phased.ULA System object

Package: phased

Uniform linear array

Description

The ULA object creates a uniform linear array.

To compute the response for each element in the array for specified directions:

  1. Define and set up your uniform linear array. See Construction.

  2. Call step to compute the response according to the properties of phased.ULA. The behavior of step is specific to each object in the toolbox.

Construction

H = phased.ULA creates a uniform linear array (ULA) System object™, H. The object models a ULA formed with identical sensor elements. The origin of the local coordinate system is the phase center of the array. The positive x-axis is the direction normal to the array, and the elements of the array are located along the y-axis.

H = phased.ULA(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).

H = phased.ULA(N,D,Name,Value) creates a ULA object, H, with the NumElements property set to N, the ElementSpacing property set to D, and other specified property Names set to the specified Values. N and D are value-only arguments. To specify a value-only argument, you must also specify all preceding value-only arguments. You can specify name-value pair arguments in any order.

Properties

Element

Element of array

Specify the element of the sensor array as a handle. The element must be an element object in the phased package.

Default: An isotropic antenna element that operates between 300 MHz and 1 GHz

NumElements

Number of elements

An integer containing the number of elements in the array.

Default: 2

ElementSpacing

Element spacing

A scalar containing the spacing (in meters) between two adjacent elements in the array.

Default: 0.5

Taper

Element tapering

Element tapering specified as a complex-valued scalar or a complex-valued 1-by-N row vector. In this vector, N represents the number of elements of the array. Tapers, also known as weights, are applied to each sensor elements in the sensor array and modify both the amplitude and phase of the received data. If 'Taper' is a scalar, the same weights are applied to each element. If 'Taper' is a vector, each weight is applied to the corresponding sensor element.

Default: 1

Methods

cloneCreate ULA object with same property values
collectPlaneWaveSimulate received plane waves
directivityDirectivity of uniform linear array
getElementPositionPositions of array elements
getNumElementsNumber of elements in array
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
getTaperArray element tapers
isLockedLocked status for input attributes and nontunable properties
isPolarizationCapablePolarization capability
plotGratingLobeDiagramPlot grating lobe diagram of array
plotResponsePlot response pattern of array
releaseAllow property value and input characteristics
stepOutput responses of array elements
viewArrayView array geometry

Examples

expand all

Plot Response of 4-Element Antenna Array

Create a 4-element undersampled ULA and find the response of each element at boresight. Plot the array response at 1 GHz for azimuth angles between -180 and 180 degrees. The default element spacing is 0.5 meters.

ha = phased.ULA('NumElements',4);
fc = 1e9;
ang = [0;0];
resp = step(ha,fc,ang)
c = physconst('LightSpeed');
plotResponse(ha,fc,c)
resp =

     1
     1
     1
     1

Plot Response of 10-Element Microphone ULA

Construct a 10-element uniform linear array of omnidirectional microphones spaced 3 mm apart. Then, plot the array response at 100 Hz.

hmic = phased.OmnidirectionalMicrophoneElement(...
    'FrequencyRange',[20 20e3]);
Nele = 10;
hula = phased.ULA('NumElements',Nele,...
    'ElementSpacing',3e-3,...
    'Element',hmic);
fc = 100;
ang = [0; 0];
resp = step(hula,fc,ang);
c = 340;
plotResponse(hula,fc,c,'RespCut','Az','Format','Polar');

Plot Response of Array of Polarized Short-Dipole Antennas

Build a tapered uniform line array of 5 short-dipole sensor elements. Because short dipoles support polarization, the array should as well. Verify that it supports polarization by looking at the output of the isPolarizationCapable method.

h = phased.ShortDipoleAntennaElement(...
    'FrequencyRange',[100e6 1e9],'AxisDirection','Z');
ha = phased.ULA('NumElements',5,'Element',h,...
    'Taper',[.5,.7,1,.7,.5]);
isPolarizationCapable(ha)
ans =

     1

Then, draw the array using the viewArray method.

viewArray(ha,'ShowTaper',true,'ShowIndex','All')

Compute the horizontal and vertical responses.

fc = 150e6;
ang = [10];
resp = step(ha,fc,ang);

Display the horizontal polarization response.

resp.H
ans =

     0
     0
     0
     0
     0

Display the vertical polarization response.

resp.V
ans =

   -0.6124
   -0.8573
   -1.2247
   -0.8573
   -0.6124

Plot an azimuth cut of the vertical polarization response.

c = physconst('LightSpeed');
plotResponse(ha,fc,c,'RespCut','Az','Format',...
    'Polar','Polarization','V');

References

[1] Brookner, E., ed. Radar Technology. Lexington, MA: LexBook, 1996.

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

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