如何理解和掌握快速傅里叶变换的计算和概念 快速傅里叶变换和离散傅里叶变换的主要区别是什么?哪个准确?
\u5982\u4f55\u7406\u89e3\u5085\u91cc\u53f6\u53d8\u6362\u516c\u5f0f1\u3001\u5085\u91cc\u53f6\u53d8\u6362\u516c\u5f0f
\u516c\u5f0f\u63cf\u8ff0\uff1a\u516c\u5f0f\u4e2dF(\u03c9)\u4e3af(t)\u7684\u50cf\u51fd\u6570\uff0cf(t)\u4e3aF(\u03c9)\u7684\u50cf\u539f\u51fd\u6570\u3002
2\u3001\u5085\u7acb\u53f6\u53d8\u6362\uff0c\u8868\u793a\u80fd\u5c06\u6ee1\u8db3\u4e00\u5b9a\u6761\u4ef6\u7684\u67d0\u4e2a\u51fd\u6570\u8868\u793a\u6210\u4e09\u89d2\u51fd\u6570\uff08\u6b63\u5f26\u548c/\u6216\u4f59\u5f26\u51fd\u6570\uff09\u6216\u8005\u5b83\u4eec\u7684\u79ef\u5206\u7684\u7ebf\u6027\u7ec4\u5408\u3002\u5728\u4e0d\u540c\u7684\u7814\u7a76\u9886\u57df\uff0c\u5085\u7acb\u53f6\u53d8\u6362\u5177\u6709\u591a\u79cd\u4e0d\u540c\u7684\u53d8\u4f53\u5f62\u5f0f\uff0c\u5982\u8fde\u7eed\u5085\u7acb\u53f6\u53d8\u6362\u548c\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\u3002\u6700\u521d\u5085\u7acb\u53f6\u5206\u6790\u662f\u4f5c\u4e3a\u70ed\u8fc7\u7a0b\u7684\u89e3\u6790\u5206\u6790\u7684\u5de5\u5177\u88ab\u63d0\u51fa\u7684\u3002
3\u3001\u76f8\u5173
\u5085\u91cc\u53f6\u53d8\u6362\u5c5e\u4e8e\u8c10\u6ce2\u5206\u6790\u3002
\u5085\u91cc\u53f6\u53d8\u6362\u7684\u9006\u53d8\u6362\u5bb9\u6613\u6c42\u51fa\uff0c\u800c\u4e14\u5f62\u5f0f\u4e0e\u6b63\u53d8\u6362\u975e\u5e38\u7c7b\u4f3c;
\u6b63\u5f26\u57fa\u51fd\u6570\u662f\u5fae\u5206\u8fd0\u7b97\u7684\u672c\u5f81\u51fd\u6570\uff0c\u4ece\u800c\u4f7f\u5f97\u7ebf\u6027\u5fae\u5206\u65b9\u7a0b\u7684\u6c42\u89e3\u53ef\u4ee5\u8f6c\u5316\u4e3a\u5e38\u7cfb\u6570\u7684\u4ee3\u6570\u65b9\u7a0b\u7684\u6c42\u89e3.\u5728\u7ebf\u6027\u65f6\u4e0d\u53d8\u7684\u7269\u7406\u7cfb\u7edf\u5185\uff0c\u9891\u7387\u662f\u4e2a\u4e0d\u53d8\u7684\u6027\u8d28\uff0c\u4ece\u800c\u7cfb\u7edf\u5bf9\u4e8e\u590d\u6742\u6fc0\u52b1\u7684\u54cd\u5e94\u53ef\u4ee5\u901a\u8fc7\u7ec4\u5408\u5176\u5bf9\u4e0d\u540c\u9891\u7387\u6b63\u5f26\u4fe1\u53f7\u7684\u54cd\u5e94\u6765\u83b7\u53d6\uff1b
\u5377\u79ef\u5b9a\u7406\u6307\u51fa\uff1a\u5085\u91cc\u53f6\u53d8\u6362\u53ef\u4ee5\u5316\u590d\u6742\u7684\u5377\u79ef\u8fd0\u7b97\u4e3a\u7b80\u5355\u7684\u4e58\u79ef\u8fd0\u7b97\uff0c\u4ece\u800c\u63d0\u4f9b\u4e86\u8ba1\u7b97\u5377\u79ef\u7684\u4e00\u79cd\u7b80\u5355\u624b\u6bb5\uff1b
