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Are metamaterial antennas nonreciprocal?

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fishyxl

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Hi, my friends,
Just a few days ago, my friend showed me a metamaterial antenna, which is made up of a monopole surrounded by the metamaterial (left-hand material, printed periodic structure). As we know, when the waves come at the metamaterial, it acts like a lens, the waves will be concentrated and the Directivity will be improved (when n==0).
But what will happen if this antenna is a receive antenna. As I see, when the plane wave arrives at the metamaterial, it will not act in the same way as it is the transmit antenna.
If you have insights into this antenna, can you share your experience and tell me whether it conforms to the reciprocity theorem like the ordinary antennas?
Thank you very much
 

fishyxl,could pls upload ur antenna u talk about ,here,may we can comment about it
regards
 

Since the metamaterial antenna is made up of a feed (like monopole or horn or other antennas) and a lens (the metamaterials), it is similar to the reflector antennas. Therefore I will make a comparision between these two antennas and I have attached a drawing to illustrate my wiewpoints better.
In Figure 1, we can find the reflector antenna. When transmit, the EM waves from the horn will be transformed into plane wave by the reflector, and its gain will be enhanced. When receives, the plane wave will be absorbed by the horn according to the well-known optical theorems. In this way, we can claim that the reflector antenna is reciprocal. Next we shall deal with the metamaterial antenna. When transmit, as the n of the metamaterial equals to 0 (shown in Figure 2), plane wave will be generated like the a line source in a zero-index medium you mentioned. But what will happen when the antenna receives? As the metamaterials are made up of homogeneous periodic structures, I think the plane wave may be directed to another direction and will not be directed to the monopole antenna. (Please take a look at the attachment).
Looking forward to your reply!
Thank you!
 

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