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Micromachines
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Microwave Antennas: From Fundamental Research to Applications
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Microwave Antennas: From Fundamental Research to Applications

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E：Engineering and Technology".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 45459

Special Issue Editors

Dr. Nikola Basta

E-Mail Website
Guest Editor
School of Electrical Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11120 Belgrade, Serbia
Interests: microwave antennas; GNSS antennas; antenna arrays; digital beamforming
Prof. Dr. Milka Potrebic

E-Mail Website
Guest Editor
School of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11120 Belgrade, Serbia
Interests: microwave circuits; microwave filters; frequency-selective surfaces; memristive systems; circuit theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Recent developments in the areas of 5G and future 6G mobile communications drove a great deal of antenna technology research towards higher-frequency bands, i.e., the millimeter waves (30 GHz–300 GHz). These new, large bands allow for enhanced mobile broadband, including more connected devices, greater connection speeds, lower latency, and reliable vehicle as well as other machine communications, whereas higher frequencies allow for packing very small antennas and antenna arrays with beamforming capability into final commercial products.

However, the lower portions of the microwave band (300 MHz–30 GHz) still remain in the focus of many researchers due to exciting novel applications in the areas of navigation and communications. These applications include GNSS reflectometry, local radiodetermination systems, smart sensor networks, the Internet of things (IoT), and low-cost, low-power, and long-range (LoRa) communications systems.

Advances in computational electromagnetics as well as the smart usage of computational resources, such as GPUs, make it possible to perform electromagnetic-simulation-driven antenna design on a modern desktop PC. In particular, the application of artificial intelligence (AI) offers new paths in the design and optimization of complex structures.

In order to inspire fruitful discussion and offer an overview of state-of-the-art technologies, we invite researchers from both industry and academia to contribute to this Special Issue with their ongoing research and visions of the future trends in microwave antennas. The contributions should consider, but are not limited to, the following topics:

  • Antenna elements;
  • Antenna arrays;
  • Antenna elements and arrays for navigation;
  • Antenna design and optimization techniques;
  • Antennas for automotive and airborne communications;
  • IoT antennas;
  • Antenna measurement;
  • Antennas and antenna arrays signal processing;
  • Filtering antennas;
  • Frequency-selective surfaces.

We look forward to your submissions.

Dr. Nikola Basta
Prof. Dr. Milka Potrebic
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microwave antennas
  • antenna arrays
  • antenna array signal processing
  • antenna measurements
  • filtering antennas
  • frequency-selective surface

Published Papers (23 papers)

