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step

System object: phased.MVDRBeamformer
Package: phased

Perform MVDR beamforming

Syntax

Y = step(H,X)
Y = step(H,X,XT)
Y = step(H,X,ANG)
Y = step(H,X,XT,ANG)
[Y,W] = step(___)

Description

Y = step(H,X) performs MVDR beamforming on the input, X, and returns the beamformed output in Y. This syntax uses X as the training samples to calculate the beamforming weights.

Y = step(H,X,XT) uses XT as the training samples to calculate the beamforming weights. This syntax is available when you set the TrainingInputPort property to true.

Y = step(H,X,ANG) uses ANG as the beamforming direction. This syntax is available when you set the DirectionSource property to 'Input port'.

Y = step(H,X,XT,ANG) combines all input arguments. This syntax is available when you set the TrainingInputPort property to true and set the DirectionSource property to 'Input port'.

[Y,W] = step(___) returns the beamforming weights, W. This syntax is available when you set the WeightsOutputPort property to true.

    Note:   The object performs an initialization the first time the step method is executed. This initialization locks nontunable properties and input specifications, such as dimensions, complexity, and data type of the input data. If you change a nontunable property or an input specification, the System object™ issues an error. To change nontunable properties or inputs, you must first call the release method to unlock the object.

Input Arguments

H

Beamformer object.

X

Input signal, specified as an M-by-N matrix. If the sensor array contains subarrays, N is the number of subarrays; otherwise, N is the number of elements. If you set the TrainingInputPort to false, M must be larger than N; otherwise, M can be any positive integer.

XT

Training samples, specified as a P-by-N matrix. If the sensor array contains subarrays, N is the number of subarrays; otherwise, N is the number of elements. P must be larger than N.

ANG

Beamforming directions, specified as a two-row matrix. Each column has the form [AzimuthAngle; ElevationAngle], in degrees. Each azimuth angle must be between –180 and 180 degrees, and each elevation angle must be between –90 and 90 degrees.

Output Arguments

Y

Beamformed output. Y is an M-by-L matrix, where M is the number of rows of X and L is the number of beamforming directions.

W

Beamforming weights. W is an N-by-L matrix, where L is the number of beamforming directions. If the sensor array contains subarrays, N is the number of subarrays; otherwise, N is the number of elements.

Examples

Apply an MVDR beamformer to a 5-element ULA. The incident angle of the signal is 45 degrees in azimuth and 0 degree in elevation.

% Signal simulation
t = (0:1000)';
x = sin(2*pi*0.01*t);
c = 3e8; Fc = 3e8;
incidentAngle = [45; 0];
ha = phased.ULA('NumElements',5);
x = collectPlaneWave(ha,x,incidentAngle,Fc,c);
noise = 0.1*(randn(size(x)) + 1j*randn(size(x)));
rx = x+noise;

% Beamforming
hbf = phased.MVDRBeamformer('SensorArray',ha,...
    'PropagationSpeed',c,'OperatingFrequency',Fc,...
    'Direction',incidentAngle,'WeightsOutputPort',true);
[y,w] = step(hbf,rx);

See Also

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