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4-4
Section IV – Operating Instructions
P
SubM
= Power measured terminating mount
P
SubF
= Power measured Feed-through mount
In all calibrations, calibration factors are transferred from a terminating reference, to a feed-through
stand, and then into the DUT. In some procedures, this transfer occurs all in one session, and in others
time is saved by transferring into the feed-through once and then using that feed-through calibration
factor to calibrate DUT for some time.
In a perfect world, the terminating sensor would present a perfect load, and then by reorganizing the
above two definitions with incident and output power equal, we would have,
𝑘
𝑀
=
𝑘
𝐹
𝑃
𝑆𝑆𝑆𝑀
𝑃
𝑆𝑆𝑆𝐹
Because power sensors are always imperfect loads, additional analysis and sometimes correction is
required.
Figure 4.1 shows a signal flow diagram of two one-port devices connected together. The left-hand port is
the “output”, or “generator” port and is designated on the diagram using the subscript, “g”. The right-
hand port is the “input”, or “load” port and is designated using the subscript “l”. It’s clear from the
diagram that port reflections dominated by the Gamma vectors generally cause the power that the
generator port would output into an ideal load,
𝑃
𝑔
𝑧0
, to not be equal to the power
𝑃
𝑖
, incident on the load.
We really have to take into account the combination of reflections, or “port match” to come up with a
general understanding of calibration transfer.
Start with the signal flow diagram. In this case, a Generator “g” is represented by an ideal source “s”,
and its port reflection, and the sensor is termed the load, “l”.
