【matlab】freqz函数的使用(一)

>> help freqz

freqz - Frequency response of filter

        滤波器的频率响应

    This MATLAB function returns the frequency response h and the corresponding

    frequencies w at which the filter response of hfilt is computed.

         当计算滤波器响应hfilt时  这个MATLAB函数返回频率响应h 和 相应频率w

    [h,w] = freqz(hfilt)
    [h,w] = freqz(hfilt,n)
    freqz(hfilt)
    [h,w] = freqz(hs)
    [h,w] = freqz(hs,n)
    [h,w] = freqz(hs,Name,Value)
    freqz(hs)

>> wn3 = hamming(10)% 2^(10-1)wn3 =    0.0800    0.1876    0.4601    0.7700    0.9723    0.9723    0.7700    0.4601    0.1876    0.0800

>> [h1,w3] = freqz(wn3,1)  % 2^(10-1)h1 =   4.9400 + 0.0000i   4.9378 - 0.1364i   4.9312 - 0.2726i   4.9201 - 0.4085i   4.9047 - 0.5439i   4.8848 - 0.6787i   4.8607 - 0.8127i   4.8322 - 0.9458i   4.7994 - 1.0777i   4.7624 - 1.2085i   4.7212 - 1.3378i   4.6759 - 1.4655i   4.6265 - 1.5916i   4.5732 - 1.7159i   4.5159 - 1.8382i   4.4548 - 1.9583i   4.3899 - 2.0763i   4.3213 - 2.1918i   4.2492 - 2.3049i   4.1736 - 2.4153i   4.0946 - 2.5230i   4.0123 - 2.6279i   3.9269 - 2.7297i   3.8384 - 2.8286i   3.7470 - 2.9242i   3.6528 - 3.0166i   3.5560 - 3.1057i   3.4565 - 3.1913i   3.3547 - 3.2733i   3.2506 - 3.3518i   3.1443 - 3.4267i   3.0360 - 3.4978i   2.9258 - 3.5651i   2.8139 - 3.6286i   2.7005 - 3.6882i   2.5855 - 3.7439i   2.4693 - 3.7956i   2.3520 - 3.8434i   2.2336 - 3.8871i   2.1144 - 3.9268i   1.9945 - 3.9624i   1.8741 - 3.9940i   1.7532 - 4.0216i   1.6321 - 4.0451i   1.5108 - 4.0646i   1.3896 - 4.0800i   1.2686 - 4.0915i   1.1479 - 4.0990i   1.0276 - 4.1025i   0.9080 - 4.1022i   0.7890 - 4.0979i   0.6710 - 4.0899i   0.5539 - 4.0781i   0.4379 - 4.0627i   0.3232 - 4.0435i   0.2099 - 4.0209i   0.0981 - 3.9947i  -0.0122 - 3.9651i  -0.1207 - 3.9321i  -0.2274 - 3.8959i  -0.3321 - 3.8565i  -0.4348 - 3.8140i  -0.5354 - 3.7685i  -0.6338 - 3.7202i  -0.7298 - 3.6690i  -0.8235 - 3.6151i  -0.9146 - 3.5587i  -1.0033 - 3.4998i  -1.0893 - 3.4385i  -1.1726 - 3.3749i  -1.2532 - 3.3092i  -1.3310 - 3.2415i  -1.4060 - 3.1718i  -1.4780 - 3.1003i  -1.5471 - 3.0272i  -1.6133 - 2.9525i  -1.6764 - 2.8764i  -1.7365 - 2.7989i  -1.7936 - 2.7203i  -1.8476 - 2.6405i  -1.8985 - 2.5598i  -1.9463 - 2.4782i  -1.9910 - 2.3959i  -2.0327 - 2.3130i  -2.0712 - 2.2296i  -2.1067 - 2.1459i  -2.1392 - 2.0618i  -2.1686 - 1.9776i  -2.1950 - 1.8934i  -2.2184 - 1.8092i  -2.2388 - 1.7252i  -2.2563 - 1.6414i  -2.2710 - 1.5581i  -2.2828 - 1.4752i  -2.2919 - 1.3929i  -2.2982 - 1.3112i  -2.3018 - 1.2303i  -2.3028 - 1.1503i  -2.3012 - 1.0711i  -2.2971 - 0.9930i  -2.2905 - 0.9160i  -2.2816 - 0.8401i  -2.2704 - 0.7655i  -2.2569 - 0.6922i  -2.2412 - 0.6202i  -2.2235 - 0.5497i  -2.2037 - 0.4807i  -2.1820 - 0.4132i  -2.1585 - 0.3473i  -2.1331 - 0.2831i  -2.1061 - 0.2205i  -2.0774 - 0.1597i  -2.0472 - 0.1006i  -2.0156 - 0.0433i  -1.9825 + 0.0122i  -1.9482 + 0.0658i  -1.9127 + 0.1175i  -1.8761 + 0.1674i  -1.8384 + 0.2153i  -1.7997 + 0.2613i  -1.7602 + 0.3054i  -1.7199 + 0.3476i  -1.6789 + 0.3878i  -1.6372 + 0.4261i  -1.5950 + 0.4625i  -1.5523 + 0.4970i  -1.5092 + 0.5296i  -1.4657 + 0.5602i  -1.4220 + 0.5890i  -1.3781 + 0.6159i  -1.3341 + 0.6410i  -1.2901 + 0.6643i  -1.2460 + 0.6858i  -1.2020 + 0.7055i  -1.1582 + 0.7235i  -1.1146 + 0.7398i  -1.0712 + 0.7544i  -1.0282 + 0.7675i  -0.9855 + 0.7789i  -0.9432 + 0.7887i  -0.9014 + 0.7971i  -0.8601 + 0.8040i  -0.8194 + 0.8094i  -0.7793 + 0.8135i  -0.7398 + 0.8162i  -0.7010 + 0.8177i  -0.6628 + 0.8179i  -0.6255 + 0.8169i  -0.5889 + 0.8147i  -0.5531 + 0.8115i  -0.5181 + 0.8071i  -0.4839 + 0.8018i  -0.4507 + 0.7956i  -0.4183 + 0.7884i  -0.3868 + 0.7803i  -0.3562 + 0.7715i  -0.3266 + 0.7619i  -0.2979 + 0.7515i  -0.2701 + 0.7405i  -0.2433 + 0.7289i  -0.2174 + 0.7167i  -0.1925 + 0.7040i  -0.1685 + 0.6908i  -0.1455 + 0.6771i  -0.1235 + 0.6631i  -0.1023 + 0.6486i  -0.0821 + 0.6339i  -0.0629 + 0.6189i  -0.0445 + 0.6036i  -0.0271 + 0.5882i  -0.0105 + 0.5726i   0.0051 + 0.5568i   0.0199 + 0.5410i   0.0339 + 0.5251i   0.0470 + 0.5091i   0.0593 + 0.4932i   0.0708 + 0.4773i   0.0815 + 0.4614i   0.0915 + 0.4456i   0.1007 + 0.4300i   0.1092 + 0.4144i   0.1170 + 0.3990i   0.1242 + 0.3838i   0.1307 + 0.3688i   0.1365 + 0.3539i   0.1418 + 0.3393i   0.1465 + 0.3250i   0.1506 + 0.3109i   0.1541 + 0.2971i   0.1572 + 0.2835i   0.1597 + 0.2702i   0.1618 + 0.2573i   0.1635 + 0.2446i   0.1647 + 0.2323i   0.1655 + 0.2203i   0.1659 + 0.2086i   0.1660 + 0.1973i   0.1657 + 0.1863i   0.1651 + 0.1756i   0.1642 + 0.1652i   0.1631 + 0.1552i   0.1616 + 0.1456i   0.1599 + 0.1363i   0.1580 + 0.1273i   0.1559 + 0.1186i   0.1536 + 0.1103i   0.1512 + 0.1024i   0.1486 + 0.0947i   0.1458 + 0.0874i   0.1429 + 0.0804i   0.1399 + 0.0737i   0.1368 + 0.0673i   0.1336 + 0.0612i   0.1303 + 0.0554i   0.1270 + 0.0499i   0.1236 + 0.0446i   0.1201 + 0.0397i   0.1167 + 0.0350i   0.1132 + 0.0306i   0.1096 + 0.0264i   0.1061 + 0.0225i   0.1026 + 0.0188i   0.0991 + 0.0153i   0.0956 + 0.0121i   0.0921 + 0.0091i   0.0887 + 0.0063i   0.0853 + 0.0037i   0.0819 + 0.0013i   0.0785 - 0.0010i   0.0752 - 0.0030i   0.0720 - 0.0049i   0.0687 - 0.0066i   0.0656 - 0.0081i   0.0625 - 0.0095i   0.0595 - 0.0107i   0.0565 - 0.0118i   0.0536 - 0.0127i   0.0507 - 0.0135i   