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14 pages, 5909 KiB

Open AccessCommunication

The Design of a Circularly Polarized Antenna Array with Flat-Top Beam for an Electronic Toll Collection System

by Tianfan Xu, Mengchi Xu and Xiao Cai

Sensors 2023, 23(23), 9388; https://doi.org/10.3390/s23239388 - 24 Nov 2023

Viewed by 689

Electronic toll collection (ETC), known as a non-stop toll collection system which can automatically realize payment by setting the identification antenna at the entrance, is always suffering from information exchange interruption caused by beam switching. A circularly polarized sector beam antenna array operating [...] Read more.

Electronic toll collection (ETC), known as a non-stop toll collection system which can automatically realize payment by setting the identification antenna at the entrance, is always suffering from information exchange interruption caused by beam switching. A circularly polarized sector beam antenna array operating at 5.8 GHz with flat-top coverage is proposed, based on the weighted constrained method of the maximum power transmission efficiency (WCMMPTE). By setting the test receiving antennas at the specific angles of the ETC antenna array to be designed, constraints on the received power are introduced to control the radiation pattern and obtain the optimized distribution of excitations for antenna elements. A 1-to-16 feeding network, based on the microstrip transmission line theory is designed to feed a 4 × 4 antenna array. Simulation results show that the half-power beamwidth covers an angular range of −30° to 30° while the axial ratio is below 3dB, which meets the ETC requirements. Furthermore, the gain fluctuation among the needed range of −30° to 30° is lower than 0.7 dB, which is suitable for the ETC system to achieve a stable signal strength and uninterrupted communication. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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12 pages, 5131 KiB

Open AccessCommunication

A Printed Dipole Array with Bidirectional Endfire Radiation for Tunnel Communication

by Tianfan Xu, Mengchi Xu, Haitao Lu and Xiao Cai

Sensors 2023, 23(22), 9137; https://doi.org/10.3390/s23229137 - 13 Nov 2023

Viewed by 626

Abstract

Tunnel communication always suffers from path loss and multipath effects caused by surrounding walls. Meanwhile, the traditional leaky coaxial cables are expensive to deploy, inconvenient to operate, and difficult to maintain, leading to many problems in practical use. To solve the abovementioned problems, [...] Read more.

Tunnel communication always suffers from path loss and multipath effects caused by surrounding walls. Meanwhile, the traditional leaky coaxial cables are expensive to deploy, inconvenient to operate, and difficult to maintain, leading to many problems in practical use. To solve the abovementioned problems, a low-profile printed dipole array operating at 3.5 GHz with bidirectional endfire radiation is designed based on the method of maximum power transmission efficiency (MMPTE). By setting two virtual test receiving dipoles at the two opposite endfire directions and then maximizing the power transmission efficiency between the printed dipole array to be designed and the test receiving antennas, the optimal amplitudes and phases for the array elements are obtained. Based on the optimal distributions of excitations, the simulation results show that the proposed eight-element printed dipole array can simultaneously generate two mirrored endfire beams towards opposite directions. Furthermore, the corresponding normalized cross-polarization levels are lower than −22.3 dBi both in the azimuth and elevation planes. The peak endfire gain is 10.7 dBi with maintenance of higher than 10 dBi from 3.23 GHz to 3.66 GHz, which is suitable for tunnel communication. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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21 pages, 6141 KiB

Open AccessArticle

Miniaturized Antenna Array-Based Novel Metamaterial Technology for Reconfigurable MIMO Systems

by Humam Hussein, Ferhat Atasoy and Taha A. Elwi

Sensors 2023, 23(13), 5871; https://doi.org/10.3390/s23135871 - 25 Jun 2023

Cited by 2 | Viewed by 1302

Abstract

In this work, a highly miniaturized microstrip antenna array based on two elements is proposed for multiple inputs multiple outputs (MIMO) application systems at sub-6 GHz frequency bands. The antenna is structured from a meander line in conjugate with an interdigital capacitor when [...] Read more.

