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Isotropic Antenna Element

Support for Isotropic Antenna Elements

An isotropic antenna element radiates equal power in all nonbaffled directions. To construct an isotropic antenna, use phased.IsotropicAntennaElement. When you use this object, you must specify these aspects of the antenna:

  • Operating frequency range of the antenna

  • Whether the response of the antenna is baffled at azimuth angles outside the interval [–90,90]

You can find your isotropic antenna element's voltage response at specific frequencies and angles using the antenna element's step method.

Backbaffled Isotropic Antenna

This example shows how to construct a backbaffled isotropic antenna element with a uniform frequency response over azimuth angles from [–180,180] degrees and elevation angles from [–90,90] degrees. The antenna operates between 300 megahertz (MHz) and 1 gigahertz (GHz). Plot the antenna response at 1 GHz.

ha = phased.IsotropicAntennaElement(...
    'FrequencyRange',[3e8 1e9],'BackBaffled',false)
plotResponse(ha,1e9,'RespCut','3D','Format','Polar',...
    'Unit','pow');

plotResponse is a method of phased.IsotropicAntennaElement. By default, plotResponse plots the response of the antenna element in decibels (dB) at zero degrees elevation.

figure;
plotResponse(ha,1e9);

Setting the BackBaffled property to true limits the response to azimuth angles in the interval [–90,90].

ha.BackBaffled=true;
figure;
plotResponse(ha,1e9,'RespCut','3D','Format','Polar',...
    'Unit','pow');

Element Response of Backbaffled Isotropic Antenna Element

This example shows how to design a backbaffled isotropic antenna element and obtain the response of that element.

Construct an isotropic antenna element to operate in the IEEE® X band between 8 and 12 GHz. Backbaffle the response of the antenna. Obtain your antenna element's response at 4 GHz intervals between 6 and 14 GHz and at azimuth angles between –100 and 100 in 50-degree increments.

ha = phased.IsotropicAntennaElement(...
    'FrequencyRange',[8e9 12e9],'BackBaffled',true)
respfreqs = 6e9:4e9:14e9;
respazangles = -100:50:100;
anresp = step(ha,respfreqs,respazangles)

The antenna response in anresp is a matrix whose row dimension equals the number of azimuth angles in respazangles and whose column dimension equals the number of frequencies in respfreqs.

The response voltage in the first two and last two columns of anresp is zero because those columns contain the antenna response at 6 and 14 GHz respectively. These frequencies are not included in the antenna's operating frequency range.

Similarly, the first and last rows of anresp contain all zeros because the BackBaffled property is set to true. The first and last row contain the antenna's response at azimuth angles outside of [–90,90].

To obtain the antenna response at nonzero elevation angles, input the angles to step as a 2-by-M matrix where each column is an angle in the form [azimuth;elevation].

release(ha)
respelangles = -90:45:90;
respangles = [respazangles; respelangles];
anresp = step(ha,respfreqs,respangles)

Note that anresp(1,2) and anresp(5,2) represent the antenna voltage response at the aziumth-elevation pairs (–100,–90) and (100,90). Because the elevation angles are equal to +/– 90 degrees, these responses are equal to one even though the BackBaffled property is set to true. Thus, the resulting elevation cut degenerates into a point.

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