%?設計線性相位的FIR帶通濾波器
%?2014.03.12?
clcclear?all;
wls=0.2*pi;????????????????????????????%?阻帶最小頻率?
wlp=0.35*pi;???????????????????????????%?通帶最小頻率
whp=0.65*pi;???????????????????????????%?通帶最大頻率
whs=0.8*pi;????????????????????????????%?阻帶最大頻率?
wc=[wlp/piwhp/pi];????????????????????%?帶通濾波器的歸一化截止頻率
B=wlp-wls;?????????????????????????????%?過渡帶寬=低端通帶截止頻率-低端阻帶截止頻率?
N=ceil（6.2*pi/B）;??????????????????????%?hanning窗階數N，由過渡帶寬B=8*pi/N算出Nceil為取整函數
window=hanning（N）;?????????????????????%?窗選擇hanning窗，為N*1的矩陣/向量
n=0:1:N-1;?
[h1w]=freqz（window1）;????????????????%?window是N*1矩陣，h1是hannning窗的頻率響應
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subplot（221）;????????????????????????%?將多個圖畫在一個平面上
stem（window）;??????????????????????????%?繪制離散序列圖
axis（[0?45?0?1.2]）;????????????????????%?定義xy軸范圍?
grid;??????????????????????????????????%?顯示網格線
xlabel（‘n‘）;???????????????????????????%?x軸命名
title（‘Hanning窗函數‘）;???????????????
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subplot（222）;
plot（w/pi20*log（abs（h1）/abs（h1（1））））;?%?w來自freqz函數，為N個頻率等分點的值（N*1矩陣），后面計算的是幅度值
axis（[0?1?-350?0]）;
grid;
xlabel（‘w/pi‘）;
ylabel（‘幅度（dB）‘）;
title（‘Hanning?窗函數的頻譜‘）;
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hn=fir1（N-1wchanning（N））;????????????%?設計filter。函數fir1返回的是filter的系數h（n）即沖激相應
[h2w]=freqz（hn1512）;????????????????%?filter的頻率響應h2
subplot（223）;
stem（nhn）;
axis（[0?45?-0.25?0.25]）;
grid;
xlabel（‘n‘）;
ylabel（‘h（n）‘）;
title（‘Hanning?窗函數的單位脈沖響應‘）;
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subplot（224）;
plot（w/pi20*log（abs（h2）/abs（h2（1））））;??%?w來自freqz（與h2對應）
grid;
xlabel（‘w/pi‘）;
ylabel（‘幅度（dB）‘）;
title（‘Hanning?窗設計帶通濾波器的幅頻響應‘）;

?屬性????????????大小?????日期????時間???名稱
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?????文件???????2034??2014-03-13?21:33??FIR_BPF.m

?????文件???????1892??2014-03-13?21:34??FIR_LPF.m

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?????????????????3926????????????????????2