A new, simpler, cheaper and potentially more effective way to prevent radio antennas from picking up unwanted signals has been created by researchers at University of Texas, Austin, United States.

It is hoped with further development of the technique could also be used to help prevent thermophotovoltaic cells from re-emitting radiation they absorb.

The laws of electromagnetism work exactly the same way if you run time in the opposite direction. One logical consequence of the design is to broadcast at a certain radio frequency will also absorb radiation at that frequency.

This issue is problematic for broadcast radio antennas, which will absorb radiation that has bounced back from surrounding objects – something that can have a negative impact on operation.

The team at the University of Texas have based their design on a traditional leaky-wave antenna, in which electromagnetic waves of certain frequencies couple to the space around the antenna and "leak out" as they travel along it

Full story - http://physicsworld.com/cws/article/news/2016/mar/29/new-radio-antenna-avoids-unwanted-signals