## Simulating objects in FarField of Antenna

How to use openEMS. Discussion on examples, tutorials etc

Moderator: thorsten

samarth2020
Posts: 3
Joined: Fri 04 Sep 2020, 08:43

### Simulating objects in FarField of Antenna

I have a series-fed patch antenna whose far-field region starts at (8* lambda) units. There is a dielectric lens structure (compresses the beam) placed well in to the far-field of the antenna at about (30* lambda) units. If I use a nf2ff function to create the box around the lens and antenna volume, it will be in the far field of the antenna and I am not getting the correct directivity and beam pattern. I am presuming it should be placed within the near field of the antenna (as the name suggests). However, if I place it within the near field (8*lambda) will it still be able to correctly incorporate the effects of the lens placed in the far-field? What is the best way to find the resultant far-field properties of this combination?
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thorsten
Posts: 1464
Joined: Mon 27 Jun 2011, 12:26

### Re: Simulating objects in FarField of Antenna

A lot of details here are unclear or make little sense to me.
First of the far field of an antenna is hard to define exactly but in this case it should be well below one lambda (not 8 or something).
The question is what you want to do here? Why do you want to place a lens this far away? Usually a lense like this is placed very close on top of the antenna....

I'm really not sure how to answer your question as I'm not sure what you want to simulate...

samarth2020
Posts: 3
Joined: Fri 04 Sep 2020, 08:43

### Re: Simulating objects in FarField of Antenna

Hi Thorsten,

I guess I was not entirely clear. I was referring to the Fraunhofer distance i.e. 2*D^2/lambda as the far field distance. In my case D = 2* lambda, therefore, Fraunhofer distance = 8* lambda.

My application requires me to place the lens really far off from the antenna at about 30 * lambda. This is well in to the Fraunhofer region. I want to study the effect of this lens on the antenna, namely, the resultant directivity and beam pattern. In majority of the cases a nf2ff box around the antenna would suffice. But this may not be true for my case. How do I incorporate the effect of this far away lens ?