Theory of Operation
Coaxial RF Power Standards Instruction and Service Manual
4-5
CALIBRATION FACTORS
For a Terminating RF Power Standard (M1125, M1130, M1135) K is denoted as the measure
calibration factor (K
1
), and P
RF
is the RF power from a match-terminated source incident upon the
mount. If the mount is connected to the side arm of a coupler or a port of a power splitter (a
Feedthrough RF Power Standard), K is denoted as the monitor calibration factor (K
2
), and P
RF
is
the RF power emerging form the mount into a match terminated load. For a Feedthrough RF
Standard the calibration factor K
2
is given by:
K
2
= P
dc2
P
RF
And P
RF
is given by:
P
RF
= P
dc1
K
1
Where:
K
2
= calibration factor of the Feedthrough RF Power Standard,
P
dc2
= DC substituted power measured by the device connected to the Feedthrough RF Power
Standard,
P
RF
= Level of applied RF power,
P
dc1
= DC substituted power measured by the device connected to the Terminating RF Power
Standard,
K
1
= calibration factor of the Terminating RF Power Standard traceable to NIST
The system determines the calibration factor of the tested mount in terms of the known
calibration factor of the previously calibrated thermistor mount and the precision measurement of
the substituted DC power.
The Feedthrough RF Power Standard is used to determine the calibration factor for other
terminating powers sensors. The calibration factor for a Device Under Test (DUT) is denoted as
K
1S
and is determined by first determining P
RF
:
P
RF
= P
dc2
K
2
The DUT must be connected to a compatible power meter; the readings are then used to
determine the calibration factor of the DUT by:
K
1S
= P
m
P
RF
Where:
P
RF
= Level of applied RF power,
P
dc2
= DC substituted power measured by the device connected to the Feedthrough RF Power
Standard,
K
2
= calibration factor of the Feedthrough RF Power Standard,
K
1S
= calibration factor of the DUT,
P
m
= reading from the DUT compatible power meter.
The calibration factor is ratio of applied vs. measured power. The result of the calibration factor
calculation (K) will be a decimal value, typically between 0 and 1. Calibration factors can also be
represented as a percentage (%) or in decibels (dB):
K(%) = K * 100
K(dB) = 10 *log(K)