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13 pages, 5206 KiB  
Article
A Triple Band Substrate Integrated Waveguide with Dielectric Resonator Antenna for 4G and 5G Applications
by Irene Kong Cheh Lin, Mohd Haizal Jamaluddin and Abinash Gaya
Micromachines 2023, 14(7), 1284; https://doi.org/10.3390/mi14071284 - 22 Jun 2023
Cited by 1 | Viewed by 923
Abstract
A triple-band substrate integrated waveguide (SIW) with dielectric resonator antenna (DRA) for fourth-generation (4G) and fifth-generation (5G) applications is proposed and analyzed in this paper. Loading SIW with DRA allows for a wide bandwidth, low losses, and fabrication ease. The proposed antenna can [...] Read more.
A triple-band substrate integrated waveguide (SIW) with dielectric resonator antenna (DRA) for fourth-generation (4G) and fifth-generation (5G) applications is proposed and analyzed in this paper. Loading SIW with DRA allows for a wide bandwidth, low losses, and fabrication ease. The proposed antenna can transmit and receive data independently by covering LTE Band 3 at 1.8 GHz, LTE Band 8 at 2.6 GHz, and 5G n77 at 3.7 GHz. A U-shaped cut is applied to achieve the targeted multi-resonance frequencies. The antenna obtains high bandwidths of up to 19.50% with 4.9 dBi gain and 81.0% efficiency at 1.8 GHz, 6.58% bandwidth with 4.4 dBi and 72.7% efficiency at 2.6 GHz, and 8.21% bandwidth with 6.7 dBi and 73.5% efficiency at 3.7 GHz. The simulated and measured results agree well. The proposed antenna is feasible for 4G and 5G applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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18 pages, 14855 KiB  
Article
Multiband Microstrip Rectenna Using ZnO-Based Planar Schottky Diode for RF Energy Harvesting Applications
by Somaya I. Kayed, Dalia N. Elsheakh, Hesham A. Mohamed and Heba A. Shawkey
Micromachines 2023, 14(5), 1006; https://doi.org/10.3390/mi14051006 - 06 May 2023
Viewed by 1427
Abstract
This paper presents a single-substrate microstrip rectenna for dedicated radio frequency energy harvesting applications. The proposed configuration of the rectenna circuit is composed of a clipart moon-shaped cut in order to improve the antenna impedance bandwidth. The curvature of the ground plane is [...] Read more.
This paper presents a single-substrate microstrip rectenna for dedicated radio frequency energy harvesting applications. The proposed configuration of the rectenna circuit is composed of a clipart moon-shaped cut in order to improve the antenna impedance bandwidth. The curvature of the ground plane is modified with a simple U-shaped slot etched into it to improve the antenna bandwidth by changing the current distribution; therefore, this affects the inductance and capacitance embedded into the ground plane. The linear polarized ultra-wide bandwidth (UWB) antenna is achieved by using 50 Ω microstrip line and build on Roger 3003 substrate with an area of 32 × 31 mm2. The operating bandwidth of the proposed UWB antenna extended from 3 GHz to 25 GHz at −6 dB reflection coefficient (VSWR ≤ 3) and extended from both 3.5 to 12 GHz, from 16 up to 22 GHz at −10 dB impedance bandwidth (VSWR ≤ 2). This was used to harvest RF energy from most of the wireless communication bands. In addition, the proposed antenna integrates with the rectifier circuit to create the rectenna system. Moreover, to implement the shunt half-wave rectifier (SHWR) circuit, a planar Ag/ZnO Schottky diode uses a diode area of 1 × 1 mm2. The proposed diode is investigated and designed, and its S-parameter is measured for use in the circuit rectifier design. The proposed rectifier has a total area of 40 × 9 mm2 and operates at different resonant frequencies, namely 3.5 GHz, 6 GHz, 8 GHz, 10 GHz and 18 GHz, with a good agreement between simulation and measurement. The maximum measured output DC voltage of the rectenna circuit is 600 mV with a maximum measured efficiency of 25% at 3.5 GHz, with an input power level of 0 dBm at a rectifier load of 300 Ω. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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16 pages, 11837 KiB  
Article
A Four Element mm-Wave MIMO Antenna System with Wide-Band and High Isolation Characteristics for 5G Applications
by Mehr E. Munir, Saad Hassan Kiani, Huseyin Serif Savci, Mohamed Marey, Jehanzeb Khan, Hala Mostafa and Naser Ojaroudi Parchin
Micromachines 2023, 14(4), 776; https://doi.org/10.3390/mi14040776 - 30 Mar 2023
Cited by 11 | Viewed by 2070
Abstract
In this article, we propose a light weight, low profile Multiple Input Multiple Output (MIMO) antenna system for compact 5th Generation (5G) mmwave devices. Using a RO5880 substrate that is incredibly thin, the suggested antenna is made up of circular rings stacked vertically [...] Read more.
In this article, we propose a light weight, low profile Multiple Input Multiple Output (MIMO) antenna system for compact 5th Generation (5G) mmwave devices. Using a RO5880 substrate that is incredibly thin, the suggested antenna is made up of circular rings stacked vertically and horizontally on top of one another. The single element antenna board has dimensions of 12 × 12 × 0.254 mm3 while the size of the radiating element is 6 × 2 × 0.254 mm3 (0.56λ0 × 0.19λ0 × 0.02λ0). The proposed antenna showed dual band characteristics. The first resonance showed a bandwidth of 10 GHz with a starting frequency of 23 GHz to an ending frequency point of 33 GHz followed by a second resonance bandwidth of 3.25 GHz ranging from 37.75 to 41 GHz, respectively. The proposed antenna is transformed into a four element Linear array system with size of 48 × 12 × 0.254 mm3 (4.48λ0 × 1.12λ0 × 0.02λ0). The isolation levels at both resonance bands were noted to be >20 dB which shows high levels of isolation among radiating elements. The MIMO parameters such as Envelope Correlation Co-efficient (ECC), Mean Effective Gain (MEG) and Diversity Gain (DG) were derived and were found to be in satisfactory limits. The proposed MIMO system model is fabricated and through validation and testing of the prototype, the results were found to be in good agreement with simulations. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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15 pages, 5583 KiB  
Article
Employment of Self-Adaptive Bayesian Neural Network for Systematic Antenna Design: Improving Wireless Networks Functionalities
by Khaled Aliqab, Muhammad Ammar Sohaib, Farman Ali, Ammar Armghan and Meshari Alsharari
Micromachines 2023, 14(3), 594; https://doi.org/10.3390/mi14030594 - 02 Mar 2023
Cited by 1 | Viewed by 1186
Abstract
The performance of wireless networks is related to the optimized structure of the antenna. Therefore, in this paper, a Machine Learning (ML)-assisted new methodology named Self-Adaptive Bayesian Neural Network (SABNN) is proposed, aiming to optimize the antenna pattern for next-generation wireless networks. In [...] Read more.
