Documentation

phased.RootWSFEstimator System object

Package: phased

Root WSF direction of arrival (DOA) estimator

Description

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

To estimate the direction of arrival (DOA):

  1. Define and set up your root WSF DOA estimator. See Construction.

  2. Call step to estimate the DOA according to the properties of phased.RootWSFEstimator. The behavior of step is specific to each object in the toolbox.

Construction

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

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

Properties

SensorArray

Handle to sensor array

Specify the sensor array as a handle. The sensor array must be a phased.ULA object.

Default: phased.ULA with default property values

PropagationSpeed

Signal propagation speed

Specify the propagation speed of the signal, in meters per second, as a positive scalar.

Default: Speed of light

OperatingFrequency

System operating frequency

Specify the operating frequency of the system in hertz as a positive scalar. The default value corresponds to 300 MHz.

Default: 3e8

NumSignalsSource

Source of number of signals

Specify the source of the number of signals as one of 'Auto' or 'Property'. If you set this property to 'Auto', the number of signals is estimated by the method specified by the NumSignalsMethod property.

Default: 'Auto'

NumSignalsMethod

Method to estimate number of signals

Specify the method to estimate the number of signals as one of 'AIC' or 'MDL'. 'AIC' uses the Akaike Information Criterion and 'MDL' uses the Minimum Description Length Criterion. This property applies when you set the NumSignalsSource property to 'Auto'.

Default: 'AIC'

NumSignals

Number of signals

Specify the number of signals as a positive integer scalar. This property applies when you set the NumSignalsSource property to 'Property'.

Default: 1

Method

Iterative method

Specify the iterative method as one of 'IMODE' or 'IQML'.

Default: 'IMODE'

MaximumIterationCount

Maximum number of iterations

Specify the maximum number of iterations as a positive integer scalar or 'Inf'. This property is tunable.

Default: 'Inf'

Methods

cloneCreate root WSF DOA estimator object with same property values
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
isLockedLocked status for input attributes and nontunable properties
releaseAllow property value and input characteristics changes
stepPerform DOA estimation

Examples

Estimate the DOAs of two signals received by a standard 10-element ULA with element spacing 1 m. 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 45 degrees in azimuth and 60 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;45 60]',fc);
rng default;
noise = 0.1/sqrt(2)*(randn(size(x))+1i*randn(size(x)));
hdoa = phased.RootWSFEstimator('SensorArray',ha,...
    'OperatingFrequency',fc,...
    'NumSignalsSource','Property','NumSignals',2);
doas = step(hdoa,x+noise);
az = broadside2az(sort(doas),[20 60])

References

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

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