function Hd = Fir_angle
%FIR_ANGLE 返回离散时间滤波器对象。

% MATLAB Code
% Generated by MATLAB(R) 9.9 and Signal Processing Toolbox 8.5.
% Generated on: 09-Oct-2022 15:50:58

% Equiripple Lowpass filter designed using the FIRPM function.

% All frequency values are in Hz.
Fs = 500;  % Sampling Frequency

Fpass = 0.5;               % Passband Frequency
Fstop = 3;                 % Stopband Frequency
Dpass = 5.7564627261e-05;  % Passband Ripple
Dstop = 0.0001;            % Stopband Attenuation
dens  = 20;                % Density Factor

% Calculate the order from the parameters using FIRPMORD.
[N, Fo, Ao, W] = firpmord([Fpass, Fstop]/(Fs/2), [1 0], [Dpass, Dstop]);

% Calculate the coefficients using the FIRPM function.
b  = firpm(N, Fo, Ao, W, {dens});
Hd = dfilt.dffir(b);

% [EOF]
