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In this paper, a high-isolation multiple-input/multiple-output (MIMO) microstrip monopole antenna array is investigated. To reduce the mutual coupling between antenna elements, a novel composite parasitic element constituted by a T-shaped ground branch and an isolated branch was designed and analyzed. The proposed composite parasitic element is capable of generating a unique three-dimensional weak electric field, which can effectively suppress the mutual coupling between the antenna elements. To give an intuitive illustration about the design principle and decoupling strategy of the proposed antenna, the antenna design procedure was ingeniously divided into four steps, and three types of decoupling structures during the antenna evolution were meticulously analyzed at both the theoretical and the physical level. To validate the proposed decoupling concept, the antenna prototype was fabricated, measured, and evaluated. The reflection coefficient, transmission coefficient, radiation pattern, and antenna gain were studied, and remarkable consistency between the measured and simulated results was observed. The simulations showed that the antenna has a peak gain of 3.5 dBi, a low envelope correlation coefficient (ECC < 0.001), and a high radiation efficiency (radiation efficiency > 0.9). Parameters of the proposed MIMO antenna including electrical dimension, highest isolation level, and 20 dB isolation bandwidth were evaluated. Compared with the previous similar designs, the proposed antenna exhibits attractive features including compressed dimension (0.55λ0 × 0.46λ0), extremely high isolation level (approximately 43 dB), fabulous 20 dB isolation bandwidth (3.11–3.78 GHz, 19.4%), a high diversity gain (DG > 9.99 dB), an appropriate mean effective gain (−3.5 dB < MEG < −3 dB), and low design complexity. [ABSTRACT FROM AUTHOR]

A high‐gain, low‐cost empty substrate integrated waveguide (ESIW)‐fed circularly polarized (CP) antenna array is demonstrated for millimetre‐wave 5G applications in this letter. The ESIW is formed by metallized FR4 printed circuit boards. By stacking the metallic aluminium z‐shaped radiating slots atop the ESIW feeding network, CP radiation is achieved. The proposed 1 × 8 antenna array offers a high measured gain of 17.8 dBic and high measured radiation efficiency of 89.1%. The measured impedance bandwidth for |S11| ≤ −10 dB and measured axial ratio (AR) bandwidth for AR ≤ 3 of the proposed 1 × 8 array are 11.4% (36.5–40.9 GHz) and 7.8% (37–40 GHz), respectively. [ABSTRACT FROM AUTHOR]

This paper presents a circularly polarized (CP) slot antenna array using substrate integrated waveguide (SIW)–feeding network at Q-band. To achieve CP radiation and high-gain performance simultaneously, a metallic radiating slanted cross slot is stacked atop an SIW coupling slot in the CP antenna element design. The fabricated CP antenna element features 14.6% (42.6–49.3 GHz) measured impedance bandwidth for |S11| ≤ −10 dB, 9.1% (42–46 GHz) measured 3-dB axial ratio (AR) bandwidth for AR ≤ 3, and 8.3 dBic measured peak gain, respectively. Then, a 1 × 8 antenna array is designed, fabricated, and measured. The measured results demonstrated that the impedance bandwidth and 3-dB AR bandwidth of the proposed 1 × 8 array are 14.8% (41.9–48.6 GHz) and 11% (43–48 GHz), respectively. The measured peak gain of the 1 × 8 array is 14.7 dBic at 44 GHz. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-gain circularly polarized magnetoelectric dipole antenna array for millimeter-wave is proposed. • An antenna array design method of trade-off between high gain and low profile is proposed in this paper. • The 4 × 4 antenna array achieves 20.4 dBic peak right-handed circularly polarized gain. A high-gain circularly polarized (CP) magnetoelectric (ME) dipole antenna with metallic radiating structure is presented. The proposed CP antenna element consists of two pairs of metallic posts with a supporting metallic plate, a metallic air-filled elliptical cavity, and a feeding slot on the bottom substrate integrated waveguide (SIW). The two pairs of modified rectangular metallic posts combined with the gaps between them act as radiating ME-dipoles which are surrounded by a metallic air-filled elliptical cavity. The above-mentioned radiating structures are fed by a modified cross-shaped coupling slot etched on the bottom feeding SIW to generate CP radiation, where loading the elliptical metallic cavity significantly improve the CP performance of the antenna element. Then, a 4 × 4 antenna array with full-corporate feeding network is designed, fabricated, and measured, which has an impedance bandwidth of 18.9 % from 37.4 to 45.2 GHz and a 3-dB axial ratio (AR) bandwidth of 14.2 % from 36 to 41.5 GHz. Thanks to the all-metal radiating structures, a maximum measured gain of 20.4 dBic has been achieved. The measured and simulated results are in good agreement. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel approach to address the challenge posed by large datasets in the context of antenna optimization through machine learning (ML). The approach involves a modified artificial neural network (ANN) technique. To tackle the issue of training with limited data, we introduce a method that leverages prior knowledge to create initial small datasets. Throughout the training process, these datasets are iteratively enhanced by incorporating new simulation data obtained from optimization results. In the applications presented here, ANN is used to establish a relationship model between antenna geometric variables and transmission coefficients (S 21). Subsequently, a genetic algorithm (GA) is used to optimize the decoupling of the antenna array. By implementing wideband and narrowband optimization of the S 21 between two antennas, the accuracy and efficiency of this method are verified. The initial design and optimized antennas were fabricated and measured. In summary, this proposed method not only can effectively mitigate the expenses associated with design but also generates antenna optimization solutions of high quality. [ABSTRACT FROM AUTHOR]