Low-Profile Six-Port Circular Patch Antenna With Six Triple-Shorted Dual-Resonant 60°-Disk Sectors to Generate Six Uncorrelated Waves for Wideband Mobile MIMO Antennas

Abstract

A low-profile six-port circular patch antenna generating six uncorrelated waves in a wide band of about 5.8-7.5 GHz (based on 3:1 VSWR, fractional bandwidth about 25%) is presented. The antenna thickness is 1.4 mm (about 0.027 at 5.8 GHz), which includes a 0.4 mm thick FR4 substrate with the circular patch printed thereon and an additional 1.0 mm thick air layer to achieve a low-permittivity antenna substrate. The circular patch with a diameter of 40 mm (about 0.77 at 5.8 GHz) is separated into six 60 o -disk sectors by using three linear slots across the patch center and sequentially rotated by 60 o . Each disk sector is short-circuited to the ground plane through three properly located shorting pins. It thus makes the 0.5-wavelngth and 0.25-wavelength resonant modes excited at nearby frequencies to form a dualresonant wide band for each port. Additionally, the six ports in the proposed antenna have their port isolation larger than 10 dB and the corresponding six radiating waves have very low envelope correlation coefficients (less than about 0.02) over the wide band. That is, six uncorrelated waves suitable for MIMO (multi-input-multi-output) operation are obtained. The proposed antenna can find applications for wideband mobile MIMO antennas to cover 6.425-7.125 GHz of the possible new mobile communication band or 5.925-7.125 GHz for the new unlicensed WiFi-6E band.INDEX TERMS Mobile antennas, mobile MIMO antennas, six-port single-patch MIMO antennas, lowprofile six-port patch antennas

Wideband Low-Profile Eight-Port Eight-Wave Annular-Ring Patch Antenna Based on Using Eight Dual-Shorted Dual-Resonant Ring Sectors for 8 × 8 MIMO Mobile Devices

“…For the required patch size, the proposed design uses an AR patch of size about 0.64λ 2 to accommodate eight ports. The resonant area for each port (the patch size to port number ratio) is therefore only about 0.080λ 2 , which is similar to that (0.078λ 2 ) in [18] and much smaller than those (0.135λ 2 , 0.097λ 2 ) in [19] and [20] for the six-port six-wave operation. In addition, since a single proposed antenna can be applied for 8 × 8 MIMO operation, different from the six-port patch antennas in [18], [19], and [20] and the four-port patch antennas in [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], and [17], the proposed antenna is expected to be more attractive for the 8 × 8 MIMO mobile device applications.…”

“…In order to further achieve higher MIMO antenna density, the six-port single-patch antennas for applications in the mobile device [18] or access point [19], [20] have also been reported very recently. By using such a single six-antenna element, it is still not sufficient to cover the 8 × 8 MIMO operation.…”

“…The eight-port single-patch antenna studied here is believed to be the first multiport single-patch antenna in the open literature to support eight very-low-correlated or generally uncorrelated waves for on-metal surface applications. For comparison with the reported multiport patch antennas supporting at least six radiating waves for either MIMO access points or mobile devices, Table 1 shows a comparison of the proposed eight-port eight-wave antenna (this work in the table) with the reported six-port six-wave single-patch antennas for access points [19], [20] and for mobile devices [18]. The six-port patch antennas in [19] and [20] require a very high profile of 0.25λ or 0.14λ with respect to the lower-edge frequency of their respective operating band.…”

“…On the other hand, the six-port patch antenna in [18] has a low profile of 0.027λ to be suitable for mobile device applications. The proposed eight-port patch antenna also has a comparable low profile of 0.028λ and about 20% in operating bandwidth (about 5.9-7.2 GHz), similar as those in [18] for the six-port six-wave operation.…”

“…Note that since these antennas have wide operating bands and the antenna size is generally related to the lowest operating frequency, the corresponding antenna height, patch size, and resonant area for each port are referred to the wavelength of the lowest operating frequency. Also, the operating bandwidths of the antennas in [19] and [20] are based on −10 dB impedance matching for access-point application, while that in [18] and this work are based on 3:1 VSWR or −6 dB impedance matching for mobile device application. The latter bandwidth definition is generally used for the mobile device antennas for practical application considerations, owing to the very limited space available for accommodating the antennas [7], [8], [9], [10], [21], [22].…”