Design And Research Of Digital Filter Based On FPGA

FPGA(field programmable gate array) device is a programmable logic device which developed in 1990 s. It has the characteristics of high integration, high reliability and fast processing speed. FPGA can be carried out on the hardware and software co design so that the hardware design is as flexible and convenient as the software design.Filters have important applications in many fields, such as digital communication, voice, audio, biomedical signal processing and so on. Digital filters are mainly used to change the characteristics of the time and frequency domain of the signal. The common filter is a linear time invariant filter. Because of the regular structure form of the FIR filter, in the practical application, most of the FIR filters are provided with corresponding IP core. However, IIR filters do not have a nuclear, which limit the applicability of these filters in practical engineering. At the same time, compared to FIR, IIR filters have many irreplaceable characteristics such as the same amplitude frequency characteristic which it only need to lower order. Another strong point is that using IIR filters need relatively few hardware resources.This paper introduces the theory of FIR, IIR filter and applies FIR and IIR filters whose structure are low pass, high pass or other types to create respectively the serial structure, parallel structure and distributed structure filter. At the same time, the performance of different structures are compared and analyzed in this paper. This paper generates the filter coefficients by using fdatool and design different filter according to different structures. In practical applications, if the sampling frequency is much larger than the cut-off frequency of the signal, it is difficult to design the IIR filters which only have one part and the IIR filters can only be divided into several parts of the cascade. Then the FIR filter and IIR filter are compared respectively and design of the direct type structure and the cascade structure of the IIR filter. At last, it designs the filters by the cooperative work of multiple software packages.First of all, this paper uses MATLAB simulation and uses the function of MATLAB to design according to the specified parameters. Then the corresponding parameters are obtained. it is necessary to translate parameters to hexadecimal because Quartus II can only identify binary data which are the input data of a hardware design tool(Quartus II). Then, we write the different structure of the filter by using Quartus II. The simulation tests are carried out by Using Modelsim. The program is downloaded to the de2 hardware test. And because that the FPGA filters can erase characteristics and types of filters and the parameters of passband frequencies and stopband frequencies can be changed by programming, the filter can be changed according to the actual needs.