phased.RootWSFEstimator

Root WSF direction of arrival (DOA) estimator for ULA

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Description

The RootWSFEstimator object implements a root weighted subspace fitting direction of arrival algorithm.

To estimate the direction of arrival (DOA):

  1. Create the phased.RootWSFEstimator object and set its properties.

  2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

estimator = phased.RootWSFEstimator
estimator = phased.RootWSFEstimator(Name=Value)

Description

estimator = phased.RootWSFEstimator creates a root WSF DOA estimator System object™, estimator. The object estimates the direction of arrival of the signal using the root weighted subspace fitting (WSF) algorithm with a uniform linear array (ULA).

estimator = phased.RootWSFEstimator(Name=Value) creates object, estimator, with each specified property Name set to the specified Value. You can specify additional name-value arguments in any order as (Name1=Value1,...,NameN=ValueN).

example

Properties

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Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

ULA sensor array, specified as a phased.ULA System object. If you do not specify any name-value pair properties for the ULA sensor array, the default properties of the array are used.

Signal propagation speed, specified as a real-valued positive scalar. Units are in meters per second. The default propagation speed is the value returned by physconst("LightSpeed").

Example: 3e8

Data Types: single | double

Operating frequency, specified as a positive scalar. Units are in Hz.

Example: 1e9

Data Types: single | double

Source of number of signals, specified as "Auto" or "Property".

If you specify "Auto", the phased.RootWSFEstimator System object estimates the number of signals by using the method specified by the NumSignalsMethod property.

Method to estimate number of signals, specified as "AIC" or "MDL".

  • "AIC" — Akaike Information Criterion

  • "MDL" — Minimum Description Length Criterion

Note

To specify NumSignalsMethod property, you must specify the NumSignalsSource property as "Auto".

Number of signals to estimate Root WSF DOA, specified as a positive scalar.

Note

To specify NumSignals property, you must specify the NumSignalsSource property as "Property".

Data Types: single | double

Iterative method to estimate Root WSF DOA, specified as "IMODE" or "IQML".

Maximum number of iteration, specified as a positive integer.

Data Types: single | double

Usage

Syntax

ANG = estimator(X)

Description

ANG = estimator(X) estimates the broadside angle ANG from the specified channels X.

Note

The object performs an initialization the first time the object 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.

example

Input Arguments

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Channels to estimate spatial spectrum, specified as a P-by-Q matrix. P is the number of elements in the sensor array and Q is the number of channels.

The size of the first dimension of the input matrix can vary to simulate a changing signal length. A size change can occur, for example, in the case of a pulse waveform with variable pulse repetition frequency.

Data Types: single | double

Output Arguments

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Broadside angles, returned as a Q-element row vector. Q is the number of channels. Units are in degrees.

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

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stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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First, estimate the DOAs of two signals received by a standard 10-element ULA with element spacing of 1 meter. The antenna operating frequency is 150 MHz. The actual direction of the first signal is 10° in azimuth and 20° in elevation. The direction of the second signal is 45° in azimuth and −5° in elevation.

Create the signals with added noise. Then, create the ULA System object™.

fs = 8000;
t = (0:1/fs:1).';
x1 = cos(2*pi*t*300);
x2 = cos(2*pi*t*400);
array = phased.ULA(NumElements=10,ElementSpacing=1);
array.Element.FrequencyRange = [100e6 300e6];
fc = 150.0e6;
x = collectPlaneWave(array,[x1 x2],[10 20; 45 60]',fc);
noise = 0.1*(randn(size(x)) + 1i*randn(size(x)));

Construct WSF estimator System object.

estimator = phased.RootWSFEstimator(SensorArray=array, ...
    OperatingFrequency=fc, ...
    NumSignalsSource="Property",NumSignals=2);

Estimate the DOAs.

doas = estimator(x + noise);
doas = broadside2az(sort(doas),[20 -5])

doas =

   10.0002   20.7934

Algorithms

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References

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

Extended Capabilities

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Version History

Introduced in R2011a

See Also

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