OTA (Over-The-Air) performance of MIMO (Multiple-Input Multiple-Output) mobile terminals employing multi-antennas must be evaluated using the spatial channel emulator which reproduces the multi-path propagation environment around the mobile terminal. Antenna properties of an antenna correlation in addition to the branch power should be adequately evaluated in the spatial channel emulator. In this paper, we investigate based on the calculation the alignment of probe antennas for a spatial channel emulator considering the power angular spectrum of cluster model taking an antenna correlation that has a substantial impact on MIMO performance as the criterion and we clarify that probe antennas should be appropriately aligned, in terms of spacing and numbers, depending on an intended angular spread of arriving waves.
This paper investigates the fundamental monopole antenna array arrangement for actual mobile terminals that satisfies the requirements for beam-steering, diversity and multiple-input-multiple-output (MIMO) transmission. We take particular note of the range below 0.5 for the element spacing, which is a topic of interest for compact antenna arrays at mobile terminals. Using multiple monopole antennas with an element spacing of greater than 0.2 mounted on the mobile terminals, simulated by the card-type and laptop PC type terminals, resulted in approximately 2.5 dB and 5.0 dB more power in twoand four-element configurations, respectively, compared to the single-antenna configuration. Furthermore, the two-and four-element configurations yield a correlation coefficient of less than 0.7, and achieve 1.6 and 3.2 fold higher MIMO capacity, respectively, compared to single-antenna configuration. From a comprehensive perspective, multiple monopole antennas mounted on an actual mobile terminal with an element spacing of greater than 0.2 can operate at high gain according to the array size with the desired diversity gains and acceptable MIMO channel capacity.
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