phased.MVDREstimator

MVDR (Capon) spatial spectrum estimator for ULA

Description

The MVDREstimator object computes a minimum variance distortionless response (MVDR) spatial spectrum estimate for a uniform linear array. This DOA estimator is also referred to as a Capon DOA estimator.

To estimate the spatial spectrum:

Define and set up your MVDR spatial spectrum estimator. See Construction.
Call step to estimate the spatial spectrum according to the properties of phased.MVDREstimator. The behavior of step is specific to each object in the toolbox.

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.

Construction

H = phased.MVDREstimator creates an MVDR spatial spectrum estimator System object, H. The object estimates the incoming signal's spatial spectrum using a narrowband MVDR beamformer for a uniform linear array (ULA).

H = phased.MVDREstimator(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`
`NumPhaseShifterBits`	Number of phase shifter quantization bits The number of bits used to quantize the phase shift component of beamformer or steering vector weights. Specify the number of bits as a non-negative integer. A value of zero indicates that no quantization is performed. Default: `0`
`ForwardBackwardAveraging`	Perform forward-backward averaging Set this property to `true` to use forward-backward averaging to estimate the covariance matrix for sensor arrays with conjugate symmetric array manifold. Default: `false`
`SpatialSmoothing`	Spatial smoothing Specify the number of averaging used by spatial smoothing to estimate the covariance matrix as a nonnegative integer. Each additional smoothing handles one extra coherent source, but reduces the effective number of element by 1. The maximum value of this property is M–2, where M is the number of sensors. Default: `0`, indicating no spatial smoothing
`ScanAngles`	Scan angles Specify the scan angles (in degrees) as a real vector. The angles are broadside angles and must be between –90 and 90, inclusive. You must specify the angles in ascending order. Default: `-90:90`
`DOAOutputPort`	Enable DOA output To obtain the signal's direction of arrival (DOA), set this property to `true` and use the corresponding output argument when invoking `step`. If you do not want to obtain the DOA, set this property to `false`. Default: `false`
`NumSignals`	Number of signals Specify the number of signals for DOA estimation as a positive scalar integer. This property applies when you set the `DOAOutputPort` property to true. Default: `1`

Methods

plotSpectrum	Plot spatial spectrum
reset	Reset states of MVDR spatial spectrum estimator object
step	Perform spatial spectrum estimation

Common to All System Objects
`release`	Allow System object property value changes

Examples

collapse all

Estimate DOA of Two Signals Using MVDR

Open Live Script

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 60° in azimuth and −5° in elevation. Then, plot the MVDR spatial spectrum.

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;60 -5]',fc);
noise = 0.1*(randn(size(x)) + 1i*randn(size(x)));

Construct MVDR estimator System object.

estimator = phased.MVDREstimator('SensorArray',array,...
    'OperatingFrequency',fc,'DOAOutputPort',true,'NumSignals',2);

Estimate the DOAs.

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

doas = 1×2

    9.5829   60.3813

Plot the spectrum.

plotSpectrum(estimator)

Figure contains an axes object. The axes object with title MVDR Spatial Spectrum, xlabel Broadside Angle (degrees), ylabel Power (dB) contains an object of type line. This object represents 1 GHz.