
Lighter, Cheaper Radio Wave Device Could Transform Telecommunications - shitehawk
http://www.utexas.edu/news/2014/11/10/radio-wave-device-alu/
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aethertap
I had no idea what a circulator was or what purpose it served. The wikipedia
link has a good description of what it is, and the pdf link is a paper about
how to achieve full duplex radio operation, and shows where the circulator
fits into the picture.

1\.
[https://en.wikipedia.org/wiki/Circulator](https://en.wikipedia.org/wiki/Circulator)

2\.
[http://web.stanford.edu/~skatti/pubs/sigcomm13-fullduplex.pd...](http://web.stanford.edu/~skatti/pubs/sigcomm13-fullduplex.pdf)

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_Adam
My initial impression is that this is a very significant advance; enabling
full-duplex on a single frequency band effectively doubles the communication
bandwidth. But, I'm not sure if this translates to the real world.

Can any RF engineers comment on this?

~~~
Aloha
No. The circulator itself is not a new invention, this is just a new way of
building them.

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CamperBob2
Not clear how this is different from any other Wheatstone bridge-like
structure used for directional sensing at microwave frequencies. Lower loss,
presumably? Active circulators by themselves aren't new (
[https://www.google.com/?gws_rd=ssl#safe=off&q=wenzel+active+...](https://www.google.com/?gws_rd=ssl#safe=off&q=wenzel+active+circulator)
).

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createacc123
This is not an active circulator, there are no amplifiers. It's a parametric-
modulated circulator - the capacitance is modulated. Not a new concept in
microwave engineering. Not very useful in real-life: the PR-heavy letter
neglects to mention (1) the poor instantaneous bandwidth <0.5% (figure 4c),
(2) the poor linearity / poor power handling: Vm and Vdc are few volts in
high-Q environment, which translates into maximum power handling well below
0dBm (3) the high sensitivity to analog component variation (fig 4c again) -
not something you want in mass-produced components operating at
commercial/industrial temperature ranges.

They neglected to mention the power level they used to measure the
S-parameters in the letter or the supplementary material. No self-respecting
RF engineer would forget to mention power levels - it again hints at very poor
linearity / poor power handling. Typical university "research".

