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BI 1: THC HIN CC B LC FIR TRN KIT C6713DSK . I- Thit k b lc thng chn di bng phng php Kaiser WindowCc thng s cn thit k: N=89. Fc1 =2500 Fc2=2900 Hz . = 4. Fs=8000 Hz. 1. Tm p ng xung h: M MATLAB trong ca s Command g lnh : >>sptool Xut hin hp thoi SPTool , nhp chn Edit
Nhp cc thng s nh yu cu thit k v nhp vo Design Filter :
i tn : startup.spt editnamefilt1 , t li tn: bandstop 1
Xut ra workspace : T ca s SPTool, chn File EportTrong Export list xut hin chn Filter :bandstop [ design] ri nhn Export to Workspace.
Sang ca s chnh ca chng trnh MATLAB, double click vo bandstop trong tab Workspace xem cc h s trn t ca hm truyn (num):
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Ta quan st thy c 89 h s vi gi tr rt nh. thc hin b lc thng qua phn mm CCS ta chuyn ln gi tr ln hn bng dng lnh sau : (Sau nhp p vo bin cof trong workspace quan st) >>h=round(bandstop.tf.num*2^15);
Mc ch ca vic ny l gim sai s trong qu trnh lng t ha .Sau qu trnh lng t ha thi ta chuyn v gi tri ban u bng cch dch qua phi 15 bits qua dng lnh trong CCS l : output_sample(yn>>15);
2.
Thc hin b M c6713dsk:
lc :
Kt ni CCS vi KIT: Debug Connect
M tp tin project c tn FIR.pjt trong C:\Program Files\CCStudio_v3.1\myproject\FIR.
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M tp tin coeficients.h trong phn include m rng thuc project view.
Nhp s liu : N=89, copy ma trn h t Array Editor MatLab v thay khong trng bng du , (Bng lnh Ctr + H)
Bin dch: Project Rebuild All Sau khi CCS chy xong :
Vo File Load Program dn ti file FIR.out
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Chy chng trnh Debug Run :
3.
Kim tra b lc va thit k:M DSP_Tools.exe :
T File m: Oscillocope, Spectrum Analyzer, Get real time signal from soundcard quan st tn hiu ra trn KIT :
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iu chnh dao ng k vi tn s vo l:
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2700 Hz
Nhn xt: fi nm trong khong chn nn tn hiu b trit tiu. 2Khz
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3.4Khz
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9
Nhn xt: Vi ng vo l 2000 Hz v 3400 Hz th ta thu c tn hiu ging tn hiu vo
II - Thit k b lc thng di bng phng php Kaiser Window: N=81 Fc1=1500 Fc2=2000 Hz. = 5. Fs=8000Hz
Thc hin tng t phn 1. Kt qu thu c nh sau : + p ng thu c khi thit k bng Matlab:
Thu c cc gi tr ca b lc h sau :
Thc hin tng t nh thao tc trn,ta thc hin m phng bng DSP,thu c kt qu nh sau: 1 Khz
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1.7 Khz
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2.4 Khz
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Nhn xt: Vi tn s ng vo l 1 Khz, 2.4 Khz th ng ra b trit tiu. V tn s 1.7 Khz thuc khong 1.5Khz 2 Khz nn tn hiu khng b trit tiu.
III - Thit k b lc thng cao bng phng php Kaiser Window:Cc thng s cn thit k: N=81 . Fc =2200 = 4. Fs=8000 Hz. p ng thu c trn Matlab:
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Kim tra p ng vi bng chng trnh DSP vi f=1 Khz :
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Nhn xt: Ph thu c gn nh l 1 vch ph 3Khz. Ta bit sng vung khi phn tch Fourier l tng ca cc hi l, v bin cc hi ny gim dn theo chiu tng ca tn s. Vi tn hiu vo l 1Khz th ta phn tch ra c cc hi l 1Khz, 3Khz, 5Khz, Khi cho qua b lc thng cao tn s ct 2.2Khz th ta ch cho qua cc hi t 3Khz tr ln qua, do bin cc hi 5Khz, 7Khz, qu nh nn ta hu nh khng quan st thy trn Spectrum Analyzer.
IV - Thit k b lc FIR Multiband:Cc thng s cn thit k: Tn s trung tm ln lt l 2500Hz, 3500Hz. Bng thng mi di l 500Hz. Tn s ly mu l 8000Hz ln xung (gi s) l 100Hz Bng ch s ca b lc:
Di 1 2 3 4 5
Tn s (Hz) 0 -- 2150 2250 -- 2750 2850 3150 3250 3750 3850 -- 4000
Tn s chun ha f/FN 0 0.5375 0.5625 0.6875 0.7125 0.7875 0.8125 0.9375 0.9625 -- 1
Bin 0 1 0 1 0
Thc hin M-file vi code nh sau :
Chy file ny ta thu c 2 Figure l p ng ca b lc nh sau :
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Kim tra vi tn hiu ng vo l 800Hz : Dng sng :
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P
h : Gii thch dng ph : Ta thy c 2 vch ph l 800Hz, 2400Hz Sng vung 800Hz khi phn tch Fourier ta thu c cc hi c tn s 800Hz, 2400Hz, 4000Hz, ,(2k+1)*800Hz. Khi cho qua b lc Multiband trn (da theo p ng ca CCS) th ch cho qua tn s 2400Hz, cc tn s cn li b suy hao, nhng do hi c bn l 800Hz c bin ln nn tuy b suy hao nhng ta vn quan st c. Thay i tn s ng vo (tn hiu sin) : 0.5Khz :
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1Khz :
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2.3Khz :
3Khz:
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3.3Khz 20
Nhn xt: Tng dn tn s tn hiu vo, cc tn s nm ngoi 2 di thng b suy hao ng k.
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