Four-Port Wide-Band Cavity-Backed Antenna With Isolating X-Shaped Block for Sub-6 GHz 5G Indoor Base Stations

Abstract

A four-port wideband cavity-backed antenna is presented for indoor base stations applications. The antenna is composed of a square open cavity with an X-shaped isolating block and 4 feeding monopoles symmetrically and orthogonally arranged in the aperture of the cavity. A novel methodology based on Characteristic Modes Analysis (CMA) is used for identifying the modes which are contributing to the coupling. As a result of this analysis, an X-shaped isolating block placed at the center of the cavity is proposed for increasing the isolation between ports. A wide-band four-port antenna with unidirectional radiation patterns is obtained with a measured impedance bandwidth (S 11 <-10 dB) ranging from 1.55 to 6 GHz (118%), covering most of the sub-6 GHz 5G bands. The proposed antenna provides four independent radiation patterns, with 16 dB of measured minimum isolation between ports and an efficiency higher than 84%. Multiple-input multiple-output (MIMO) compatibility is confirmed with a 4×4 MIMO simulated system with an envelope correlation coefficient (ECC)<0.5 in different propagation conditions. The antenna is easy to fabricate and presents a compact size of 129.5×129.5×28.2 mm 3 (0.68λ×0.68λ×0.15λ, at a frequency f=f min =1.55 GHz). Moreover, the antenna has the advantage of avoiding complex feeding structures with baluns or directional couplers.

Gain and isolation enhancement of a wideband MIMO antenna using metasurface for 5G sub-6 GHz communication systems

“…Although the antennas reported in 5 , 46 offers higher isolation than our suggested antenna, however, these antennas suffer from large dimension, low gain, narrow bandwidth, and poor MIMO performance. The 4-port MIMO antenna presented in 45 demonstrated high gain and efficiency, but this design offers low isolation, large dimension and poor diversity performance. On the other side, the small size antenna system is suggested in 47 with very low gain and operating bandwidth, whereas our proposed 4-port MS-based MIMO system exhibits a small dimension with high gain, high isolation and better MIMO performance.…”

“…isolation (dB) Max. isolation (dB) ECC (dB) DG (dB) 44 75 × 150 MIMO + Parasitic structure 3.4–3.8 6.5 60–70% ≥ 15 29 < 0.01 Not given 5 150 × 70 MIMO + Neutral line 3.1–3.85 4.8–6 Not given 60–75% ≥ 17 24 < 0.06 Not given 45 129.5 × 129.5 MIMO + cavity-backed 1.55–6 10 80–84% ≥ 15 36 < 0.05 Not given 46 150 × 150 Annular-ring patch 3.3–5 6.8 84–92% ≥ 16.5 26 < 0.05 Not given 47 26 × 26 MIMO (slot antenna) 5.6–5.8 1.7 Not given ≥ 15.4 32 < 0.01 Not given Prop. work 80 × 80 MIMO + MS 3.08–7.75 8.3 73–84% ≥ 15.5 36.2 ...…”

16-ports indoor base station MIMO array for sub-6 GHz 5G applications

“…The proposed array design consists of 16 antenna elements, which is twice the number of elements in [4] of the same size, with an acceptable isolation value. By comparing the antenna efficiency, the proposed antenna element has an efficiency of 93.2%, which is better than other antennas in [4,9], and [16].…”

“…Many 5G MIMO array designs have recently been proposed. For MIMO indoor base station applications, a fourport wide-band antenna with unidirectional and independent radiation patterns is described in [9]. As this design is made up of four T-shaped monopoles that are grouped in an orthogonal and symmetrical pattern.…”

16-Ports Indoor Base Station MIMO Array for Sub-6 GHz 5G Applications

“…Many 5G MIMO array designs have recently been proposed. For MIMO indoor base station applications, a four-port wideband antenna with unidirectional and independent radiation patterns is described [9]. Where this design is made up of four T-shaped monopoles that are grouped in an orthogonal and symmetrical pattern.…”