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Abstract A simple wideband magneto‐electric (ME) dipole antenna is presented in this letter. In particular, two pairs of L‐shaped slots with different sizes are successively etched out of the pair of horizontal patches of electric dipole, which can enlarge the bandwidth of ME dipole antenna without increasing the antenna size. Two new resonant frequency points are generated respectively at the lower and upper frequency region. To improve the impedance matching characteristics, two vertical rectangular patches are loaded in the middle of the horizontal portion of the Г‐shaped feed structure. A prototype is fabricated and measured, and an overlapped bandwidth of 101.3% (from 1.36 to 4.15 GHz) in terms of VSWR ≤ 2 is achieved, which can simultaneously cover the n50 (1.432–1.517 GHz), n51 (1.427–1.432 GHz), n78 (3.300–3.800 GHz) and 52.5% of n77 (3.8–4.4 GHz) bands of sub‐6G. It should be highlighted that other excellent properties of ME dipole antenna, such as stable radiation pattern, high gain, and low cross‐polarization level (CRPL), are maintained, which makes the proposed ME dipole antenna a good candidate for sub‐6G applications.

In this article, a miniaturized antenna is proposed for 4G/5G multiple input, multiple output (MIMO) applications for smartphones. The proposed antenna is composed of an inverted L-shaped antenna with decoupled elements to cover 4G (2000–2600 MHz), and a planar inverted-F antenna (PIFA) with a J-slot to cover 5G (3400–3600 MHz and 4800–5000 MHz). Furthermore, to achieve the purposes of miniaturization and decoupling, the structure adopts a feeding stub, shorting stub, and outstanding floor, additionally adding the slot to the PIFA, to generate additional frequency bands. Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and a compact structure, the proposed antenna design is attractive for 4G/5G smartphones. The antenna array is printed on an FR4 dielectric board, measuring 140 × 70 × 0.8 mm3, with the 4G antenna located on a top 15 mm-long headroom.

A dual-band MIMO antenna with high isolation is designed in this paper for coal mine applications. Each of the two elements in the designed MIMO antenna is composed of a bident-shaped monopole structure which is designed to cover the 5G NR frequency region (2.51-2.67 GHz, 3.4-3.6 GHz) allocated for coal mine scenario. The two elements are symmetrically placed to achieve high isolation at lower frequency region with an element spacing of 0.09λ at the lowest operating frequency. To further reduce the mutual coupling between the two elements, the decoupling network technique is utilized. In particular, a neutralization line is loaded with an adjustable capacitor and two adjustable inductors on the ground. In this way, an isolation of higher than 20 dB is achieved over the two operating frequency bands for the MIMO antenna, i.e., the isolation is increased by more than 11 dB and 10 dB for the lower and higher bands, respectively. Besides, the good performance of the designed MIMO antenna in terms of correlation values and diversity gain makes it a suitable candidate for 5G MIMO applications under coal mine scenarios. [ABSTRACT FROM AUTHOR]

A highly-isolated dual-polarized magnetoelectric (ME) dipole antenna is proposed in this letter, where a modified cross-shaped differentially-feeding structure is designed to realize dual-linear polarizations (LPs). To broaden the bandwidth of the differentially-driven ME dipole antenna, a pair of L-shaped branches are loaded on the positions where a triangle is cut out of each patch to introduce a new resonant frequency at the upper frequency region. Meanwhile, a two-stepped structure is added to each of the four ports of the cross-shaped differentially-feeding structure to improve the impedance matching characteristic of the antenna. In this way, the 10 dB bandwidth is improved from 64.9% (1.54–3.02 GHz) to 83.5% (1.52–3.70 GHz), i.e., 28.7% bandwidth enhancement is achieved. A prototype is fabricated and measured. The results show that the proposed antenna can achieve a high differential port-to-port isolation of better than 38 dB, cross-polarization level (CRPL) lower than −25 dB, and peak gain up to 10.5 dBi. [ABSTRACT FROM AUTHOR]

