Hi, I'm just confused with the thermal noise power.
We just had an exam.
the question was something like this:
Given an amplifier with a fixed noise figure of 15.6dB, which antenna will give more SNR at the output?
a 50ohm antenna or a 60ohm antenna? (antenna -> input of amp -> amp -> output of amp to next stage) **assuming same bandwidth and same input signal power
So I thought I need to figure out first what is the thermal power of the antenna so that i can get the SNR at the input.
This is where I got problems. in this slide that we used (refer to PAGE 8). it says noise power = variance = 4kTRB, where: k=boltzman constant, T=temp in K, R=resistance, B=bandwith(Hz)
I consulted with my classmates before the class, they told me to do as in the slides.. so I did, but it really gets to me since i've read in other sources that power is independent of resistance since you have to divide the variance with 4R.
Now Pnoise=kTB... Is this the one that should be used in the calculation of input SNR?
Enlighten me please... THanks!
We just had an exam.
the question was something like this:
Given an amplifier with a fixed noise figure of 15.6dB, which antenna will give more SNR at the output?
a 50ohm antenna or a 60ohm antenna? (antenna -> input of amp -> amp -> output of amp to next stage) **assuming same bandwidth and same input signal power
So I thought I need to figure out first what is the thermal power of the antenna so that i can get the SNR at the input.
This is where I got problems. in this slide that we used (refer to PAGE 8). it says noise power = variance = 4kTRB, where: k=boltzman constant, T=temp in K, R=resistance, B=bandwith(Hz)
I consulted with my classmates before the class, they told me to do as in the slides.. so I did, but it really gets to me since i've read in other sources that power is independent of resistance since you have to divide the variance with 4R.
Now Pnoise=kTB... Is this the one that should be used in the calculation of input SNR?
Enlighten me please... THanks!