Multiple PSD in same graph - Matlab

Question

I intend to plot multiple Power Spectral Densities on the same graph. I am using the following to plot the power spectral density for a single signal.

hss = dsp.SpectrumAnalyzer('SampleRate', Fs); 
step(hss,rx);
release(hss);

However, if I were to plot another signal in the same spectrum analyzer using hold on doesn't seem to help

hss = dsp.SpectrumAnalyzer('SampleRate', Fs); 
step(hss,rx); hold on;
step(hss,tx);
release(hss);

Could someone guide me on how to go about with this.

EDIT: Here's a snippet of my code:

Fs = 12e6;
data = randi([0 1],1000,1);
%% OQPSK Modulate data
hMod = comm.OQPSKModulator('BitInput',true); 
tx = step(hMod, data);
%% Add noise
hAWGN = comm.AWGNChannel('EbNo',2);
rx = step(hAWGN, tx);

Now I need a way to plot the PSD of both tx and rx in the same graph.

One way the "hold on" command would work is if you were calling plot() with the frequency and psd vectors. — willpower2727, Jun 30 '15 at 12:51
I did not understand what you meant @willpower2727. I have already tried using `hold on` but i think it would work only in case of `plot()` or `semilog() `but not in case of `step()` — smyslov, Jun 30 '15 at 12:57
Yes I think "hold on" may not work for step(). Can you post a more complete example of your code? Like maybe with a sample data, Fs? — willpower2727, Jun 30 '15 at 13:05
@ smyslov awesome, thanks, is the variable "chip_sequence" defined above? is it an input option? When I try to run your code it cannot tell what chip_sequence is. — willpower2727, Jun 30 '15 at 13:57
My bad. I've edited my code. It should have been data instead of chip_sequence. — smyslov, Jun 30 '15 at 14:07

score 1 · Accepted Answer · answered Jun 30 '15 at 14:38

Ok I think I've figure it out, you need to pass in more than one data to the same step call like so:

Fs = 12e6;
hss = dsp.SpectrumAnalyzer('SampleRate', Fs); 
data = randi([0 1],2000,1);%I had to increase the # of points
%% OQPSK Modulate data
hMod = comm.OQPSKModulator('BitInput',true); 
tx = step(hMod, data);
%% Add noise
hAWGN = comm.AWGNChannel('EbNo',2);
rx = step(hAWGN, tx);

%This is the line that makes it work, passing in a matrix of input data
step(hss,[rx tx]);

enter image description here

score 0 · Answer 2 · answered May 23 '20 at 12:12

You can use the below code in Matlab.

assume you have two signal, signal1, and signal2.

rmc = lteRMCDL('R.0');
[signal1,~,info] = lteRMCDLTool(rmc,[1;0;0;1]); %

signal2 = 100*signal1;

scope = dsp.SpectrumAnalyzer;
scope.PlotAsTwoSidedSpectrum = true;
scope.SampleRate = info.SamplingRate;

% You should replace your samplerate whit info.samplerate

scope([signal1 signal2])

Multiple PSD in same graph - Matlab

2 Answers2