0.0479 - 0.0142i   0.0452 - 0.0148i   0.0425 - 0.0152i   0.0400 - 0.0156i   0.0374 - 0.0158i   0.0350 - 0.0159i   0.0326 - 0.0159i   0.0303 - 0.0158i   0.0281 - 0.0157i   0.0259 - 0.0154i   0.0238 - 0.0151i   0.0218 - 0.0147i   0.0199 - 0.0142i   0.0180 - 0.0136i   0.0162 - 0.0130i   0.0145 - 0.0123i   0.0128 - 0.0115i   0.0113 - 0.0106i   0.0098 - 0.0098i   0.0083 - 0.0088i   0.0070 - 0.0078i   0.0057 - 0.0067i   0.0045 - 0.0056i   0.0034 - 0.0045i   0.0024 - 0.0033i   0.0014 - 0.0021i   0.0005 - 0.0008i  -0.0003 + 0.0005i  -0.0010 + 0.0018i  -0.0017 + 0.0032i  -0.0023 + 0.0046i  -0.0027 + 0.0060i  -0.0032 + 0.0075i  -0.0035 + 0.0089i  -0.0037 + 0.0104i  -0.0039 + 0.0119i  -0.0040 + 0.0134i  -0.0040 + 0.0149i  -0.0039 + 0.0164i  -0.0037 + 0.0180i  -0.0035 + 0.0195i  -0.0032 + 0.0210i  -0.0028 + 0.0225i  -0.0023 + 0.0240i  -0.0017 + 0.0255i  -0.0011 + 0.0269i  -0.0003 + 0.0283i   0.0005 + 0.0298i   0.0013 + 0.0311i   0.0023 + 0.0325i   0.0033 + 0.0338i   0.0044 + 0.0351i   0.0056 + 0.0363i   0.0069 + 0.0375i   0.0082 + 0.0386i   0.0096 + 0.0397i   0.0110 + 0.0407i   0.0125 + 0.0417i   0.0141 + 0.0426i   0.0157 + 0.0434i   0.0174 + 0.0442i   0.0191 + 0.0449i   0.0208 + 0.0455i   0.0227 + 0.0461i   0.0245 + 0.0465i   0.0264 + 0.0469i   0.0283 + 0.0472i   0.0302 + 0.0474i   0.0322 + 0.0476i   0.0342 + 0.0476i   0.0362 + 0.0476i   0.0382 + 0.0474i   0.0402 + 0.0472i   0.0422 + 0.0469i   0.0442 + 0.0464i   0.0462 + 0.0459i   0.0482 + 0.0453i   0.0502 + 0.0446i   0.0521 + 0.0438i   0.0540 + 0.0430i   0.0559 + 0.0420i   0.0577 + 0.0409i   0.0595 + 0.0398i   0.0613 + 0.0385i   0.0630 + 0.0372i   0.0646 + 0.0358i   0.0662 + 0.0343i   0.0677 + 0.0328i   0.0691 + 0.0312i   0.0705 + 0.0295i   0.0718 + 0.0277i   0.0730 + 0.0259i   0.0741 + 0.0240i   0.0752 + 0.0220i   0.0761 + 0.0201i   0.0769 + 0.0180i   0.0777 + 0.0159i   0.0783 + 0.0138i   0.0789 + 0.0117i   0.0793 + 0.0095i   0.0797 + 0.0074i   0.0799 + 0.0052i   0.0800 + 0.0029i   0.0800 + 0.0007i   0.0799 - 0.0015i   0.0797 - 0.0037i   0.0794 - 0.0059i   0.0790 - 0.0080i   0.0784 - 0.0102i   0.0778 - 0.0123i   0.0771 - 0.0143i   0.0762 - 0.0164i   0.0752 - 0.0184i   0.0742 - 0.0203i   0.0730 - 0.0222i   0.0718 - 0.0240i   0.0705 - 0.0257i   0.0690 - 0.0274i   0.0675 - 0.0290i   0.0660 - 0.0305i   0.0643 - 0.0319i   0.0626 - 0.0332i   0.0608 - 0.0344i   0.0589 - 0.0356i   0.0570 - 0.0366i   0.0550 - 0.0375i   0.0530 - 0.0383i   0.0510 - 0.0390i   0.0489 - 0.0396i   0.0468 - 0.0401i   0.0447 - 0.0405i   0.0425 - 0.0407i   0.0404 - 0.0409i   0.0382 - 0.0409i   0.0361 - 0.0408i   0.0339 - 0.0405i   