Full-Azimuth Beam Steering MIMO Antenna Arranged in a Daisy Chain Array Structure

Abstract

This paper presents a multiple-input, multiple-output (MIMO) antenna system with the ability to perform full-azimuth beam steering, and with the aim of realizing greater than 20 Gbps vehicular communications. The MIMO antenna described in this paper comprises 64 elements arranged in a daisy chain array structure, where 32 subarrays are formed by pairing elements in each subarray; the antenna yields 32 independent subchannels for MIMO transmission, and covers all communication targets regardless of their position relative to the array. Analytical results reveal that the proposed antenna system can provide a channel capacity of more than 200 bits/s/Hz at a signal-to-noise power ratio (SNR) of 30 dB over the whole azimuth, which is equivalent to 20 Gbps for a bandwidth of 100 MHz. This remarkably high channel capacity is shown to be due to two significant factors; the improved directivity created by the optimum in-phase excitation and the low correlation between the subarrays due to the orthogonal alignment of the array with respect to the incident waves. Over-the-air (OTA) experiments confirm the increase in channel capacity; the proposed antenna can maintain a constant transmission rate over all azimuth angles.

A Method of Implementing a 4 × 4 Correlation Matrix for Evaluating the Uplink Channel Properties of MIMO Over-the-Air Apparatus

“…One of the most common approaches to analyze a MIMO antenna system is to use Monte Carlo simulation, where many scatterers are arranged on a circle, known as Clarke’s model [ 28 ], to simulate a multipath fading channel in a mobile propagation environment; this results in the evaluation of the MIMO terminal performance [ 24 ]. A multipath propagation environment is simulated by the amplitude and phase of each wave radiated from the scatterers, which is an aggregation of all the information in the radio waves emitted by the BS antennas.…”

“…The MIMO terminal is located at the center of the emulator. This fading emulator functions as an operating algorithm based on the same formulation described in [ 24 ]. The instruments, such as the network analyzer (Keysight, HP8753E), power combiner/divider (mini circuit, ZAPD-2-S+ and ZB8PD-252-S+), and phase shifter (mini circuit, JSPHS-23+), have bidirectional characteristics at the measurement frequency.…”

“…The disadvantage of this method is that it requires many instruments, such as a probe antenna, a power divider, and a phase shifter. However, a fading emulator is capable of emulating realistic and accurate multipath environments [ 20 , 21 , 22 , 23 , 24 ].…”

Over-the-Air Testing of a Massive MIMO Antenna with a Full-Rank Channel Matrix

“…Most of the activity so far undertaken in developing massive MIMO systems has been directed toward providing large-scale MIMO antennas at the BS, with antennas comprising more than 100 antenna elements [ 4 , 5 ], and there are few reports of doing something similar at the MS [ 6 ]. The author is currently developing a method to achieve a large-scale MIMO antenna system that maintains an invariable channel capacity over the full-azimuth at the MS, such as, for example, a connected ground-based or flying car [ 7 ].…”

“…To analyze the capability of the developed antenna [ 7 ], the author proposed a Monte Carlo simulation with randomly arranged scatterers [ 10 ]. A small number of differently positioned scatterers were set for each BS antenna using random numbers, confirming that the channel matrix created can achieve full-rank status similar to conventional Monte Carlo simulation.…”