1、課 程 設(shè) 計(jì)課程設(shè)計(jì)名稱:基于Blackman窗的FIR數(shù)字低通濾波器設(shè)計(jì)專業(yè)班級(jí) ： 電信1003 學(xué)生姓名 ： 星空 學(xué) 號(hào) ： 指 導(dǎo) 教 師 ： 課程設(shè)計(jì)時(shí)間： 2013. 數(shù)字信號(hào)處理 專業(yè)課程設(shè)計(jì)任務(wù)書學(xué)生姓名星空專業(yè)班級(jí)電信1003學(xué)號(hào)題 目基于Blackman窗的FIR數(shù)字低通濾波器設(shè)計(jì)課題性質(zhì)工程技術(shù)研究課題來源自擬課題指導(dǎo)教師同組姓名主要內(nèi)容 設(shè)計(jì)一個(gè)具有如下性能指標(biāo)的FIR數(shù)字帶通濾波器：=0.25，=0.4；窗函數(shù)為Blackman窗；分析最后設(shè)計(jì)結(jié)果性能。任務(wù)要求1. 溫習(xí)窗函數(shù)法設(shè)計(jì)數(shù)字FIR濾波器的原理和設(shè)計(jì)方法；2. 求出最后所設(shè)計(jì)出的濾波器沖激響應(yīng)系數(shù)；3.

2、 繪制所設(shè)計(jì)濾波器的增益響應(yīng)曲線。參考文獻(xiàn)1 胡廣書. 數(shù)字信號(hào)處理理論、算法與實(shí)現(xiàn)M. 北京: 清華大學(xué)出版社, 1997.2 R. Lyons. Understanding Digital Signal Processing M. 2nd ed. Prentice Hall PTR., 2004.3 A.V.奧本海姆, R.W.謝弗 and J.R.巴克. 離散時(shí)間信號(hào)處理M. 第二版. 西安交通大學(xué)出版社, 2001.4 S. K. Mitra. Digital Signal Processing: A Computer-Based ApproachM. 3rd ed. McGraw-H

3、ill, 2005.審查意見指導(dǎo)教師簽字：李相國教研室主任簽字： 年 月 日 說明：本表由指導(dǎo)教師填寫，由教研室主任審核后下達(dá)給選題學(xué)生，裝訂在設(shè)計(jì)（論文）首頁1 需求分析數(shù)字濾波器可以理解為是一個(gè)計(jì)算程序或算法，將代表輸入信號(hào)的數(shù)字時(shí)間序列轉(zhuǎn)化為代表輸出信號(hào)的數(shù)字時(shí)間序列，并在轉(zhuǎn)化過程中，使信號(hào)按預(yù)定的形式變化。數(shù)字濾波器有多種分類，根據(jù)數(shù)字濾波器沖激響應(yīng)的時(shí)域特征，可將數(shù)字濾波器分為兩種，即無限長沖激響應(yīng)（iir）濾波器和有限長沖激響應(yīng)（fir）濾波器。iir數(shù)字濾波器具有無限寬的沖激響應(yīng)，與模擬濾波器相匹配。所以iir濾波器的設(shè)計(jì)可以采取在模擬濾波器設(shè)計(jì)的基礎(chǔ)上進(jìn)一步變換的方法。fir數(shù)

4、字濾波器的單位脈沖響應(yīng)是有限長序列。它的設(shè)計(jì)問題實(shí)質(zhì)上是確定能滿足所要求的轉(zhuǎn)移序列或脈沖響應(yīng)的常數(shù)問題，設(shè)計(jì)方法主要有窗函數(shù)法、頻率采樣法和等波紋最佳逼近法等。因此設(shè)計(jì)FIR濾波器的方法之一可以從時(shí)域出發(fā)，截取有限長的一段沖擊響應(yīng)作為H(z)的系數(shù)，沖擊響應(yīng)長度N就是系統(tǒng)函數(shù)H(z)的階數(shù)。只要N足夠長，截取的方法合理，總能滿足頻域的要求。一般這種時(shí)域設(shè)計(jì)、頻域檢驗(yàn)的方法要反復(fù)幾個(gè)回合才能成功。要設(shè)計(jì)一個(gè)線性相位的FIR數(shù)字濾波器，首先要求理想頻率響應(yīng)。是w的周期函數(shù)，周期為，可以展開成傅氏級(jí)數(shù)： 其中是與理想頻響對(duì)應(yīng)的理想單位抽樣響應(yīng)序列。但不能用來作為設(shè)計(jì)FIR DF用的h(n)，因?yàn)橐话?/p>

