An isotropic antenna element radiates equal power in all directions.
If the antenna element is backbaffled, the antenna radiates equal
power in all directions for which the azimuth angle satisfies *–90
≤ φ ≤ 90* and zero power in all other
directions. To construct an isotropic antenna, use the `phased.IsotropicAntennaElement`

System object™.
When you use this object, you must specify these antenna properties:

The operating frequency range of the antenna using the

`FrequencyRange`

property.Whether or not the response of the antenna is backbaffled at azimuth angles outside the interval

*[–90,90]*using the`BackBaffled`

property.

You can determine the voltage response of the isotropic antenna
element at specified frequencies and angles using the `step`

method.

This example shows how to construct a backbaffled isotropic antenna element with a uniform frequency response over a range of azimuth angles from [-180,180] degrees and elevation angles from [-90,90] degrees. The antenna operates between 300 Mhz and 1 GHz.

sIsoAnt = phased.IsotropicAntennaElement(... 'FrequencyRange',[300e6 1e9],'BackBaffled',false); pattern(sIsoAnt,1e9,[-180:180],[-90:90],'CoordinateSystem','polar',... 'Type','power')

Using the antenna `pattern`

method, plot the antenna response at zero degrees elevaton for all azimuth angles at 1 GHz.

pattern(sIsoAnt,1e9,[-180:180],0,'CoordinateSystem','rectangular',... 'Type','powerdb')

Setting the `BackBaffled`

property to `true`

restricts the antenna response to azimuth angles in the interval [-90,90] degrees. In this case, plot the antenna response in three dimensions.

sIsoAnt.BackBaffled = true; pattern(sIsoAnt,1e9,[-180:180],[-90:90],'CoordinateSystem','polar',... 'Type','power')

This example shows how to design a backbaffled isotropic antenna element and obtain its response. First, construct an X-band isotropic antenna element that operates from 8 to 12 GHz setting the `Backbaffle`

property to `true`

. Obtain the antenna element response at 4, 10, and 14 GHz at azimuth angles between -100 and 100 degrees in 50 degree increments. All elevation angles are by default equal to zero.

sIsoAnt = phased.IsotropicAntennaElement(... 'FrequencyRange',[8e9 12e9],'BackBaffled',true); respfreqs = [6:4:14]*1e9; respazangles = -100:50:100; anresp = step(sIsoAnt,respfreqs,respazangles)

anresp = 0 0 0 0 1 0 0 1 0 0 1 0 0 0 0

The antenna response in `anresp`

is a matrix having row dimension equal to the number of azimuth angles in `respazangles`

and column dimension equal to the number of frequencies in `respfreqs`

. The response voltage in the first and last columns of `anresp`

are zero because those columns contain the antenna response at 6 and 14 GHz, respectively. These frequencies lie outside the antenna operating frequency range. Similarly, the first and last rows of `anresp`

contain all zeros because `BackBaffled`

property is set to `true`

. The first and last row contain the antenna 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(sIsoAnt) respelangles = -90:45:90; respangles = [respazangles; respelangles]; anresp = step(sIsoAnt,respfreqs,respangles)

anresp = 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0

Notice that `anresp(1,2)`

and `anresp(5,2)`

represent the antenna voltage response at the azimuth-elevation angle pairs (-100,-90) and (100,90) degrees. Although the azimuth angles lie in the baffled region, because the elevation angles are equal to +/- 90 degrees, the responses are unity. In this case, the resulting elevation cut degenerates to a point.

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