数字滤波器设计及其应_毕业设计论文.docxVIP

数字滤波器设计及其应用 在本文中，我们分别研究了在MATLAB环境下IIR数字滤波器的典型设计和完全设计等方法。典型设计是先按一定规则将给出的数字滤波器的技术指标转换成模拟低通滤波器的技术指标，据此产生模拟滤波器原型，然后把模拟低通滤波器原型转换成模拟低通、高通、带通、带阻滤波器，最后再把模拟滤波器转换成数字滤波器。完全设计方法中我们利用函数直接设计出低通、高通、带通和带 阻滤波器，并分别用巴特沃斯（Butterworth )滤波器、切比雪夫 (Chebyshev)滤波器、椭圆（Cauw)滤波器来实现，并比较了各自的频率响应曲线。在FIR滤波器的设计中，我们用切比雪夫窗和海明窗设计的带通滤波器的频率响应进行对照，结果表面用海明窗设计的滤波器的频率 特性几乎在任何频带上都比切比雪夫窗设计的滤波器的频率特性好， 只是海明窗设计的滤波器下降斜度较小。本文利用不同的滤波器研究了 MATLAB环境下的图像处理技术。 对一张无锡马山园林的风景照片进行的二种修正，取得了不同的 效果:先对原图进行线性变换增加了对比度和亮度对这张图像，图像 效果有了 一定的改善。后来我们用非锐化滤波器对修正后的图像再进 行了处理，对图像的过渡失真进行了补偿。：本文还对一幅加噪声婚纱照片的去噪效果进行了研究。比较去噪 效果证明，用小波变换的方法进行去噪，图像处理效果更佳。关键词：数字滤波器；图像处理；小波变换；作 者：王蔚指导教师：顾济华AbstractIn this thesis，the typical and complete designs under MATLAB are studied.The typical design gets the technical parameters from digital filters that should be designed, and then transformed into the analog parameters of a low-pass analog filter prototype. The prototype is converted into the analog low-pass，high-pass，band-pass and the band-stop filters respectively, which are transformed into the digital ones.The complete design uses the given functions and releases the low-pass，high-pass， band-pass and the band-stop filters directly. But ter worth, Chebyshev and Caoer filters are used for the implementations.In the FIR filter designs, Chebyshev and Hamming windows are used for a band-pass filter. Their frequency responses are compared. The advantage of Hamming window is shown on all bands.Finally, the image processing functions using filters under MATLAB are studied.A photo (Wuxi Garden) is modified with two different processes and the different effects can be seen. The linear transformation improved the contrast and brightness of the photo, while the un-sharpening filter compensated the transitions.Another photo is modified with the wavelet transformation, which shows the better effects on reducing noises.Keywords: digital filter, image processing，wavelet transformationAuthor: Wang WeiDirected by Gu Ji-Hua第一章 绪数字滤波在通信、图像编码、语音编码、雷达等许多领域中有着 十分广泛的应用1n[2]。目前，数字信