5、都是無限長、非因果的，物理上無法實(shí)現(xiàn)。為了設(shè)計(jì)出頻響類似于理想頻響的濾波器，可以考慮用h(n)來近似。窗函數(shù)的基本思想：先選取一個(gè)理想濾波器（它的單位抽樣響應(yīng)是非因果、無限長的），再截取（或加窗）它的單位抽樣響應(yīng)得到線性相位因果FIR濾波器。這種方法的重點(diǎn)是選擇一個(gè)合適的窗函數(shù)和理想濾波器。設(shè)x(n)是一個(gè)長序列，w(n)是長度為N的窗函數(shù)，用w(n)截?cái)鄕(n)，得到N點(diǎn)序列xn(n)，即xn(n) = x(n) w(n) 在頻域上則有 由此可見，窗函數(shù)w(n)不僅僅會(huì)影響原信號(hào)x(n)在時(shí)域上的波形，而且也會(huì)影響到頻域內(nèi)的形狀。加矩形窗后的頻譜和理想頻譜可得到以下結(jié)論：加窗使過渡帶變寬，過

6、渡帶的帶寬取決于窗譜的主瓣寬度。矩形窗情況下的過渡帶寬是。N越大，過渡帶越窄、越陡；過渡帶兩旁產(chǎn)生肩峰，肩峰的兩側(cè)形成起伏振蕩。肩峰幅度取決于窗譜主瓣和旁瓣面積之比。矩形窗情況下是8.95，與N無關(guān)。工程上習(xí)慣用相對(duì)衰耗來描述濾波器，相對(duì)衰耗定義為 這樣兩個(gè)肩峰點(diǎn)的相對(duì)衰耗分別是0.74dB和-21dB。其中（-0.0895）對(duì)應(yīng)的點(diǎn)的值定義為阻帶最小衰耗。以上的分析可見，濾波器的各種重要指標(biāo)都是由窗函數(shù)決定，因此改進(jìn)濾波器的關(guān)鍵在于改進(jìn)窗函數(shù)。窗函數(shù)譜的兩個(gè)最重要的指標(biāo)是：主瓣寬度和旁瓣峰值衰耗。旁瓣峰值衰耗定義為： 旁瓣峰值衰耗20lg(第一旁瓣峰值主瓣峰值) 為了改善濾波器的性能，需使窗

7、函數(shù)譜滿足：主瓣盡可能窄，以使設(shè)計(jì)出來的濾波器有較陡的過渡帶；第一副瓣面積相對(duì)主瓣面積盡可能小，即能量盡可能集中在主瓣，外泄少，使設(shè)計(jì)出來的濾波器的肩峰和余振小。但上面兩個(gè)條件是相互矛盾的，實(shí)際應(yīng)用中，折衷處理，兼顧各項(xiàng)指標(biāo)。本次設(shè)計(jì)要求以窗函數(shù)為Blackman窗為基礎(chǔ)，設(shè)計(jì)一個(gè)具有如下性能指標(biāo)的FIR數(shù)字帶通濾波器： =0.25，=0.4 2 概要設(shè)計(jì)如果所希望的濾波器的理想的頻率響應(yīng)函數(shù)為，則其對(duì)應(yīng)的單位脈沖響應(yīng)為窗函數(shù)設(shè)計(jì)法的基本原理是用有限長單位脈沖響應(yīng)序列逼近。由于往往是無限長序列，而且是非因果的，所以用窗函數(shù)將截?cái)啵⑦M(jìn)行加權(quán)處理，得到：就作為實(shí)際設(shè)計(jì)的FIR數(shù)字濾波器的單位脈沖

