Demystifying over-the-air (OTA) Testing - Important Antenna Parameters,Test System Setup and Calibration

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  • Author: Alexander Nähring

Today, given the increasing integration of chip-sets and antennas as well as usage of higher frequencies, the lines between testing chip-sets, RF testing and antenna characterization have become blurred. In upcoming mm-wave architectures (involving signals with wavelengths in the general millimeter region), there will be no connector between RF components like chip-sets, a power amplifier (PA) and the attached antennas. Therefore, the chip-set cannot be tested without the antenna and vice versa. Both analog and digital improvements are leading to the use of multiple radio frequency (RF) front-ends, massive antenna arrays even in consumer grade hardware, and a combination of beam-forming and multiple-input multiple-output (MIMO) technology known as massive MIMO, enhancing multi-user MIMO (MU-MIMO) and supporting high user capacities in the 5G New Radio (NR) standard.Whether in low-cost devices targeting the IoT market, highly integrated radio front-ends for satellite communications links, or mm-wave devices, integrated antennas are becoming more common with each development cycle. Therefore, OTA testing is becoming more important (or even mandatory) for a broader audience. The step from conducted measurements to OTA testing changes the measurement requirements to a certain degree. New user groups are thus required to have a basic understanding of antennas and antenna measurements.

This paper will provide an introduction to antennas in general, their parameters and different types, as well as antenna characterization and testing in Chapter 2. For more in-depth examination of antenna theory and design, suggested literature is referenced at the end of this paper.Chapter 3 will focus on the importance and execution of OTA test setup calibration. The general concepts are valid for any OTA setup, e.g. in-chamber or lab-desk. Afterwards,
calibration verification is discussed.The last chapter will briefly discuss array antenna calibration methodologies.

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