The performance of wireless networks is related to the optimized structure of the antenna. Therefore, in this paper, a Machine Learning (ML)-assisted new methodology named Self-Adaptive Bayesian Neural Network (SABNN) is proposed, aiming to optimize the antenna pattern for next-generation wireless networks. In addition, the statistical analysis for the presented SABNN is evaluated in this paper and compared with the current Gaussian Process (GP). The training cost and convergence speed are also discussed in this paper. In the final stage, the proposed model’s measured results are demonstrated, showing that the system has optimized outcomes with less calculation time. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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20 pages, 6904 KiB  
Article
Circularly Polarized Textile Sensors for Microwave-Based Smart Bra Monitoring System
by Dalia N. Elsheakh, Yasmine K. Elgendy, Mennatullah E. Elsayed and Angie R. Eldamak
Micromachines 2023, 14(3), 586; https://doi.org/10.3390/mi14030586 - 28 Feb 2023
Cited by 6 | Viewed by 1682
Abstract
This paper presents a conformal and biodegradable circularly polarized microwave sensor (CPMS) that can be utilized in several medical applications. The proposed textile sensor can be implemented in a Smart Bra system for breast cancer detection (BCD) and a wireless body area network [...] Read more.
This paper presents a conformal and biodegradable circularly polarized microwave sensor (CPMS) that can be utilized in several medical applications. The proposed textile sensor can be implemented in a Smart Bra system for breast cancer detection (BCD) and a wireless body area network (WBAN). The proposed sensor is composed of a wideband circularly polarized (CP) textile-based monopole antenna with an overall size of 33.5 × 33.5 mm2 (0.2 λo × 0.2 λo) and CPW feed line. The radiating element and ground are fabricated using silver conductive fabric and stitched to a cotton substrate of thickness 2 mm. In the proposed design, a slot is etched in the radiating element to extend bandwidth from 1.8 to 8 GHz at |S11| ≤ −10 dB. It realizes a circularly polarized output with AR ≤ 3 dB operation band from 1.8 to 4 GHz and an average gain of 6 dBi. The proposed CPMS’s performance is studied both off-body (air) and on-body in proximity to breast models with and without tumors using near-field microwave imaging. Moreover, the axial ratio is recorded as a feature for a circularly polarized antenna and adds another degree of freedom for cancer detection and data analysis. It assists in detecting tumors in the breast by analyzing the magnitude of the electric field components in vertical and horizontal directions. Finally, the radiation properties are recorded, as well as the specific absorption rate (SAR), to ensure safe operation. The proposed CPMS covers a bandwidth of 1.8–8 GHz with SAR values following the 1 g and 10 g standards. The proposed work demonstrates the feasibility of using textile antennas in wearables, microwave sensing systems, and wireless body area networks (WBANs). Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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10 pages, 7083 KiB  
Article
A Broadband Vortex Beam Generator Based on Single-Layer Hybrid Phase-Turning Metasurface
by Cheng Fu, Jianing Zhao, Fang Li and Hao Li
Micromachines 2023, 14(2), 465; https://doi.org/10.3390/mi14020465 - 17 Feb 2023
Cited by 3 | Viewed by 1387
Abstract
Vortex beams carrying orbital angular momentum (OAM) have become a research frontier due to the prospect of improving spectral efficiency and transmission capacity in communication systems. In this work, a hybrid phase-turning meta-atom that combines resonance and geometric (Pancharatnam-Berry) phase modulation is used [...] Read more.
Vortex beams carrying orbital angular momentum (OAM) have become a research frontier due to the prospect of improving spectral efficiency and transmission capacity in communication systems. In this work, a hybrid phase-turning meta-atom that combines resonance and geometric (Pancharatnam-Berry) phase modulation is used to form a single-layer metasurface. A linearly polarized broadband vortex beam of mode l = −1 is obtained by the metasurface. An experimental prototype of the vortex beam generator has been fabricated and measured. The simulated and measured results demonstrate that the whole vortex beam generator exhibits over 70% mode purity from 26.5 GHz to 40 GHz (the relative bandwidth is 38.57%). In addition, a wide 3 dB gain bandwidth and low crosstalk are also provided by the proposed generator. This indicates that the proposed generator has important application value for vortex beam communication and its related applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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17 pages, 5536 KiB  
Article
Broadband Flexible Microstrip Antenna Array with Conformal Load-Bearing Structure
by Can Tang, Hongxing Zheng, Ziwei Li, Kanglong Zhang, Mengjun Wang, Chao Fan and Erping Li
Micromachines 2023, 14(2), 403; https://doi.org/10.3390/mi14020403 - 08 Feb 2023
Cited by 1 | Viewed by 1526
Abstract
To enhance the load-bearing mechanical properties and broadband electromagnetic characteristics of the conformal antenna, a broadband microstrip antenna array with a conformal load-bearing structure is proposed in this paper, which consists of three flexible substrate layers and two honeycomb core layers stacked on [...] Read more.
To enhance the load-bearing mechanical properties and broadband electromagnetic characteristics of the conformal antenna, a broadband microstrip antenna array with a conformal load-bearing structure is proposed in this paper, which consists of three flexible substrate layers and two honeycomb core layers stacked on each other. By combining the antenna and honeycomb core layer in a structural perspective, the antenna array is implemented in the composition function of surface conformability and load-bearing. Additionally, the sidelobe level of the antenna is suppressed based on the reflection surface loaded. Meanwhile, an equivalent model of a honeycomb core layer has been established and applied in the design of a conformal antenna with a load-bearing structure. The presented model increases the accuracy of simulated results and reduces the memory consumption and time of the simulation. The overall size of the proposed antenna array is 32.84 × 36.65 × 4.9 mm (1.36 λ0 × 1.52 λ0 × 0.2 λ0, λ0 is the wavelength at 12.5 GHz). The proposed antenna element and array have been fabricated and measured in the flat state and under other various bending states. Experiment results show the operating relative bandwidth of the antenna array is 20.68% (11.67–13.76 GHz and 14.33–14,83 GHz) in the flat state. Under different bending conditions, the proposed antenna array covers 24.16% (11.08–14.1 GHz), 23.82% (10.63–13.5 GHz), and 23.12% with 30°, 60°, and 90° in the xoz plane (11.55–14.33 GHz). In terms of mechanical load bearing, the structure has better performance than the traditional single-layer honeycomb core load-bearing structure antenna. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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23 pages, 9790 KiB  
