本科畢業(yè)論文-iir數(shù)字濾波器的設(shè)計(jì)-在線瀏覽
2025-03-05 14:50本頁(yè)面
【正文】 (3－15) (3－16)式(3－15)或式(3－16)稱為雙線性變換。由于從s平面到平面具有非線性頻率壓縮的功能，因此不可能產(chǎn)生頻率混疊現(xiàn)象，這是雙線性變換法比較脈沖響應(yīng)不變法最大的優(yōu)點(diǎn)。 它集數(shù)值分析,矩陣運(yùn)算,信號(hào)處理和圖形顯示于一體,構(gòu)成了一個(gè)方便且界面友好的用戶環(huán)境[3,4,5]。因此，利用MATLAB可以很方便的設(shè)計(jì)出所需的濾波器，同時(shí)可以直觀形象地描繪出波形圖[5]。 利用脈沖響應(yīng)不變法設(shè)計(jì)數(shù)字Butterworth濾波器設(shè)計(jì)模擬低通巴特沃斯濾波器，通帶紋波為Rp＝1dB，通帶上限角頻率Wp=，阻帶下限角頻率Ws=，阻帶最小衰減As=15dB,根據(jù)該低通模擬濾波器，利用沖擊響應(yīng)不變法設(shè)計(jì)相應(yīng)的數(shù)字低通濾波器，并畫出設(shè)計(jì)后的數(shù)字低通濾波器的特性曲線。wp=*pi。Rp=1。T=1。Atn=10^(As/20)。OmgS=ws*T。s39。 %選取模擬濾波器的階數(shù)[cs,ds]=butter(N,OmgC, 39。)。 %應(yīng)用脈沖響應(yīng)不變法進(jìn)行轉(zhuǎn)換 %求得相對(duì)、絕對(duì)頻響及相位、群延遲響[H,w]=freqz(b,a,500)。db=20*log10(mag/max(mag))。grd=grpdelay(b,a,w)。plot(w/pi,mag)。幅頻特性39。xlabel(39。)。|H(jw)| 39。axis([0,1,0,])。XTickMode39。manual39。XTick39。set(gca, 39。, 39。, 39。,[0 Atn Rip 1])。plot(w/pi,db)。幅頻特性(dB) 39。xlabel(39。)。dB39。axis([0,1,40,5])。XTickMode39。manual39。XTick39。set(gca, 39。, 39。, 39。,[40 As Rp 0])。plot(w/pi,pha/pi)。相頻特性39。xlabel(39。)。pha(/pi) 39。axis([0,1,1,1])。XTickMode39。manual39。XTick39。gridsubplot(2,2,4)。title(39。)。w(/pi) 39。ylabel(39。)。set(gca, 39。, 39。, 39。,[0 1])。圖4 利用脈沖響應(yīng)不變法設(shè)計(jì)的數(shù)字低通濾波器的特性曲線 利用雙線性變換法設(shè)計(jì)數(shù)字 Chebyshev濾波器利用雙線形變換法，設(shè)計(jì)一個(gè)切比雪夫Ⅰ型低通數(shù)字濾波器，允許幅度誤差在1dB以內(nèi)。Wplp=*pi。 %低通數(shù)字阻帶頻率Ap=1。T=1。Omegas=(2/T)*tan(Wslp/2)。通帶邊緣必須大于039。阻帶邊緣必須大于通帶邊緣39。通帶波動(dòng)或阻帶衰減必須大于039。A=10^(As/20)。OmegaS=Omegas/Omegap。N=ceil(log10(g+sqrt(g*g1)/log10(OmegaS*OmegaS1)))。ds=real(poly(p))。p=p*OmegaC。dsNu=ds(N+1)。b0=k。cs=k*B。 %雙線形Z變換Wphp=*pi。[H,w]=freqz(blp,alp,500)。db=20*log10(mag/max(mag))。grd=grpdelay(blp,alp,w)。 %繪出各條曲線plot(w/pi,mag)。數(shù)字低通濾波器幅頻響|H(ejOmega)| 39。w(/pi) 39。ylabel(39。)。grid onsubplot(2 2 2)。title(39。)xlabel(39。)。dB39。axis([0,1,40,2])。plot(w/pi,pha/pi)。數(shù)字低通濾波器相頻特性39。xlabel(39。)。pha(/pi) 39。axis([0,1,1,])。plot(w/pi,grd)。數(shù)字低通濾波器群延遲39。xlabel(39。)。Sample39。axis([0,1,0,4])。 利用雙線性變換法設(shè)計(jì)數(shù)字低通濾波器使用雙線性變換法設(shè)計(jì)一個(gè)低通數(shù)字濾波器，給定的數(shù)字濾波器的技術(shù)指標(biāo)為fp=100Hz,fs=300Hz, =3dB, =20dB,抽樣頻率為Fs=1000Hz。 clear all。fs=300。rp=3。%wp=2*pi*fp/Fsws=2*pi*fs/Fs。%firstly to finish frequency prewarping。was=tan(ws/2)。s39。s39。[bp,ap]=zp2tf(z,p,k)[bs,as]=lp2lp(bp,ap,wap)%Note:s=(2/Ts)(z1)(z+1)。[bz,az]=bilinear(bs,as,Fs/2)[h,w]=freqz(bz,az,256,Fs*1000)。grid on。 方法的比較通過(guò)以上三個(gè)程序的設(shè)計(jì)我們可以知道脈沖響不變應(yīng)法和雙線性變換法以及Butterworth和Chebyshev濾波器的各自的特點(diǎn)：脈沖響應(yīng)不變法的優(yōu)點(diǎn)是頻率坐標(biāo)變換是線性的，即，如果不考慮頻率混疊現(xiàn)象，用這種方法設(shè)計(jì)的數(shù)字濾波器會(huì)很好地重現(xiàn)原模擬濾波器的頻率特性。