0.0318 - 0.0402i   0.0297 - 0.0398i   0.0276 - 0.0392i   0.0256 - 0.0385i   0.0236 - 0.0377i   0.0216 - 0.0368i   0.0197 - 0.0358i   0.0179 - 0.0347i   0.0161 - 0.0335i   0.0144 - 0.0321i   0.0127 - 0.0307i   0.0112 - 0.0292i   0.0097 - 0.0277i   0.0083 - 0.0260i   0.0070 - 0.0243i   0.0058 - 0.0225i   0.0048 - 0.0206i   0.0038 - 0.0187i   0.0029 - 0.0167i   0.0021 - 0.0147i   0.0015 - 0.0126i   0.0009 - 0.0105i   0.0005 - 0.0084i   0.0002 - 0.0062i   0.0000 - 0.0040i  -0.0000 - 0.0019i   0.0000 + 0.0003i   0.0002 + 0.0025i   0.0005 + 0.0047i   0.0009 + 0.0068i   0.0014 + 0.0089i   0.0021 + 0.0110i   0.0029 + 0.0131i   0.0037 + 0.0151i   0.0047 + 0.0171i   0.0058 + 0.0190i   0.0070 + 0.0208i   0.0083 + 0.0226i   0.0097 + 0.0243i   0.0112 + 0.0259i   0.0128 + 0.0275i   0.0144 + 0.0289i   0.0162 + 0.0303i   0.0180 + 0.0315i   0.0199 + 0.0327i   0.0218 + 0.0338i   0.0238 + 0.0347i   0.0259 + 0.0356i   0.0280 + 0.0363i   0.0301 + 0.0369i   0.0323 + 0.0374i   0.0344 + 0.0378i   0.0366 + 0.0380i   0.0389 + 0.0381i   0.0411 + 0.0382i   0.0433 + 0.0380i   0.0455 + 0.0378i   0.0477 + 0.0374i   0.0499 + 0.0370i   0.0520 + 0.0364i   0.0541 + 0.0357i   0.0561 + 0.0348i   0.0582 + 0.0339i   0.0601 + 0.0328i   0.0620 + 0.0317i   0.0638 + 0.0304i   0.0656 + 0.0291i   0.0672 + 0.0276i   0.0688 + 0.0261i   0.0703 + 0.0244i   0.0717 + 0.0227i   0.0730 + 0.0209i   0.0742 + 0.0191i   0.0753 + 0.0172i   0.0763 + 0.0152i   0.0772 + 0.0132i   0.0780 + 0.0111i   0.0786 + 0.0090i   0.0791 + 0.0068i   0.0796 + 0.0046i   0.0798 + 0.0024i   0.0800 + 0.0002i   0.0800 - 0.0020i   0.0799 - 0.0042i   0.0797 - 0.0064i   0.0794 - 0.0086i   0.0789 - 0.0107i   0.0783 - 0.0129i   0.0776 - 0.0149i   0.0768 - 0.0170i   0.0759 - 0.0190i   0.0748 - 0.0210i   0.0737 - 0.0228i   0.0724 - 0.0247i   0.0711 - 0.0264i   0.0696 - 0.0281i   0.0681 - 0.0297i   0.0664 - 0.0312i   0.0647 - 0.0326i   0.0629 - 0.0339i   0.0611 - 0.0351i   0.0591 - 0.0362i   0.0571 - 0.0372i   0.0551 - 0.0380i   0.0530 - 0.0388i   0.0509 - 0.0394i   0.0487 - 0.0400i   0.0465 - 0.0404i   0.0443 - 0.0406i   0.0421 - 0.0408i   0.0398 - 0.0408i   0.0376 - 0.0407i   0.0354 - 0.0405i   0.0331 - 0.0401i   0.0309 - 0.0397i   0.0288 - 0.0391i   0.0267 - 0.0383i   0.0246 - 0.0375i   0.0225 - 0.0366i   0.0205 - 0.0355i   0.0186 - 0.0343i   0.0168 - 0.0331i   0.0150 - 0.0317i   0.0133 - 0.0302i   0.0117 - 0.0286i   0.0101 - 0.0270i   0.0087 - 0.0252i   0.0073 - 0.0234i   0.0061 - 0.0215i   0.0050 - 0.0196i   0.0039 - 0.0175i   0.0030 - 0.0155i   0.0022 - 0.0134i   0.0016 - 0.0112i   0.0010 - 0.0090i   0.0006 - 0.0068i   