The Design Of IIR Digital Audio Filter Based On FPGA

In the current, analog audio processing technology is gradually replaced by digital audio processing technology, which has obtained a rapid popularization and development. Digital filtering technology can realize the digitization of audio processing through transforming the collected audio signal. Digital filter is the study hotspot inside the industry, and is one of key signal processing technology. Because the structure of multiplier is huge, the audio processing system of traditional digital filter is inadequate in volume and processing speed. With the development of programmable logic device, FPGA has obvious advantages in performance, cost, flexibility and power. The signal processor based on FPGA already has been widely used in signal processing field.This paper studied the basic theory of digital filter, digital audio processing method and all phase data pretreatment method, and completed the IIR digital audio filter of design and implementation based on FPGA.Firstly, all phase data pretreatment method had the advantage of reducing truncated effect when it was applied to digital audio processing. Take all phase windowless data preprocessing as an example when N=4, and do the pretreatment for audio signal. The results show that the head and tail waveforms of audio signal are smooth; maintain the continuity; narrow the leaked scope of side spectrum; reduce the interference between spectrum. Waveform distortion and leak inhibition have got a very good improvement, thus reduce truncation errors.The realization method of IIR parallel processing is improved, from the two parallel processing improvement to four ways of parallel processing. This paper offers a parallel processing implementation scheme of the filter based on FPGA, using four ways of parallel processing method to design digital filter, and put audio signal after the pretreatment through windowless all phase data as the input for four ways parallel processing filter. Eight ways parallel processing method is proposed to design digital filter, then we proof the validity and practicality of four and eight parallel processing by VHDL realized the design.QuartusⅡsoftware not only has strong compile comprehensive functions, but also provides certain waveform simulation function. Because its input and output are given in the form of waveform, it is difficult to get quantitative analysis of results. In order to strengthen QuartusⅡsimulation function and improve the design efficiency, this paper mainly take MATLAB and QuartusⅡjoint simulation way. With the audio signal after pretreatment by windowless all phase data as the input signal, the filter effect of designed filters is tested.Experimental results show that the clock frequency of designedⅡR audio filter is increased, and the filtering speed is improved. The clock frequency of four ways parallel processingⅡR filter is 98.41 MHz, and two parallel processingⅡR filter is 95.29 MHz; the former than the latter 3.12 MHz and meet the design requirements.