Does this mean there have been non-solid-state receivers at this frequency? Or is this a use of 'solid state' I'm not familiar with?
http://en.wikipedia.org/wiki/Backward_wave_oscillator http://apl.aip.org/applab/v93/i14/p141108_s1?isAuthorized=no http://www.sron.nl/index.php?option=com_content&view=art...
It looks like the existing receivers at this frequency range are of the heterodyne type, possibly without any RF gain. A heterodyne receiver mixes the RF signal with a local RF oscillator, which results in a lower frequency IF signal which is easier to work with.
At these frequencies, it looks like the local oscillator is a "backward wave oscillator" or a "quantum cascade laser", and the mixer is some kind of esoteric non-linear device like a "hot electron bolometric mixer", whatever that means.
The highest frequency amplifier I know of is the "traveling-wave tube" amplifier, which goes up to something like 50 GHz. It's a crazy vacuum tube device and it's found on satellite transmitters. Making these things solid-state would be awesome because the tubes take up so much space and power on the satellites.
Summary: There are vacuum tubes that operate in this range, and there are receivers without gain in this range.
"quantum cascade laser"
"hot electron bolometric mixer"
"traveling-wave tube"
Computer scientists, take note: start naming your ideas like this and you will get more grant money.
But personaly I don't like the term as it is not as clear-cut in all peoples perspectives. You could say one solid-state is digital and non solid state is not 100% digital. Though some would also argue that digital is mearly a perception of measurement in a analogue World.
I'll let you read the wiki on it and draw your own conclusions:
http://en.wikipedia.org/wiki/Solid-state_(electronics)http://en.wikipedia.org/wiki/Solid-state_physics#Crystal_str...