Interference of UWB to other services

[Debeli]

I am interested if there any comments about interference of UWB to other services (or vice-versa) up to 10 GHz. For reminder, by FCC recommendation 15 the limit is set up on -41.3 dBm/MHz with some lower values (-75 dBm/MHz) in 1-3 GHz.
I especially invite people involved in radioastronomy or passive satelite servicees to make comments. They should be not only oriented on UWB interference and can include some comments on other unintentional radiators.

Many thanks
D.

 

[sergio mariotti]

Thanks for invite!
by definition, astrophysical scientists wants the highest possible sensitivity, namely confusion limit. Such sensitivity is incompatible with any human emission.

Follow my personal opinion:
Practically speaking, some techniques, like VLBI, are largely insensitive to local received RFI.
Single dish observation, especially on the continuum, are limitated by Equivalent Flux (the G/T parameter for telecommunication people), by the atmosphere drift, by strong traditional RFI, etc. etc. So the UWB emission are now at the end of the list of limitation effects.

In any case, RFI still remain one of the most important cause of radio blindness :-(

 

[Debeli]

Thank you very much for your response. I would like to take an opportunity and post a few additional questions.
First, for qlarification I shall guess that VLBI is Very Large Base Integration or something like it, how it can suppress many noise-like interferers?
Second, I would like to consider a following scenario: we have flat densely populated land like the Nederlands and radioastronomical observatory that starts to track an object low above the horisont (take 10 or 15 degrees measured to the earth surface as starting elevation angle, I do not know actualy what are realistic values for such large dish). We can assume that the interference from a village few km away can be accepted through a sidelobe of the antenna. Is it possible that several thousends devices that are compatible to proposed limits in aggregate make harmfull interference? What are actually the expectad values of sidelobe gains for radioastronomy antennas (is there some recommendation or article)? Can interference noise from large city like Amsterdam 200 km away also be accepted due tropospheric sccater or similar propagation effect?

I would be glad if I got comment on any of these questions I posted.
Thank you very much again.

 

[sergio mariotti]

Thank you very much for your response. I would like to take an opportunity and post a few additional questions.
First, for qlarification I shall guess that VLBI is Very Large Base Integration or something like it, how it can suppress many noise-like interferers?

Very Long Baseline Interferometry.
The antennas are thousands kilometers far each one, the received signal is then correlated, so intrinsecally a local RFI will not be correlated. In your country (NL ?), ASTRON is a partner of JIVE, the institute that host the big correlator.

Is it possible that several thousends devices that are compatible to proposed limits in aggregate make harmfull interference?

Yes it's! For many reason: technical and "political".

What are actually the expectad values of sidelobe gains for radioastronomy antennas (is there some recommendation or article)?

It's very variable vs antenna type and scientific project.
For 20+ meters Diameter paraboloid, usually 1st side lobe is <-20dB

Can interference noise from large city like Amsterdam 200 km away also be accepted due tropospheric sccater or similar propagation effect?

Generally tropo scatter levels apply to X band and are a low level signal.
I'think the big "enemies" for radioastronomy are the terrestrial broadcasting (20KW TX power), the Radars (1MW TX power)
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