Analysis and Realization of Digital Filter in Communication System

Size: px

Start display at page:

Download "Analysis and Realization of Digital Filter in Communication System"

Francis Gray
5 years ago
Views:

1 , pp Analysis and Realization of Digital Filter in Communication System Guohua Zou School of software, East China University of Technology, anchang, , China Abstract. Digital filters are extensively used in video processing, digital communications, frequency analysis, auto control and so on. Digital filter is one of the most important part of digital signal process, almost appeared in all digital signal process system. Based on theory, the digital filters can be divided into FIR digital filter and IIR digital filter. FIR digital filter is achieved for these requirements and then widely used in modern signal processing. IIR digital filter is a ind of digital filter that its unit pulse response is unlimited long, and is also an important research tas in modern electronics, communication and signal processing, many scholars did much research on the optimization design of IIR digital filter. High-density FPGA have real-time performance and flexibility, and it can provide powerful hardware support for the implementation of digital filters. In this dissertation, author will mae some analysis on digital filters, and mae realization of digital filters based on FPGA. Keywords: Digital Filter; FIR; IIR; FPGA Introduction Digital filter is hardware or software that can mae filtrate of input signals, and it plays good roles on signal processing or other fields. It filters based on math operations and it is one side of signal processing theory, because of the advantages such as important and flexible []. Therefore, digital filter is wide used in digital communication, video and image processing, model distinguish, auto control and others. Based on the development of DSP (Digital Signal Processor) and FPGA (Field Programmable Gate Array), there are more ways to realize digital filter by hardware [2]. Compared with analog filter, digital filter has many advantages that will be described in the following. () Flexibility. The performance of digital filter is based on the coefficients of multiplication. These coefficients are store in memorizer. It can be fit to many of the system, through changing the coefficients in memorizer. It will be easier and more convenience; (2) High reliability. The signal includes only 0 or in digital system, and it will be not easy to be affected by noise. But analog filter will be affected by temperature, shoc, electromagnetism distraction. On the other side, digital filter will be realized in large scale integrate circuit, the ratio of stoppage will reduce [3]; (3) It is easy to be built in large scale integrate circuit. Compared with analog filter, digital ISS: ASTL Copyright 206 SERSC

2 filter will have many advantages such as volume, weight, performance; (4) Quic processing. Digital filter can mae signal process more quicly than analog filter; In this dissertation, author will realize digital filter based on FPGA. In the following, the analysis of digital filter and realization of digital filter will be described. 2 The Analysis of Digital Filter 2. The definition and Classification of Digital Filter Digital filter is the device that can achieve the function of signal filter, and the input is a set of amount, and the output will be a set of amount. Therefore, the digital filter can be a special used computer or a procedure. During the development of digital technology, digital filter is used by more and more engineers. The digital filter can be divided into FIR digital filter and IIR digital filter. In this section, the theory and instruction of these filters will be described. The analysis of FIR Digital Filter: The function of FIR digital filter can be described in the following equation. H z hn z n0 n The conversion for above equation is as following. y n h x n 0 The above two equations can be change into multiplications. M M2 i 2 H z H z H z The value of H and H 2 are described in the following. () () (2) (2) (2) 2 H z a a z a z H z a a z Through the analysis on the theory of FIR digital filter. The instruction of FIR digital filter can be shown in the following figures. 38 Copyright 206 SERSC

3 x(n) Z - Z - Z - x ( n ) Z - Z - Z - h(0) h() h(2) h(-2) h(-) h h ( h ( h 0 ( ( ) 2 ) ) y(n) y ( n (a) Direct Structure of FIR Digital Filter (b) Connect In Level Structure of FIR Digital Filter Fig.. Structure of FIR Digital Filter The analysis of IIR Digital Filter: The function of IIR digital filter can be described in the following equation. M r0 H z bz r r az The conversion for above equation is as following. M r y n b x n r a y n r0 The structure of IIR digital filter will be shown in figure 2 based on above equation. If M=, the above equations will be changed. r0 Y z Y z W z r H z br z X z W z X z az Therefore, the zero point for first subsystem will be described in the following. r br z W z yn br wn r Y z r0 The zero point for second subsystem will be described in the following. r0 H z 2 W z X z az w n x n a wn W z X z a z W z Through above analysis, the structure of IIR digital filter can be design in figure 2. Copyright 206 SERSC 39

