phased.UCA

Uniform circular array

Description

The phased.UCA System object™ creates a uniform circular array (UCA). A UCA is formed from identical sensor elements equally spaced around a circle.

To compute the response for the array for specified directions:

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

2. Call step to compute the response according to the properties of phased.UCA. 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

sUCA = phased.UCA creates a uniform circular array (UCA) System object, sUCA, consisting of five identical isotropic antenna elements,phased.IsotropicAntennaElement. The elements are equally spaced around a circle of radius 0.5 meters.

sUCA = phased.UCA(Name,Value) creates a System object, sUCA, 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).

sUCA = phased.UCA(N,R) creates a UCA System object, sUCA, with the NumElements property set to N and the Radius property set to R. This syntax creates a UCA consisting of isotropic antenna elements, phased.IsotropicAntennaElement.

sUCA = phased.UCA(N,R,Name,Value) creates a UCA System object, sUCA, with the NumElements property set to N, the Radius property set to R, and other specified property Names set to the specified Values.

Properties

Element — phased array element

isotropic antenna element System object with default properties (default) | Phased Array System Toolbox™ antenna, microphone, or transducer element System object | Antenna Toolbox™ antenna System object

Phased array element, specified as a Phased Array System Toolbox antenna, microphone, or transducer element or Antenna Toolbox antenna.

Example: phased.CosineAntennaElement

NumElements — Number of array elements

5 (default) | integer greater than one

Number of array elements, specified as an integer greater than one.

Example: 3

Radius — Array radius

0.5 (default) | positive scalar

Array radius, specified as a positive scalar in meters.

Example: 2.5

ArrayNormal — Array normal direction

'z' (default) | 'x' | 'y'

Array normal direction, specified as one of 'x', 'y', or 'z'. UCA elements lie in a plane orthogonal to the array normal direction. Element boresight vectors lie in the same plane and point radially outward from the origin.

ArrayNormal Property Value	Element Positions and Boresight Directions
'x'	Array elements lie on the yz-plane. All element boresight vectors lie in the yz-plane and point outward from the array center.
'y'	Array elements lie on the zx-plane. All element boresight vectors lie in the zx-plane and point outward from the array center.
'z'	Array elements lie on the xy-plane. All element boresight vectors lie in the xy-plane and point outward from the array center.

Example: 'y'

Taper — Element tapering

1 (default) | complex-valued scalar | complex-valued 1-by-N row vector | complex-valued N-by-1 column vector

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

Example: [1 2 3 2 1]

Methods

Specific to phased.UCA Object
beamwidth	Compute and display beamwidth of an array
collectPlaneWave	Simulate received plane waves
directivity	Directivity of uniform circular array
getElementNormal	Normal vectors for array elements
getElementPosition	Positions of array elements
getElementSpacing	Spacing between array elements
getNumElements	Number of elements in array
getTaper	Array element tapers
isPolarizationCapable	Polarization capability
pattern	Plot UCA array pattern
patternAzimuth	Plot UCA array directivity or pattern versus azimuth
patternElevation	Plot UCA array directivity or pattern versus elevation
perturbations	Perturbations defined on phased array
perturbedArray	Apply perturbations to phased array
perturbedPattern	Compute and plot azimuth pattern of perturbed array
step	Output responses of array elements
viewArray	View array geometry

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

Examples

Pattern of 11-Element UCA Antenna Array

Create an 11-element uniform circular array (UCA) having a 1.5 m radius and operating at 500 MHz. The array consists of short-dipole antenna elements. First, display the vertical component of the response at 45 degrees azimuth and 0 degrees elevation. Then plot the azimuth and elevation directivities.

antenna = phased.ShortDipoleAntennaElement(...
    'FrequencyRange',[50e6,1000e6],...
    'AxisDirection','Z');
array = phased.UCA('NumElements',11,'Radius',1.5,'Element',antenna);
fc = 500e6;
ang = [45;0];
resp = array(fc,ang);
disp(resp.V)

   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247
   -1.2247

Display the azimuth directivity pattern at 500 MHz for azimuth angles between -180 and 180 degrees.

c = physconst('LightSpeed');
pattern(array,fc,[-180:180],0,'Type','directivity','PropagationSpeed',c)

Display the elevation directivity pattern at 500 MHz for elevation angles between -90 and 90 degrees.

pattern(array,fc,[0],[-90:90],'Type','directivity','PropagationSpeed',c)

Algorithms

A UCA is formed from N identical sensor elements equally spaced around a circle of radius R. The circle lies in the xy-plane of the local coordinate system whose origin lies at the center of the circle. The positions of the elements are defined with respect to the local array coordinate system. The circular array lies in the xy-plane of the coordinate system. The normal to the UCA plane lies along the positive z-axis. The elements are oriented so that their main response directions (normals) point radially outward in the xy-plane.

If the number of elements of the array is odd, the middle element lies on the x-axis. If the number of elements is even, the midpoint between the two middle elements lies on the x-axis. For an array of N elements, the azimuth angle of the position of the nth element is given by

$${\phi }_n=(-(N-1)/2+n-1)\cdot 360/Nn=1,\dots ,N$$

The azimuth angle is defined as the angle, in the xy-plane, from the x-axis toward the y-axis. The elevation angle is defined as the angle from the xy-plane toward the z-axis. The angular distance between any two adjacent elements is 360/N degrees. Azimuth angle values are in degrees. Elevation angles for all array elements are zero.

References

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

[2] Van Trees, H. Optimum Array Processing. New York: Wiley-Interscience, 2002, pp. 274–304.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• pattern, patternAzimuth, patternElevation, plotResponse, and viewArray methods are not supported.

• See System Objects in MATLAB Code Generation (MATLAB Coder).

Version History

Introduced in R2015a