iaadoa

Estimate direction of signal arrival

Since R2024a

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Syntax

ang = iaadoa(X,elempos)

[ang,spec,azimuthspecang,elevationspecang] = iaadoa(X,elempos)

[___] = iaadoa(X,elempos,'NumSignals',nsig)

[___] = iaadoa(X,elempos,'AzimuthScanAngles',azimuthscanang)

[___] = iaadoa(X,elempos,'ElevationScanAngles',elevationscanang)

[___] = iaadoa(X,elempos,...,'NumIterations',niter)

[___] = iaadoa(X,elempos,...,'Tolerance',tol)

Description

example

ang = iaadoa(X,elempos) returns the estimated direction of arrival, ang, of the signal X at element positions elempos. The function uses the Iterative Adaptive Approach (IAA) algorithm,

[ang,spec,azimuthspecang,elevationspecang] = iaadoa(X,elempos) also returns the spatial power spectrum spec and the corresponding scan angles azimuthspecang along the azimuth direction and elevationspecang along the elevation direction.

example

[___] = iaadoa(X,elempos,'NumSignals',nsig) also returns the nsig largest peaks of the spatial power spectrum.

[___] = iaadoa(X,elempos,'AzimuthScanAngles',azimuthscanang) searches the azimuth scan angles azimuthscanang and returns the nsig angles corresponding to the highest peaks in the spatial power spectrum the search region.

[___] = iaadoa(X,elempos,'ElevationScanAngles',elevationscanang) searches the elevation scan angles elevationscanang and returns the nsig angles corresponding to the highest peaks in the spatial power spectrum in the search region.

[___] = iaadoa(X,elempos,...,'NumIterations',niter) returns the spatial power spectrum and directions of arrival after a maximum of niter iterations. In cases where any other stopping criteria are not met, the algorithm terminates after the maximum number of iterations.

[___] = iaadoa(X,elempos,...,'Tolerance',tol) returns the spatial power spectrum and directions of arrival, taking into account the specified stop criteria, tol. The 'Tolerance' Name-value pair sets the criteria for stopping, determined by the relative difference between the estimated spectrum of the current iteration and that of the previous iteration.

Examples

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Direction of Arrival of Signals at ULA

Open Live Script

Calculate the directions of arrival of four uncorrelated signals impinging on a 20-element ULA with half-wavelength spacing. Assume the signals are coming from azimuth 0, -25, 45, and 60 degrees, respectively. The noise is white across all elements and the SNR is 10 dB.

Set up array element positions.

N = 20;
d = 0.5; 
elementPos = (0:N-1)*d;

Set up signal directions.

angles = [0 -25 45 60];
Nsig = 4;

Create single snapshot of received signal.

[x,xcov] = sensorsig(elementPos,1,angles,db2pow(-10));
doas = iaadoa(x,elementPos,'NumSignals',Nsig);
disp(doas)

     0    45   -25    60
     0     0     0     0

Plot IAA Magnitude Spectrum

Open Live Script

Set up array element positions.

N = 20;
d = 0.5; 
elementPos = (0:N-1)*d;

Set up signal directions.

angles = [0 -25 45 60];
Nsig = 4;

Create single snapshot of received signal.

[x,xcov] = sensorsig(elementPos,1,angles,db2pow(-10));
[doa,spec,specang] = iaadoa(x,elementPos,'NumSignals',Nsig);

Plot spectrum.

plot(specang,10*log10(spec))
xlabel('Broadside Angles (degrees)')
ylabel('Magnitude Spectrum (dB)')
title('IAA Spatial Spectrum')

Plot Power Spectrum of 10-by-10 URA

Open Live Script

Calculate the directions of arrival of 2 uncorrelated signals impinging on a 10-by-10 URA with half-wavelength spacing. Assume the signals are coming from azimuth -37, and 17 degrees, and elevation 0, and 20 degrees, respectively. The noise is white across all elements and the SNR is 10 dB.

N = 10; % Elements in array
d = 0.5; % sensor spacing half wavelength
array = phased.URA(N); % generate 2D URA
doa1 = [-37;0];
doa2 = [17;20];
elementPos = getElementPosition(array);
Nsig = 2;

Generate 10 snapshots of received single.

x = sensorsig(elementPos,10,[doa1,doa2],db2pow(-10));

Solve for the directions of arrival.

[doas,spec,azimuthSpecAng,elevationSpecAng] = iaadoa(x,elementPos, ...
    "AzimuthScanAngles", -60:60, ...
    "ElevationScanAngles", -60:60, 'NumSignals',Nsig);
imagesc(azimuthSpecAng,elevationSpecAng,spec)
xlabel('Azimuth (degrees)')
ylabel('Elevation (degrees)')
title('IAA Spatial Spectrum')
axis equal
axis tight

Input Arguments

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`X` — Received signal
N_s-by-N complex-valued matrix

Received signal, specified as an N_s-by-N complex-valued matrix representing N_s snapshots of a signal at the N-elements of a sensor array.

Data Types: single | double
Complex Number Support: Yes

`elempos` — Array sensor element positions
real-valued 1-by-N vector | 2-by-N real-valued matrix | 3-by-N real-valued matrix

Array sensor element positions, specified as a real-valued 1-by-N vector, a real-valued 2-by-N matrix, or a real-valued 3-by-N matrix where N is the number of elements in the sensor array.

A 1-by-N vector represents the y-coordinates of the elements of a linear array along the yaxis.
A 2-by-N matrix represents an array lying in the yz-plane. Each column of elempos represents the [y;z] coordinates of an array element.
A 3-by-N matrix represents an array of arbitrary shape. A each column of elempos represents the [x;y;z] coordinates of an array element.

Units are wavelength.