This paper presents a broadband high-isolated MIMO antenna operating in the C and X bands simultaneously. The antenna is expected to be applied in wireless systems such as satellites and radar. A modified Vivaldi element is firstly designed by etching a rectangular structure out of the top metal, and then arranged symmetrically to form a 2-element broadband MIMO antenna with element spacing of 0.28λ (λ is the wavelength at 9 GHz). The operating frequency the MIMO antenna in terms of S11 ≤ −9.0 dB is from 4.0 GHz to 13.5 GHz. However, the mutual coupling between the two elements is quite strong, which can be as high as 8.0 dB, indicating a severe mutual coupling effect between the elements. To improve the isolation level, a defect-ground structure (DGS) is designed and loaded on the ground plane. The decoupling structure of the DGS achieves decoupling in the C and X bands, with a particular emphasis on decoupling in the C band by blocking the current flow between antenna elements. The simulated result shows that the S21 can be lowered to less than −23.4 dB across the whole operating frequency region, i.e., an isolation improvement of 15 dB is achieved. A prototype is fabricated and measured. The measured results are in good agreement with the simulated ones, indicating that the designed broadband MIMO antenna is a good candidate for reliable communication in the C and X bands. [ABSTRACT FROM AUTHOR]

At present, 5G technology is gradually applied in coal mine applications. Under this circumstance, a microstrip patch antenna based on a multi-branch structure is firstly designed which can operate at the allocated 5G NR (2.51-2.68 GHz, 3.40-3.60 GHz, and 4.80-4.90 GHz) for coal mine. Nevertheless, this antenna exhibits a large size, even at the lowest operating frequency (0.41λ×0.41λ at 2.51 GHz). To reduce the size of the antenna, the three branches are separately bent into C, S, and L shapes from left to right, and a size of 0.33λ × 0.33λ at 2.51 GHz is realized, i.e., 35% size reduction is achieved. To further achieve a compact size, a new structure is designed. In particular, two inverted J-shaped branches and a rectangular branch acting as radiating portion are respectively arranged and optimized to cover the above three frequency bands where the rectangular branch is located between the two inverted J-shaped branches. To enhance the impedance matching characteristic of the antenna, a T-shaped structure is loaded on the other side of the substrate. The resultant size of this antenna is 0.20λ × 0.16λ at 2.51 GHz, which is around 81% and 71% smaller than the first and second designed antennas. The measured results of the antennas are in good agreement with the simulated ones. Therefore, the third antenna is a good candidate for coal mine applications due to its relatively small size, low profile, and easy integration with equipment. [ABSTRACT FROM AUTHOR]

In this letter, a quad-band high-isolated MIMO microstrip antenna is designed for coal mine communications, which can operate at DCS1800, UMTS, WiMAX, WiFi, and 5G NR simultaneously. Firstly, the qual-band property is realized by designing a quaddent structure. In particular, three L-shaped branches (separately operating at 2.6 GHz, 3.5 GHz, and 4.8 GHz) are successively loaded on a monopole antenna (operating at 1.9 GHz). In the sequel, by symmetrically placing two quaddent structures with spacing of 0.19λ, a MIMO antenna is designed. At this time, the isolation level of the MIMO antenna can be as high as around 8 dB. To improve the performance of the MIMO antenna, an inverted cross-shaped branch is loaded on and two rectangular slots are etched off the ground successively between the two elements. In this way, an isolation level of over 20 dB can be achieved across the whole operating frequency bands. To verify the performance of the designed antenna, a prototype is fabricated and tested, and good agreement between the simulated and measured results indicates that the proposed antenna can completely cover DCS1800, UMTS, WiMAX, WiFi, and 5G NR (1.67 ~ 2.28 GHz, 2.39 ~ 2.79 GHz, 3.13 ~ 3.74 GHz and 4.69 ~ 5.34 GHz) for mining. [ABSTRACT FROM AUTHOR]