This paper presents a new methodology of the over-the-air (OTA) assessment for vertically arranged multiple-input multiple-output (MIMO) array antennas. Particular emphasis is placed on how well handset MIMO antennas with a vertically arranged structure are characterized using the limited number of scatterers implemented in a fading emulator. First we studied the mechanism of the arrangement of scatterers on the variation of channel responses using a proposed three-dimensional analytical model. It is shown that the condition of a 3D-OTA with the prescribed parameters allows the correlation to be reduced, which permits the channel capacity to increase in the same manner that sufficient scatterers are distributed over the entire solid angle. Then the appropriate scatterers arrangement for a 3D-OTA instrument considering the number of DUT antenna elements and multipath characteristics is investigated. The analytical results show that a suitable scatterers arrangement can be determined for various conditions of multipath environments and numbers of array elements, and that the arrangement can be employed for designing an actual 3D-OTA apparatus.

This paper presents a new methodology for realizing a Rice channel in BAN Over-The-Air (OTA) testing using a fading emulator with a dynamic phantom. For the proposed apparatus to be effective, the fading emulator must be provided with an appropriate K-factor that represents the actual propagation environment indoors. Further, an implementation of the Rice channel to the proposed fading emulator in a BAN situation is presented. Thereafter, a calibration method for the fading emulator to adjust the actual K-factor of the on-body Rice channel is advanced. This calibration method is validated by analyzing the variations in the instantaneous K-factor attributed to the arm-swinging motion. Finally, an experiment is conducted for a continuous human walking motion with the fading emulator using an arm-swinging dynamic phantom. The results show that the developed fading emulator allows BAN-OTA testing to replicate the actual Rice channel propagation environment with the consideration of the dynamic characteristics of human walking motion.

This paper presents a spatial fading emulator for evaluating handset MIMO antennas in a cluster environment. The proposed emulator is based on Clarke's model and has the ability to control RF signals directly in spatial domain to generate an accurate radio propagation channel model, which includes both uniform and non-uniform angular power spectra (APS) in the horizontal plane. Characteristics of a propagation channel such as fading correlations, eigenvalues and MIMO channel capacities of handset antennas located in the vicinity of the emulator's ring can be evaluated. The measured results show that the fading emulator with 31 antenna probes is sufficient to evaluate fading correlation and MIMO channel capacity of handset antenna in the case of a narrow APS with the standard deviation of more than 20 degrees.

This paper describes a spatial fading emulator based on Clarke's model that can evaluate spatial correlation characteristics between signals received by handset antennas including human-body effect under emulated multipath propagation environments. The proposed model is composed of scatterers, phase-shifters and attenuators. The scatterers are located at equal intervals on the circumference of a circle. Phase shifters and attenuators in a control circuit are used to control the phase and amplitude of each wave radiated from the scatterers in order to emulate multi-path propagation environments, such as Rayleigh or Nakagami-Rice distribution, to be generated at their center. In this paper, the maximum distance between receiving antennas that could be used to evaluate spatial correlation characteristics between antennas was investigated experimentally. The measurement results show that 15 scatterers with a radius of 1.5 m are sufficient to evaluate spatial correlation characteristics within the branch separation of 1.7 λ when parallel dipole antennas are used as receiving antennas.