学习QAM-OFDM时编写的MATLAB实验代码

function y = filter_lowpass_1_20(x) %FILTER_LOWPASS_1_20 对输入 x 进行滤波并返回输出 y。 % MATLAB Code % Generated by MATLAB(R) 9.9 and DSP System Toolbox 9.11. % Generated on: 30-Jan-2022 16:46:46 %#codegen % 要通过此函数生成 C/C++ 代码，请使用 codegen 命令。有关详细信息，请键入 'help codegen'。 persistent Hd; if isempty(Hd) % 设计滤波器系数时使用了以下代码: % % Equiripple Lowpass filter designed using the FIRPM function. % % % All frequency values are in Hz. % Fs = 1000; % Sampling Frequency % % Fpass = 1; % Passband Frequency % Fstop = 2; % Stopband Frequency % Dpass = 0.057501127785; % Passband Ripple % Dstop = 0.0031622776602; % 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 = dsp.FIRFilter( ... 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