The millimeter-wave phased array in the user equipment (UE) for 5G communication is studied in this letter. In particular, the body effect on the phased array in the UE at 15 GHz is investigated with the 3-D measurement data, and its impact on some key parameters for phased array in the UE, such as the total scan pattern, the coverage efficiency, and the probability of detection, are analyzed.

User Body Effect on Phased Array in User Equipment for the 5G mmWave Communication System

It is generally believed that antenna correlations of up to 0.5 in magnitude have negligible effects on the performance of multi-antenna systems, and that antenna correlation only affects the system performance via its magnitude. In this paper, we show that antenna correlations of 0.5 in magnitude that has negligible effect in capacity (i.e., theoretically maximum data rate) can cause noticeable degradation on the throughput (i.e., actual achievable data rate); and that, when the number of antennas is larger than two, the phase of the correlation also has an impact on the performance of multi-antenna system. We demonstrated these via simulations and measurements in a reverberation chamber.

https://www.jpier.org/pierb/pierb62/15.15012805.pdf

Antenna Correlation and its Impact on Multi-Antenna System

We present simulations of near-field plane wave synthesis by a planar array. The focus is on minimization of reference signal errors within the test zone for Random Line-Of-Sight Over-The-Air characterization of wireless devices on cars. The analysis considers the output of the ideal digital threshold receiver model of the device under test as a Probability of Detection curve. The dimensions, the interelement spacings and the number of elements in a planar array comprising Huygens sources are investigated to produce an absolute error less than 0.5 dB.

https://publications.lib.chalmers.se/records/fulltext/246540/local_246540.pdf

Simulations of a planar array arrangement for automotive Random-LOS OTA testing

We evaluate the performance of a dual-polarized wideband antenna in terms of polarization-MIMO in Random-LOS for two different modes of operation: 2 and 4-port excited mode. The 2-port mode was obtained by differential excitation of two opposite ports of the 4-port design by using two baluns. The Zero-Forcing receiver throughput is evaluated based on the Probability of Detection of two bitstreams when orthogonal polarizations provide the MIMO subchannels. Assuming a uniform distribution for the Angle of Arrivals and orthogonally polarized waves incident on the antennas, the overall PoD over coverage cones of 30°, 60° and 90° are presented. The 2-bitstream multiplexing MIMO efficiency defined at the 95% Probability of Detection is evaluated for the two modes of operation at different frequencies and for different coverage cones. The 2-bitstream coverage pattern of the antenna for the two modes are plotted over the range of Angles-of-Arrival (AoA), by choosing fixed polarization (horizontal and vertical) for the incoming waves. The coverage pattern is significantly degraded for the 2-port mode, in particular in the middle of the band.

https://publications.lib.chalmers.se/records/fulltext/240832/local_240832.pdf

Comparison of 2-bitstream polarization-MIMO performance of 2 and 4-port bowtie antennas for LTE in random-LOS

In this paper we look into a near-field measurement setup consisting of a cylindrical reflector and a linear array feed. The main application is Random Line-Of-Sight Over-The- Air measurements in anechoic or semi-anechoic chambers (i.e., anechoic chamber with reflecting floor). More specifically, the aim is testing the wireless communication systems on automotive vehicles. The aim is to generate the uniform field distribution of a plane wave over a pre-defined test zone containing the car or at least the part of the car containing the antenna(s). The field intensity variations over the testing zone have been investigated for reference measurements over the testing frequency bandwidth, i.e., 1.6–2.8 GHz.

http://publications.lib.chalmers.se/records/fulltext/246234/local_246234.pdf

Array-fed cylindrical reflector antenna for automotive OTA tests in Random Line-Of-Sight

Wireless systems have become more and more advanced in terms of handling the statistical properties of wireless channels. For example, the 4G long term evolution (LTE) system takes advantage of multiport antennas [multiple-input multiple-output (MIMO) technology] and orthogonal frequency division multiplexing (OFDM) to improve the detection probability of single bitstream by diversity in the spatial and frequency domains, respectively. The 4G system also supports transmission of two bitstreams by appropriate signal processing of the MIMO subchannels. The reverberation chamber emulates according to previous works rich isotropic multipath (RIMP) and has proven to be very useful for characterizing smart phones for LTE systems. The measured throughput can be accurately modeled by the simple digital threshold receiver, accounting accurately for both the MIMO and OFDM functions. The throughput is equivalent to the probability of detection (PoD) of the transmitted bitstream. The purpose of this paper is to introduce a systematic approach to include the statistical properties of the user and his or her terminal, when characterizing the performance. The user statistics will have a larger effect in environments with stronger line-of-sight (LOS), because the angle of arrival and the polarization of the LOS contribution vary due to the user’s orientation and practices. These variations are stochastic, and therefore, we introduce the term random-LOS to describe this. This paper elaborates on the characterization of an example antenna in both RIMP and random-LOS. The chosen antenna is a wideband microbase transceiver station (BTS) antenna.
We show how to characterize the micro-BTS by the PoD of one and two bitstreams in both RIMP and random-LOS, by considering the user randomly located and oriented within the angular coverage sector. We limit the treatment to a wall-mounted BTS antenna, and assume a desired hemispherical coverage. The angular coverages of both one and two bitstreams for the random-LOS case are plotted as MIMO-coverage radiation patterns of the whole four-port digital antenna system. Such characterizations in terms of PoD have never been done before on any practical antenna system. The final results are easy to interpret, and they open up a new world of opportunities for designing and optimizing 5G antennas on system level.

MIMO Characterization on System Level of 5G Microbase Stations Subject to Randomness in LOS

Unfortunately, we had mixed up some results when we plotted the graphs in Figure 7 of the above paper. This affected only the two blue curves in each of the three graphs, for $2\times 2$ MIMO in Random-LOS with LP and CP incidences, and had no influence on the discussion and conclusions in the paper. The correct graphs of Figure 7 are given here, in addition to an explanation of how the best level of the curves are related to the directivity of the antenna under test.

Zhengzhao Shen

Papers

MIMO Characterization on System Level of 5G Microbase Stations Subject to Randomness in LOS

Correction to “MIMO Characterization on System Level of 5G Micro Base Stations Subject to Randomness in LOS”