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step

System object: phased.BeamscanEstimator
Package: phased

Perform spatial spectrum estimation

Syntax

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

Description

    Note:   Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Y = step(H,X) estimates the spatial spectrum from X using the estimator, H. X is a matrix whose columns correspond to channels. Y is a column vector representing the magnitude of the estimated spatial spectrum.

The size of the first dimension of this input matrix can vary to simulate a changing signal length, such as a pulse waveform with variable pulse repetition frequency.

[Y,ANG] = step(H,X) returns additional output ANG as the signal's direction of arrival (DOA) when the DOAOutputPort property is true. ANG is a row vector of the estimated broadside angles (in degrees).

    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.

Examples

Estimate the DOAs of two signals received by a standard 10-element ULA with element spacing 1 meter. The antenna operating frequency is 150 MHz. The actual direction of the first signal is 10 degrees in azimuth and 20 degrees in elevation. The direction of the second signal is 60 degrees in azimuth and -5 degrees in elevation.

fs = 8000; t = (0:1/fs:1).';
x1 = cos(2*pi*t*300); x2 = cos(2*pi*t*400);
ha = phased.ULA('NumElements',10,'ElementSpacing',1);
ha.Element.FrequencyRange = [100e6 300e6];
fc = 150e6;
x = collectPlaneWave(ha,[x1 x2],[10 20;60 -5]',fc);
noise = 0.1*(randn(size(x))+1i*randn(size(x)));
hdoa = phased.BeamscanEstimator('SensorArray',ha,...
    'OperatingFrequency',fc,...
    'DOAOutputPort',true,'NumSignals',2);
[y,doas] = step(hdoa,x+noise);
doas = broadside2az(sort(doas),[20 -5]);
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