Article
Lightweight Fan-Beam Microstrip Grid Antenna for Airborne Microwave Interferometric Radiometer Applications
by Chunwang Gu, Hao Liu and Min Yi
Micromachines 2023, 14(1), 228; https://doi.org/10.3390/mi14010228 - 15 Jan 2023
Viewed by 1312
Abstract
The microwave interferometric radiometer (MIR) uses aperture synthesis technology to equate multiple small-aperture antennas into a large-aperture antenna to improve spatial resolution. At present, MIR antennas that operate at frequencies above the C-band mostly use horn antennas, waveguide slot antennas, etc., which have [...] Read more.
The microwave interferometric radiometer (MIR) uses aperture synthesis technology to equate multiple small-aperture antennas into a large-aperture antenna to improve spatial resolution. At present, MIR antennas that operate at frequencies above the C-band mostly use horn antennas, waveguide slot antennas, etc., which have the disadvantages of a high profile and large mass. In this paper, a new type of miniaturized, low-profile, and lightweight K-band fan-beam microstrip grid antenna is designed for the airborne campaign of the K-band one-dimensional MIR of a Microwave Imager Combined Active and Passive (MICAP) onboard a Chinese Ocean Salinity Mission (COSM). With a limited size constraint (12.33 mm) on the antenna width, a fan-beam shape antenna pattern was achieved with a 5.34° 3-dB beamwidth in the narrow beam direction and up to a 55° 3-dB beamwidth in the fan-beam direction. A periodic structural unit is proposed in this paper to reduce the design complexity of Taylor weighting, achieving desirable performances on gain (19.1 dB) and sidelobe level (<−20 dB) in the H-plane. Four antenna elements were fabricated and arranged in a non-redundant sparse array. The performance of the four-element sparse array was evaluated with a simulation and real measurement in an anechoic chamber. The coupling between antenna elements was less than −25 dB, and the consistency of phase patterns was better than 3.4°. These results verify the feasibility of the proposed K-band microstrip grid antenna for airborne MIR applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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13 pages, 3950 KiB  
Article
Design of 4 × 4 Low-Profile Antenna Array for CubeSat Applications
by Diana Alondra Jiménez, Alberto Reyna, Luz Idalia Balderas and Marco Antonio Panduro
Micromachines 2023, 14(1), 180; https://doi.org/10.3390/mi14010180 - 10 Jan 2023
Cited by 1 | Viewed by 1836
Abstract
This paper presents a low-profile microstrip antenna with high gain for fifth-generation (5G) CubeSat applications. The proposed design consists of 16 miniaturized patch antennas distributed in a uniform 4 × 4 topology with a feeding network on Rogers TMM10 substrate. The antenna array [...] Read more.
This paper presents a low-profile microstrip antenna with high gain for fifth-generation (5G) CubeSat applications. The proposed design consists of 16 miniaturized patch antennas distributed in a uniform 4 × 4 topology with a feeding network on Rogers TMM10 substrate. The antenna array was simulated in CST Studio Suite® software and fabricated for performance testing on the CubeSat structure. The prototype works perfectly from 3.46 GHz to 3.54 GHz. The simulated and measurement results reveal remarkable performance. The design obtained a measured gain of 8.03 dBi and a reflection coefficient of −17.4 dB at the center frequency of 3.5 GHz. Due to its reduced dimensions of 10 × 10 cm, this design is an excellent alternative for mounting on a CubeSat structure as it combines efficient performance with a low profile. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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11 pages, 8856 KiB  
Article
2-Dimensional (2D) Beam Steering-Antenna Using Active PRS for 5G Applications
by Misha Nadeem, Nosherwan Shoaib, Aimen Raza, Warda Saeed, Imran Shoaib and Sultan Shoaib
Micromachines 2023, 14(1), 110; https://doi.org/10.3390/mi14010110 - 30 Dec 2022
Cited by 1 | Viewed by 1609
Abstract
This paper presents a compact coaxial-fed square microstrip patch antenna integrated with a beam-steering Partially Reflective Surface (PRS). The proposed design has a two-dimensional (2-D) Fabry-Perot Cavity (FPC) antenna acting as a radiator and the PRS as a beam-steering superstrate operating at 5.5 [...] Read more.
This paper presents a compact coaxial-fed square microstrip patch antenna integrated with a beam-steering Partially Reflective Surface (PRS). The proposed design has a two-dimensional (2-D) Fabry-Perot Cavity (FPC) antenna acting as a radiator and the PRS as a beam-steering superstrate operating at 5.5 GHz. The PRS consists of 6 × 6 reconfigurable unit cells etched on Rogers 5880 with a thickness of 1.57 mm. By controlling the switching of PIN diodes in different sections of PRS, beam steering can be achieved up to ±47° in the azimuth plane with a gain of 9.1 dB and 10.2 dB and ± 15° steering in an elevation plane with a measured gain of 9.3 dB and 8.9 dB, respectively. The antenna prototype is 2.56 λ × 2.56 λ at 5.5 GHz, and the measured gain values are around 10 dBi for all the states. The beam is able to radiate at boresight or tilted to 42° in two azimuthal directions and 45° in elevation direction by adjusting the PIN diodes ON/OFF states. The 10 dB impedance bandwidth of 5.4–5.52 GHz is achieved. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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10 pages, 2522 KiB  
Article
Time-Modulated Antenna Arrays for Ultra-Wideband 5G Applications
by Gonzalo Maldonado, Alberto Reyna Maldonado, Luz I. Balderas and Marco A. Panduro
Micromachines 2022, 13(12), 2233; https://doi.org/10.3390/mi13122233 - 16 Dec 2022
Cited by 1 | Viewed by 1721
Abstract
This research presents the design of time-modulated antenna arrays with UWB performance. The antenna arrays consider a linear topology with eight UWB disk-notch patch antennas. The technological problem is to find out the optimum antenna positions and/or time sequences to reduce the side [...] Read more.
This research presents the design of time-modulated antenna arrays with UWB performance. The antenna arrays consider a linear topology with eight UWB disk-notch patch antennas. The technological problem is to find out the optimum antenna positions and/or time sequences to reduce the side lobes and the sidebands in all of the UWB frequency ranges. The design process is formulated as a bacterial foraging optimization. The results show that the uniform array generates a better SLL performance whereas the non-uniform array obtains a wider bandwidth. The uniform array obtains an SLL < −20 dB from 3.37 GHz to 4.8 GHz and the non-uniform array generates an SLL < −7 dB from 2.97 GHz to 5.26 GHz. The sideband levels are very similar for both cases with a value of around −17 dB. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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23 pages, 10351 KiB  
Article
