Optimization design method for dynamically adjustable variable fractional delay filter

When there is a relative difference in the delay scale of different frequency component signals input to a variable fractional delay filter, adjusting a certain sub filter parameter alone cannot flexibly adjust the filter group delay, resulting in distortion errors in the signal spectrum at the output of the filter. An optimization design method for dynamically adjustable variable fractional delay filter is proposed for this purpose. It generates the delay response frequency of an ideal variable fraction filter under the Farrow structure. Based on trapezoidal curves, the multi-scale Fourier spectrum interpolation method is used to linearly combine the sub filters in the Farrow structure to reduce group delay distortion errors. Then, it derives the polynomial parameters of the Farrow structure’s sub filters, and optimizes the sub filter parameters uniformly. The method performs real time calculation and updating of adjustable parameters through PID algorithm to optimize and adjust the fractional delay parameters of VFD filters, achieving flexible and adjustable group delay of VFD filters. Through experiments, it has been proven that the VFD filter designed in this paper has low maximum amplitude error, normalized root mean square error, and maximum group delay error. The amplitude frequency response and group delay response can be adjusted flexibly, and it has good application effects.