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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?

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.

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2 Answers

Answer by Bert Jan Keultjes on 15 Oct 2019
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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, Bert, thank you for your kind and valuable answer.
Congratulations on your success in designing 3 element yagi.
I also used another software, NEC2. Using the values obtained by NEC2 another calculation is performed by using MATLAB.
Then, I thought the calculations using NEC2 could be replaced with those using Antenna Toolbox.

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Answer by Bert Jan Keultjes on 17 Oct 2019

Hi Saito, Clear. Several sientists have already applied varactors in microwave antennas. But few on vhf. The starting point is normale sizes for the lowest frequency added with about 5 %. A funny thing is that, for a limited bandwidth you can turn a reflector into a director and a director into reflector. So change directivity by 180 degrees.

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