8、響應(yīng)序列，其頻率響應(yīng)函數(shù)為式中，N為所選窗函數(shù)的長度。我們知道，用窗函數(shù)法設(shè)計(jì)的濾波器性能取決于窗函數(shù)的類型及窗口長度N的取值。設(shè)計(jì)過程中，要根據(jù)對(duì)阻帶最小衰減和過渡帶寬度的要求選擇合適的窗函數(shù)類型和窗口長度N 。主程序框圖如圖4.1所示。其中幅度特性要求用dB表示。開始計(jì)算并讀入窗口長度N計(jì)算hd(n)調(diào)用窗函數(shù)子程序求w(n)調(diào)用子程序（函數(shù)）計(jì)算H(k)=DFTh(n)調(diào)用繪圖子程序（函數(shù)）繪制H(k)幅度相位曲線結(jié)束圖1 主程序框圖計(jì)算h(n)= hd(n) w(n)布萊克曼窗函數(shù)布萊克曼窗函數(shù)的時(shí)域形式可以表示為 它的頻域特性為：其中，為矩形窗函數(shù)的幅度頻率特性函數(shù)。布萊克曼窗函數(shù)的

9、最大旁瓣值比主瓣值低57dB，但是主瓣寬度是矩形窗函數(shù)的主瓣寬度的3倍，為12/N。Blackman函數(shù)調(diào)用方式： w = blackman (n)：輸入?yún)?shù)n是窗函數(shù)的長度；輸出參數(shù)w是由窗函數(shù)的值組成的n階向量。3 運(yùn)行環(huán)境軟件環(huán)境：1.Windows xp2. MATLAB6.54 開發(fā)工具和編程語言開發(fā)工具:MATLAB桌面和命令窗口、歷史命令窗口、編輯器和調(diào)試器、路徑搜索和用于用戶瀏覽幫助、工作空間、文件的瀏覽器。MATLAB一個(gè)高級(jí)的矩陣/陣列語言，它包含控制語句、函數(shù)、數(shù)據(jù)結(jié)構(gòu)、輸入和輸出和面向?qū)ο缶幊烫攸c(diǎn)。用戶可以在命令窗口中將輸入語句與執(zhí)行命令同步，也可以先編寫好一個(gè)較大的復(fù)

10、雜的應(yīng)用程序（M文件）后再一起運(yùn)行。5 詳細(xì)設(shè)計(jì) 算法實(shí)現(xiàn)的源程序：（1）計(jì)算實(shí)際濾波器的幅度，相位響應(yīng)function db,mag,pha,grd,w=myfreqz(b,a); N=1000;H,w=freqz(b,a,N,'whole');H=(H(1:1:501)'w=(w(1:1:501)'mag=abs(H);db=20*log10(mag+eps)/max(mag);pha=angle(H);grd=grpdelay(b,a,w); （2）求濾波器的理想脈沖響應(yīng)function hd=ideal_lp(wc,M);al=(M-1)/2;n=0:(

11、M-1);m=n-al+eps;hd=sin(wc*m)./(pi*m);（3）主程序：wst=0.4*pi;wp=0.25*pi;deltaw=wst-wp; %過渡帶寬w的計(jì)算N0=ceil(11*pi/deltaw); %按布萊克曼窗計(jì)算所需的濾波器長度N=N0+mod(N0+1,2);%為了實(shí)現(xiàn)第一類偶對(duì)稱濾波器，應(yīng)確保其長度N為奇數(shù)n=0:1:N-1;wc=(wst+wp)/2; %截止頻率取為兩邊緣頻率的平均值hd=ideal_lp(wc,N); %求理想脈沖響應(yīng)wdbla=(blackman(N)' %求窗函數(shù)h=hd.*wdbla; %設(shè)計(jì)的脈沖響應(yīng)應(yīng)為理想脈沖響應(yīng)與窗

12、函數(shù)乘積db,mag,pha,grd,w=myfreqz(h,1); %對(duì)設(shè)計(jì)結(jié)果進(jìn)行檢驗(yàn)dw=2*pi/2000; %頻率分辨率Rp=-(min(db(1:wp/dw+1) %檢驗(yàn)通帶波動(dòng)As=-round(max(db(wst/dw+1:501) %檢驗(yàn)最小阻帶衰減figure(1)subplot(2,2,1);stem(n,wdbla);title('布萊克曼窗') %繪制布萊克曼窗axis(0 N-1 0 1.1);ylabel('w(n)');text(N+1,0,'n')subplot(2,2,2);stem(n,h);title(&

