MM0474
(6) 1 - Power Standard Assembly, SK-D-4850-18-7 (P/N MT9024-30-7).
(7) 1 - Adapter, Model 11528A.
(8) 1 - Case, SK-681000 (P/N MT9024-11).
(9) 1 - Cushion Insert, SK-D-4850-19 (P/N MT9024-12 and -13).
d. Application.
(1) The Power Standards Set contains power standard assemblies which are
basic instruments for precision microwave power measurements and as a means to
accurately monitor power in a circuit without terminating all of the power in
the measuring device. These devices are used as a standard of comparison for
calibrating other power measuring devices connected to the coupler main arm
output or for any case of making accurate-in-line measurements of incident
power. The basis of a power standard assembly as shown in Figure 17 is the
"Power Standard Calibration Factor" defined as:
(2) Where Pdc substituted is equal to DC power substituted in the
thermistor element and P wave incident is equal to microwave power incident to
a non-reflective load terminating the coupled main arm output.
(3) The thermistor mount is of the broadband variety, and is attached to
the auxiliary arm of a high directivity directional coupler as shown in Figure
17. The calibration factor, Kc, is measured at specific frequencies within the
band and includes the effects of mismatch between thermistor mount and coupler
auxiliary arm, and the bolometer mount efficiency.
(4) When Kc is known for the power standard assembly, it is then
possible to determine an unknown incident power by measuring Pdc substituted.
Figure 17.
Power standard assembly.
133
Previous Page