In this work, a highly miniaturized microstrip antenna array based on two elements is proposed for multiple inputs multiple outputs (MIMO) application systems at sub-6 GHz frequency bands. The antenna is structured from a meander line in conjugate with an interdigital capacitor when excited through the monopole basic antenna. The proposed antenna elements are separated with a Minkowski factor-shaped metamaterial (MTM) column to achieve a separation distance (D) of 0.08λ at 3 GHz when printed on an FR-4 substrate. Later on, the antenna performance in terms of bandwidth and gain is controlled using a photonic process based on optical active switches based on light-dependent resistances (LDR). Therefore, the reconfiguration complexity with such a technique can be eliminated significantly without the need for a biasing circuit. The antenna design was conducted through several parametric studies to arrive at the optimal design that realizes the frequency bandwidth between 3 and 5.5 GHz with a maximum gain of about 4.5 dBi when all LDR terminals are off. For a wireless channel performance study-based massive MIMO environment, the proposed antenna is suitable to be configured in arrays of 64 × 64 elements. From this study, it was found the maximum bit error rate (BER) does not exceed 0.15 with a channel capacity (CC) of 2 Gbps. For validation, the antenna was fabricated based on two elements and tested experimentally. Finally, it was revealed that the measured results agree very well with simulations after comparing the theoretical calculations with the measured data. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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14 pages, 8880 KiB

Open AccessArticle

Low-Profile Broadband Dual-Polarized Dipole Antenna for Base Station Applications

by Hao Feng, Mengyuan Li, Zhiyi Zhang, Jiahui Fu, Qunhao Zhang and Yulin Zhao

Sensors 2023, 23(12), 5647; https://doi.org/10.3390/s23125647 - 16 Jun 2023

Viewed by 2154

Abstract

A low-profile broadband dual-polarized antenna is investigated for base station applications. It consists of two orthogonal dipoles, fork-shaped feeding lines, an artificial magnetic conductor (AMC), and parasitic strips. By utilizing the Brillouin dispersion diagram, the AMC is designed as the antenna reflector. It [...] Read more.

A low-profile broadband dual-polarized antenna is investigated for base station applications. It consists of two orthogonal dipoles, fork-shaped feeding lines, an artificial magnetic conductor (AMC), and parasitic strips. By utilizing the Brillouin dispersion diagram, the AMC is designed as the antenna reflector. It has a wide in-phase reflection bandwidth of 54.7% (1.54–2.70 GHz) and a surface-wave bound range of 0–2.65 GHz. This design effectively reduces the antenna profile by over 50% compared to traditional antennas without an AMC. For demonstration, a prototype is fabricated for 2G/3G/LTE base station applications. Good agreement between the simulations and measurements is observed. The measured −10-dB impedance bandwidth of our antenna is 55.4% (1.58–2.79 GHz), with a stable gain of 9.5 dBi and a high isolation of more than 30 dB across the impedance passband. As a result, this antenna is an excellent candidate for miniaturized base station antenna applications. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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14 pages, 4240 KiB

Open AccessCommunication

Design of a Reconfigurable Ultra-Wideband Terahertz Polarization Rotator Based on Graphene Metamaterial

by Guowen Ding, Yanjun Zhou, Shuyang Zhang, Xinyao Luo and Shenyun Wang

Sensors 2023, 23(12), 5449; https://doi.org/10.3390/s23125449 - 8 Jun 2023

Cited by 3 | Viewed by 1328

Abstract

In this work, a reconfigurable ultra-wideband transmissive terahertz polarization rotator based on graphene metamaterial is proposed that can switch between two states of polarization rotation within a broad terahertz band by changing the Fermi level of graphene. The proposed reconfigurable polarization rotator is [...] Read more.

In this work, a reconfigurable ultra-wideband transmissive terahertz polarization rotator based on graphene metamaterial is proposed that can switch between two states of polarization rotation within a broad terahertz band by changing the Fermi level of graphene. The proposed reconfigurable polarization rotator is based on a two-dimensional periodic array of multilayer graphene metamaterial structure, which is composed of metal grating, graphene grating, silicon dioxide thin film, and a dielectric substrate. The graphene metamaterial can achieve high co-polarized transmission of a linearly polarized incident wave at the off-state of the graphene grating without applying the bias voltage. Once the specially designed bias voltage is applied to change the Fermi level of graphene, the polarization rotation angle of linearly polarized waves is switched to 45° by the graphene metamaterial at the on-state. The working frequency band with 45-degree linear polarized transmission remaining above 0.7 and the polarization conversion ratio (PCR) above 90% is from 0.35 to 1.75 THz, and the relative bandwidth reaches 133.3% of the central working frequency. Furthermore, even with oblique incidence at large angles, the proposed device retains high-efficiency conversion in a broad band. The proposed graphene metamaterial offers a novel approach for the design of a terahertz tunable polarization rotator and is expected to be applied in the applications of terahertz wireless communication, imaging, and sensing. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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14 pages, 8424 KiB

