Radio Frequency Integrated Circuit Design - Webs

Issues in RFIC Design, Noise, Linearity, and Filtering
F = i 2 ns + |i n + v nY s | 2
i 2 ns
= N o (total)
No (source)
15
(2.18)
This can also be interpreted as the ratio of the total output noise to the
total output noise due to the source admittance.
In (2.17), it was assumed that the two input noise sources were correlated
with each other. In general, they will not be correlated with each other, but
rather the current in will be partially correlated with v n and partially uncorrelated.
We can expand both current and voltage into these two explicit parts:
in = ic + iu
vn = vc + vu
In addition, the correlated components will be related by the ratio
ic = Y c v c
where Yc is the correlation admittance.
The noise figure can now be written as
NF = 1 + i 2 u + |Yc + Ys | 2 v 2 c + v 2 u |Ys | 2
i 2
ns
(2.19)
(2.20)
(2.21)
(2.22)
The noise currents and voltages can also be written in terms of equivalent
resistance and admittance (these resistors would have the same noise behavior):
R c =
R u =
Gu =
Gs =
v 2 c
4kT�f
v 2 u
4kT�f
i 2 u
4kT�f
i 2 ns
4kT�f
(2.23)
(2.24)
(2.25)
(2.26)