Similar to 5G networks and devices supporting mmWave frequencies, antenna systems and RF transceiver modules for future mobile communications standards or automotive radar applications will share the same features that make their testing a challenge. Their wide frequency range, a greater number of antenna elements and the lack of conventional external RF connectors will demand testing over-the-air in a shielded environment. Rohde & Schwarz and Innovations for High Performance Microelectronics (IHP) GmbH have transferred this test method successfully into sub-THz range: They demonstrated the first full 2D/3D over-the-air (OTA) measurements of a radar module at D-Band frequencies.
The test setup consists of the R&S ATS1000 antenna test system, the R&S ZNA43 vector network analyzer and the R&S AMS32 antenna measurement software from Rohde & Schwarz. The R&S ATS1000 antenna test system is a compact and mobile shielded chamber solution for OTA and antenna measurements, ideal for 5G mmWave applications. To cover the D-Band frequencies, extensions from Radiometer Physics GmbH, a Rohde & Schwarz company, are used in the setup, which allow direct frequency conversion at the probe in both transmit and receive directions. No mechanical modifications or additional RF cabling to the antenna test system is necessary. The setup can measure the amplitude and phase coherent response of a devices under test (DUT) radiating in the D-Band. Fully automated 3D-pattern measurements including post-processing can be performed in short time thanks to the R&S AMS32 software options for nearfield to farfield transformation and the highly accurate precision positioner.
IHP provided four different DUT, based on the same D-Band radar transceiver chipset but with different antenna structures, including on-chip single and stacked patches with air trenches and an on-chip antenna array. The over-the-air characterization verified the wider bandwidth provided by the stacked patches than that by the single patch.
The performance of the various DUTs was characterized by spherical measurements, using two different setups. By increasing the angular theta step-size from 1 degree to 5 degree, the total test times for a DUT could be reduced from 70 to 12 minutes. By comparing the different DUT designs based on the obtained measurement data, researchers of IHP were able to analyze the effect of the finite on-board reflector area on the radar sensor field of view (FoV).
Prof. Gerhard Kahmen, managing director of IHP, said, “Sub-THz frequency systems are getting more and more attention in research and many fields of application. The Rohde & Schwarz OTA test system, extended to D-Band, provides an excellent way to characterize radiation patterns of the complex antenna structures, realized in our D-Band radar chips, in a time efficient and precise way. For IHP, these measurements are valuable to understand the physics of the antenna structures and to further improve their performance. The very successful cooperation with an industrial partner leading in the field of wireless and mmWave communication shows the benefit of close interaction between research and application.”
Alexander Pabst, vice president of Systems & Projects at Rohde & Schwarz said, “We are excited to work with such an excellent partner as Innovations for High Performance Microelectronics on advancing our industry-leading test solutions for over-the-air testing. These joint efforts will help researchers and key industry players to test and characterize antenna systems and transceiver modules for future automotive radar applications and wireless communication standard, that we eventually call 6G.”