5G operation at mmWave frequencies relies on beamforming technology through antenna arrays with many elements. As the industry strives to reduce the size and cost of producing these 5G beamforming devices operating at mmWave, many of them lack conventional external RF ports, becoming integrated Antenna-in-Package (AiP) and Antenna-in-Module (AiM) devices. This industry shift presents a tough challenge for engineers in charge of characterization and validation of integrated beamforming designs, prompting them to look for accurate, over-the-air (OTA), radiated test solutions.

One challenge in OTA far-field (FF) characterization is to keep the measurement accuracy high and the measurement errors low. This can be done by calibrating out as much as possible systematic errors of the measurement system as well as analyzing the resulting measurement uncertainty. The key for doing such an analysis is an accurate transmission model including for example the effects of the measurement instrument, the measurement chamber as well as the used antennas. When having an accurate measurement model, including the system-level artifacts that influence the measurement results, one can derive a common measurement and calibration methodology, that should provide measurement results of the DUT. These measurement results should be independent of the measurement system. Artifacts that cannot be calibrated away will end up in the uncertainty budget. Also, the repeatability of the measurement system will be part of the uncertainty budget. Being able to formulate the measurement model, the calibration process and the uncertainty budget in combination with a demonstration of the approach across 3 measurement systems will ultimately increase the acceptance of the obtained results.

This project is to develop an OTA FF methodology in Tx and Rx direction as well as to implement calibration techniques to reduce the error budget and estimate the uncertainty of key characteristics and its derived quantities. This shall also include OTA measurement methodology results from NIST as well as 3GPP. The OTA FF measurement methodology shall be validated using three independent measurement systems where the measurement results shall be compared and correlated through the uncertainty budget between the different approaches. First the focus shall be on continuous wave (CW) measurements taking into account that measurements under modulation conditions shall be investigated at a later stage and correlated to the CW measurements. As reference test device, a phased array antenna (PAA) with corresponding information will be provided that is used for all measurements to ensure comparability. One specific goal of the work is to learn about improvements for the test architecture by applying novel calibration techniques and analyzing as well as reducing the measurement uncertainty. A long-term goal is to align the methodology with the NIST OTA FF measurement methodology to allow for traceable measurements.

This research position (within the electromagnetics group in the faculty of electrical engineering) takes place in cooperation with industrial and academic partners.

• PhD degree (or soon to defend) in electrical engineering or similar.
• Familiar with metrology and uncertainty estimation.
• Background in antennas and/or RF technology is preferred.
• Ability to work independently with a systematic approach.
• Fluently spoken and written English.

• Challenging job in a dynamic and ambitious university and a stimulating internationally renowned research environment.
• Full-time temporary appointment for 2 years.
• The gross salary for a post-doc researcher lies between € 3.255 and € 4.274, depending on experience and knowledge.
• An extensive package of fringe benefits (e.g. excellent technical infrastructure, the possibility of child care and excellent sports facilities).
• Moreover, an 8% holiday allowance and 8.3% end-of-year allowance is provided annually.