Applied Sciences

Editorial

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6 pages, 199 KiB

Open AccessEditorial

Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects

by Hosung Choo

Appl. Sci. 2022, 12(13), 6819; https://doi.org/10.3390/app12136819 - 5 Jul 2022

Cited by 1 | Viewed by 1982

Abstract

In recent decades, novel and significant approaches to the design of antennas for various microwave and millimeter-wave applications have been attempted [...] Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

Research

Jump to: Editorial

17 pages, 5888 KiB

Open AccessArticle

A Novel Single-Fed Dual-Band Dual-Circularly Polarized Dielectric Resonator Antenna for 5G Sub-6GHz Applications

by Javed Iqbal, Usman Illahi, Muhammad Abbas Khan, Abdul Rauf, Esraa Mousa Ali, Inam Bari, Haider Ali, Muhammad Amir Khan, Mohammad Alibakhshikenari and Mariana Dalarsson

Appl. Sci. 2022, 12(10), 5222; https://doi.org/10.3390/app12105222 - 21 May 2022

Cited by 18 | Viewed by 2504

Abstract

In this research article, a single-fed dual-band circular polarized (CP) dielectric resonator antenna (DRA) for dual-function communication, such as GPS and WLAN, was made. Initially, the proposed design process was initiated by designing a linearly polarized singly fed-DRA. To attain CP fields, the [...] Read more.

In this research article, a single-fed dual-band circular polarized (CP) dielectric resonator antenna (DRA) for dual-function communication, such as GPS and WLAN, was made. Initially, the proposed design process was initiated by designing a linearly polarized singly fed-DRA. To attain CP fields, the cross-shape conformal metal strip was optimized to excite the fundamental and the high-order mode in the two frequency bands. The metallic strip (parasitic) was utilized on top of the rectangular DRA to improve and widen the impedance and axial ratio (AR) bandwidth. This step led to a 2.73% improvement on the lower band and an impact of 6.5% on the upper band while on the other side a significant improvement was witnessed in the AR bandwidth in both frequency bands. A prototype was designed and fabricated in order to validate its operations. The measurement outcomes of the proposed antennas authenticated wideband impedance bandwidths of 6.4% and 25.26%, and 3-dB axial ratios (AR) of 21.26% and 27.82% respectively. The prototype is a decent candidate for a global positioning system (GPS) and wireless local area network (WLAN). Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 5626 KiB

Open AccessArticle

mmWave Four-Element MIMO Antenna for Future 5G Systems

by Muhammad Abbas Khan, Abdullah G. Al Harbi, Saad Hassan Kiani, Anis Nurashikin Nordin, Mehr E Munir, Sohail Imran Saeed, Javed Iqbal, Esraa Mousa Ali, Mohammad Alibakhshikenari and Mariana Dalarsson

Appl. Sci. 2022, 12(9), 4280; https://doi.org/10.3390/app12094280 - 23 Apr 2022

Cited by 38 | Viewed by 3434

Abstract

This paper presents an S-shape four-port Multiple Input Multiple Output (MIMO) wideband mmWave antenna with bandwidth of 25 GHz to 39 GHz. The antenna is designed on 0.254 mm ultra-thin RO5880 with permittivity of 2.3. The dimensions of proposed S-shape antenna are 10 [...] Read more.

This paper presents an S-shape four-port Multiple Input Multiple Output (MIMO) wideband mmWave antenna with bandwidth of 25 GHz to 39 GHz. The antenna is designed on 0.254 mm ultra-thin RO5880 with permittivity of 2.3. The dimensions of proposed S-shape antenna are 10 × 12 mm for single element and 24 × 24 mm for four-port MIMO configuration. A decoupling network is introduced to further compress mutual coupling among MIMO elements. The peak gain achieved is 7.1 dBi and MIMO assembly delivers diversity scheme. The proposed MIMO antenna is fabricated, and simulated results are found to be in excellent agreement with simulations. Through the results obtained, the proposed MIMO antenna system can be considered as a potential candidate for future mmWave devices. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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13 pages, 6538 KiB

