MATLAB: In Antenna Toolbox, is it possible to analyze type of ESPAR (Electronically Steerable Passive Array Radiator) antenna which consists of parasitic elements with variable capacitance

Antenna Toolboxparasitic (non-fed) elementvariable capacitor

In Antenna Toolbox, is it possible to design a type of ESPAR (Electronically Steerable Passive Array Radiator) antenna?

ESPAR antenna consists of one fed element (active element) and several parasitic (non-fed) elements.

The parasitic elements are conntected by variable capacitor to change the reactance of the element to form a desired directivity.

As I checked, Yagi-Uda antenna model cannot set capacitance connected to directors or reflectors.

Also, in array antenna model, any antenna elements need to be fed. In other words, no parasitic element is set in the model.

Which model or in which way, we can design such type of antennas.

Best Answer

Hi Saito, I also can't find a possibility to do this. However I built such antennas. A 3 elements yagi for 87 till 108 Mhz. It has 3 varactors BB640. I can tune it remote with 3 potmeters and it works pretty good. Also for 174 till 227 Mhz.

I used mmana to design it. However it shouldn't be very difficult to integrate this in a tool like antenna toolbox.

Bert Jan pa1bj

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Hi Shahar,

The plot is of directivity, not gain (confusingly, directivity is sometimes called directive gain). Since directivity is determined by using the total radiated power, the input power to the antenna does not matter. But to find gain = directivity x [radiated power / input power], the input power must be known. Since this antenna is a theoretical construct, you are free to assume the input power is the same as the radiated power, in which case gain and directivity are the same thing. For a more realistic case you could add resistivity to the antenna elements (not having the antenna toolbox I don't know how the toolbox would give you radiated power vs input power, but I'm sure it will). You could also take the half wave dipole input impedance of 73.1 ohms and assume a mismatch between that value and the output impedance of the driving source. That will lead to wasted power, an antenna efficiency less than 1, and reduced gain.

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Hi Pomisov,

There are two ways you can see the directivity information.

The first one is to plot the radiation pattern. For example

fc = 3e8; c = 3e8;
h = phased.ULA(4,0.5);
plotResponse(h,fc,c,'format','polar')

You can also use ArrayGain. It is the SNR gain achieved by the array compared to a single element. It is not exactly the directivity but it is related to that.

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h = phased.ULA(4,0.5);
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g = step(hag,fc,[0;0])

HTH,

Best Answer

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