Isolation Enhancement of a Two-Monopole MIMO Antenna Array with Various Parasitic Elements for Sub-6 GHz Applications
by Yitao Liu, Zhuo Yang, Ping Chen, Jun Xiao and Qiubo Ye
Micromachines 2022, 13(12), 2123; https://doi.org/10.3390/mi13122123 - 30 Nov 2022
Cited by 9 | Viewed by 1697
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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15 pages, 7567 KiB  
Article
Compact 5G Nonuniform Transmission Line Interdigital Bandpass Filter for 5G/UWB Reconfigurable Antenna
by Sahar Saleh, Mohd Haizal Jamaluddin, Faroq Razzaz and Saud M. Saeed
Micromachines 2022, 13(11), 2013; https://doi.org/10.3390/mi13112013 - 18 Nov 2022
Cited by 3 | Viewed by 1829
Abstract
In this study, at two different fifth generation (5G) low-frequency bands (3.7–4.2 GHz and 5.975–7.125 GHz) and based on nonuniform transmission lines (NTLs) theory, a compact three-quarter-wave resonators interdigital bandpass filter (IBPF) is analyzed, designed, and fabricated. The compact proposed filter is considered [...] Read more.
In this study, at two different fifth generation (5G) low-frequency bands (3.7–4.2 GHz and 5.975–7.125 GHz) and based on nonuniform transmission lines (NTLs) theory, a compact three-quarter-wave resonators interdigital bandpass filter (IBPF) is analyzed, designed, and fabricated. The compact proposed filter is considered as a good candidate for reconfigurable 5G low-frequency bands and ultrawide band (UWB) antenna, which will reduce the size of the final RF communication system. Firstly, a uniform transmission line (UTL) IBPF at these two bands is designed and tested; then the NTL concept is applied for compactness. For both UTL and NTL IBPFs, different parametric studies are performed for optimization. At the first frequency band, size reductions of 16.88% and 16.83% are achieved in the first (symmetrical to the third resonator) and second λ/4 resonator of UTL IBPF, respectively, with up to 36.6% reduction in the total area. However, 16.46% and 16.33% size reductions are obtained in the first (symmetrical to the third resonator) and second λ/4 resonator, respectively, at the second frequency band with a 40.53% reduction in the whole circuit area. The performance of the proposed NTL IBPF is compared with the UTL IBPF. The measured reflection coefficient of the proposed NTL IBPF, S11, appears to be less than −10.53 dB and −11.27 dB through 3.7–4.25 GHz and 5.94–7.67 GHz, respectively. However, the transmission coefficient, S12 is around −0.86 dB and–1.7 dB at the center frequencies, fc = 3.98 GHz and 6.81 GHz, respectively. In this study, simulations are carried out using high-frequency structure simulator (HFSS) software based on the finite element method (FEM). The validity of the proposed theoretical schematic of this filter is proved by design simulations and measured results of its prototype. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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15 pages, 5207 KiB  
Article
Novel Design Techniques for the Fermat Spiral in Antenna Arrays, for Maximum SLL Reduction
by Kleiverg Encino, Marco A. Panduro, Alberto Reyna and David H. Covarrubias
Micromachines 2022, 13(11), 2000; https://doi.org/10.3390/mi13112000 - 17 Nov 2022
Cited by 1 | Viewed by 1311
Abstract
This paper presents novel design techniques for the Fermat spiral, considering a maximum side lobe level (SLL) reduction. The array system based on a Fermat spiral configuration considers techniques based on uniform and non-uniform amplitude excitation. The cases of uniform amplitude excitation are [...] Read more.
This paper presents novel design techniques for the Fermat spiral, considering a maximum side lobe level (SLL) reduction. The array system based on a Fermat spiral configuration considers techniques based on uniform and non-uniform amplitude excitation. The cases of uniform amplitude excitation are the golden angle and the optimization of the angular separations. The cases of non-uniform amplitude excitations consider a raised cosine distribution and the optimization of the amplitude excitations through the Fermat spiral array. In this study, the method of genetic algorithms (GA) was used in the cases to find the values of the angular separations and the amplitude excitations of the Fermat spiral array. A performance evaluation was conducted for all these design cases, considering the Fermat spiral geometry. These design cases were validated using electromagnetic simulation to take mutual coupling into account and consider the effect of the antenna element pattern in each proposed design case. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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12 pages, 9395 KiB  
Article
A Novel Metasurface-Based Monopulse Antenna with Improved Sum and Difference Beams Radiation Performance
by Jianing Zhao, Li Hao, Hao Li, Zihao Tong, Tianming Li, Haiyang Wang, Biao Hu, Yihong Zhou, Fang Li, Cheng Fu and Qian Li
Micromachines 2022, 13(11), 1927; https://doi.org/10.3390/mi13111927 - 08 Nov 2022
Cited by 1 | Viewed by 1670
Abstract
This paper proposes a novel metasurface-based monopulse antenna. A multimode pyramidal horn with four ports is selected as the feed of the proposed monopulse antenna. The 3-dB couplers and the optimized waveguide phase shifters are employed to design the monopulse comparator. In order [...] Read more.
This paper proposes a novel metasurface-based monopulse antenna. A multimode pyramidal horn with four ports is selected as the feed of the proposed monopulse antenna. The 3-dB couplers and the optimized waveguide phase shifters are employed to design the monopulse comparator. In order to obtain good sum and difference beams performance, metasurfaces are mounted on a bowl structure to radiate the electromagnetic wave from the sub-reflector. An experimental prototype of the proposed design has been fabricated and measured at Ku-band. The measured results show that the gain ratio between the sum and difference beams is 2.8 dB and 3.7 dB, respectively. More importantly, the peak gain of the sum beam at 16 GHz is 27.1 dB, without considering the loss of the comparator, with a corresponding aperture efficiency of about 41.4%. This indicates that the proposed structure is beneficial for improving the sum and difference beams performance of the monopulse antenna, which is suitable for tracking platforms. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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21 pages, 10002 KiB  
Article
Design and Analysis of a Flexible Smart Apparel MIMO Antenna for Bio-Healthcare Applications
by Thennarasi Govindan, Sandeep Kumar Palaniswamy, Malathi Kanagasabai, Sachin Kumar, Mohamed Marey and Hala Mostafa
Micromachines 2022, 13(11), 1919; https://doi.org/10.3390/mi13111919 - 06 Nov 2022
Cited by 10 | Viewed by 1765
Abstract
This paper presents the design and development of a quad-port smart textile antenna for bio-healthcare applications. The antenna is designed to operate in the ultra-wideband (UWB) spectrum (3.1–12 GHz) with an impedance bandwidth of 8.9 GHz. The size of the unit cell and [...] Read more.
