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step

System object: phased.PhaseShiftBeamformer
Package: phased

Perform phase shift beamforming

Syntax

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

Description

Y = step(H,X) performs phase shift beamforming on the input, X, and returns the beamformed output in Y.

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,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.

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 phase shift beamforming to the signal received by a 5-element ULA. The beamforming direction is 45 degrees azimuth and 0 degrees elevation.

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

Algorithms

The phase shift beamformer uses the conventional delay-and-sum beamforming algorithm. The beamformer assumes the signal is narrowband, so a phase shift can approximate the required delay. The beamformer preserves the incoming signal power.

For further details, see [1].

References

[1] Van Trees, H. Optimum Array Processing. New York: Wiley-Interscience, 2002.

See Also

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