First calibrations of power sensors up to a frequency of 170 GHz

In the last three years, the frequency range for the calibration of radio frequency (RF) power sensors at PTB has been extended from 110 GHz to 170 GHz. This was advanced both within the framework of an industrial cooperation and, in parallel, by research and comparison measurements with other metrology institutes within the EU metrology research project “TEMMT”. Since the beginning of 2021, several national and international customers already have placed orders for calibration services.

New applications originating from research and industry are raising the need for precise measurement technology at ever higher frequencies. Directional radio and communication systems, such as mobile radio and wireless computer networks, are covering frequency ranges up to 60 GHz already for some time. While the current mobile radio standard 5G still remains below 100 GHz, the successor standard 6G will likely be applied well above 100 GHz. Applications like radar or radio telescopes already cover almost the entire millimeter-wave range from about 30 GHz up to 330 GHz, or even go beyond that into the submillimeter or terahertz range.

The challenges for traceable measurements of the quantity RF power consist in the construction and characterization of a calorimetric measurement set-up (PTB in-house construction) and the availability of suitable primary and transfer standards. For the latter reason, frequency range extensions from 50 GHz upwards at PTB were carried out in close cooperation with industry, to not only ensure unit realization and reproduction, but also the dissemination of the measurand quantity.

First measurements on suitable standards already took place at PTB in 2019, and relative measurement uncertainties of about 3 % were achieved (see Figure). Further measurements in the EU project “TEMMT” followed, and in 2021 PTB started the calibration service for RF power up to 170 GHz. If transfer standards are used which cannot be calibrated directly with the PTB microcalorimeter set-up, the measurement uncertainty presently is increased by about one to two percentage points, since a suitable transfer set-up needs to be involved.

Figure: Calibration result of the generalized efficiency (left panel) of a thermoelectric RF sensor measured with a microcalorimeter set-up (right panel)

Department 2.2 „ High Frequency and Electromagnetic Fields“