Radio Frequency Integrated Circuit Design - Webs

Mixers
These two noise sources are voltage-divided at the input by the source
and matching resistors. They will also see the same gain to the output. Thus,
the output noise generated by each of these two noise sources von(source) is
von(source) = v n(source)
2
A v =
1.29 nV
√Hz � 5.6
2
V nV
= 3.6
V √Hz The other noise source of importance is R E . It produces a current
in(R E ) of
in(R E ) = √ 4kT
R E
= 15.3 pA
√ Hz
This current produces an output voltage vno(R E ) of
vno(R E ) = 2
� in(R E ) � 2R L = 7.81 nV
√ Hz
Now the total output noise voltage vno(total) (assuming these are the only
noise sources in the circuit) is
vno(total) = √ (vno(R E )) 2 + (vno(source)) 2 + (vno_source) 2 = 9.32 nV
√ Hz
Thus, the single-sideband noise figure can be calculated by
vno(total)
9.32
NF = 20 log von(source) = 20 � � log� = 11.3 dB
2.54�
√2 Note that in the single-sideband noise figure, only the source noise from
one sideband is considered; thus, we divided by √ 2.
Now the circuit is simulated. The results are summarized in Table 7.3.
The voltage gain was simulated to be 13.6 dB, which is 1.4 dB lower than
what was calculated. The main source of error in this calculation is ignoring
current lost into R cc. Since the impedance of R cc is about ten times that of
the path leading into the quad, it draws 1/10th of the total current causing a
1-dB loss in gain. Thus, in a second iteration, R C could be raised to a higher
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