Spectrum Analyzer Input Channels
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Nizamettin Taha Tanaçar on 27 Oct 2021
I have a task in which I need to do spectral analysis on a given signal utilizing "dsp.SpectralAnalyzer()". However whenever I try to do this I face the error message: "The number of input channels cannot exceed 100.". Which is as far as I understood a problem regarding the validation of the data to be analyzed in terms of number of channels. However, I haven't found much information on the dsp.SpectralAnalyzer help page regarding the input channels. Thus I don't know what values to change to get it to work. I tried shortening the "time vector" I created in my code and I succeded on getting the Spectrum Analyzer to appear. However this time I couldn't get it to work as it indicated that I didn't have enough samples. I believe my sample number is above what is requested but it my task indicates that I cannot change anything related to sampling. I don't know how I can get the analyzer to work by coming around this issue.
% command window cleanup
fm1 = 5;
fm2 = 10;
Amessage = 2;
% Definition for signal generation
fSampling = 200;
tSample = 5*10^-3;
fCarrier = 40;
% Definitions for de/modulation process
tMessage = 0:tSample:50;
% Time vector creation to generate signals with pre-determined slicing.
m1 = Amessage * sin(2*pi*fm1*tMessage);
m2 = Amessage * sin(2*pi*fm2*tMessage);
m = m1 + m2;
% Signal Generation
% sDBS = amDSBSC(m, fCarrier, fSampling);
% sL = amSSB(m, fCarrier, fSampling, 'lower');
% sU = amSSB(m, fCarrier, fSampling, "upper");
% % Modulation
scope = dsp.SpectrumAnalyzer();
% Spectral Analysis,
I commented out a section as it contains functions I wrote as it wouldn't work here. But the general problem is the same. Even if I try to analyze the signals that I create, I can't do so.
Ashutosh Singh Baghel on 16 Nov 2021
I understand that you wish to analyze signal 'm' using 'dsp.SpectrumAnalyzer()'. The input to the spectrum analyzer must be a column vector and not a row vector. The different values in a row vector represent different channels, and column vector values correspond to the signal values.
A simple transpose would solve this problem.
One more method to analyze the signal could be done using pspectrum as follows.
frequencyLimits = [0 1]*pi; % Normalized frequency (rad/sample)
timeLimits = [1 10001]; % number of samples
m_1 = m(:);
m_1 = m_1(timeLimits(1):timeLimits(2));
% Compute spectral estimate
% Run the function call below without output arguments to plot the results
[pxx, f] = pspectrum(m_1, 'FrequencyLimits',frequencyLimits);
Refer to the following MATLAB Documentation page for further information.