Open AccessArticle

Quasi-Isotropic Hybrid Dielectric Resonator Antenna—Bow-Tie Patch with Harmonic Suppression

by Taeyong Jeong, Jong Seon Lee, Dong Geun Lee, Jun Hee Kim, Jinsu Park, Dong Hyee Hwang and Keum Cheol Hwang

Appl. Sci. 2022, 12(8), 3842; https://doi.org/10.3390/app12083842 - 11 Apr 2022

Cited by 3 | Viewed by 1907

Abstract

This paper proposes a quasi-isotropic hybrid dielectric resonator antenna (DRA) and bow-tie patch with harmonics suppression. The suggested antenna consists of a DRA, a bow-tie patch, and a microstrip seventh-order Chebyshev low-pass filter. By loading a bow-tie patch on the designed DRA, a [...] Read more.

This paper proposes a quasi-isotropic hybrid dielectric resonator antenna (DRA) and bow-tie patch with harmonics suppression. The suggested antenna consists of a DRA, a bow-tie patch, and a microstrip seventh-order Chebyshev low-pass filter. By loading a bow-tie patch on the designed DRA, a quasi-isotropic pattern is realized. The seventh-order Chebyshev low-pass filter was applied to the feed line, and harmonics were reduced in the section separate to the operating band to remove harmonics generated by the proposed antenna. The simulated

S 11

that satisfies below −10 dB is 3.09–3.3 GHz (6.25%), and the measured S11 is 3.10–3.28 GHz (5.64%). The simulated gain difference considering all radiating regions (

0^{\circ} \leq φ \leq 360^{\circ}

and

0^{\circ} \leq θ \leq 180^{\circ}

) is 7.211 dB. Compared with the antenna without a filter, the harmonic gain was reduced by 10.847 and 15.774 dB. The measured gain isolation of the operating band and the second and third harmonics are 10.10 and 18.94 dB, respectively. The proposed antenna is considered to be applicable to applications that require radio wave reception in all directions such as wireless point access points, internet of things and radio frequency identification, and is expected to contribute to reducing the size of the RF system. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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14 pages, 4262 KiB

Open AccessArticle

Uni-Planar MIMO Antenna for Sub-6 GHz 5G Mobile Phone Applications

by Umair Rafique, Suleman Khan, Muhammad Mansoor Ahmed, Saad Hassan Kiani, Syed Muzahir Abbas, Sohail Imran Saeed, Mohammad Alibakhshikenari and Mariana Dalarsson

Appl. Sci. 2022, 12(8), 3746; https://doi.org/10.3390/app12083746 - 8 Apr 2022

Cited by 30 | Viewed by 3139

Abstract

This article presents the design of a uni-planar MIMO antenna system for sub-6 GHz 5G-enabled smartphones. The MIMO antenna designed comprises four loop-shaped radiators placed at each corner of the mobile phone board, which follows the principle of pattern diversity. The single-antenna element [...] Read more.

This article presents the design of a uni-planar MIMO antenna system for sub-6 GHz 5G-enabled smartphones. The MIMO antenna designed comprises four loop-shaped radiators placed at each corner of the mobile phone board, which follows the principle of pattern diversity. The single-antenna element resonates at 3.5 GHz, its impedance bandwidth is noted to be 1.28 GHz (3–4.28 GHz) for S

_{11} \leq

−6 dB, and it is equal to 720 MHz (3.18–3.9 GHz) for S

_{11} \leq

−10 dB. For a single-antenna element, a peak gain of 3.64 dBi is observed with an antenna efficiency of >90%. The isolation of >10 dB between antenna elements is achieved for the MIMO configuration. Furthermore, the MIMO antenna designed provides enough radiation coverage to support different sides of the mobile phone board, which is an important feature for future 5G-enabled handsets. In addition, the impacts of human hands and heads on MIMO antenna performance are investigated, and acceptable performance in the data and conversation modes is observed. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 6688 KiB

Open AccessArticle

Design of a Polarization-Selective EM Transparent Mesh-Type E-Shaped Antenna for Shared-Aperture Radar Applications

by Sungsik Wang, Hyunsoo Kim, Hyun Kim and Hosung Choo

Appl. Sci. 2022, 12(4), 1862; https://doi.org/10.3390/app12041862 - 11 Feb 2022

Cited by 4 | Viewed by 1655

Abstract

In this paper, we propose a polarization-selective electromagnetic (EM) transparent mesh-type E-shaped antenna unit-cell in a shared aperture. The proposed antenna unit-cell, which can be expanded to a larger array in a modular way, has one S-band antenna on the upper layer and [...] Read more.

