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Comparing NEP and noise temperature?

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Feb11-13, 03:33 PM
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So I don't have a lot of noise theory background (or, really, any) and I'm having trouble with this. I'm hoping someone can expalin and/or point me to some good resources for looking these things up (I have access to a good academic library, so I should be able to get any not-too-obscure resource).

I have a pair-breaking-based photon detector and an amp. I know the noise temperature for the amp, and I know the NEP for the detector and I need to compare them (to make sure I'm not going to be amp noise limited). Is there a reasonable way to convert between noise temp and NEP?

Alternatively, in principle I know everything about the detector (I designed it), so I suppose I ought to be able to calculate the noise temperature of the detector, but I don't know how. What about if I imagine I am photon (shot) noise limited in the detector? (not quite true, but a reasonable simple case to start with). How would one calculate the noise temp of the detector then?
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Feb12-13, 07:35 AM
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I don't think the two are equivalent, when talking about noise temperature it is implied that the amplifier is impedance matched to the source. I am not sure how you would apply that to a "generic" detector.
However, there is nothing stopping you from just relating them using Te=NEP/kB*B, where B is the bandwidth of your system. Then Te would be the temperature of a resistor with some value R that is sending out a noise power equivalent to your NEP.

But again, I suspect this would only be suitable for a detector that is actually matched to the load, say a power detector in a MW system.

Btw, what kind of detector are we talking about? Kinetic indctance?
Feb12-13, 11:16 AM
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Quote Quote by f95toli View Post
what kind of detector are we talking about? Kinetic indctance?
Yes, I'm getting together a test setup for a LEKID. Finding I've been spending too much time worrying about the solid state theory end of things, and not nearly enough time thinking about the practical electronics side of things.

Thanks for the response.

For future folks finding this thread by googling their problems, there's some helpful info for amp noise in kinetic inductance detectors in Jonas Zmuidzinas's 2012 paper in Annual Review of Condensed Matter Physics.

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