This paper presents the design and development of a quad-port smart textile antenna for bio-healthcare applications. The antenna is designed to operate in the ultra-wideband (UWB) spectrum (3.1–12 GHz) with an impedance bandwidth of 8.9 GHz. The size of the unit cell and multiple-input multiple-output (MIMO) antenna are 0.25λ0 × 0.2λ0 × 0.015λ0 and 0.52λ0 × 0.52λ0 × 0.015λ0, respectively. The antenna has a maximum efficiency of 93% and a peak gain of 4.62 dBi. The investigation of diversity metrics is performed and the results obtained are found to be ECC < 0.08 and DG < 9.99 dB. The computed CCL and TARC values are <0.13 bits/s/Hz and <−12 dB, respectively. The SAR analysis of the antenna shows a value of 0.471 Watt/Kg at 4 GHz, 0.39 Watt/Kg at 7 GHz, and 0.22 Watt/Kg at 10 GHz. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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15 pages, 5386 KiB  
Article
Bandwidth Enhancement and Generation of CP of Yagi-Uda-Shape Feed on a Rectangular DRA for 5G Applications
by Inam Bari, Javed Iqbal, Haider Ali, Abdul Rauf, Muhammad Bilal, Naveed Jan, Usman Illahi, Muhammad Arif, Muhammad Amir Khan and Rania M. Ghoniem
Micromachines 2022, 13(11), 1913; https://doi.org/10.3390/mi13111913 - 04 Nov 2022
Cited by 4 | Viewed by 1420
Abstract
A wideband circularly polarized rectangular dielectric resonator antenna (DRA) fed by a single feeding mechanism has been studied theoretically and experimentally. The purpose of the study is to determine how adding a parasitic strip next to the flat surface metallic feed would affect [...] Read more.
A wideband circularly polarized rectangular dielectric resonator antenna (DRA) fed by a single feeding mechanism has been studied theoretically and experimentally. The purpose of the study is to determine how adding a parasitic strip next to the flat surface metallic feed would affect various far- and near-field antenna characteristics. Initially, the basic antenna design, i.e., the T-shape feed known as antenna A, produced a 4.81% impedance matching bandwidth (|S11| −10 dB). Due to the narrow and undesirable results of the initial antenna design, antenna-A was updated to the antenna-B design, i.e., Yagi-Uda. The antenna-B produced a decent result (7.89% S11) as compared to antenna-A but still needed the bandwidth widened, for this, a parasitic patch was introduced next to the Yagi-Uda antenna on the rectangular DRA at an optimized location to further improve the results. This arrangement produced circular polarization (CP) waves spanning a broad bandwidth of 28.21% (3.59–3.44 GHz) and a broad impedance |S11| bandwidth of around 29.74% (3.71–3.62 GHz). These findings show that, in addition to producing CP, parasite patches also cause the return loss to rise by a factor of almost three times when compared to results obtained with the Yagi-Uda-shape feed alone. Computer simulation technology was used for the simulation (CST-2017). The planned antenna geometry prototype was fabricated and measured. Performance indicators show that the suggested antenna is a good fit for 5G applications. The simulated outcomes and measurements match up reasonably. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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11 pages, 2378 KiB  
Article
A Deployable and Cost-Effective Kirigami Antenna for Sub-6 GHz MIMO Applications
by Saad Hassan Kiani, Mohamed Marey, Umair Rafique, Syed Imran Hussain Shah, Muhammad Adil Bashir, Hala Mostafa, Sai-Wai Wong and Naser Ojaroudi Parchin
Micromachines 2022, 13(10), 1735; https://doi.org/10.3390/mi13101735 - 13 Oct 2022
Cited by 5 | Viewed by 1597
Abstract
In this work, a low-cost, deployable, integratable, and easy-to-fabricate multiple-input multiple-output (MIMO) Kirigami antenna is proposed for sub-6 GHz applications. The proposed MIMO antenna is inspired by Kirigami art, which consists of four radiating and parasitic elements. The radiating and parasitic elements are [...] Read more.
In this work, a low-cost, deployable, integratable, and easy-to-fabricate multiple-input multiple-output (MIMO) Kirigami antenna is proposed for sub-6 GHz applications. The proposed MIMO antenna is inspired by Kirigami art, which consists of four radiating and parasitic elements. The radiating and parasitic elements are composed of a rectangular stub. These elements are placed in such a way that they can provide polarization diversity. The proposed MIMO antenna is designed and fabricated using a soft printed board material called flexible copper-clad laminate (FCCL). It is observed from the results that the proposed MIMO antenna resonates in the 2.5 GHz frequency band, with a 10 dB reflection coefficient bandwidth of 860 MHz ranging from 2.19 to 3.05 GHz. It is worthwhile to mention that the isolation between adjacent radiating elements is higher than 15 dB. In addition, the peak realized gain of the MIMO antenna is around 11 dBi, and the total efficiency is more than 90% within the band of interest. Moreover, the envelope correlation coefficient (ECC) is noted to be less than 0.003, and the channel capacity is ≥17 bps/Hz. To verify the simulated results, a prototype was fabricated, and excellent agreement between the measured and computed results was observed. By observing the performance attributes of the proposed design, it can be said that there are many applications in which this antenna can be adopted. Because of its low profile, it can be used in 5G small-cell mobile MIMO base stations, autonomous light mobility vehicles, and other applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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10 pages, 3713 KiB  
Communication
A Compact MIMO Antenna with Improved Isolation for ISM, Sub-6 GHz, and WLAN Application
by Batchingis Bayarzaya, Niamat Hussain, Wahaj Abbas Awan, Md. Abu Sufian, Anees Abbas, Domin Choi, Jaemin Lee and Nam Kim
Micromachines 2022, 13(8), 1355; https://doi.org/10.3390/mi13081355 - 20 Aug 2022
Cited by 23 | Viewed by 2421
Abstract
This paper presents a compact two-element MIMO antenna with improved isolation for triple-band applications. The antenna consists of two radiating elements with the shared ground plane and a novel decoupling structure. Each antenna element has three stubs with different lengths, which work as [...] Read more.
This paper presents a compact two-element MIMO antenna with improved isolation for triple-band applications. The antenna consists of two radiating elements with the shared ground plane and a novel decoupling structure. Each antenna element has three stubs with different lengths, which work as quarter-wavelength monopoles to give a triple-band operation. The decoupling system is made by etching various slots in an inverted H-shape stub attached to two quarter-circles at its lower ends. The simulated and measured results show that the antenna operates (|S11| < −10 dB) at the key frequency bands of 2.4 GHz (2.29–2.47 GHz), 3.5 GHz (3.34–3.73 GHz), and 5.5 GHz (4.57–6.75 GHz) with a stable gain and radiation patterns. Moreover, the MIMO antenna shows good isolation characteristics. The isolation is more than 20 dB, the envelope correlation coefficient is <0.003, and diversity gain is 9.98 dB, within the frequency band of interest. Furthermore, the MIMO antenna has a compact size of 48 mm × 31 mm × 1.6 mm. These features of the proposed antenna make it a suitable candidate for I.S.M., 5G sub-6 GHz, and WLAN applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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19 pages, 12376 KiB  
