Digital Filter Design Under The MATLAB Environment And Its Applications

In 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. Butterworth, 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.