\u79bb\u6563\u5f62\u5f0f\u7684\u5085\u7acb\u53f6\u53d8\u6362\u53ef\u4ee5\u5229\u7528\u6570\u5b57\u8ba1\u7b97\u673a\u5feb\u901f\u5730\u7b97\u51fa\uff08\u5176\u7b97\u6cd5\u79f0\u4e3a\u5feb\u901f\u5085\u91cc\u53f6\u53d8\u6362\u7b97\u6cd5\uff08FFT))\u3002
\u6269\u5c55\u8d44\u6599\uff1a
\u6839\u636e\u539f\u4fe1\u53f7\u7684\u4e0d\u540c\u7c7b\u578b\uff0c\u53ef\u4ee5\u628a\u5085\u91cc\u53f6\u53d8\u6362\u5206\u4e3a\u56db\u79cd\u7c7b\u522b\uff1a
1\u3001\u975e\u5468\u671f\u6027\u8fde\u7eed\u4fe1\u53f7\u5085\u91cc\u53f6\u53d8\u6362\uff08Fourier Transform\uff09
2\u3001\u5468\u671f\u6027\u8fde\u7eed\u4fe1\u53f7\u5085\u91cc\u53f6\u7ea7\u6570(Fourier Series)
3\u3001\u975e\u5468\u671f\u6027\u79bb\u6563\u4fe1\u53f7\u79bb\u6563\u65f6\u57df\u5085\u91cc\u53f6\u53d8\u6362\uff08Discrete Time Fourier Transform\uff09
4\u3001\u5468\u671f\u6027\u79bb\u6563\u4fe1\u53f7\u79bb\u6563\u5085\u91cc\u53f6\u53d8\u6362(Discrete Fourier Transform)
FFT(Fast Fourier Transformation)\uff0c\u5373\u4e3a\u5feb\u901f\u5085\u6c0f\u53d8\u6362\uff0c\u662f\u79bb\u6563\u5085\u6c0f\u53d8\u6362\u7684\u5feb\u901f\u7b97\u6cd5\uff0c\u5b83\u662f\u6839\u636e\u79bb\u6563\u5085\u6c0f\u53d8\u6362\u7684\u5947\u3001\u5076\u3001\u865a\u3001\u5b9e\u7b49\u7279\u6027\uff0c\u5bf9\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\u7684\u7b97\u6cd5\u8fdb\u884c\u6539\u8fdb\u83b7\u5f97\u7684\u3002\u5b83\u5bf9\u5085\u6c0f\u53d8\u6362\u7684\u7406\u8bba\u5e76\u6ca1\u6709\u65b0\u7684 \u53d1\u73b0\uff0c\u4f46\u662f\u5bf9\u4e8e\u5728\u8ba1\u7b97\u673a\u7cfb\u7edf\u6216\u8005\u8bf4\u6570\u5b57\u7cfb\u7edf\u4e2d\u5e94\u7528\u79bb\u6563\u5085\u7acb\u53f6\u53d8\u6362\uff0c\u53ef\u4ee5\u8bf4\u662f\u8fdb\u4e86\u4e00\u5927\u6b65\u3002
FFT\u63d0\u9ad8\u4e86\u8fd0\u7b97\u901f\u5ea6\uff0c\u4f46\u662f\uff0c\u4e5f\u5bf9\u53c2\u4e0e\u8fd0\u7b97\u7684\u6837\u672c\u5e8f\u5217\u4f5c\u51fa\u4e86\u9650\u5236\uff0c\u5373\u8981\u6c42\u6837\u672c\u6570\u4e3a2^N\u70b9\u3002\u79bb\u6563\u5085\u91cc\u53f6\u53d8\u6362DFT\u5219\u65e0\u4e0a\u8ff0\u9650\u5236\u3002