0.0003 - 0.0045i   0.0001 - 0.0023iw3 =         0    0.0061    0.0123    0.0184    0.0245    0.0307    0.0368    0.0430    0.0491    0.0552    0.0614    0.0675    0.0736    0.0798    0.0859    0.0920    0.0982    0.1043    0.1104    0.1166    0.1227    0.1289    0.1350    0.1411    0.1473    0.1534    0.1595    0.1657    0.1718    0.1779    0.1841    0.1902    0.1963    0.2025    0.2086    0.2148    0.2209    0.2270    0.2332    0.2393    0.2454    0.2516    0.2577    0.2638    0.2700    0.2761    0.2823    0.2884    0.2945    0.3007    0.3068    0.3129    0.3191    0.3252    0.3313    0.3375    0.3436    0.3497    0.3559    0.3620    0.3682    0.3743    0.3804    0.3866    0.3927    0.3988    0.4050    0.4111    0.4172    0.4234    0.4295    0.4357    0.4418    0.4479    0.4541    0.4602    0.4663    0.4725    0.4786    0.4847    0.4909    0.4970    0.5031    0.5093    0.5154    0.5216    0.5277    0.5338    0.5400    0.5461    0.5522    0.5584    0.5645    0.5706    0.5768    0.5829    0.5890    0.5952    0.6013    0.6075    0.6136    0.6197    0.6259    0.6320    0.6381    0.6443    0.6504    0.6565    0.6627    0.6688    0.6750    0.6811    0.6872    0.6934    0.6995    0.7056    0.7118    0.7179    0.7240    0.7302    0.7363    0.7424    0.7486    0.7547    0.7609    0.7670    0.7731    0.7793    0.7854    0.7915    0.7977    0.8038    0.8099    0.8161    0.8222    0.8283    0.8345    0.8406    0.8468    0.8529    0.8590    0.8652    0.8713    0.8774    0.8836    0.8897    0.8958    0.9020    0.9081    0.9143    0.9204    0.9265    0.9327    0.9388    0.9449    0.9511    0.9572    0.9633    0.9695    0.9756    0.9817    0.9879    0.9940    1.0002    1.0063    1.0124    1.0186    1.0247    1.0308    1.0370    1.0431    1.0492    1.0554    1.0615    1.0677    1.0738    1.0799    1.0861    1.0922    1.0983    1.1045    1.1106    1.1167    1.1229    1.1290    1.1351    1.1413    1.1474    1.1536    1.1597    1.1658    1.1720    1.1781    1.1842    1.1904    1.1965    1.2026    1.2088    1.2149    1.2210    1.2272    1.2333    1.2395    1.2456    1.2517    1.2579    1.2640    1.2701    1.2763    1.2824    1.2885    1.2947    1.3008    1.3070    1.3131    1.3192    1.3254    1.3315    1.3376    1.3438    1.3499    1.3560    1.3622    1.3683    1.3744    1.3806    1.3867    1.3929    1.3990    1.4051    1.4113    1.4174    1.4235    1.4297    1.4358    1.4419    1.4481    1.4542    1.4603    1.4665    1.4726    1.4788    1.4849    1.4910    1.4972    1.5033    1.5094    1.5156    1.5217    1.5278    1.5340    1.5401    1.5463    