4 b(0) Advanced Science and Technology Letters a() a() a(2) a(2) a() a() x(n) Z - Z - Z - y(n) x(n) Z - Z - Z - Z - Z - Z - b(n-) b(n) b(n-) b(n) b() y(n) b(0) b() (a) Direct Structure I of IIR Digital Filter Fig. 2. Structure of IIR Digital Filter (b) Direct Structure IIof IIR Digital Filter 2.2 Performance Comparison between FIR Digital Filter and IIR Digital Filter In the field of video and signal process, the digital filter can realize the function of the choice of frequency. Therefore, the range and phase will be in linear in frequency domain. FIR digital filter can get linear phase exactly. But IIR digital filter cannot get phase exactly, because it only consider the rang of the signal. On the side of performance, the pole can be configured by recursion instruction in IIR digital filter, and the poles are in on one round. But the pole will be jitter, that will cause the stabilize problem and parasitic oscillation. In opposite, FIR digital filter will not have above problems and this digital filter will have advantage of quic speed of calculate. On the tool of design, IIR digital filter will not have many capacities of calculation, that it does not need good design tools. In opposite, FIR digital filter will have many capacities of calculation, that it will need good design tools to finish the function of FIR digital filter. Above all, FIR digital filter and IIR digital filter will have their advantages and disadvantages. In different application side, we will choose appropriate digital filter in different condition. 3 The Realization of Digital Filter Based on FPGA FPGA is the short of Field programmable gates array. And it is a new type of PLD, the first production manufacturers is named Xilinx in America in 985. It becomes more and more famous even when it is invented. The device has become a good choice for the electronic design engineer because of the feature of large scale, high flexibility, more widely realization of logic function [4]. The speed requirement of circuit becomes higher and higher, with the development of the computer science and the communication technology. The traditional circuit cannot meet the requirement of the high efficiency and real-time processing, and it need time to produce new type devices. But FPGA can be a good choice, it can meet the requirement of the design, and it can be reusable, the confidentiality of FPGA design is better than the other devices. We can use hardware modulated system will be based on the FPGA. 40 Copyright 206 SERSC

5 3. The Realization of FIR Digital Filter based on FPGA (a) Result of Simulation by Multiplication Structure Core Fig. 3. Results of Simulation of Two Ways to Achieve FIR Digital Filter (b) Result of Simulation by Xilinx There are many algorithms that have been invented to achieve FIR digital filter such as multiplication, distributed algorithm and others [4]. In this dissertation, author will achieve FIR digital filter by multiplication and that will have advantage of simple and function perfect. Using Xilinx FPGA, the FIR core have been invented by Xilinx, therefore, the FIR digital filter can be also achieved by Xilinx core. The results of simulation of the two ways are shown in figure 3. In figure 3, picture (a) is the simulation by multiplication structure, picture (b) is the simulation by Xilinx core. The results can prove that the function of FIR digital filter is achieved. 3.2 The Realization of IIR Digital Filter based on FPGA There are also many algorithms having been invented to achieve IIR digital filter including Butterworth digital filter, Chebyshev digital filter, Ellips digital filter and others [5]. In this dissertation, author use Ellips digital filter. The result of simulation and structure are shown in figure 4. (a) Result of Simulation of IIR Digital Filter Copyright 206 SERSC 4

6 (b) The Structure of IIR Digital Filter Fig. 4. Result of Simulation and Structure of IIR Digital Filter In above figure, picture (a) is the result of simulation and picture (b) is the structure of IIR digital filter. That can prove that the function of IIR digital filter having been achieved. 4 Summary In this dissertation, author maes analysis on digital filter including FIR digital filter and IIR digital filter, describes the method of FIR digital filter and IIR digital filter. Compare the structures of FIR digital filter and IIR digital filter, the disadvantages and advantages are also described. Author also realize FIR digital filter and IIR digital filter by FPGA, that can prove that the function of digital filter having been achieved. That can prove the analysis and realization of digital filter in communication system can be accepted. Acnowledgements. The paper is supported by the Science & Technology Support Program of anchang City of China under Grant o. 204HZZC00. References. Hatimaz, I., Gurayna, F K., Leblebici, Y.: A Modular and Scalable Architecture for the Realization of High-Speed Programmable Ran Order Filters [A], Communication technology, Vol. p Peled, A., Liu, B.: A ew Hardware Realization of Digital Filters [J], IEEE Trans on Acoustic Speech and Signal Processing ewsletter, Vol. 3. p Su, C.L., Hwang, Y.T., Jen, C.W.: A ovel Recursive Digital Filter Based on Signed Digit Distributed Arithmetic Circuits and Systems, Proceeding of 2007 IEEE International Symposium, Vol. 3. p Copyright 206 SERSC

COMPARISON OF DIFFERENT REALIZATION TECHNIQUES OF IIR FILTERS USING SYSTEM GENERATOR

COMPARISON OF DIFFERENT REALIZATION TECHNIQUES OF IIR FILTERS USING SYSTEM GENERATOR Prof. SunayanaPatil* Pratik Pramod Bari**, VivekAnandSakla***, Rohit Ashok Shah****, DharmilAshwin Shah***** *(sunayana@vcet.edu.in)