OTA measurement of wireless devices with single and multiple antennas in anechoic chamber

For a SISO system in which we have one TX antenna (BTS) and one RX antenna (UE), the OTA measurement consists in determining the transmitter and receiver characteristics of the wireless device in a controlled uniform environment such as the anechoic chamber. TRP (Total Receiver Power) and TIS (Total Isotropic Sensitivity) are the FoMs to be considered. The reference specifications for such measurements are the CTIA OTA Test Plan v.3.2.2 and the 3GPP TS 34.114 [1-2]. In MIMO systems, the spatial correlation, a function of both antenna and propagation characteristics, plays a key role. Indeed, the level of correlation cannot be determined based on propagation characteristics without knowing the characteristics of the antenna. Similarly, the level of correlation cannot be determined based on the antenna characteristics without knowing the propagation characteristics. Therefore, it is necessary to include both antenna and propagation characteristics at the same time when testing multi-antenna terminals. In order to understand the end-to-end reception performance of a multiple antenna device, Over-the-Air (OTA) testing is needed. Due to the complexity of multiple antenna setup, a flexible and fast accurate testing solution becomes a major asset in the antenna design cycle and final product verification (and consequently, Time To Market). The Anechoic Chamber Based OTA simulates a complex multipath environment at the location of the device in a repeatable way by using radio channel emulators connected to a circular array of probes [3-4-5]. This paper will describe the features of both SISO and MIMO OTA systems setups and highlight the advantages of the anechoic chamber based OTA method for MIMO performance testing.