High isolation of side by side subarrays
High isolation of side by side subarrays
(OP)
Dears
In microwave and millimeter communication, diplexer is used for division of TX and RX. But one of our supplier provide a solution by two high isolated side by side subarrays. By the 75dB~90dB isolation(with same polarization), the diplexer can be obviated. I guess this merits is obtain by super high supressed sidelobe. I suppose this idea is borrowed from satelite communication, but I'm not sure whether the spectrum utilization is improved? For example, the whole frequency band both applied to TX and RX. This idea is revolutionary, for the FDD and TDD both thrown to the history, and more free configuration of the channel become reality.
Anyone with deep background can solve the puzzle for me.
Thank you
Lewis
In microwave and millimeter communication, diplexer is used for division of TX and RX. But one of our supplier provide a solution by two high isolated side by side subarrays. By the 75dB~90dB isolation(with same polarization), the diplexer can be obviated. I guess this merits is obtain by super high supressed sidelobe. I suppose this idea is borrowed from satelite communication, but I'm not sure whether the spectrum utilization is improved? For example, the whole frequency band both applied to TX and RX. This idea is revolutionary, for the FDD and TDD both thrown to the history, and more free configuration of the channel become reality.
Anyone with deep background can solve the puzzle for me.
Thank you
Lewis
RE: High isolation of side by side subarrays
Other than some niche applications (e.g. certain low power Doppler radar applications), I can't think of any communications systems that use full duplex on a single (Tx and Rx) frequency. In theory, one could null out any one frequency, but the sidebands wouldn't be precisely nulled.
Some full duplex systems are sensitive even to Passive Intermodulation (PIM) in the cables, connectors, and any mounting hardware within the beam.
RE: High isolation of side by side subarrays
http://www.ehow.com/list_7551272_13-ghz-microwave-...
http://www.commconnect.com/wp-content/uploads/2011...
This could possibly be done with polarization separation, i.e., H/V or right/left. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&a...
Seems like there are analogies to conventional wired comm duplexing, ala RS-232.
TTFN
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RE: High isolation of side by side subarrays
TTFN
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RE: High isolation of side by side subarrays
I've followed all the links and I didn't see anything that indicated that anyone had cracked the nut of achieving full duplex using only a single frequency (Tx and Rx full duplex within one channel). It would be very exciting if it's been made practical. Did I miss a detail on those references?
RE: High isolation of side by side subarrays
Although, some people claim to have done it:
http://sing.stanford.edu/fullduplex/
TTFN
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RE: High isolation of side by side subarrays
They mention 45dB and 73dB cancellation.
The 45dB is not at all impressive; that could be achieved with the twigs and a bit of moss
The 73dB is achieved "in the digital domain". Of course, these are the easy 73dB (at the fat end). If a practical system needs (for example) 146dB isolation to match the system path loss (so that the Rx signal can stand above the local Tx signal), then they've got a lot more work to do at the more difficult tiny end.
They should look into the echo cancellation techniques used by long distance telephone carriers. They should feed forward a clean sample of the Tx signal to the DSP so that it knows what to look for. Correlate and kill. Repeat because there will be multiple echoes. The practical implementation may involve significant buffering and thus latency. Latency is the enemy of high speed bi-directional data. It should be integrated with the demodulating and data decoding.
Years ago I invented an application for this sort of technology to make crypto voice systems more usable. It got buried by the company. Oh well, ideas are a dime a dozen.
RE: High isolation of side by side subarrays
I want to explain the system with more detail. For Eband(71~86G), the pathloss is 92.4+20*log80Ghz+20*log2km=136.4dB, and each subarray's gain is 40dB, so the receive singnal will attenuate 136.4-40*2=56.4dB, if we plus addtional rain and oxygen effect, it will be larger.And without additional bandpass filter, the isolation of locate end is 75~90dB, which is not enough for same channel working of TX and RX.
But what I concerned is the double reflection of feed line can also cause a -30dB weaker echo. And the multipath reflection also can cause a -25dB echo. So what's the difference of this echos with the locate end leakage? Further more, if the leakage obvious tiny than the RSL from far end, do this decreased the correlation and cancellation work load? Of course,if same channel working is impossible, the adjacent channel working of TX and RX also make it a superior virtual diplexer with high isolation, low group delay, and reconfigutable.
BTW, the antenna is fully integrated planar subarrays.
RE: High isolation of side by side subarrays
RE: High isolation of side by side subarrays
If you E plane couple and they are real close to each other, it's a 30 dB worse problem.
Isolation needs to be defined too. Input to output single connector is different than individual antenna Tx to Rx antenna. You can swamp a Rx input amp and still pretend isolation out the Rx connector is ok.
RE: High isolation of side by side subarrays
RE: High isolation of side by side subarrays
http://www.ubnt.com/airfiber
RE: High isolation of side by side subarrays
http://etrij.etri.re.kr/Cyber/Download/PublishedPa...
If I understand it (?), then it's simply a hybrid combination of FDD (frequency division) and TDD (time division). Thus it still avoids the present-day-impossibility of full duplex on a single radio channel.