Open AccessCommunication

MIMO 5G Smartphone Antenna with Tri-Band and Decoupled Elements

by Jianqiang Hou, Yuxuan Peng, Jiajun Huang, Zhefei Wang and Tayeb A. Denidni

Sensors 2023, 23(11), 5186; https://doi.org/10.3390/s23115186 - 30 May 2023

Cited by 2 | Viewed by 3038

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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14 pages, 3601 KiB

Open AccessArticle

Design and Analysis of a Fluid-Filled RF MEMS Switch

by Hongyu Zhu, Wenhao Cui, Yanzhang Li and Mingxin Song

Sensors 2023, 23(5), 2692; https://doi.org/10.3390/s23052692 - 1 Mar 2023

Cited by 2 | Viewed by 1645

Abstract

In the present study, a fluid-filled RF MEMS (Radio Frequency Micro-Electro-Mechanical Systems) switch is proposed and designed. In the analysis of the operating principle of the proposed switch, air, water, glycerol and silicone oil were adopted as filling dielectric to simulate and research [...] Read more.

In the present study, a fluid-filled RF MEMS (Radio Frequency Micro-Electro-Mechanical Systems) switch is proposed and designed. In the analysis of the operating principle of the proposed switch, air, water, glycerol and silicone oil were adopted as filling dielectric to simulate and research the influence of the insulating liquid on the drive voltage, impact velocity, response time, and switching capacity of the RF MEMS switch. The results show that by filling the switch with insulating liquid, the driving voltage can be effectively reduced, while the impact velocity of the upper plate to the lower plate is also reduced. The high dielectric constant of the filling medium leads to a lower switching capacitance ratio, which affects the performance of the switch to some extent. By comparing the threshold voltage, impact velocity, capacitance ratio, and insertion loss of the switch filled with different media with the filling media of air, water, glycerol, and silicone oil, silicone oil was finally selected as the liquid filling medium for the switch. The results show that the threshold voltage is 26.55 V after filling with silicone oil, which is 43% lower under the same air-encapsulated switching conditions. When the trigger voltage is 30.02 V, the response time is 10.12 μs and the impact speed is only 0.35 m/s. The frequency 0–20 GHz switch works well, and the insertion loss is 0.84 dB. To a certain extent, it provides a reference value for the fabrication of RF MEMS switches. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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12 pages, 5456 KiB

Open AccessCommunication

UWB Frequency-Selective Surface Absorber Based on Graphene Featuring Wide-Angle Stability

by Zhefei Wang, Jiajun Huang, Dongjiao Sun, Qingsheng Zeng, Mingxin Song and Tayeb A. Denidni

Sensors 2023, 23(5), 2677; https://doi.org/10.3390/s23052677 - 1 Mar 2023

Cited by 3 | Viewed by 1948

Abstract

In this paper, an ultra-wideband and polarization-insensitive frequency-selective surface absorber is presented with oblique incident stable behavior. Different from conventional absorbers, the absorption behavior is much less deteriorated with the increase in the incidence angle. Two hybrid resonators, which are realized by symmetrical [...] Read more.

In this paper, an ultra-wideband and polarization-insensitive frequency-selective surface absorber is presented with oblique incident stable behavior. Different from conventional absorbers, the absorption behavior is much less deteriorated with the increase in the incidence angle. Two hybrid resonators, which are realized by symmetrical graphene patterns, are employed to obtain the desired broadband and polarization-insensitive absorption performance. The optimal impedance-matching behavior is designed at the oblique incidence of electromagnetic waves, and an equivalent circuit model is used to analyze and facilitate the mechanism of the proposed absorber. The results indicate that the absorber can maintain a stable absorption performance with a fractional bandwidth (FWB) of 136.4% up to 40°. With these performances, the proposed UWB absorber could be more competitive in aerospace applications. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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12 pages, 3368 KiB

Open AccessCommunication

Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material

by Shuang Ma, Xue-Nan Li, Zhan-Dong Li and Jun-Jun Ding

Sensors 2023, 23(5), 2556; https://doi.org/10.3390/s23052556 - 25 Feb 2023

Cited by 2 | Viewed by 1892

Abstract

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) [...] Read more.

