The Design Of All Phase Filter Based On FRM Technique And Its Hardware Implementation

Frequency response masking technique is the most effective technology to reduce hardware complexity, and achieve a sharp transition band filter design. It reduces the computational complexity at the cost of increasing a small amount of filter group delay. The basic idea behind the FRM technique is to receive a sharp transition band and arbitrary bandwidth with several short sub-filters, including a pair of complementary interpolated band-edge shaping filters, and two masking filters. All-phase approach can be an effective solution to the signal processing performance degradation caused by data truncation. Due to considering all the cases of data truncation, it greatly enhances the performance of inhibiting spectral leakage. All-phase digital filtering theory has many features, owing to this, there is a large combination space between the all-phase digital filtering theory and FRM technique.Based on understanding and mastering the classical FRM structure and a variety of improved structures, to design an all-phase low pass FRM filter with low computational complexity and good performance, all-phase design method and FRM technique was efficiently combined. By comparing performance of different FRM structures, better filtering structure was selected and combined with all-phase half band filter with small pass band ripple, large stop band attenuation and without overshooting whether in pass band or stop band; because of the advantage of all-phase notch filter and little study about FRM notch filter recently, an implementation structure of high efficiency notch filter combining techniques of FRM and all-phase filtering was proposed. Based on the analysis of double phase-shift combination all-phase notch filter’s insufficient notching depth, it was pointed out that the significantly increased notching depth is essentially caused by all-phase single convolution window, which is inside prototype filter and masking filter. Moreover, the expression of notch filter frequency response was theoretically derived, and it was testified that attenuation at notching frequency could reach about -200dB without any compensation or corrective measures, even if the shifting parameterλis not an integer multiple of 1/2.The proposed design models, including all-phase low-pass FRM filter and all-phase FRM notch filter, were built through system generator, and completed hardware co-simulation using the Xilinx development board ML605.The hardware testing results verify the proposed methods’correctness and practicality.