ARLA/CLUSTER: Novo tipo de antena evita sinais indesejados

[João Costa > CT1FBF]

New radio antenna avoids unwanted signals

Physicsworld report that a new, simpler, cheaper and potentially more
effective way to prevent radio antennas from picking up unwanted
signals has been created by researchers in the US.

With further development, the technique could also be used to help
prevent thermophotovoltaic cells from re-emitting radiation they
absorb – according to the team.

The laws of electromagnetism work exactly the same way if you run time
in the opposite direction. One logical consequence of this is that an
antenna designed to broadcast at a certain radio frequency will also
be very good at absorbing radiation at that frequency. This 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 their operation. While there are ways of
minimizing the effect of these echoes, they can be expensive and
reduce the performance of the antenna.

Now, Andrea Alù and colleagues at the University of Texas at Austin
have developed a new way of dealing with echoes. Their design is based
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

Read the full Physicsworld article
http://physicsworld.com/cws/article/news/2016/mar/29/new-radio-antenna-avoids-unwanted-signals