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) transmission line theory. Through a multi-separated metal layer, the double LC layers can be loaded with controllable bias voltage independently. Therefore, the LC material exhibits four extreme states, among which the permittivity of LC can be varied linearly. On the strength of the dual-tuned mode of LC, a CRLH unit cell is elaborately designed on three-layer substrates with balanced dispersion values under arbitrary LC state. Then five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna on a downlink Ku satellite communication band with dual-tuned characteristics. The simulated results demonstrate that the metamaterial antenna features’ continuous electronic beam-steering capacity from broadside to −35° at 14.4 GHz. Furthermore, the beam-steering properties are implemented in a broad frequency band from 13.8 GHz to 17 GHz, with good impedance matching. The proposed dual-tuned mode can make the regulation of LC material more flexible and enlarge the beam-steering range simultaneously. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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14 pages, 5147 KiB

Open AccessArticle

Dual-Band Wide-Angle Reflective Circular Polarization Converter with Orthogonal Polarization Modes

by Bianmei Zhang, Chenghui Zhu, Ran Zhang, Xiaofan Yang, Ye Wang and Xiaoming Liu

Sensors 2022, 22(24), 9728; https://doi.org/10.3390/s22249728 - 12 Dec 2022

Cited by 3 | Viewed by 1777

Abstract

Herein a dual-band wide-angle reflective circular polarization converter, based on a metasurface was developed. The unit cell is composed of a split square ring and a nested square patch. The split square ring plays the role of creating polarization conversion. The square patch [...] Read more.

Herein a dual-band wide-angle reflective circular polarization converter, based on a metasurface was developed. The unit cell is composed of a split square ring and a nested square patch. The split square ring plays the role of creating polarization conversion. The square patch is useful for improving the quality of axial ratio. It was verified that the structure could transform the x-polarized incident wave into left-hand circular polarization in the lower frequency band, and to right-hand circular polarization in the higher frequency band. For y-polarized incidence, the transformation has orthogonal modes to that for x-polarized incidence. Moreover, the 3 dB axial ratio takes place in the ranges of 8.42–12.32 GHz and 18.74–29.73 GHz, corresponding to a relative bandwidth of 37.61%, and 45.35%, respectively. In addition, the polarization conversion efficiency is greater than 99% in the ranges of 8.65–11.83 GHz and 19.55–29.36 GHz. Furthermore, for oblique incidence, the axial ratio remains stable, even at 50° incidence, for the lower frequency band. Lastly, a prototype is fabricated and measured for experimental verification. The measured and simulated results were in good agreement. Compared with other designs in the literature, the proposed converter operates with good performance in dual-band, with high-efficiency, and with angular stability. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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13 pages, 3243 KiB

Open AccessArticle

Design and Analysis of the Capacitive RF MEMS Switches with Support Pillars

by Hongbo Feng, Jiabin Zhao, Chengsi Zhou and Mingxin Song

Sensors 2022, 22(22), 8864; https://doi.org/10.3390/s22228864 - 16 Nov 2022

Cited by 5 | Viewed by 2376

Abstract

Conventional parallel capacitive RF MEMS switches have a large impact during the suction phase. In general, RF MEMS switches have to be switched on and off in a considerably fast manner. Increasing the driving voltage enables fast switching but also increases the impact [...] Read more.

Conventional parallel capacitive RF MEMS switches have a large impact during the suction phase. In general, RF MEMS switches have to be switched on and off in a considerably fast manner. Increasing the driving voltage enables fast switching but also increases the impact force, which causes the beam membrane to be prone to failure. In the present study, the addition of two support pillars was proposed for slowing down the fall of the beam membrane based on the conventional RF MEMS parallel switch, so as to reduce the impact velocity. As such, a novel RF MEMS switch was designed. Further, simulation software was used to scan and analyze the positioning and height of the support pillars with respect to electromechanical and electromagnetic performance. The simulation results show that the optimal balance of impact velocity and pull-in time was achieved at a height of 0.8 um, a distance of 10 um from the signal line, and an applied voltage of 50 V. The impact velocity was reduced from 1.8 m/s to 1.1 m/s, decreasing by nearly 40%. The turn off time increased from 3.9 us to 4.2 us, representing an increase of only 0.05%. The insertion loss was less than 0.5 dB at 32 GHz, and the isolation was greater than 50 dB at 40 GHz. Full article

(This article belongs to the Special Issue Microwave Communication and Signal Transmission Based on Antennas and Metamaterials)

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