Characterizations of Mutual Coupling Effects on Switch-Based Phased Array Antennas for 5G Millimeter-Wave Mobile Communications

Abstract

The fifth generation (5G) millimeter-wave (mmWave) handset demands a cost-effective mmWave array antenna with beam steering capability to overcome the high-pass loss and to ensure seamless connectivity. Unlike sub-6-GHz handsets, emerging mmWave handsets usually employ phased array antennas with a reasonably large number of elements. Unfortunately, due to the legacy of a few antennas in sub-6-GHz handsets, the mutual coupling effect on the mmWave handset has not been thoroughly investigated. In this paper, we study the mutual coupling effect on the mmWave handset performance by comparing array antennas with different inter-element spacing and different configurations. It is found that mutual coupling tends to increase the active reflection (especially at large scanning angles), which in turn reduces the realized gain and maximum scanning angle of the phased array antenna. For a sub-6-GHz multiple-input multiple-output handset with two or four antenna ports and fully digital precoding/decoding, 10-dB isolation is usually regarded as good enough. It is shown in this paper, however, that the outage capacity of the mmWave handset can be clearly improved by reducing the mutual coupling. INDEX TERMS Active reflection, handset array, millimeter-wave (mmWave), multiple-input multipleoutput (MIMO), mutual coupling.

A Green Downlink Power Allocation Scheme for Cell-Free Massive MIMO Systems

“…By recalling the objective function of problem P 1 , we have the lower bound in (16) which is presented at the top of the next page. In (16), (a) directly results from the assumption R min k ≥ 1 in Theorem 1 and (b) follows from the well-known log-sum inequality 5 . Now, we define…”

“…More importantly, multi-user interferences are mitigated owing to the desirable phenomena of channel hardening and favorable propagation in the context of m-MIMO systems [1], [2]. The mutual coupling effect, which is a common issue in collocated m-MIMO systems [3]- [5], can also be alleviated since the large-scale array gain is achieved by a large number of separated APs which are normally equipped with only a small number of antennas.…”

Planar LTE/sub‐6 GHz 5G MIMO antenna integrated with mmWave 5G beamforming phased array antennas for V2X applications

“…However, as the distance between the radiating elements increases, a large grating lobe occurs [23]. Therefore, to obtain the wide beam scanning performance and high isolation level without increasing the distance between the adjacent elements, an additional structure is required to improve the isolation level while keeping the distance between the radiating elements less than λ/2 [24]. In this work, a stub and two slits are adopted in the array design to reduce the mutual coupling while the distance between adjacent ports is less than λ/2 (4.8 mm≃0.44 λ at 28 GHz), as shown in Fig.…”

Development Challenges of Millimeter‐Wave 5G Beamformers

“…In line with the concept of using multiple antennas on hand-set, a switched based beamformer is studied in (Chen et al, 2019). Mutual coupling impact is thoroughly investigated with different inter-element spacing and different orientational configurations of antenna units.…”