Noise figure and minimum detectable signal

Thread Starter

baby_2

Joined Jan 6, 2017
11
Hello
Here is my circuit that I want to calculate minimum Si

Here is book calculations
\( NF_{act}=1+(NF_{stan}-1)(\frac{T_{0}}{T_{s}})=1+(6.3-1)(\frac{290}{2000})=1.769 \)
\( NF_{act}=\frac{(S/N)i}{(S/N)o}=>S_{i}=N_{i}+NF_{act}+(S/N)_{o} , N_{i}=10Log(K(Ts)Bw) \)

my problem is that why did the writer calculate NF @Ts=2000 because the receiver is not at the Ts=2000 and we calculate Ts for input noise.Am I right?
and if we should calculate NF system for input antenna temperature what should we do for this system? how can calculate NF(act)

In addition , Could you introduce me a good reference with a lot examples in NF and its calculation with their solutions to improve myself in NF?

Thanks in advance
 
Last edited:

Thread Starter

baby_2

Joined Jan 6, 2017
11
Dear Papabravo
Thanks for your comment and taking your time.
Actually I am seeking the answer of my question in the first post not the only online computation.
yes , the Ta and T0 are in kelvin
 

Papabravo

Joined Feb 24, 2006
21,158
Can you explain the use of the very high Kelvin temperatures? A system temperature of 293 °K ≡ 20 °C ≡ 68 °F makes sense to me. 2000 °K and 3000 °K are both hotter than molten steel.
Also, what value are you using for k (Boltzman's Constant). If you are going to multiply k, Ts, and Bw together you better have the units right or the answer will be nonsense.
Do you ever track your units when working on a problem?
The units for Boltzman's constant are Joules/°K, the units for temperature, according to you, are °K, and bandwidth has units of sec^(-1). Is that what was intended?
It is true that Joules per second is the same thing as watts.
 
Last edited:
Top