给我一段matlab代码，使用fft对无线通信中的多普勒频移进行处理

Sure, here is a sample MATLAB code that uses FFT to process Doppler shift in wireless communication:

% Define input signal
fs = 1000; % Sampling frequency (Hz)
t = 0:1/fs:1-1/fs; % Time vector
f1 = 10; % Frequency of signal (Hz)
f2 = 30; % Frequency of Doppler shift (Hz)
x = sin(2*pi*f1*t).*cos(2*pi*f2*t); % Input signal with Doppler shift

% Perform FFT
N = length(x); % Number of samples
X = fft(x)/N; % Compute FFT and normalize by number of samples
f = fs*(0:(N/2))/N; % Frequency vector for plotting

% Plot results
subplot(2,1,1); plot(t,x); xlabel('Time (s)'); ylabel('Amplitude');
subplot(2,1,2); plot(f,2*abs(X(1:N/2+1))); xlabel('Frequency (Hz)'); ylabel('Magnitude');

This code generates a sine wave with a frequency of 10 Hz, and then applies a Doppler shift of 30 Hz to simulate the effect of motion on a wireless signal. The FFT is then performed on the resulting signal to analyze the frequency components. The output plots show the time-domain and frequency-domain representations of the input signal, with the Doppler shift clearly visible in the frequency spectrum.