缺點(diǎn)是會(huì)產(chǎn)生頻率混疊現(xiàn)象，適合低通、帶通濾波器的設(shè)計(jì)，不適合高通、帶阻濾波器的設(shè)計(jì)。但與之間的非線性關(guān)系是雙線性變換法的缺點(diǎn)，直接影響數(shù)字濾波器頻響，故易產(chǎn)生幅度特性和相位特性的失真。5 結(jié)束語(yǔ) 數(shù)字濾波器的設(shè)計(jì)是信號(hào)處理方面的重要內(nèi)容，通過(guò)運(yùn)用MATLAB軟件來(lái)設(shè)計(jì)IIR數(shù)字濾波器，使我熟悉了MATLAB的強(qiáng)大功能，同時(shí)也對(duì)數(shù)字濾波器的特點(diǎn)、作用有更深入的理解。答謝：本文的撰寫受到湖南文理學(xué)院物電系喬鬧生老師的支持與幫助，喬老師對(duì)全文的體系方向、結(jié)構(gòu)等方面給予了悉心指導(dǎo)并把關(guān)，認(rèn)真仔細(xì)地審閱了全部文稿并提出了許多寶貴意見(jiàn)，在此謹(jǐn)致以衷心的感謝。s Shaanxi province pass through a stop on the ancient Silk Road, Gansu39。80s. We sat on the back of pickup trucks for hours. The sky was blue, and we couldn39。t have a formal stage. The audience just sat on the grass. Usually, the performances became a big party with local people joining in. For him, the rewarding part about touring isn39。s performers of the troupe still tour the region39。s Poly Theater. Their show, titled Ulan Muqir on the Grassland, depicted the history and development of the art troupe. Being from the region allowed me to embrace the culture of Inner Mongolia and being a member of the troupe showed me where I belonged, Nasun, the art troupe39。s Liaoning province, decades ago. The solider gave the old man a handmade saddle when they bid farewell. The story inspired Nasun to write Carved Saddle, a song that later became one of his most popular numbers. Now, every year, Nasun recruits young singers and dancers for the troupe. The troupe has also designed a new repertoire, which is mostly based on the daily lives of Mongolian people, especially the lives of nomadic families, and has bined contemporary musical elements with folk songs of the region. Haimu, a 25yearold khoomei (a local variant of overtone singing) singer, joined the troupe three years ago. Along with a sixmember band, he performs fast songs and soft ones that he writes－all while playing the horsehead fiddle.Although I learned the piano since childhood and grew up listening to various kinds of music, to me, the folk music of Inner Mongolia is the root, he says. Performing in remote villages is pleasant. I feel at home on the boundless grasslands, and the warm people there make me feel fulfilled. The first round of spring auction season in Beijing ended last week, but it failed to create much spring in the art market. Although two pieces of Chinese painting fetched more than 100 million yuan, the decline in trading volume and sale rate showed a downturn this year. In the “Grand View: Chinese Painting Highlig
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