In this paper, we propose a polarization-selective electromagnetic (EM) transparent mesh-type E-shaped antenna unit-cell in a shared aperture. The proposed antenna unit-cell, which can be expanded to a larger array in a modular way, has one S-band antenna on the upper layer and nine X-band antennas on the lower layers. The simple E-shaped structure, which has a low profile with a good bandwidth, is used for the antenna elements. However, due to the limited aperture size of the stacked configuration, the lower-layer elements can be physically blocked by the upper-layer element. To reduce this blockage effect, the S-band element is rotated 90 degrees with respect to X-band elements so that the polarizations between the S- and X-band elements are perpendicular to each other. Moreover, to minimize performance degradation due to the blockage effect, a mesh structure is applied for S-band elements for EM transparent characteristics, thereby improving EM transparency from −30 dB to −1.5 dB. The extended via cavity wall is also employed outside the nine X-band elements to minimize the mutual coupling and to reduce antenna size. To confirm the effectiveness of the proposed design, the proposed antenna unit-cell is fabricated, and the radiation characteristics are measured, in a full anechoic chamber. The average bore-sight gains in the S- and X-band are 5 dBi and 4.5 dBi, respectively. The results confirm that the proposed design is suitable for shared-aperture radar applications. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 5601 KiB

Open AccessArticle

Novel Beam Scan Method of Fabry–Perot Cavity (FPC) Antennas

by Wook Jang, Yeong-geun Jeon, Han-jun Maeng, Jongyeong Kim and Dongho Kim

Appl. Sci. 2021, 11(22), 11005; https://doi.org/10.3390/app112211005 - 20 Nov 2021

Cited by 6 | Viewed by 3247

Abstract

A new beam scanning method of a Fabry–Perot cavity (FPC) antenna is proposed. To obtain high gain in a target direction with a reduced sidelobe level (SLL), we devised a tapered partially reflective surface (PRS) as a superstrate. Moreover, to attain various beam [...] Read more.

A new beam scanning method of a Fabry–Perot cavity (FPC) antenna is proposed. To obtain high gain in a target direction with a reduced sidelobe level (SLL), we devised a tapered partially reflective surface (PRS) as a superstrate. Moreover, to attain various beam scanning directions, a phase-controllable artificial magnetic conductor (AMC) ground plane with a broad reflection phase range and high reflection magnitudes was introduced. In the proposed method, a new formula to satisfy an FP resonance condition in a cavity for a scanned beam is also suggested. According to the formula, the FPC antenna can precisely scan the main beam in designed target directions with well-maintained high gain, which has been hardly achievable. In addition, our method demonstrates the potential of electrical beam-scanning antennas by employing active RF chips on the AMC cells. To validate the method, we fabricated a prototype FPC antenna for a scanned beam at θ = 30°. Furthermore, we conducted an additional simulation for a different beam scanning angle as well. Good agreement between the expected and experimental results verifies our design approach. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 11254 KiB

Open AccessArticle

Machine Learning Technique to Improve an Impedance Matching Characteristic of a Bent Monopole Antenna

by Jaeyul Choo, Thi Ha Anh Pho and Yong-Hwa Kim

Appl. Sci. 2021, 11(22), 10829; https://doi.org/10.3390/app112210829 - 16 Nov 2021

Cited by 5 | Viewed by 2766

Abstract

We designed the wire monopole antenna bent at three points by applying a machine learning technique to achieve a good impedance matching characteristic. After performing the deep neural network (DNN)-based training, we validated our machine learning model by evaluating mean squared error and [...] Read more.

