Spectrum Analyzer Input Channels

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.

Thanks.

clc;
clear;
% 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();
scope(m);
% 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.

Answer 1

[Ashutosh Singh Baghel]

Hi Nizamettin,

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.

scope(m');

A simple transpose would solve this problem.

One more method to analyze the signal could be done using pspectrum as follows.

% Parameters
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);
plot(f/pi,10*log10(pxx));

Refer to the following MATLAB Documentation page for further information.