【正文】 The first is absolute indicators. It provides a function to respond to the demands of the general application of FIR filter design. The second indicator is the relative indicators. Its value in the form of answers to decibels. In engineering practice, the most popular of such indicators. For phase response indicators forms, usually in the hope that the system with a linear phase frequency bands human. Using linear phase filter design with the following response to the indicators strengths： ① it only contains a few algorithms, no plural operations； ② there is delay distortion, only a fixed amount of delay。 類比電子電路模擬用的 濾波 部分組成 ， 例如由電阻 、 電容和生產所需的 濾波 效果 。 這些計算通常涉及多方面的投入和增加產品 取值 的共同因素 。它的缺點 是相位的非線性；若需要線性相位，則要采用全通網絡進行相位校正。由此可知， FIR 濾波器應用比較廣，而 IIR 濾波器則用 在相位要求不是很嚴格的場合。它提供對幅度響應函數的要求，一般應用于 FIR 濾波器的設計。根據這個描述用硬件或者計算機軟件來實現它。 利用 MATLAB設計濾波器，可以隨時對比設計要求和濾波器特性調整參數，直觀簡便，極大的減輕了工作量，有利于濾波器設計的最優(yōu)化。 。目前微機保護和二次信號處理軟件主要采用數字濾波器。除具備卓越的數值計算能力外，它還提供了專業(yè)水平 的符號計算，文字處理，可視化建模仿真和實時控制等功能。它以分貝值的形式給出要求。 A1 (f) A2 (f) 1 1 0 f2c f 0 f 2c f (a) (b) A3 (f) A4 (f) 1 1 0 f1c f2c f 0 f1c f2c f (c) (d) 圖中四類濾波器的幅頻特性 (a)低通 (b)高通 (c)帶通 (d)帶阻 數字濾波器的設計 數字濾波器設計的 基本要求 ， 數字濾波器設計要經過三個步驟： （ 1）確定指標：在設計一個濾波器前，必須有一些指標。而 FIR 數字濾波器可以實現線性相位，又可具有任意幅度特性。 看 到一個數字 濾波器 ,信號是由一系列數字 組成 ,而不是電壓或 電流。 有完善的技術標準設計的模擬電路進行 濾波的 特定要求 。s top mathematical software applications, with a strong engineering puting, algorithms research, engineering drawings, applications development, data analysis and dynamic simulation, and other functions, in aerospace, mechanical manufacturing and construction fields playing an increasingly important role. And the C language function rich, the use of flexibility, highefficiency goals procedures. High language both advantages as well as low level language features. Therefore, C language is the most widely used programming language. Although MATLAB is a plete, fully functional programming environment, but in some cases, data and procedures with the external environment of the world is very necessary and useful. Filter design using Matlab, could be adjusted with the design requirements and filter characteristics of the parameters, visual simple, greatly reducing the workload for the filter design optimization. In the electricity system protection and secondary puter control, many signal processing and analysis are based on are certain types Yeroskipou and the second harmonics of the system voltage and curre