MIMO over-the-air testing for electrically large objects in non-anechoic environments

Abstract

With the development of advanced communication systems such as ITS-G5 (C2C, C2I), mobile, and in-car communication systems, more and more systems are operating simultaneously. To verify their reliability in a coexistence scenario, all systems have to be tested under realistic conditions. The so-called two-stage method provides a test procedure for such systems. Unfortunately, it does not consider self or inter-system interference for which the radiated two-stage method was developed. Based on this method, this contribution proposes an approach which allows to test large objects with multiple antennas/antenna-systems under realistic propagation conditions. It is realized in an over-the-air setup for wide-band applications by creating orthogonal wireless channels, a technique also known as wireless cable

MIMO Terminal Performance Evaluation With a Novel Wireless Cable Method

“…With the reference method, an isolation level up to 18 and 20.5 dB were reported in [13] and [14], respectively. In [19], the wireless cable technique was applied for measuring large objects in a nonanechoic scenario. However, the transfer matrix A was directly measured.…”

“…The measured radiation patterns are then incorporated with target channel models in the CE in the second stage. To direct signals from each probe antenna to desired DUT antenna port without RF cable connection, a transfer matrix between CE output ports and DUT antenna ports needs to be measured and calibrated out to achieve a "wireless cable transmission" in the second stage [10], [13], [14], [19]. With the MPAC method, the DUT is evaluated in the emulated RF propagation environments as it would operate in real world.…”

“…The wireless cable concept is highly attractive. With this concept, the number of required RF interface channels for the CE is required only to match the number of receive (Rx) antennas on the DUT, regardless of the complexity of the chosen channel model and DUT size [6], [10], [19]. Note that mobile terminals are often equipped with few Rx antennas, due to the small form factor.…”

“…Note that mobile terminals are often equipped with few Rx antennas, due to the small form factor. The wireless cable concept has been discussed for evaluating MIMO handsets in the radiated two-stage method [10] and for electrically large objects [19]. However, the existing method to achieve wireless cable is practically challenging, since there is a need to measure the transfer matrix in an accurate way.…”

A Flexible Millimeter-Wave Radio Channel Emulator Design With Experimental Validations

“…For the radiated two-stage method (aka. wireless cable method), transfer matrix between the OTA antenna and DUT antenna can be measured and then calibrated out in the radio CE [3], [5], [6]. It was described in [7], [8] that antenna arrays at the BS and mobile terminal side, along with the propagation channels, can be emulated in the CE.…”