whats state of the art in microwave noise floor?

[CopperCone]

What is considered state of the art for a 'experimental' laboratory receiver?

I figure that radio astronomy might have the best equipment, but they also have big dishes, so I am not sure what field to look at.

If compared to a spectrum analyzer, -? dBm.. I guess like -220dBm?

are there cryogenic equivalents to things like squids?

[KJDS]

Without cooling, I've done LNAs at 2GHz with 0.3dB noise figure. Thermal noise floor in a 1Hz bandwidth in 50ohms is -174dBm. That can be reduced by cooling. Noise = kTBR with T in Kelvin, so you need to get to -120 degrees C to half the noise floor, ie a 3dB improvement.

[CopperCone]

what kind of LNA is that?

[retrolefty]

what kind of LNA is that?

 An expensive one I bet. 

[CopperCone]

me too. Is it a wideband amplifier you put into a spectrum analyzer with spectrum limited?

Are there special coaxial cables? Does a regular good coaxial cable (like rf141) work at -100C? How about liquid nitrogen temps?

I would be interested in getting an amplifier setup that uses liquid nitrogen (i have a dewar)... liquid helium is off the budget right now though.

[DaJMasta]

I think in Dave's video to the Canberra DSN comm center they mentioned that they could get a usable signal at -160 to -165dB or so using cryo cooled LNAs directly on the back of the antenna.  I'd imagine that in a lab environment you could do better, maybe a couple orders of magnitude, but I think it's a real tall order to get to even -200dBm without a ton of software averaging noise reduction or something.... even then, that's quite a ways below the stuff I've heard of.

[Antonio84e]

Once you have a good LNA with very low noise floor then, as KDJS was saying, Noise = kTB. If you want to lower the noise floor, you are going to need a good filter. Do you know the bandwidth you require to cover?

[CopperCone]

I was looking for more a 'near theoretical measurements' graph as a go to. I don't have a specific signal in mind.

A case study if you will.