1.5524    1.5585    1.5647    1.5708    1.5769    1.5831    1.5892    1.5953    1.6015    1.6076    1.6137    1.6199    1.6260    1.6322    1.6383    1.6444    1.6506    1.6567    1.6628    1.6690    1.6751    1.6812    1.6874    1.6935    1.6997    1.7058    1.7119    1.7181    1.7242    1.7303    1.7365    1.7426    1.7487    1.7549    1.7610    1.7671    1.7733    1.7794    1.7856    1.7917    1.7978    1.8040    1.8101    1.8162    1.8224    1.8285    1.8346    1.8408    1.8469    1.8530    1.8592    1.8653    1.8715    1.8776    1.8837    1.8899    1.8960    1.9021    1.9083    1.9144    1.9205    1.9267    1.9328    1.9390    1.9451    1.9512    1.9574    1.9635    1.9696    1.9758    1.9819    1.9880    1.9942    2.0003    2.0064    2.0126    2.0187    2.0249    2.0310    2.0371    2.0433    2.0494    2.0555    2.0617    2.0678    2.0739    2.0801    2.0862    2.0923    2.0985    2.1046    2.1108    2.1169    2.1230    2.1292    2.1353    2.1414    2.1476    2.1537    2.1598    2.1660    2.1721    2.1783    2.1844    2.1905    2.1967    2.2028    2.2089    2.2151    2.2212    2.2273    2.2335    2.2396    2.2457    2.2519    2.2580    2.2642    2.2703    2.2764    2.2826    2.2887    2.2948    2.3010    2.3071    2.3132    2.3194    2.3255    2.3317    2.3378    2.3439    2.3501    2.3562    2.3623    2.3685    2.3746    2.3807    2.3869    2.3930    2.3991    2.4053    2.4114    2.4176    2.4237    2.4298    2.4360    2.4421    2.4482    2.4544    2.4605    2.4666    2.4728    2.4789    2.4850    2.4912    2.4973    2.5035    2.5096    2.5157    2.5219    2.5280    2.5341    2.5403    2.5464    2.5525    2.5587    2.5648    2.5710    2.5771    2.5832    2.5894    2.5955    2.6016    2.6078    2.6139    2.6200    2.6262    2.6323    2.6384    2.6446    2.6507    2.6569    2.6630    2.6691    2.6753    2.6814    2.6875    2.6937    2.6998    2.7059    2.7121    2.7182    2.7243    2.7305    2.7366    2.7428    2.7489    2.7550    2.7612    2.7673    2.7734    2.7796    2.7857    2.7918    2.7980    2.8041    2.8103    2.8164    2.8225    2.8287    2.8348    2.8409    2.8471    2.8532    2.8593    2.8655    2.8716    2.8777    2.8839    2.8900    2.8962    2.9023    2.9084    2.9146    2.9207    2.9268    2.9330    2.9391    2.9452    2.9514    2.9575    2.9637    2.9698    2.9759    2.9821    2.9882    2.9943    3.0005    3.0066    3.0127    3.0189    3.0250    3.0311    3.0373    3.0434    3.0496    3.0557    3.0618    3.0680    3.0741    3.0802    3.0864    3.0925    3.0986    3.1048    3.1109    3.1170    3.1232    3.1293    3.1355