We designed the wire monopole antenna bent at three points by applying a machine learning technique to achieve a good impedance matching characteristic. After performing the deep neural network (DNN)-based training, we validated our machine learning model by evaluating mean squared error and R-squared score. Considering the mean squared error of about zero and R-squared score of about one, the performance prediction by the resulting machine learning model showed a high accuracy compared with that by the numerical electromagnetic simulation. Finally, we interpreted the operating principle of the antennas with a good impedance matching characteristic by analyzing equivalent circuits corresponding to their structures. The accomplished works in this research provide us with the possibility to use the machine learning technique in the antenna design. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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17 pages, 2186 KiB

Open AccessArticle

Axial-Symmetric Diffraction Radiation Antenna with a Very Narrow Funnel-Shaped Directional Diagram

by Yuriy Sirenko, Seil Sautbekov, Merey Sautbekova, Nataliya Yashina, Nursaule Burambayeva and Assel Begimova

Appl. Sci. 2021, 11(21), 10381; https://doi.org/10.3390/app112110381 - 5 Nov 2021

Cited by 2 | Viewed by 2060

Abstract

The paper is focused on reliable modeling and analysis of axially symmetric radiators with a very narrow (throat) funnel-shaped radiation pattern. When such a diagram is formed, a wave analogue of Smith–Purcell coherent radiation is realized—the surface wave of a radial dielectric waveguide [...] Read more.

The paper is focused on reliable modeling and analysis of axially symmetric radiators with a very narrow (throat) funnel-shaped radiation pattern. When such a diagram is formed, a wave analogue of Smith–Purcell coherent radiation is realized—the surface wave of a radial dielectric waveguide ‘sweeps out’ with its exponentially decaying part a concentric periodic grating, the fundamental spatial harmonic of which, propagating without attenuation in a direction close to the symmetry axis of the structure, generates a radiation field with the required characteristics. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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14 pages, 1627 KiB

Open AccessFeature PaperArticle

Near-Field-Based 5G Sub-6 GHz Array Antenna Diagnosis Using Transfer Learning

by Hong Jun Lim, Dong Hwan Lee, Hark Byeong Park and Keum Cheol Hwang

Appl. Sci. 2021, 11(21), 10164; https://doi.org/10.3390/app112110164 - 29 Oct 2021

Cited by 2 | Viewed by 2163

Abstract

In this paper, we propose a method for near-field-based 5G sub 6-GHz array antenna diagnosis using transfer learning. A classification network was implemented for normal/abnormal operation of the array antenna and the failure of a specific port. Furthermore, a regression network that could [...] Read more.

In this paper, we propose a method for near-field-based 5G sub 6-GHz array antenna diagnosis using transfer learning. A classification network was implemented for normal/abnormal operation of the array antenna and the failure of a specific port. Furthermore, a regression network that could predict the amplitude and phase of the excitation signal of the array antenna was employed. Additionally, to accelerate the array antenna diagnosis, several near-field lines were sampled and reflected in the regression network. The proposed method was verified by measuring a fabricated 5G sub-6 GHz band 4

\times

4 array antenna in various scenarios using a divider and coaxial cables. The tests showed that the trained network accurately diagnosed 29 of 30 measurement results. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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21 pages, 13772 KiB

Open AccessArticle

A Dual-Band Dual-Polarized Antenna with Improved Isolation Characteristics for Polarimetric SAR Applications

by Daesung Park and Jaehoon Choi

Appl. Sci. 2021, 11(21), 10025; https://doi.org/10.3390/app112110025 - 26 Oct 2021

Cited by 5 | Viewed by 3595

Abstract

A dual-band dual-polarized antenna with high isolation characteristics is proposed for polarimetric synthetic aperture radar (PolSAR) applications. The antenna consists of four dipole antennas and 2 × 2 patch antenna arrays operating at the P-band (450–730 MHz) and Ka-band (34–36 GHz), respectively. The [...] Read more.

