If you look at the thermal analysis, it is incomplete. They are only considering the thermal noise of the reflector. The noise temperature of an antenna is a function of temperature AND aperture efficiency, with the latter set by the conductivity of the reflector. Plasma is not a great conductor (compared to metal), as is shown by the nested antennas. High performance satcom (e.g. NASA DSN) not only cool the electronics, they cool the feeds also.
There is another paper where they show a tube covering a LNB. Looks like some BS. I don’t see any actual measurements of noise temperature (which are very easy to do).
I didn’t see any of the papers published in IEEE APS.
I design antennas for a living, and this sets my BS detector off, and it did 10 years ago too. They look fine for TX (the patterns look good), but the noise data is conspicuously absent.
Here is another noise analysis, but again it is incomplete. Just show some measurements.
If you look at plasma attenuation of a reentry body, it’s about 30 dB. Even a thin sheet of foil or perforated screen is way more (> 100 dB).
They just need to hook an antenna to a spectrum analyzer (with low noise path) and measure the noise density. If it is anywhere slightly above -174 dBm/Hz, then it is not going to function well as a satcom antenna.
That picture they show of the tube taped onto the LNB feed, they say it “intercepted” the signal. Do they mean it blocked it? Sure, it will if the plasma is conductive enough, but it should also drop the noise coming out of the receiver. Maybe it swamped the receiver with noise. Can’t tell. If they can pattern the lower frequency antennas, they can certainly take the time to do some noise measurements.
Maybe the issue is exciting the plasma, and that is noisy. I’d think you couldn’t do it with pulse excitation unless you limited the rise time. You could do it with CW, say a magnetron, way outside your operating band.
http://nebula.wsimg.com/d0cadaec2cf44c9682cebb1610ce1a91?Acc...
If you look at the thermal analysis, it is incomplete. They are only considering the thermal noise of the reflector. The noise temperature of an antenna is a function of temperature AND aperture efficiency, with the latter set by the conductivity of the reflector. Plasma is not a great conductor (compared to metal), as is shown by the nested antennas. High performance satcom (e.g. NASA DSN) not only cool the electronics, they cool the feeds also.
There is another paper where they show a tube covering a LNB. Looks like some BS. I don’t see any actual measurements of noise temperature (which are very easy to do).
http://nebula.wsimg.com/48f10bd80f702313a1d8d094fc7d6b01?Acc...
I didn’t see any of the papers published in IEEE APS.
I design antennas for a living, and this sets my BS detector off, and it did 10 years ago too. They look fine for TX (the patterns look good), but the noise data is conspicuously absent.
Here is another noise analysis, but again it is incomplete. Just show some measurements.
http://nebula.wsimg.com/754ac5460a5e1531953c79dd1c4863b7?Acc...