Xavier Carreño

Measurement Verification of Plane Wave Synthesis Technique Based on Multi-Probe MIMO-OTA Setup

Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring. This paper investigates the extent to which we can approach the synthesized plane wave in practical measurement systems. Both single plane wave with certain AoA and multiple plane waves with different AoAs and power weightings are synthesized and measured. Deviations of the measured plane wave and the simulated plane wave field are presented in terms of phase and power. Possible reasons for the deviations are also investigated.

Antenna Pattern Impact on MIMO OTA Testing

This paper investigates the impact of the DUT antenna pattern on the test area performance for multi-probe based MIMO OTA setup in terms of received voltage and spatial correlation. The plane wave synthesis (PWS) technique has been proposed for vertical polarization in the literature, where the goal is to approximate plane waves with arbitrary directions. The received voltage at the antenna terminal depends on the antenna radiation pattern and the impinging plane waves. A novel closed form technique to reproduce the received voltage with arbitrary incoming plane waves based on trigonometric interpolation is presented. The proposed technique provides a closed form solution for the PWS when the probe ring radius is infinite. The proposed technique shows that the impact of the antenna pattern on the induced received voltage accuracy is ruled by Nyquist sampling theory. Furthermore, the impact of the antenna pattern on spatial correlation accuracy for prefaded signal synthesis (PFS) technique is investigated as well. Simulation and measurement results show that the number of required probes depend directly on the DUT antenna pattern. To test realistic DUTs with higher variations in directivity, we need more probes to maintain the same received voltage and spatial correlation accuracy level.

Probe Selection in Multiprobe OTA Setups

Standardization work for over-the-air (OTA) testing of multiple-input-multiple-output (MIMO) capable terminals is currently ongoing in COST IC1004, 3GPP, and CTIA, where a multiprobe anechoic chamber based method is a promising candidate. Setting up a multiprobe configuration with channel emulators is costly, so finding ways to limit the number of probes while still reproducing the target channels accurately could make the test system both cheaper and simpler to implement. Several probe selection algorithms are presented in this paper to address this issue. The proposed techniques provide a probe selection framework for the channel emulation techniques published in the literature. Simulation results show that good channel emulation accuracy can be achieved with the selected subset of probes for the considered target channel models. The probe selection algorithm is further supported by measurement results in a practical multiprobe setup.

Over-the-Air Testing of MIMO-Capable Terminals: Evaluation of Multiple-Antenna Systems in Realistic Multipath Propagation Environments Using an OTA Method

A new over-the-air (OTA) testing method is required for evaluating multiple-antenna systems in realistic multipath propagation environments. Antenna design and propagation channels are the two key parameters that ultimately determine the multiple-input, multiple-output (MIMO) device performance. As antennas are inherently included in OTA testing, it is important to also consider realistic channel models for MIMO device-performance evaluation. This article shows that the multiprobe anechoic chamber (MPAC) setup is capable of emulating realistic and accurate multipath environments, making it a suitable method for testing terminals equipped with multiple antennas. In comparison to the mode-stirred reverberation chamber (RC) setup that represents an isotropic multipath environment, the MPAC method is capable of generating arbitrary spatial channel models with polarization characteristics.

3D Channel Model Emulation in a MIMO OTA Setup

This paper presents a new channel reconstruction technique for 3D geometry-based channels in a multi- probe based MIMO OTA setup. The proposed method provides a general channel reconstruction framework for any spherical power spectrum. The channel reconstruction is formed as convex optimization problems, which give global optimal reconstruction accuracy and allow for a relatively low computational complexity.

Channel Verification Results for the SCME Models in a Multi-Probe Based MIMO OTA Setup

MIMO OTA testing methodologies are being intensively investigated by CTIA and 3GPP, where various MIMO test methods have been proposed which vary widely in how they emulate the propagation channels. Inter- lab/inter-technique OTA performance comparison testing for MIMO devices is ongoing in CTIA, where the focus is on comparing results from various proposed methods. Channel model verification is necessary to ensure that the target channel models are correctly implemented inside the test area. This paper shows that the all the key parameters of the SCME models, i.e., power delay profile, temporal correlation, spatial correlation and cross polarization ratio, can be accurcately reproduced in a multi-probe anechoic chamber based MIMO OTA setup.

Impact of probe placement error on MIMO OTA test zone performance

Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring, and the EM field for each probe is obtained using FDTD simulation. This paper investigates the extent to which we can control the field structure inside the test zone where the device under test is located. The focus is on performance deterioration introduced by probe placement error including OTA probe orientation error and location mismatch, which are general non-idealities in practical MIMO OTA test systems.

Loughborough Antennas & Propagation Conference (LAPC)

Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring, and the EM field for each probe is obtained using FDTD simulation. This paper investigates the extent to which we can control the field structure inside the test zone where the device under test is located. The focus is on performance deterioration introduced by probe placement error including OTA probe orientation error and location mismatch, which are general non-idealities in practical MIMO OTA test systems.