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Sensor Array Analyzer

Analyze beam pattern of linear, planar, and conformal sensor arrays

Description

The Sensor Array Analyzer app enables you to construct and analyze common sensor array configurations. These configurations range from 1-D to 3-D arrays of antennas and microphones.

After you specify array parameters, the app displays basic performance characteristics such as array directivity and array dimensions. You can then create a variety of plots and images.

You can use this app to generate the directivity of the following arrays:

  • Uniform Linear Array (ULA)

  • Uniform Rectangular Array (URA)

  • Uniform Circular Array

  • Uniform Hexagonal Array

  • Circular Plane Array

  • Concentric Array

  • Spherical Array

  • Cylindrical Array

  • Arbitrary Geometry

Available Elements

The following elements are available to populate an array:

  • Isotropic Antenna

  • Cosine Antenna

  • Omnidirectional Microphone

  • Cardioid Microphone

  • Custom Antenna

Available Plots

The Sensor Array Analyzer app can create the following plots:

  • Array Geometry

  • 2D Array Directivity

  • 3D Array Directivity

  • Grating Lobes

Open the Sensor Array Analyzer App

  • MATLAB® Toolstrip: On the Apps tab, under Signal Processing and Communications, click the app icon.

  • MATLAB command prompt: Enter sensorArrayAnalyzer.

Examples

expand all

This example shows how to analyze a 10-element uniform linear array (ULA) in a sonar application with omnidirectional microphones.

A uniform linear array has sensor elements that are equally-spaced along a line.

Set the Array Type to Uniform Linear and the Element Type to Omnidirectional Microphone.

Design the array to find the arrival direction of a 10 kHz signal by setting Signal Frequencies to 10000 and the Element Spacing to 0.5 wavelengths.

Set the signal Propagation Speed to equal the speed of sound in water, 1500 m/s.

In the View dropdown menu, choose the Array Geometry option to draw the shape of the array.

Next, examine the directivity of the array. To do so, select 2D Array Directivity in the View drop-down list. The 2-D array directivity is shown below.

You can see the mainlobe of the array directivity function (also called the main beam) at 0° and another mainlobe at ±180°. Two mainlobes appear because of the cylindrical symmetry of the ULA array.

A beamscanner works by successively pointing the array mainlobe in different directions. Setting the Steering option to On lets you steer the mainlobe in the direction specified by the Steering Angles option.

In this case, set the steering angle to [30;0] to point the mainlobe to 30° in azimuth and 0° elevation. In the next figure, you can see two mainlobes, one at 30° as expected, and another at 150°. Again, two mainlobes appear because of the cylindrical symmetry of the array.

A disadvantage of the ULA is its large side lobes. An examination of the array directivity shows two side lobes close to each mainlobe, each down by about only 13 dB. A strong sidelobe inhibits the ability of the array to detect a weaker signal in the presence of a larger nearby signal. By using array tapering, you can reduce the side lobes.

Use the Taper option to specify the array taper as a Taylor window with Sidelobe Attenuation set to 30 dB. The next figure shows how the Taylor window reduces all side lobes to –30 dB—but at the expense of broadening the mainlobe.

This example shows how to construct a 6-by-6 uniform rectangular array (URA) designed to detect and localize a 100 MHz signal.

Set the Array Type to Uniform Rectangular, the Element Type to Isotropic Antenna, and the Size to [6 6].

Design the array to find the arrival direction of a 100 MHz signal by setting Signal Frequencies to 100e+6 and the row and column Element Spacing to 0.5 wavelength.

Set both the Row Taper and Column Taper to a Taylor window.

The shape of the array is shown in the figure below.

Finally, display the 3-D array directivity by setting the View option to 3D Array Directivity, as shown in the following figure:

A significant performance criterion for any array is its array directivity. You can use the app to examine the effects of tapering on array directivity. Without tapering, the array directivity for this URA is 17.2 dB. With tapering, the array directivity loses 1 dB to yield 16.0 dB.

This example shows the grating lobe diagram of a 4-by-4 uniform rectangular array (URA) designed to detect and localize a 300 MHz signal.

Set the Array Type to Uniform Rectangular, the Element Type to Isotropic Antenna, and the array Size to [4 4].

Set the Signal Frequencies to 300e+6.

By setting the row and column Element Spacing to 0.7 wavelengths, you create a spatially undersampled array.

This figure shows the grating lobe diagram produced when you beamform the array towards the angle [20,0]. The mainlobe is designated by the small black-filled circle. The multiple grating lobes are designated by the small unfilled black circles. The larger black circle is called the physical region, for which u2+ v2 ≤ 1. The mainlobe always lies in the physical region. The grating lobes may or may not lie in the physical region. Any grating lobe in the physical region leads to an ambiguity in the direction of the incoming wave. The green region shows where the mainlobe can be pointed without any grating lobes appearing in the physical region. If the mainlobe is set to point outside the green region, a grating lobe moves into the physical region.

The next figure shows what happens when the pointing direction lies outside the green region. In this case, one grating lobe moves into the physical region.

This example shows how to construct a triangular array of three isotropic antenna elements.

You can specify an array which has an arbitrary placement of sensors. In this example, the elements are placed at [0,0,0]', [0,1,0.5]', and [0,0,0.866]'. All elements have the same normal direction [0,20], pointing to 0° in azimuth and 20° in elevation.

Plot the 3-D array directivity in polar coordinates.

This example shows how to specify an array which has an arbitrary placement of sensors, but in this case, create MATLAB variables or arrays at the command line and use them in the appropriate sensorArrayAnalyzer fields

At the MATLAB command line, create an element position array, pos, an element normal array, nrm, and a taper value array, tpr.

pos = [0,0,0;0,1,0.5;0,0,0.866];
nrm = [0,0,0;20,20,20];
tpr = [1,1,1];

Enter these variables in the appropriate sensorArrayAnalyzer fields.

Related Examples

Introduced in R2014b

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