13、#39;實(shí)際脈沖響應(yīng)') %繪制實(shí)際脈沖響應(yīng)axis(0 N-1 -0.4 0.5);xlabel('n');ylabel('h(n)')subplot(2,2,3);plot(w/pi,db); %繪制幅度響應(yīng);title('幅度響應(yīng)（單位：dB)');grid;axis(0 1 -150 10);xlabel('頻率（單位： pi)');ylabel('分貝數(shù)')set(gca,'XTickMode','manual','XTick',0,0.2,0.35

14、,0.65,0.8,1)set(gca,'YTickMode','manual','YTick',-60,0)subplot(2,2,4);plot(w,pha);title('相位響應(yīng)'); %繪制相頻特性axis(0 2 -4 4);xlabel('頻率（單位:pi)');ylabel('相位()')6 調(diào)試分析設(shè)計(jì)低通濾波器時(shí)首先要計(jì)算出過渡帶寬，然后查表得到所設(shè)計(jì)窗函數(shù)所需要的階數(shù)，不同的窗函數(shù)所設(shè)計(jì)的濾波器的形狀各有差異，尤其在主瓣寬度、旁瓣的形狀以及主瓣與旁瓣的高度差上有比較明顯得差別，

15、實(shí)際應(yīng)用中應(yīng)根據(jù)實(shí)際情況，折衷處理，兼顧各項(xiàng)指標(biāo)。實(shí)際中遇到的離散時(shí)間信號(hào)總是有限長的，因此不可避免地要遇到數(shù)據(jù)截?cái)鄦栴}。而在信號(hào)處理中，對(duì)離散序列的數(shù)據(jù)截?cái)嗍峭ㄟ^序列與窗函數(shù)相乘來實(shí)現(xiàn)的。7 測(cè)試結(jié)果測(cè)試結(jié)果有錯(cuò)，初始參數(shù)為ws=0.4*pi;wp=0.25*pi，運(yùn)行出錯(cuò)，錯(cuò)誤在主程序最后一行：axis(0 2 -4 4);xlabel('頻率（單位:pi)');ylabel('相位()')，最后檢查出來為標(biāo)點(diǎn)出錯(cuò)，應(yīng)為英文輸入法下的標(biāo)點(diǎn)運(yùn)行結(jié)果(圖):參考文獻(xiàn)1劉泉 信號(hào)與系統(tǒng) 高等教育出版社 2006 2 丁玉美，高西全編著. 數(shù)字信號(hào)處理.西安：西安電

16、子科技大學(xué)出版社，20003劉泉 數(shù)字信號(hào)處理原理與實(shí)現(xiàn) 電子工業(yè)出版社 20054 黃文梅，熊桂林，楊勇編著. 信號(hào)分析與處理-MATLAB語言及應(yīng)用.長沙：國防科技大學(xué)出版社5 張宗橙，張玲華，曹雪虹編著. 數(shù)字圖像處理與應(yīng)用。南京：東南大學(xué)出版社，1997心得體會(huì)通過對(duì)該課程的學(xué)習(xí)，我對(duì)數(shù)字通信理論有了更進(jìn)一步的理解；通過對(duì)該數(shù)字濾波器的設(shè)計(jì)，我也了解了數(shù)字濾波器的基本結(jié)構(gòu)和基本特性，而且還掌握了基本的撰寫論文的形式和思路。作為一個(gè)電子信息工程專業(yè)的學(xué)生，數(shù)字信號(hào)處理是我們的重要專業(yè)課程，是我們將來從事通信事業(yè)的基本保障。通過對(duì)作為該論文的重要部分MATLAB的運(yùn)用，大大提高了我們對(duì)集計(jì)

