AM Demodulation code error

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Matt
Matt 2023-12-14
评论： Matt 2023-12-30
Ran in:
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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回答（1 个）

Image Analyst
Image Analyst 2023-12-14
编辑：Image Analyst 2023-12-14
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
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Image Analyst
Image Analyst 2023-12-14
Not to me. Why would adding in that comment change anything?
Matt
Matt 2023-12-30
time has originated from my carrier signal code:
mod_ind = 1; % AM modulation index
f_carrier = 550e3; % frequency of carrier sine wave
A_carrier = std(audio)/mod_ind; % amplitude of carrier sine wave
y_carrier = A_carrier*sin(2*pi*f_carrier*time');
carrier_FD = fft(y_carrier); % calculate frequency domain of audio
carrier_FD_amp = abs(carrier_FD)/no_of_pnts; % calculate the amplitude of frequency domain
carrier_FD_amp_adj = fftshift(carrier_FD_amp); % adjust the frequency sides

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