【文章內(nèi)容簡介】 t(w/pi,db)。title(39。數(shù)字低通濾波器幅頻響(dB) 39。)xlabel(39。w(/pi) 39。)。ylabel(39。dB39。)。axis([0,1,40,2])。grid onsubplot(2,2,3)。plot(w/pi,pha/pi)。title(39。數(shù)字低通濾波器相頻特性39。)。xlabel(39。w(/pi) 39。)。ylabel(39。pha(/pi) 39。)。axis([0,1,1,])。grid onsubplot(2,2,4)。plot(w/pi,grd)。title(39。數(shù)字低通濾波器群延遲39。)。xlabel(39。w(/pi) 39。)。ylabel(39。Sample39。)。axis([0,1,0,4])。grid on該數(shù)字濾波器的幅頻特性曲線如圖5所示。 利用雙線性變換法設(shè)計數(shù)字低通濾波器使用雙線性變換法設(shè)計一個低通數(shù)字濾波器，給定的數(shù)字濾波器的技術(shù)指標為fp=100Hz,fs=300Hz, =3dB, =20dB,抽樣頻率為Fs=1000Hz。MATLAB程序如下所示。 clear all。fp=100。fs=300。Fs=1000。rp=3。rs=20。%wp=2*pi*fp/Fsws=2*pi*fs/Fs。Fs=Fs/Fs。%firstly to finish frequency prewarping。wap=tan(wp/2)。was=tan(ws/2)。[n,wn]=buttord(wap,was,rp,rs,39。s39。)%Note:39。s39。![z,p,k]=buttap(n)。[bp,ap]=zp2tf(z,p,k)[bs,as]=lp2lp(bp,ap,wap)%Note:s=(2/Ts)(z1)(z+1)。Ts=1,that is 2fs=1,fs=。[bz,az]=bilinear(bs,as,Fs/2)[h,w]=freqz(bz,az,256,Fs*1000)。plot(w,abs(h))。grid on。圖5 利用雙線形變換法設(shè)計的數(shù)字低通濾波器的特性曲線該數(shù)字濾波器的幅頻特性曲線如圖6所示。 方法的比較通過以上三個程序的設(shè)計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：脈沖響應(yīng)不變法的優(yōu)點是頻率坐標變換是線性的，即，如果不考慮頻率混疊現(xiàn)象，用這種方法設(shè)計的數(shù)字濾波器會很好地重現(xiàn)原模擬濾波器的頻率特性。另外一個優(yōu)點是數(shù)字濾波器的單位脈沖響應(yīng)完全模仿模擬濾波器的單位沖激響應(yīng)，時域特性逼近好。缺點是會產(chǎn)生頻率混疊現(xiàn)象，適合低通、帶通濾波器的設(shè)計，不適合高通、帶阻濾波器的設(shè)計。圖6 基于雙線性變換法設(shè)計的數(shù)字濾波器的幅頻響應(yīng)特性而雙線性變換法的優(yōu)點是不可能產(chǎn)生頻率混疊現(xiàn)象，這是雙線性變換法比脈沖響應(yīng)不變法的最大優(yōu)點。但與之間的非線性關(guān)系是雙線性變換法的缺點，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。Butterworth具有單調(diào)下降的幅頻特性，而Chebyshev濾波器的幅頻特性在通帶或者在阻帶有波動，可以提高選擇性。5 結(jié)束語 數(shù)字濾波器的設(shè)計是信號處理方面的重要內(nèi)容，通過運用MATLAB軟件來設(shè)計IIR數(shù)字濾波器，使我熟悉了MATLAB的強大功能，同時也對數(shù)字濾波器的特點、作用有更深入的理解。了解了熟練的利用MATLAB這一功能強大的軟件來設(shè)計數(shù)字濾波器對數(shù)字信號處理這一領(lǐng)域有著重要的意義與價值。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)，認真仔細地審閱了全部文稿并提出了許多寶貴意見，在此謹致以衷心的感謝。參考文獻[1] 高西全、丁玉美 編著 《數(shù)字信號處理》西安：西安電子科技大學(xué)出版社，[2] 張立材 、吳冬梅 編著 《數(shù)字信號處理》 北京：北京郵電大學(xué)出版社，[3] 飛思科技產(chǎn)品研發(fā)中心 編著 《MATLAB7基礎(chǔ)與提高》北京：電子工業(yè)出版社，[4] 王宏 編著 《》 北京：清華大學(xué)出版社，[5] 飛思科技產(chǎn)品研發(fā)中心 編著 《MATLAB7輔助信號處理技術(shù)與應(yīng)用》北京：電子工業(yè)出版社， [6] Taylor R Filter Design Handbook. New York:Marce Dekker,Inc.,1983[7] Manolakis Dimitris G et and Adaptive Signal Processing:McGrawHill,2000您好，為你提供優(yōu)秀的畢業(yè)論文參考資料，請您刪除以下內(nèi)容，O(∩_∩)O謝謝！??！A large group of tea merchants on camels and horses from Northwest China39。s Shaanxi province pass through a stop on the ancient Silk Road, Gansu39。s Zhangye city during their journey to Kazakhstan, May 5, 2015. The caravan, consisting of more than 100 camels, three horsedrawn carriages and four support vehicles, started the trip from Jingyang county in Shaanxi on Sept 19, 2014. It will pass through Gansu province and Xinjiang Uygur autonomous region, and finally arrive in Almaty, formerly known as AlmaAta, the largest city in Kazakhstan, and Dungan in Zhambyl province. The trip will cover about 15,000 kilometers and take the caravan more than one year to plete. The caravan is expected to return to Jingyang in March 2016. Then they will e back, carrying specialty products from Kazakhstan A small art troupe founded six decades ago has grown into a household name in the Inner Mongolia autonomous region. In the 1950s, Ulan Muqir Art Troupe was created by nine young musicians, who toured remote villages on horses and performed traditional Mongolian music and dances for nomadic families. The 54yearold was born in Tongliao, in eastern Inner Mongolia and joined the troupe in says there are 74 branch troupes across Inner Mongolia and actors give around 100 shows every year to local nomadic people. I can still recall the days when I toured with the troupe in the early 39。80s. We sat on the back of pickup trucks for hours. The sky was blue, and we couldn39。t help but sing the folk songs, Nasun says. The vastness of Inner Mongolia and the lack of entertainment options for people living there, made their lives lonely. The nomadic people were very excited about our visits, Nasun recalls. We didn39。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。t just about sharing art with nomadic families but also about gaining inspiration for the music and dance. Ulan Muqir literally translates as red burgeon, and today39。s performers of the troupe still tour the region39。s villages and entertain nomadic families, but their fame has spread around the world. On May 16 and 17, nearly 100 singers and dancers from the troupe performed at Beijing39。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 president, who is also a renowned tenor, tells China Daily. During a tour in 1985, he went to a village and met an elderly local man, who told him a story about his friendship with a solider from Shenyang, capital of Nor