Article
A Wideband High-Gain Microstrip Array Antenna Integrated with Frequency-Selective Surface for Sub-6 GHz 5G Applications
by Husam Alwareth, Imran Mohd Ibrahim, Zahriladha Zakaria, Ahmed Jamal Abdullah Al-Gburi, Sharif Ahmed and Zayed A. Nasser
Micromachines 2022, 13(8), 1215; https://doi.org/10.3390/mi13081215 - 29 Jul 2022
Cited by 38 | Viewed by 5803
Abstract
This paper presents a wideband and high-gain rectangular microstrip array antenna with a new frequency-selective surface (FSS) designed as a reflector for the sub-6 5G applications. The proposed antenna is designed to meet the US Federal Communications Commission (FCC) standard for 5G in [...] Read more.
This paper presents a wideband and high-gain rectangular microstrip array antenna with a new frequency-selective surface (FSS) designed as a reflector for the sub-6 5G applications. The proposed antenna is designed to meet the US Federal Communications Commission (FCC) standard for 5G in the mid-band (3.5–5 GHz) applications. The designed antenna configuration consists of 1 × 4 rectangular microstrip array antenna with an FSS reflector to produce a semi-stable high radiation gain. The modeled FSS delivered a wide stopband transmission coefficient from 3.3 to 5.6 GHz and promised a linearly declining phase over the mid-band frequencies. An equivalent circuit (EC) model is additionally performed to verify the transmission coefficient of the proposed FSS structure for wideband signal propagation. A low-cost FR-4 substrate material was used to fabricate the antenna prototype. The proposed wideband array antenna with an FSS reflector attained a bandwidth of 2.3 GHz within the operating frequency range of 3.5–5.8 GHz, with a fractional bandwidth of 51.12%. A high gain of 12.4 dBi was obtained at 4.1 GHz with an improvement of 4.4 dBi compared to the antenna alone. The gain variation was only 1.0 dBi during the entire mid-band. The total dimension of the fabricated antenna prototype is 10.32 λo × 4.25 λo ×1.295 λo at a resonance frequency of 4.5 GHz. These results make the presented antenna appropriate for 5G sub-6 GHz applications. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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20 pages, 5185 KiB  
Article
Mutual Coupling Reduction through Defected Ground Structure in Circularly Polarized, Dielectric Resonator-Based MIMO Antennas for Sub-6 GHz 5G Applications
by Anwar Ali, Jijun Tong, Javed Iqbal, Usman Illahi, Abdul Rauf, Saeed Ur Rehman, Haider Ali, Muhammad Mansoor Qadir, Muhammad Amir Khan and Rania M. Ghoniem
Micromachines 2022, 13(7), 1082; https://doi.org/10.3390/mi13071082 - 08 Jul 2022
Cited by 20 | Viewed by 1985
Abstract
This paper describes a singly-fed circularly polarized rectangular dielectric resonator antenna (RDRA) for MIMO and 5G Sub 6 GHz applications. Circular polarization was achieved for both ports using a novel-shaped conformal metal strip. To improve the isolation between the radiators, a “S” shaped [...] Read more.
This paper describes a singly-fed circularly polarized rectangular dielectric resonator antenna (RDRA) for MIMO and 5G Sub 6 GHz applications. Circular polarization was achieved for both ports using a novel-shaped conformal metal strip. To improve the isolation between the radiators, a “S” shaped defective ground plane structure (DGPS) was used. In order to authenticate the estimated findings, a prototype of the suggested radiator was built and tested experimentally. Over the desired band, i.e., 3.57–4.48 GHz, a fractional impedance bandwidth of roughly 36.63 percent (−10 dB as reference) was reached. Parallel axial ratio bandwidth of 28.33 percent is achieved, which is in conjunction with impedance matching bandwidth. Between the ports, isolation of −28 dB is achieved Gain and other far-field parameters are also calculated and found to be within their optimum limits Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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15 pages, 8048 KiB  
Article
High Performance Eight-Port Dual-Band MIMO Antenna System for 5G Devices
by Saad Hassan Kiani, Muhammad Abbas Khan, Umair Rafique, Mohamed Marey, Abdullah G. Alharbi, Hala Mostafa, Muhammad Amir Khan and Syed Muzahir Abbas
Micromachines 2022, 13(6), 959; https://doi.org/10.3390/mi13060959 - 17 Jun 2022
Cited by 9 | Viewed by 2306
Abstract
This study provides an eight-component multiple-input multiple-output (MIMO) antenna architecture for fifth-generation (5G) mobile communication systems. The single antenna element is comprised of an L-shaped radiating component, an L-shaped parasitic element, and a ground plane with a rectangular slot. The main element with [...] Read more.
This study provides an eight-component multiple-input multiple-output (MIMO) antenna architecture for fifth-generation (5G) mobile communication systems. The single antenna element is comprised of an L-shaped radiating component, an L-shaped parasitic element, and a ground plane with a rectangular slot. The main element with a slot-loaded ground plane helps to draw current from a coaxial feed from the other side of the board, while the parasitic element helps to elongate the current path and improve the impedance of the system. This enables the system to radiate at two different frequency ranges: 3.34–3.7 GHz and 4.67–5.08 GHz, with 360 MHz and 410 MHz bandwidths, respectively. For MIMO configuration, the radiating elements are designed on either side of a 0.8 mm thick FR-4 substrate, allowing space to accommodate a battery, radio frequency (RF) systems and subsystems, and camera and sensor modules. The corner and the middle elements are arranged in such a manner so that they can provide spatial and pattern diversity. Furthermore, at least 12 dB of isolation is established between any two radiating elements. Various MIMO performance parameters were evaluated, e.g., mean effective gain (MEG), channel capacity (CC), envelope correlation coefficient (ECC), realized gain, far-field characteristics, and efficiency. Single- and double-hand mode evaluations were performed to further demonstrate the capability of the proposed MIMO antenna. A prototype of the proposed MIMO antenna was manufactured and assessed to verify the simulated data. The measured and simulated results were found to be in good agreement. On the basis of its performance characteristics, the designed MIMO system could be used in 5G communication systems. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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Review