A dual-band dual-polarized antenna with high isolation characteristics is proposed for polarimetric synthetic aperture radar (PolSAR) applications. The antenna consists of four dipole antennas and 2 × 2 patch antenna arrays operating at the P-band (450–730 MHz) and Ka-band (34–36 GHz), respectively. The dipole antennas and the patch antenna arrays need dual-linear polarization characteristics to acquire PolSAR data. Improvements in the isolation characteristics at the P-band are achieved by inserting a metamaterial absorber with a fractal geometry between the transmitting (Tx) and receiving (Rx) dipole antennas. Without the absorber, the simulated isolation characteristics between the Tx and Rx antennas are lower than 19.2 dB over the target band. On the other hand, with the absorbers, the simulated isolation characteristics are higher than 23.44 dB over the target band, and remarkable improvement is achieved around the resonance frequency of the absorber. The measured results are in good agreement with the simulated ones, showing that the proposed antenna can be a good candidate for PolSAR applications. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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11 pages, 7359 KiB

Open AccessFeature PaperArticle

Study of Mesh Pattern for Optically Transparent Flexible Antenna with Feedline

by Seulgi Yu, Soyeong Lee, Hoosung Lee and Yong Bae Park

Appl. Sci. 2021, 11(21), 10002; https://doi.org/10.3390/app112110002 - 26 Oct 2021

Cited by 7 | Viewed by 2637

Abstract

This paper presents a systematic parameter study on mesh pattern for optically transparent flexible antenna with feedline. In implementing a transparent flexible antenna using a metal mesh, transparency and performance of antenna and feedline are opposite factors. To understand how both elements are [...] Read more.

This paper presents a systematic parameter study on mesh pattern for optically transparent flexible antenna with feedline. In implementing a transparent flexible antenna using a metal mesh, transparency and performance of antenna and feedline are opposite factors. To understand how both elements are affected by the design parameters of the mesh, we analyze the performance of the feedlines and antennas according to the design parameters of diamond and square meshes. Moreover, the effect of the difference in the shape of diamond mesh and square mesh on performance is analyzed. The measured results of the fabricated samples offer the feasibility of implementing transparent feedlines and antennas with similar performance to nontransparent feedlines and antennas. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 4771 KiB

Open AccessArticle

Design of a Printed 5G Monopole Antenna on Vehicle Window Glass Using Parasitic Elements and a Lattice-Structure Reflector for Gain Enhancement

by Changhyeon Im, Tae-Heung Lim, Doyoung Jang, Nak-Kyoung Kong and Hosung Choo

Appl. Sci. 2021, 11(21), 9953; https://doi.org/10.3390/app11219953 - 25 Oct 2021

Cited by 5 | Viewed by 2365

Abstract

This letter proposes a novel design for a printed 5G monopole antenna on a vehicle window glass. The proposed antenna consists of a coplanar waveguide (CPW), a monopole radiator, parasitic elements, and a lattice-structure reflector. The parasitic elements are placed on either side [...] Read more.

This letter proposes a novel design for a printed 5G monopole antenna on a vehicle window glass. The proposed antenna consists of a coplanar waveguide (CPW), a monopole radiator, parasitic elements, and a lattice-structure reflector. The parasitic elements are placed on either side of the monopole radiator to improve the bore-sight gain. To solve the radiation pattern distortion problem that occurs due to the thick vehicle window glass, the lattice-structure reflector is printed on the opposite side of the monopole radiator. Through fabrication and measurement of the proposed antenna, it is confirmed that the design improves bore-sight gain, and minimizes the radiation pattern distortion. The results demonstrate that the proposed 5G monopole antenna with parasitic elements and the lattice-structure reflector is suitable for 5G communication in vehicle applications. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 45177 KiB

Open AccessArticle

A Cross-Correlation-Based Approach to Pattern Distortion and Mutual Coupling for Shared-Aperture Antennas

by Jin Myeong Heo, Jongwon Yoon, Hyun Kim, Youngwan Kim and Gangil Byun

Appl. Sci. 2021, 11(20), 9652; https://doi.org/10.3390/app11209652 - 15 Oct 2021

Cited by 2 | Viewed by 1892

Abstract

This paper proposes a pattern distortion coefficient as a new figure of merit to quantitatively evaluate both mutual coupling and pattern distortions in multi-antenna systems. The proposed coefficient is defined as a cross correlation between unaffected and affected far-field patterns of antennas under [...] Read more.

