OTA - Over-The-Air Characterization of Active Integrated Antennas for Mobile Systems

Research Project, 2019 – 2023

The goal of this project is to examine the fundamental capabilities and limitations of innovative ‘hybrid’ physical testing environments for Over-The-Air characterization of integrated active antenna systems for mobile communications.

Through the past decades, the research area of antenna measurements (AMs) has undergone disruptive changes which have been stimulated by the development of novel multiple-input multiple-output (MIMO) antenna systems and beamforming applications for wireless communications (e.g., 5G). The modern area of AM research can be referred to as Over-The-Air (OTA) characterization of antenna systems. OTA evaluates the impact of hardware, wave propagation, signal processing on the overall antenna system with regard to the most relevant performance metrics of a wireless network. The key game changers and associated challenges that shape the modern OTA research come from the global shift towards massive MIMO antenna systems, more advanced (hybrid analog-digital) signal processing, and much higher levels of integration between individual components (e.g. antennas, power amplifiers, filters, etc). Performance testing of such new systems requires sophisticated test methods and often new types of measurement tools. Moreover, until recently, testing of radio base stations could be performed conductively (i.e. not wirelessly) at a test port. This option is not sustainable for a large number of antenna ports, and technically impossible with Massive MIMO systems operating at higher frequency bands, eg., at the mmWave frequency bands. OTA is therefore indispensable to characterize the performance of radio base stations at mmWaves, and is also beneficial at lower bands.

Today, there are no commercially available antenna measurement ranges or techniques that support all required performance figures-of-merit for radio base stations in order to test their conformance to international standards using a single measurement setup or even a single antenna measurement chamber. Moreover, standardized measurement chambers and techniques are in many cases too complex, and hence not so cost-efficient.

Therefore this OTA programme aims to investigate innovative solutions providing an unprecedented flexibility of generating, and reconfiguring any desired antenna testing conditions in a single measurement environment, i.e., chamber. At the same time, the solution aims keeping the measurement time and costs at reasonable levels. More specifically, we propose a hybrid solution that combines the best of two worlds, i.e., the anechoic and the reverberation chambers that currently are realized as separate OTA systems, in a single measurement system.