Jump to: Research

40 pages, 14031 KiB  
Review
Broadband Circular Polarised Printed Antennas for Indoor Wireless Communication Systems: A Comprehensive Review
by Ahmed Jamal Abdullah Al-Gburi, Zahriladha Zakaria, Hussein Alsariera, Muhammad Firdaus Akbar, Imran Mohd Ibrahim, Khalid Subhi Ahmad, Sarosh Ahmad and Samir Salem Al-Bawri
Micromachines 2022, 13(7), 1048; https://doi.org/10.3390/mi13071048 - 30 Jun 2022
Cited by 26 | Viewed by 3143
Abstract
With the rapid changes in wireless communication systems, indoor wireless communication (IWC) technology has undergone tremendous development. Antennas are crucial components of IWC systems that transmit and receive signals within indoor environments. Thus, the development of indoor technology is highly dependent on the [...] Read more.
With the rapid changes in wireless communication systems, indoor wireless communication (IWC) technology has undergone tremendous development. Antennas are crucial components of IWC systems that transmit and receive signals within indoor environments. Thus, the development of indoor technology is highly dependent on the development of indoor antennas. However, indoor environments with limited space require the fewest indoor antenna units and the smallest indoor antenna sizes possible. Hence, indoor antennas with compact size and broad applications have become widely preferred. In an IWC system, circularly polarised (CP) antennas are generally important, especially in dense indoor environments, because compared with linearly polarised (LP) antennas, CP antennas reduce polarisation mismatch and multipath losses. This paper combs through the existing studies related to three-dimensional (3D) geometry (nonplanar) or waveguide indoor antennas and the two common approaches to two-dimensional (2D) geometry (planar) indoor antennas, namely, broadband CP printed monopole antennas (BCPPMAs) and broadband CP printed slot antennas (BCPPSAs). The advantages, disadvantages and limitations of previous works are highlighted as well. These research works are summarised, compared and analysed to understand the recent specifications of BCPPMAs and BCPPSAs to generate the most appropriate design structure suitable for current IWC systems. Full article
(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)
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