This paper proposes a pattern distortion coefficient as a new figure of merit to quantitatively evaluate both mutual coupling and pattern distortions in multi-antenna systems. The proposed coefficient is defined as a cross correlation between unaffected and affected far-field patterns of antennas under test, and the input patterns are weighted using a Gaussian function to consider the target operation angle. The feasibility of the proposed approach is validated using a two-antenna system composed of an inverted-F antenna and a microstrip patch antenna, and the amount of mutual coupling is adjusted by changing the distance between the two antennas. The evaluation is further extended to a single-antenna system with a conducting wall that produces strong platform effects with serious pattern distortions. The results demonstrate that the proposed figure of merit provides quantitative insight into the amplitude and phase distortions of far-field patterns that can be caused by both mutual coupling and platform effects. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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13 pages, 3488 KiB

Open AccessArticle

Polarization and Incidence Angle Independent Low-Profile Wideband Metamaterial Electromagnetic Absorber Using Indium Tin Oxide (ITO) Film

by Sangmin Park, Geonyeong Shin, Hyun Kim, Youngwan Kim and Ick-Jae Yoon

Appl. Sci. 2021, 11(19), 9315; https://doi.org/10.3390/app11199315 - 8 Oct 2021

Cited by 13 | Viewed by 2703

Abstract

We use indium tin oxide (ITO), one of the representative resistive materials, for the implementation of a metamaterial electromagnetic (EM) absorber with a high absorbance in a wide frequency range. Highly symmetrical split ring resonators made of ITO film are deposited on the [...] Read more.

We use indium tin oxide (ITO), one of the representative resistive materials, for the implementation of a metamaterial electromagnetic (EM) absorber with a high absorbance in a wide frequency range. Highly symmetrical split ring resonators made of ITO film are deposited on the polyethylene terephthalate with transparent and flexible features, and such a configuration causes the proposed absorber to be insensitive to polarization and incidence angles. The proposed absorber, with a profile of only 0.171

λ

, exhibits a wideband absorbance of 7.2 GHz to 27 GHz, with a 90% absorption criterion. A prototype is built, and all the computed expectations from the full-wave EM simulations in this work are verified experimentally. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 4530 KiB

Open AccessArticle

A Compact Sequentially Rotated Circularly Polarized Dielectric Resonator Antenna Array

by Yazeed Qasaymeh, Abdullah Almuhaisen and Ali S. Alghamdi

Appl. Sci. 2021, 11(18), 8779; https://doi.org/10.3390/app11188779 - 21 Sep 2021

Cited by 6 | Viewed by 2765

Abstract

In this study, a compact 2 × 2 circularly polarized (CP) sequentially rotated (SR) dielectric resonator antenna (DRA) array operating in the IEEE 802.11a band is presented. To acquire the CP radiation, an elliptical slot (ES) was introduced to couple a rectangular dielectric [...] Read more.

In this study, a compact 2 × 2 circularly polarized (CP) sequentially rotated (SR) dielectric resonator antenna (DRA) array operating in the IEEE 802.11a band is presented. To acquire the CP radiation, an elliptical slot (ES) was introduced to couple a rectangular dielectric resonator (RDR). The ES generates two resonant frequencies corresponding to the dominant even and odd modes. The SR feeder is made of four quarter-wavelength microstrip transformers to reduce the input impedance of the elements and, consequently, maximize the power transferred to each element. Experimental and simulation verifications were conducted on a 54 × 50 × 0.813 mm³ prototype to evaluate the performance of the proposed antenna array, which achieved a VSWR < −10 dB bandwidth of 1 GHz (5.1–6.05 GHz) and axial ratio (AR) < 3 dB of 0.95 GHz (5.1–5.85 GHz). The agreement between the simulated and measured results confirmed the validity of the proposed design. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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13 pages, 6847 KiB

Open AccessFeature PaperArticle

Shape and Weighting Optimization of a Subarray for an mm-Wave Phased Array Antenna

by Taeyong Jeong, Juho Yun, Kyunghyun Oh, Jihyung Kim, Dae Woong Woo and Keum Cheol Hwang

Appl. Sci. 2021, 11(15), 6803; https://doi.org/10.3390/app11156803 - 24 Jul 2021

Cited by 9 | Viewed by 3459

Abstract

This paper discusses how to optimize the weighting of individual subarrays to derive the low sidelobe level (SLL) based on quadratic programming (QP) and how to derive QP parameters to ensure that the objective function is composed of the quadratic function form, with [...] Read more.

