Question about system noise figure calculation when every block noise figure is known

Status
Not open for further replies.

hmsheng

Full Member level 4
Joined
Dec 17, 2003
Messages
219
Helped
26
Reputation
52
Reaction score
10
Trophy points
1,298
Location
China
Activity points
1,556
If the noise figure of each block in the receiver is known, we can calculate the total noise figure of the system with the cascade noise figure formula. The calculation is based on the condition that all the blocks are matched to 50 Ohm. But this is not the fact! So the calulated result should be no sense.

Any comment on my viewpoint?
 

system noise figure

I don't think so.
the input is terminated in 50 ohms, the kTB noise level at room temperature in a 1 Hz bandwidth is –174 dBm, so it will affact NF values.
but the system NF is determined by Friis equation.
if you use 75ohm system maynot be -174dBm BW, but sys NF should change accordingly.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…