Not to belittle their announcement, but what textbook says you can't filter a signal? Or is the novelty in the degree to which they had to filter the outgoing signal?
They put the receiver in a "node" of destructive interference between two transmitting antennas. That way, the transmitting signal doesn't swamp the receiver.
> ... but what textbook says you can't filter a signal ...
i don't think any textbooks makes that claim. from the article: ...a researcher even told the students their idea was "so simple and effective, it won't work," because something that obvious must have already been tried unsuccessfully.
The much larger signal (local TX) would always capture your RF chain, being that using standard selectivity techniques in the analog domain the unwanted looks exactly like the desired. Being so large, it also would generally saturate your receiver.