This paper discusses how to optimize the weighting of individual subarrays to derive the low sidelobe level (SLL) based on quadratic programming (QP) and how to derive QP parameters to ensure that the objective function is composed of the quadratic function form, with the actual number identical to the standard objective function of QP. Next, in order to analyze the SLL, a 24 × 24 phased array antenna was compared with 96 transmit–receive modules (TRMs) attached only to the subarray stage and a phased array antenna with 576 TRMs attached to all radiating elements without a subarray. Optimized weighting was applied to the array antennas with a subarray, and Taylor weighting was applied to the array antennas without a subarray. The number of TRMs used in the phased array antenna with the optimized weighting was reduced by 83.3% compared to the phased array antenna in which TRMs were attached to all radiating elements. The SLL and the half-power beamwidths (HPBWs) of the two antennas were practically identical in a narrow beam-scanning environment. Finally, an array pattern (AP) in which mutual coupling between the radiating elements was considered was calculated to verify the optimized weighting. Moreover, the optimized weighting was applied to CST Microwave Studio (an EM full-wave simulation) to compare the results from the AP calculation and a simulation. It was confirmed that the two results above are largely indistinguishable. The analysis found that the HPBW is 3.6

^{\circ}

× 3.6

^{\circ}

and the SLL is −26.18 dB from AP calculations in the boresight direction. When each 5

^{\circ}

beam was scanned at the azimuth and elevation, the corresponding HPBW values were 3.7

^{\circ}

× 3.7

^{\circ}

and 3.7

^{\circ}

× 3.7

^{\circ}

and the SLLs were −22.70 dB and −24.44 dB according to the AP calculations. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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15 pages, 8806 KiB

Open AccessArticle

Phase Compensation Technique for Effective Heat Focusing in Microwave Hyperthermia Systems

by Seonho Lim and Young Joong Yoon

Appl. Sci. 2021, 11(13), 5972; https://doi.org/10.3390/app11135972 - 27 Jun 2021

Cited by 7 | Viewed by 2707

Abstract

In this paper, effective electromagnetic (EM) focusing achieved with a phase compensation technique for microwave hyperthermia systems is proposed. To treat tumor cells positioned deep inside a human female breast, EM energy must be properly focused on the target area. A circular antenna [...] Read more.

In this paper, effective electromagnetic (EM) focusing achieved with a phase compensation technique for microwave hyperthermia systems is proposed. To treat tumor cells positioned deep inside a human female breast, EM energy must be properly focused on the target area. A circular antenna array for microwave hyperthermia allows EM energy to concentrate on a specific target inside the breast tumor. Depending on the cancerous cell conditions in the breast, the input phases of each antenna are calculated for single and multiple tumor cell locations. In the case of multifocal breast cancer, sub-array beam focusing via the phase compensation technique is presented to enhance the ability of EM energy to concentrate on multiple targets while minimizing damage to normal cells. To demonstrate the thermal treatment effects on single and multiple tumor locations, the accumulation of the specific absorption rate (SAR) parameter and temperature changes were verified using both simulated and experimental results. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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10 pages, 2733 KiB

Open AccessArticle

Statistical Indoor Exclusion Zone Analysis by Investigating Electromagnetic Fields inside a Nuclear Power Plant

by Doyoung Jang, Sangwoon Youn, Jun-Yong Lee and Hosung Choo

Appl. Sci. 2021, 11(9), 4199; https://doi.org/10.3390/app11094199 - 5 May 2021

Cited by 2 | Viewed by 1951

Abstract

This article investigates a statistical indoor exclusion zone (EZ) that can be efficiently applied to a nuclear power plant (NPP) by examining electromagnetic fields inside the actual NPP. To obtain the statistical indoor EZ, the indoor environment of the Korea Institute of Nuclear [...] Read more.

