s-function实现DSB调制的代码

下面是一个简单的s-function实现DSB调制的代码：

function [sys,x0,str,ts] = dsb_modulation(t,x,u,flag)
%DSB_MODULATION S-function for DSB modulation
%   [SYS,X0,STR,TS] = DSB_MODULATION(T,X,U,FLAG) implements
%   a DSB modulation system using S-function.
%
%   See also SIMULINK, SFUNLIB.

switch flag,
  case 0,
    [sys,x0,str,ts] = mdlInitializeSizes;
  case 2,
    sys = mdlUpdates(t,x,u);
  case 3,
    sys = mdlOutputs(t,x,u);
  case {1, 4, 9},
    sys = [];
  otherwise
    error(['Unhandled flag = ',num2str(flag)]);
end

%=============================================================================
% Initialization functions
%=============================================================================
function [sys,x0,str,ts] = mdlInitializeSizes
sizes = simsizes;
sizes.NumContStates  = 0;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 1;
sizes.NumInputs      = 2;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 1;
sys = simsizes(sizes);
x0  = [];
str = [];
ts  = [0 0];

%=============================================================================
% Update functions
%=============================================================================
function sys = mdlUpdates(t,x,u)
sys = [];

%=============================================================================
% Output functions
%=============================================================================
function sys = mdlOutputs(t,x,u)
carrier_freq = 1000; % Carrier frequency
amplitude = 2; % Amplitude of modulating signal

% DSB modulation
modulation_signal = u(1) .* cos(2 * pi * u(2) * t); % Modulating signal
carrier_signal = amplitude * cos(2 * pi * carrier_freq * t); % Carrier signal
dsb_signal = modulation_signal .* carrier_signal; % DSB signal

sys = dsb_signal;

这个s-function实现了一个简单的DSB调制系统，其中输入分别为调制信号和载波频率，输出为调制后的DSB信号。在函数中，我们先定义了调制信号和载波频率的输入参数，然后通过cos函数生成了调制信号和载波信号，最后将它们相乘得到了DSB信号。

需要注意的是，这只是一个简单的实现示例，实际的通信系统需要考虑到更多的因素，比如滤波、功率控制等，可以根据具体需求进行定制和优化。