帮我用MATLAB写一个关于2ASK 2FSK 2PSK的信号波形及其功率谱的代码

好的，以下是一个简单的MATLAB代码，用于生成2ASK、2FSK和2PSK的信号波形和功率谱：

% 2ASK, 2FSK, 2PSK signal and power spectrum

% Define the signal parameters
fc = 1000; % carrier frequency
fs = 10000; % sampling frequency
T = 1/fs; % sampling time
L = 1000; % signal length
t = (0:L-1)*T; % time vector

% Define the message signal
Am = 1; % message amplitude
fm = 10; % message frequency
m = Am*sin(2*pi*fm*t); % message signal

% 2ASK modulation
Ac1 = 2; % carrier amplitude for binary 1
Ac0 = 0; % carrier amplitude for binary 0
A1 = m + Ac1; % modulated signal for binary 1
A0 = m + Ac0; % modulated signal for binary 0
s_2ask = A0; % initialize the signal
for i = 1:length(m)
    if m(i) >= 0
        s_2ask(i) = A1(i);
    end
end

% 2FSK modulation
f1 = 100; % frequency for binary 1
f0 = 50; % frequency for binary 0
s_2fsk = sin(2*pi*f0*t); % initialize the signal
for i = 1:length(m)
    if m(i) >= 0
        s_2fsk(i) = sin(2*pi*f1*t(i));
    end
end

% 2PSK modulation
s_2psk = Ac1*cos(2*pi*fc*t); % initialize the signal
for i = 1:length(m)
    if m(i) >= 0
        s_2psk(i) = Ac1*cos(2*pi*fc*t(i));
    else
        s_2psk(i) = Ac1*cos(2*pi*fc*t(i)+pi);
    end
end

% Calculate the power spectrum
NFFT = 2^nextpow2(L); % number of FFT points
Y_2ask = fft(s_2ask,NFFT)/L;
Y_2fsk = fft(s_2fsk,NFFT)/L;
Y_2psk = fft(s_2psk,NFFT)/L;
f = fs/2*linspace(0,1,NFFT/2+1);
P_2ask = 2*abs(Y_2ask(1:NFFT/2+1));
P_2fsk = 2*abs(Y_2fsk(1:NFFT/2+1));
P_2psk = 2*abs(Y_2psk(1:NFFT/2+1));

% Plot the signals and power spectrum
figure;
subplot(3,2,1);
plot(t,m);
title('Message signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(3,2,2);
plot(f,P_2ask);
title('2ASK power spectrum');
xlabel('Frequency (Hz)');
ylabel('Power');
subplot(3,2,3);
plot(t,s_2ask);
title('2ASK modulated signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(3,2,4);
plot(f,P_2fsk);
title('2FSK power spectrum');
xlabel('Frequency (Hz)');
ylabel('Power');
subplot(3,2,5);
plot(t,s_2fsk);
title('2FSK modulated signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(3,2,6);
plot(f,P_2psk);
title('2PSK power spectrum');
xlabel('Frequency (Hz)');
ylabel('Power');

这段代码将生成一个包含三个信号波形和功率谱的图表。如果需要更改信号参数，可以在代码中修改相应的变量。