Keysight Technologies N4373D, User Manual

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Measurement Concepts
56
Keysight
N4373D Lightwave Component Analyzer, User’s Guide
Using the above relationships, we can rewrite S
21
in terms of the
transducer responsivities R
s
and R
r
:
It is convenient to express the transducer functions
logarithmically in decibels. The system power gain from a Z
0
source to a Z
0
load can be defined using the above relationships:
S
21
b
2
a
1
------
=
I
2

I
1

---------
=
R
r
P
   
P

R
s
  
--------------------------
=
R
s
R
r

=
a
1
2
Power incident on the E/O converter =
Power delivered to a
S
21
2
b
2
2
a
1
2
------------
=
R
s
R
r
 2
=
System power gain =
20log
10
S
21
System gain in dB =
20log
10
R
s
R
r

=