17、算，編程與繪圖于一體的該應(yīng)用軟件的運(yùn)用能力。MATLAB包含的幾十個(gè)工具箱，覆蓋了通信，自動(dòng)控制，信號(hào)處理，圖象處理，財(cái)經(jīng)，化工，生命科學(xué)等科學(xué)技術(shù)領(lǐng)域，汲取了當(dāng)今世界這些領(lǐng)域的最新研究成果，已經(jīng)成為從事科學(xué)研究和工程設(shè)計(jì)不可缺少的工具軟件。該課程設(shè)計(jì)將數(shù)字信號(hào)處理的有關(guān)教學(xué)內(nèi)容和MATLAB語言緊密，有機(jī)地結(jié)合起來，使我們?cè)趯W(xué)習(xí)基礎(chǔ)理論知識(shí)的同時(shí)學(xué)會(huì)了應(yīng)用MATLAB，在學(xué)習(xí)應(yīng)用MATLAB的同時(shí)，加深了對(duì)基本知識(shí)的理解，增強(qiáng)了我們的計(jì)算機(jī)應(yīng)用能力，提高了學(xué)習(xí)效果。總之，無論是從教學(xué)知識(shí)掌握出發(fā)，還是從對(duì)MATLAB的應(yīng)用出發(fā)，通過這次學(xué)習(xí)，我不但掌握了基于Blackman窗的FIR數(shù)字帶通

18、濾波器設(shè)計(jì)的基本知識(shí)及其實(shí)際應(yīng)用的技巧，還提高了自己的編程和寫報(bào)告的能力，收獲不小,也鞏固了所學(xué)知識(shí)。 g an employment tribunal claimEmployment tribunals sort out disagreements between employers and employees.You may need to make a claim to an employment tribunal if:· you don't agree with the disciplinary action your employer has taken agai

19、nst you· your employer dismisses you and you think that you have been dismissed unfairly.For more information about dismissal and unfair dismissal, see Dismissal.You can make a claim to an employment tribunal, even if you haven't appealed against the disciplinary action your

20、employer has taken against you. However, if you win your case, the tribunal may reduce any compensation awarded to you as a result of your failure to appeal.Remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are compl

21、aining about happened. If your application is received after this time limit, the tribunal will not usually accept it.If you are worried about how the time limits apply to you, take advice from one of the organisations listed under Further help.Employment tribunals are less formal than some oth

22、er courts, but it is still a legal process and you will need to give evidence under an oath or affirmation.Most people find making a claim to an employment tribunal challenging. If you are thinking about making a claim to an employment tribunal, you should get help straight away from one of the orga

23、nisations listed under Further help.If you are being represented by a solicitor at the tribunal, they may ask you to sign an agreement where you pay their fee out of your compensation if you win the case. This is known as a damages-based agreement. In England and Wales, your solicitor can&

24、#39;t charge you more than 35% of your compensation  if you win the case.If you are thinking about signing up for  a damages-based agreement, you should make sure you're clear about the terms of the agreement. It might be best to get advice from an experienced adviser, for example, at

25、a Citizens Advice Bureau.  To find your nearest CAB, including those that give advice by e-mail, click on nearest CAB.For more information about making a claim to an employment tribunal, see Employment tribunals.The (lack of) air up there Watch mCayman Islands-based Webb, the head of

26、Fifa's anti-racism taskforce, is in London for the Football Association's 150th anniversary celebrations and will attend City's Premier League match at Chelsea on Sunday."I am going to be at the match tomorrow and I have asked to meet Yaya Toure," he told BBC Sport."For me

27、 it's about how he felt and I would like to speak to him first to find out what his experience was."Uefa has opened disciplinary proceedings against CSKA for the "racist behaviour of their fans" during City's 2-1 win.Michel Platini, president of European footbal

28、l's governing body, has also ordered an immediate investigation into the referee's actions.CSKA said they were "surprised and disappointed" by Toure's complaint. In a statement the Russian side added: "We found no racist insults from fans of CSKA."Age has reached the

29、end of the beginning of a word. May be guilty in his seems to passing a lot of different life became the appearance of the same day; May be back in the past, to oneself the paranoid weird belief disillusionment, these days, my mind has been very messy, in my mind constantly. Always feel oneself shou

