AM Demodulation code error

Question

Matt 2023-12-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060679-am-demodulation-code-error

评论： Matt 2023-12-30

f_lo = 30e3;  % frequency of local oscillator
A_lo = 1;  % amplitude of local oscillator
y_lo = A_lo*sin(2*pi*f_lo*time');
Unrecognized function or variable 'time'.
y_demod = y_lo.*filt_received'; 
demod_sig_FD = fft(y_demod);  % calculate frequency domain of audio
demod_sig_FD_amp = abs(demod_sig_FD)/no_of_pnts;  % calculate the amplitude of frequency domain
demod_sig_FD_amp_adj = fftshift(demod_sig_FD_amp);  % adjust the frequency sides
figure;
semilogy(freq, filt_rec_sig_FD_amp_adj, 'b');
hold on;
semilogy(freq, demod_sig_FD_amp_adj, 'r');
xlim([10, freq_max]);
grid minor;
box on;
xlabel('Frequency (Hz)');
ylabel('Amplitude');
legend('Filtered Received', 'Demodulated');
title('Frequency Domain of Filtered Received and Demodulated Signals');

The Error is:

y_demod = y_lo.*filt_received';

Requested 1102840x20000 (164.3GB) array exceeds maximum array size preference (7.7GB). This might cause MATLAB to become unresponsive.

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Answer 1

Image Analyst 2023-12-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060679-am-demodulation-code-error#answer_1371639

编辑：Image Analyst 2023-12-14

在 MATLAB Online 中打开

time is a built in function so your use of it is not recommended.

What is filt_received? Specifically what is its size (rows and columns)? If it's a vector, or you think it is, then it might not be the same shape as y_lo. Then with the "automatic expansion" it's making a huge 2-D matrix out of it. You might try turning both factors into column vectors and then doing it.

y_demod = y_lo(:) .* filt_received(:); % Create new column vector.

These are just normal questions that any of the rest of us would ask when debugging code. To learn how to debug: Debugging in MATLAB | Doug's MATLAB Video Tutorials