MATLAB實現最優低通濾波器的函數

% Fs???? --Data rate

% Fpass? --pass band

% Fstop? --Cutoff frequencies

% Apass? --Passband ripple

% Astop? --Stopband ripple

% Q_Bit? --Quantization bits

function coef? = LowPassFir(Fs,Fpass,Fstop,Apass,Astop,Q_Bit)

?

?

?

dens? = 20;?????????????? % Density Factor

a = [1 0];??????? % Desired amplitudes

rp = Apass;

rs = Astop;

?

% Compute deviations

dev = [(10^(rp/20)-1)/(10^(rp/20)+1),10^(-rs/20)];

?

% Calculate the order from the parameters using FIRPMORD.

[N, Fo, Ao, W] = firpmord([Fpass, Fstop]/(Fs/2), a, dev);

% Calculate the coefficients using the FIRPM function.

coef? = firpm(N, Fo, Ao, W, {dens});

coe = coef;

fft_coe = 20*log(abs(fft(coe,1024)))/log(10);

?

% x_f = [0:(Fs/length(fft_coe)):Fs/2];

% m = fft_coe(1:length(x_f));

% plot(x_f,m),grid

?

fft_shift_coe = fftshift(fft_coe);

x_f = [-Fs/2+(Fs/length(fft_shift_coe)):(Fs/length(fft_shift_coe)):Fs/2];

plot(x_f,fft_shift_coe);grid

?

HB

function Coef = LowPassHb(Fs,Fpass,Apass,n)

% -- Fs sample frequency

% -- Fpass

% -- Apass(dB)

% -- n stage of the half band fir

fp = Fpass*2/(Fs);

dev = [(10^(Apass/20)-1)/(10^(Apass/20)+1)];

% dev = Apass;

switch nargin

??? case 3

??????? Coef = firhalfband('minorder',fp,dev);

??? case 4

??????? Coef = firhalfband(n,fp);

??? otherwise

??????? error('error');

end

??????? Coef = Coef';

???

?vpa(Coef,16);

fft_coe = 20*log(abs(fft(Coef,1024)))/log(10);

?

% x_f = [0:(Fs/length(fft_coe)):Fs/2];

% m = fft_coe(1:length(x_f));

% plot(x_f,m),grid

?

fft_shift_coe = fftshift(fft_coe);

x_f = [-Fs/2+(Fs/length(fft_shift_coe)):(Fs/length(fft_shift_coe)):Fs/2];

plot(x_f,fft_shift_coe);grid

轉載于:https://www.cnblogs.com/zhongguo135/p/5916821.html

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