Measurement concepts for new, highly integrated antennas

• Applicant: Professor Dr.-Ing. Christian Waldschmidt
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251770065

This proposal is a subsequent application to the DFG project with the topic Measurement Technique Concepts for Highly Integrated Antennas. The main focus of the project were in-depth analyses of measurement concepts and of the achievable measurement accuracy for the characterization of integrated antennas from 100 GHz to 300 GHz.Minimal sensor sizes and large available absolute bandwidths lead to a high research interest towards integrated sensors in the millimeter wave range. However, the characterization of the required integrated antennas is challenging, as the small structure sizes and the short wavelengths require elaborate measurement setups. Due to the small chip dimensions the contacting fixtures, which are used to feed the antenna, are in the immediate surrounding of the AUT and are usually much bigger than the device under test itself. This leads to large systematic measurement errors. After the measurement accuracy has been improved considerably through a thorough error analysis of the setup, the remaining error mechanisms, like wafer probe reflections or interaction with bond wires and the packages, are now to be analyzed in detail. First, the desired direct radiation from the antenna is separated from the unwanted reflections to obtain the radiated field of the isolated antenna. By comparing the thereby filtered fields to the original measurements, a better understanding of the occurring error mechanisms and interactions can then be obtained. Two algorithms are employed for this, namely MARS and source reconstruction.Identifying the influence of bond wires and package can, however, be difficult due to the strong reflections from the wafer probe. Therefore, a new measurement method is realized to allow phase measurements of an AUT that is fed by a signal generated directly on the chip, instead of a signal supplied through a wafer probe from an external source.Post processing of the measurement data can also allow the characterization of integrated antennas with lower-priced standard probes. Until now accurate measurements of integrated antennas are only possible when wafer probes are used that are optimized for antenna measurements. Reflections and shadowing of the signal behind standard probes cause large measurement errors that inhibit meaningful measurements. Therefore, the post processing algorithms are used to reconstruct the actual radiation pattern and to locate the reflection centers of the probe.The accuracy of antennas can be calculated with gain and directivity of an antenna. So far the accuracy of the determined efficiency is limited by errors in the integrated antenna gain measurement. In order to improve efficiency measurements, a detailed analysis of errors, which occur in gain comparison measurements, is conducted.

• DFG Programme: Research Grants