30、ld go to do something, or write something. Twenty years of life trajectory deeply shallow, suddenly feel something, do it.一字開頭的年齡已經(jīng)到了尾聲。或許是愧疚于自己似乎把轉(zhuǎn)瞬即逝的很多個(gè)不同的日子過成了同一天的樣子；或許是追溯過去，對(duì)自己那些近乎偏執(zhí)的怪異信念的醒悟，這些天以來，思緒一直很凌亂，在腦海中不斷糾纏。總覺得自己自己似乎應(yīng)該去做點(diǎn)什么，或者寫點(diǎn)什么。二十年的人生軌跡深深淺淺，突然就感覺到有些事情，非做不可了。The end of our life, and ca

31、n meet many things really do?而窮盡我們的一生，又能遇到多少事情是真正地非做不可？During my childhood, think lucky money and new clothes are necessary for New Year, but as the advance of the age, will be more and more found that those things are optional; Junior high school, thought to have a crush on just means that the real

32、 growth, but over the past three years later, his writing of alumni in peace, suddenly found that isn't really grow up, it seems is not so important; Then in high school, think don't want to give vent to out your inner voice can be in the high school children of the feelings in a period, but

33、 was eventually infarction when graduation party in the throat, later again stood on the pitch he has sweat profusely, looked at his thrown a basketball hoops, suddenly found himself has already can't remember his appearance.童年時(shí)，覺得壓歲錢和新衣服是過年必備，但是隨著年齡的推進(jìn)，會(huì)越來越發(fā)現(xiàn)，那些東西根本就可有可無；初中時(shí)，以為要有一場(chǎng)暗戀才意味著真正的成長，但

34、三年過去后，自己心平氣和的寫同學(xué)錄的時(shí)候，突然就發(fā)現(xiàn)是不是真正的成長了，好像并沒有那么重要了；然后到了高中，覺得非要吐露出自己的心聲才能為高中生涯里的懵懂情愫劃上一個(gè)句點(diǎn)，但畢業(yè)晚會(huì)的時(shí)候最終還是被梗塞在了咽喉，后來再次站在他曾經(jīng)揮汗如雨的球場(chǎng)，看著他投過籃球的球框時(shí)，突然間發(fā)現(xiàn)自己已經(jīng)想不起他的容顏。Originally, this world, can produce a chemical reaction to an event, in addition to resolutely, have to do, and time.原來，這個(gè)世界上，對(duì)某個(gè)事件能產(chǎn)生化學(xué)反應(yīng)的，除了非做不可的堅(jiān)

35、決，還有，時(shí)間。A person's time, your ideas are always special to clear. Want, want, line is clear, as if nothing could shake his. Also once seemed to be determined to do something, but more often is he backed out at last. Dislike his cowardice, finally found that there are a lot of love, there are a lo

36、t of miss, like shadow really have been doomed. Those who do, just green years oneself give oneself an arm injection, or is a self-righteous spiritual.一個(gè)人的時(shí)候，自己的想法總是特別地清晰。想要的，不想要的，界限明確，好像沒有什么可以撼動(dòng)自己。也曾經(jīng)好像已經(jīng)下定了決心去做某件事，但更多的時(shí)候是最后又打起了退堂鼓。嫌惡過自己的怯懦，最終卻發(fā)現(xiàn)有很多緣分，有很多錯(cuò)過，好像冥冥之中真的已經(jīng)注定。那些曾經(jīng)所謂的非做不可，只是青蔥年華里自己給自己注射的一

37、支強(qiáng)心劑，或者說，是自以為是的精神寄托罷了。At the moment, the sky is dark, the air is fresh factor after just rained. Suddenly thought of blue plaid shirt; Those were broken into various shapes of stationery; From the corner at the beginning of deep friendship; Have declared the end of the encounter that haven't sta

38、rt planning. Those years, those days of do, finally, like youth, will end in our life.此刻，天空是陰暗的，空氣里有著剛下過雨之后的清新因子。突然想到那件藍(lán)格子襯衫；那些被折成各種各樣形狀的信紙；那段從街角深巷伊始的友誼；還有那場(chǎng)還沒有開始就宣告了終結(jié)的邂逅計(jì)劃那些年那些天的非做不可，終于和青春一樣，都將在我們的人生中謝幕。Baumgartner the disappointing news: Mission aborted. r plays an important role in this mission.

39、 Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb hig

40、her than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.The supersonic descent could happen as early as Sunda.The weatheThe balloon will slowly drift to the edge of space at 120,000 feet ( Then, I would assume,