New to LNA design, how to plot NF vs. freq?
时间：04-09
整理：3721RD
点击：
It must be simple because I cannot find a definitive source on this.
Maybe I should start at the beginning to make sure I understand the .noise command.
.noise V(OUT) VS
OUT is the where I want to measure the noise voltage, the plot output of this voltage is ONOISE. The output noise is referenced back to a source VS and the plot output of this voltage is INOISE.
noise factor is (the sum of the squares of each noise referenced back to the input)/(square of the noise from the input resistance): F=1+ blah blah blah.
How do I get from the ONOISE and INOISE to a noise figure?
I have figured out S11 which is zin-50/zin+50
Maybe I should start at the beginning to make sure I understand the .noise command.
.noise V(OUT) VS
OUT is the where I want to measure the noise voltage, the plot output of this voltage is ONOISE. The output noise is referenced back to a source VS and the plot output of this voltage is INOISE.
noise factor is (the sum of the squares of each noise referenced back to the input)/(square of the noise from the input resistance): F=1+ blah blah blah.
How do I get from the ONOISE and INOISE to a noise figure?
I have figured out S11 which is zin-50/zin+50
what software do you use for simulation, if you are using ADS, you can easily plot NF/freq, gain/freq, S paramter/freq in a plot.
typically if u have the output noise voltage , u can clculate the NF
is related to [ noise out /(gian * noise i)] , then u can use equation to calculate the NF
khouly
I am using LTspice
But I figured it out, posted here to prevent more suffering!
plot 10log10[V(inoise)^2/4kT(Rsource)]
It is easier on you to define a .func nfig(x)=10log10[(x^2)/4kT(Rsource)] and plot the function nfig(Vinoise)
use the ADS and it is very easy