This article investigates a statistical indoor exclusion zone (EZ) that can be efficiently applied to a nuclear power plant (NPP) by examining electromagnetic fields inside the actual NPP. To obtain the statistical indoor EZ, the indoor environment of the Korea Institute of Nuclear Safety (KINS) simulator room is modeled using the Wireless InSite commercial electromagnetic simulation software. The indoor space around the transmitting antenna is classified as multiple observation regions, and the EZ boundaries of each region are independently defined within each separate observation region. The EZ boundaries are then obtained using a margined regression model, which makes it possible to determine a reasonable boundary of the statistical indoor EZ. To validate the statistical indoor EZ, the received power inside the KINS simulator room is then measured, which agrees well with the simulated results. The results demonstrate that the proposed statistical indoor EZ can be properly obtained not only from the simulation data but also from the measurement data. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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14 pages, 8143 KiB

Open AccessArticle

Wideband-Narrowband Switchable Tapered Slot Antenna for Breast Cancer Diagnosis and Treatment

by Seonho Lim and Young Joong Yoon

Appl. Sci. 2021, 11(8), 3606; https://doi.org/10.3390/app11083606 - 16 Apr 2021

Cited by 11 | Viewed by 2388

Abstract

In this paper, a wideband-narrowband switchable tapered slot antenna (TSA) with a compact meander line resonator for an integrated microwave imaging and hyperthermia system was proposed. A compact meander line resonator, which exhibited band-pass characteristics and provided narrowband characteristics by using one PIN [...] Read more.

In this paper, a wideband-narrowband switchable tapered slot antenna (TSA) with a compact meander line resonator for an integrated microwave imaging and hyperthermia system was proposed. A compact meander line resonator, which exhibited band-pass characteristics and provided narrowband characteristics by using one PIN diode, was fabricated beneath the tapered slot of the wideband TSA to minimize the degradation of the wideband characteristics. Moreover, the electromagnetic energy was transferred to the meander line resonator with a coupling effect to ensure effective frequency switching. By adapting a PIN diode on the meander line resonator, frequency switching could be achieved. In this way, the proposed antenna could operate in a real-time frequency switching mode between the ultra-wideband (UWB; 3.1~10 GHz), which is used for microwave imaging, and the 2.45 GHz band (industrial, scientific, and medical, ISM band), which is used for microwave hyperthermia. Frequency and time-domain results proved the applicability of the proposed antenna to an integrated breast cancer detection and treatment system. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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12 pages, 37393 KiB

Open AccessArticle

Higher-Order-Mode Triple Band Circularly Polarized Rectangular Dielectric Resonator Antenna

by Muhammad Fitra Zambak, Mohd Najib Mohd Yasin, Ismahayati Adam, Javed Iqbal and Mohamed Nasrun Osman

Appl. Sci. 2021, 11(8), 3493; https://doi.org/10.3390/app11083493 - 13 Apr 2021

Cited by 8 | Viewed by 2395

Abstract

The paper presents a triband circular polarized rectangular dielectric resonator antenna. A single coaxial cable feeds the DRA to a double stub strip on the DRA side. A patch strip coupled to the feed assists in widening the bandwidth of the proposed DRA. [...] Read more.

The paper presents a triband circular polarized rectangular dielectric resonator antenna. A single coaxial cable feeds the DRA to a double stub strip on the DRA side. A patch strip coupled to the feed assists in widening the bandwidth of the proposed DRA. The degenerate mode pair

{TE}_{\partial 11}^{x}

and higher-

T E_{\partial 23}^{x}

has been excited to achieve CP and enhance the antenna gain. The higher-order mode has been excited using a low-cost simple excitation mechanism without compromising on the size and shape of the DRA. An impedance bandwidth of 48% with a gain ~6–9 dBic was achieved in all resonance frequencies. Additionally, the AR bandwidth of 5.5%, 4.2%, and 2.76% was obtained at three different frequencies. Note that the proposed DRA exhibits a wide beamwidth of 112^o, which is good for better signal reception. A comparison between the measured with simulated results shows that the measured results are matched by the simulated result trends. Full article

(This article belongs to the Special Issue Antenna Design for Microwave and Millimeter Wave Applications II: Latest Advances and Prospects)

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