. In the proposed implementations, the number of multiply-and-add units is reduced by making several coeffi-cients share one multiplier-and-add unit in a periodic fashion. Specifically, each multiply-and-add unit per-forms different coefficient scalings at different time in-stants within a period. Compared to the direct form realization, the proposed realizations reduce the hard-ware of an interpolator and a decimator by a factor of approximately U andM, respectively, while retaining the same processing speed, where U and M are the upsampling and downsampling factors, respectively. For a rational sampling rate conversion by a factor of U/M, where U and M are relatively prime, the proposed realization offers hardware reduction by a factor of approximately UM, compared to the con-ventional direct form. 1.