###### Software Testing

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The normalization of the amplitude display of the frequency response of the Matlab fvtool filter

After we design the filter with matlab, we can use fvtool to see the frequency response of the filter. For example, after we have the coefficients of the filter, we can directly use fvtool. fircoe = [0.018641, 0.018275,-0.020377,-0.071243,-0.049673,... 0.094562, 0.28841, 0.37949, 0.28841, 0.094562, -0.049673,... -0.071243,-0.020377, 0.018275, 0.018641]; fvtool(fircoe); It can be easily seen from the figure that the stopband attenuation is about 40db. But there are some filters whose gain is not