plotSpectrum

System object: phased.MUSICEstimator2D
Namespace: phased

Plot 2-D MUSIC spectrum

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Syntax

plotSpectrum(estimator)
output_args = plotSpectrum(estimator,Name,Value)
lh = plotSpectrum(___)

Description

plotSpectrum(estimator) plots the 2-D MUSIC spatial spectrum computed by the most recent execution for the phased.MUSICEstimator2D, estimator.

output_args = plotSpectrum(estimator,Name,Value) plots the 2-D MUSIC spatial spectrum with additional options specified by one or more Name,Value pair arguments.

lh = plotSpectrum(___) returns the line handle to the figure.

Input Arguments

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2-D MUSIC estimator, specified as a phased.MUSICEstimator2D System object.

Name-Value Arguments

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Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Units used for plotting, specified as the comma-separated pair consisting of 'Unit' and 'db', 'mag', or 'pow'.

Data Types: char

Plot a normalized spectrum, specified as the comma-separated pair consisting of 'NormalizedResponse' and false or true. Normalization sets the magnitude of the largest spectrum value to one.

Example: true

Data Types: char

Title of plot, specified as a comma-separated pair consisting of 'Title' and a character vector.

Example: true

Data Types: char

Output Arguments

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Line handle of plot.

Examples

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Open Live Script

Assume that two sinusoidal waves of frequencies 450 Hz and 600 Hz strike a URA from two different directions. Signals arrive from -37° azimuth, 0° elevation and 17° azimuth, 20° elevation. Use 2-D MUSIC to estimate the directions of arrival of the two signals. The array operating frequency is 150 MHz and the signal sampling frequency is 8 kHz.

f1 = 450.0;
f2 = 600.0;
doa1 = [-37;0];
doa2 = [17;20];
fc = 150e6;
c = physconst('LightSpeed');
lam = c/fc;
fs = 8000;

Create the URA with default isotropic elements. Set the frequency response range of the elements.

array = phased.URA('Size',[11 11],'ElementSpacing',[lam/2 lam/2]);
array.Element.FrequencyRange = [50.0e6 500.0e6];

Create the two signals and add random noise.

t = (0:1/fs:1).';
x1 = cos(2*pi*t*f1);
x2 = cos(2*pi*t*f2);
x = collectPlaneWave(array,[x1 x2],[doa1,doa2],fc);
noise = 0.1*(randn(size(x))+1i*randn(size(x)));

Create and execute the 2-D MUSIC estimator to find the directions of arrival.

estimator = phased.MUSICEstimator2D('SensorArray',array,...
    'OperatingFrequency',fc,...
    'NumSignalsSource','Property',...
    'DOAOutputPort',true,'NumSignals',2,...
    'AzimuthScanAngles',-50:.5:50,...
    'ElevationScanAngles',-30:.5:30);
[~,doas] = estimator(x + noise)
doas = 2×2

   -37    17
     0    20

The estimated DOAs exactly match the true DOAs.

Plot the 2-D spatial spectrum.

plotSpectrum(estimator);

Figure contains an axes object. The axes object with title 2-D MUSIC Spatial Spectrum, xlabel Azimuth Angle (degrees), ylabel Elevation Angle (degrees) contains an object of type surface.

Version History

Introduced in R2016b