A Background to Return Loss Measurement Return Loss Measurement
Agilent 8163A/B, 8164A/B, and 8166A/B User’s Guide, Fourth Edition 177
To measure the front panel delta you must measure the power
transmitted through the reference cable, “Measuring the Power
Transmitted Through the Reflection Reference” on page 172, and the
power transmitted through the measurement cable, see “Measuring
the Power Transmitted Through the Measurement Patchcord” on
page 173. The system may be represented by Figure 114:
Figure 114 Generalization of a Return Loss Measurement
The transmitted power, (E), is directly proportional P
src
.
That is:
The constant a is a multiplier giving the proportion of power that the
light source emits that is measured by the power meter.
The constants a
Ref
and a
Meas
apply to the setups described in
“Measuring the Power Transmitted Through the Reflection
Reference” on page 172 and in “Measuring the Power Transmitted
Through the Measurement Patchcord” on page 173 respectively.
This gives the following two equations:
If we divide equation 11 by equation 12, this gives the following
equation:
The loss variation, ∆L, due to exchanging the reference cable for the
measurement cable is given by:
Power Meter
E
Agilent 81610A
Reflection Reference
P
src
EaP
src
=
(12)
E
Ref
a
Ref
P
src
=
(13)
E
Meas
a
Meas
P
src
=
(14)
E
Ref
E
Meas
-------- -------
a
Ref
a
Meas
------- -------=
(15)
∆L 10–
a
Ref
a
Meas
------ --------10–
E
Ref
E
Meas
------- --------log=log=
(16)
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