\u5c0f\u7ed3:FFT\u5feb\uff0cDFT\u7075\u6d3b\uff0c\u5404\u6709\u4f18\u70b9\uff0c\u5982\u679c\u6ee1\u8db3\u5206\u6790\u8981\u6c42\uff0c\u4e24\u8005\u51c6\u786e\u5ea6\u76f8\u540c\u3002
\u5feb\u901f\u5085\u91cc\u53f6\u53d8\u6362 (fast Fourier transform), \u5373\u5229\u7528\u8ba1\u7b97\u673a\u8ba1\u7b97\u79bb\u6563\u5085\u91cc\u53f6\u53d8\u6362(DFT)\u7684\u9ad8\u6548\u3001\u5feb\u901f\u8ba1\u7b97\u65b9\u6cd5\u7684\u7edf\u79f0\uff0c\u7b80\u79f0FFT\u3002\u5feb\u901f\u5085\u91cc\u53f6\u53d8\u6362\u662f1965\u5e74\u7531J.W.\u5e93\u5229\u548cT.W.\u56fe\u57fa\u63d0\u51fa\u7684\u3002
\u91c7\u7528\u8fd9\u79cd\u7b97\u6cd5\u80fd\u4f7f\u8ba1\u7b97\u673a\u8ba1\u7b97\u79bb\u6563\u5085\u91cc\u53f6\u53d8\u6362\u6240\u9700\u8981\u7684\u4e58\u6cd5\u6b21\u6570\u5927\u4e3a\u51cf\u5c11\uff0c\u7279\u522b\u662f\u88ab\u53d8\u6362\u7684\u62bd\u6837\u70b9\u6570N\u8d8a\u591a\uff0cFFT\u7b97\u6cd5\u8ba1\u7b97\u91cf\u7684\u8282\u7701\u5c31\u8d8a\u663e\u8457\u3002
\u79bb\u6563\u5085\u91cc\u53f6\u53d8\u6362(DFT)\uff0c\u662f\u5085\u91cc\u53f6\u53d8\u6362\u5728\u65f6\u57df\u548c\u9891\u57df\u4e0a\u90fd\u5448\u73b0\u79bb\u6563\u7684\u5f62\u5f0f\uff0c\u5c06\u65f6\u57df\u4fe1\u53f7\u7684\u91c7\u6837\u53d8\u6362\u4e3a\u5728\u79bb\u6563\u65f6\u95f4\u5085\u91cc\u53f6\u53d8\u6362(DTFT)\u9891\u57df\u7684\u91c7\u6837\u3002
\u5728\u5f62\u5f0f\u4e0a\uff0c\u53d8\u6362\u4e24\u7aef(\u65f6\u57df\u548c\u9891\u57df\u4e0a)\u7684\u5e8f\u5217\u662f\u6709\u9650\u957f\u7684\uff0c\u800c\u5b9e\u9645\u4e0a\u8fd9\u4e24\u7ec4\u5e8f\u5217\u90fd\u5e94\u5f53\u88ab\u8ba4\u4e3a\u662f\u79bb\u6563\u5468\u671f\u4fe1\u53f7\u7684\u4e3b\u503c\u5e8f\u5217\u3002\u5373\u4f7f\u5bf9\u6709\u9650\u957f\u7684\u79bb\u6563\u4fe1\u53f7\u4f5cDFT\uff0c\u4e5f\u5e94\u5f53\u5c06\u5176\u770b\u4f5c\u7ecf\u8fc7\u5468\u671f\u5ef6\u62d3\u6210\u4e3a\u5468\u671f\u4fe1\u53f7\u518d\u4f5c\u53d8\u6362\u3002\u5728\u5b9e\u9645\u5e94\u7528\u4e2d\u901a\u5e38\u91c7\u7528\u5feb\u901f\u5085\u91cc\u53f6\u53d8\u6362\u4ee5\u9ad8\u6548\u8ba1\u7b97DFT\u3002
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绛旓細F(蠅) = 鈭玣(x)e^(-i蠅x)dx 鍏朵腑锛屜夎〃绀洪鐜囷紝i琛ㄧず铏氭暟鍗曚綅锛宔琛ㄧず鑷劧瀵规暟鐨勫簳鏁般傝繖涓叕寮忕殑鎰忎箟鏄皢鍑芥暟f(x)涔樹互涓涓鎸囨暟e^(-i蠅x)锛屽苟瀵规暣涓嚱鏁板湪鏃跺煙涓婅繘琛岀Н鍒嗭紝浠庤屽緱鍒板湪棰戝煙涓婄殑琛ㄧずF(蠅)銆鍌呴噷鍙跺彉鎹鍏紡鐨鐞嗚В闇瑕佸鏁板鍜岀墿鐞嗗鐨勭煡璇嗘湁涓瀹氱殑浜嗚В锛屼絾鏄浜庡ぇ澶氭暟浜烘潵...
