This is warmed over news. What the authors describe is a way to implement in effect the combination of a circulator and an antenna. The previous paper (referenced in the Reg article) described just a circulator.
Circulators are non-reciprocal and usually use lumps of magnetised ferrite. They were used in early mobile phones (and in a host of other systems to this day) to allow a single antenna to be used for both Tx and Rx, but methods were developed of making duplexers that didn't need circulators (and indeed worked better). GSM didn't need a duplexer anyway as it is in effect TDD (like Wi-Fi), but 3G and 4G phones do. (Actually there is a new generation of sub-miniature ferrite circulators now available that are finding their way back into phones to help solve the multi-band nightmare.)
Another way to make a circulator is to use an active device such as an amplifier (which amplify one way but normally not the other). Another type of active device is a parametric amplifier which works by "pumping" a variable capacitor at a different frequency from the one you're trying to amplify - it needs input RF power just as a conventional amplifier needs input DC power. Since a major design criterion for a duplexer is power loss (attenuation), having to put additional power *into* a device to make it work is not very attractive.
Parametric amplifiers were quite popular in the 60s when RF transistors were poor but you could use things like klystrons to generate RF power as a pump, but generally are now an engineering footnote. I remember doing a whole exam course on "non-linear and parametric circuits" in my degree, just in timefor them to go out of fashion.
As power consumption is a major issue for mobile devices, I think this technology will remain a curiosity at least for mainstream systems.
Biting the hand that feeds IT
