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step

System object: phased.BeamscanEstimator2D
Package: phased

Perform 2-D 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 matrix representing the magnitude of the estimated 2-D spatial spectrum. Y has a row dimension equal to the number of elevation angles specified in ElevationScanAngles and a column dimension equal to the number of azimuth angles specified in AzimuthScanAngles.

[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 two row matrix where the first row represents the estimated azimuth and the second row represents the estimated elevation (in degrees).

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.

    Note:   The object performs an initialization the first time the step method is executed. This initialization locks nontunable properties (MATLAB) 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

expand all

Estimate the DOAs of two sinusoidal signals received by a 50-element URA with a rectangular lattice. The antenna operating frequency is 150 MHz. The actual direction of the first signal is -37° in azimuth and 0° in elevation. The direction of the second signal is 17° in azimuth and 20° in elevation.

Create the signals and solve for the DOA's.

fs = 8000;
t = (0:1/fs:1).';
x1 = cos(2*pi*t*300);
x2 = cos(2*pi*t*400);
array = phased.URA('Size',[5 10],'ElementSpacing',[1 0.6]);
array.Element.FrequencyRange = [100e6 300e6];
fc = 150e6;
x = collectPlaneWave(array,[x1 x2],[-37 0; 17 20]',fc);
noise = 0.1*(randn(size(x)) + 1i*randn(size(x)));
estimator = phased.BeamscanEstimator2D('SensorArray',array, ...
    'OperatingFrequency',fc, ...
    'DOAOutputPort',true,'NumSignals',2, ...
    'AzimuthScanAngles',-50:50, ...
    'ElevationScanAngles',-30:30);
[~,doas] = estimator(x + noise)
doas =

   -37    17
     0    20

Plot the spatial spectrum.

plotSpectrum(estimator)

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