绛旓細浠庣幇浠f暟瀛︾殑鐪煎厜鏉ョ湅锛鍌呴噷鍙跺彉鎹鏄竴绉嶇壒娈婄殑绉垎鍙樻崲銆傚畠鑳藉皢婊¤冻涓瀹氭潯浠剁殑鏌愪釜鍑芥暟琛ㄧず鎴愭寮﹀熀鍑芥暟鐨勭嚎鎬х粍鍚堟垨鑰呯Н鍒嗐傚湪涓嶅悓鐨勭爺绌堕鍩燂紝鍌呴噷鍙跺彉鎹㈠叿鏈夊绉嶄笉鍚岀殑鍙樹綋褰㈠紡锛屽杩炵画鍌呴噷鍙跺彉鎹㈠拰绂绘暎鍌呴噷鍙跺彉鎹鍌呯珛鍙跺彉鎹灞炰簬璋冨拰鍒嗘瀽鐨勫唴瀹广"鍒嗘瀽"浜屽瓧锛屽彲浠瑙i噴涓烘繁鍏ョ殑鐮旂┒銆備粠瀛楅潰涓婃潵鐪...
绛旓細鎬荤粨鏉ヨ锛屽倕閲屽彾鍙樻崲涓嶄粎鏄竴涓叕寮忥紝鏇存槸涓绉嶆濈淮鏂瑰紡鐨勮浆鍙樸傚畠鏁欏鎴戜滑濡備綍浠庝竴涓淮搴﹁烦鍒板彟涓涓紝鐢ㄩ鍩熺殑璇█鐞嗚В閭d簺鍘熸湰鍦ㄦ椂鍩熶笅闅句互鎹夋懜鐨勭幇璞° 浠庡績鐢靛浘鐨勬尝褰㈠垎鏋愬埌鎭愰緳涓庡皬鐚殑鍥惧儚妯℃嫙锛鍌呴噷鍙跺彉鎹㈢殑鍔涢噺鏃犲涓嶅湪锛屽畠鍦ㄧ瀛︾殑鎺㈢储涔嬫梾涓紝鎵紨鐫涓嶅彲鎴栫己鐨勮鑹层
绛旓細闃惰穬鍑芥暟鏄竴绉嶅父瑙佺殑淇″彿鍑芥暟锛岀敤绗﹀彿u(t)琛ㄧず锛屽畠鍦╰=0澶勪粠0璺宠穬鍒1銆傞樁璺冨嚱鏁扮殑鍌呴噷鍙跺彉鎹㈠彲浠ラ氳繃鍌呴噷鍙跺彉鎹㈢殑瀹氫箟鍜屾ц川鏉ヨ〃绀恒傛牴鎹倕閲屽彾鍙樻崲鐨勫畾涔夛紝瀵逛簬闃惰穬鍑芥暟u(t)锛屽叾鍌呴噷鍙跺彉鎹(蠅)瀹氫箟涓猴細U(蠅) = 鈭玔0,鈭) u(t) * exp(-j蠅t) dt 鏍规嵁闃惰穬鍑芥暟鐨勫畾涔夛紝鍦╰=0涔嬪墠u(...