RF/Microwave Circuits for 5G and Beyond

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microwave and Wireless Communications".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 47103

Special Issue Editors


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Guest Editor
Biomedical and Electronics Engineering, Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK
Interests: reconfigurable antennas; microwave filters; tunable filters; linear and nonlinear circuits; MIMO/diversity antennas; differentially fed structures; balanced antennas; 5G/6G antennas; RFID antennas; power amplifiers; applied electromagnetics; RF/microwave sensors
Special Issues, Collections and Topics in MDPI journals
James Watt School of Engineering, University of Glasgow, Glasgow, UK
Interests: computer-aided design; AI-driven design of microwave devices; AI-driven design of analog integrated circuits; optimization machine learning

Special Issue Information

Dear Colleagues,

The progress from fourth-generation (4G) networks to fifth-generation (5G) technology has transformed industry and society by enabling an unprecedented level of innovation on the radiofrequency (RF), microwave and millimeter wave (mmWave) components. 5G is widely seen as the generation of wireless communications that will enable RF/microwave applications to expand into a completely new set of use, case, and vertical markets. Given that 5G is still in its initial stages commercially, much work still needs to be done onchannel modeling, radio link performance, and finally, chipset development before the first realistic applications can be deployed. As the commercial deployment of the 5G technology is well under way in many countries of the world, academic as well as industrial research groups have turned their consideration to what comes next. Thus, one might reasonably expect a “6G” release to arrive at some point in the future.

It is clear that future front and systems must be multistandard radio, supported by identical RF transceivers within the infrastructures and on the user terminal, and they must also take advantage of new technology models such as reconfigurability and software‐defined radio (SDR). RF/microwave circuits and their applications, such as antennas, filters, power amplifiers, phase shifters, power dividers, mixers, multiplexers, ceramics, and integrated systems, are representing essential elements in such devices, which significantly affect the whole performance of the 5G/6G front end transceivers.

This Special Issue invites academic and industrial scholars and researchers to contribute original research articles as well as review articles that seek to address the issues, trends, and challenges of design and application of RF/microwave components for 5G and beyond systems to support multistandard radio flexibility both at the base station and at the user terminal, whilst being energy-efficient in an energy‐conscious world.

Dr. Yasir Al-Yasir
Dr. Chan Hwang See
Dr. Bo Liu
Guest Editors

Manuscript Submission Information

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Keywords

  • RF transceivers
  • Antennas and propagation
  • Microwave filters
  • Power amplifiers
  • Multiplexers
  • Power dividers
  • MIMO systems
  • Phased array and beamforming
  • Metamaterial
  • 5G/6G

Published Papers (18 papers)

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13 pages, 3667 KiB  
Communication
Ka-Band Three-Stack CMOS Power Amplifier with Split Layout of External Gate Capacitor for 5G Applications
by Junhyuk Yang, Jaeyong Lee, Seongjin Jang, Hayeon Jeong and Changkun Park
Electronics 2023, 12(2), 432; https://doi.org/10.3390/electronics12020432 - 13 Jan 2023
Cited by 3 | Viewed by 1819
Abstract
In this study, we designed a Ka-band two-stage differential power amplifier (PA) using a 65 nm RFCMOS process. To enhance the output power of the PA, a three-stack structure was utilized in the power stage, while the driver stage of the PA [...] Read more.
In this study, we designed a Ka-band two-stage differential power amplifier (PA) using a 65 nm RFCMOS process. To enhance the output power of the PA, a three-stack structure was utilized in the power stage, while the driver stage of the PA was designed with a common-source structure to minimize power consumption in the driver stage. The layout of an external gate capacitor for the stacked power stage was split to maximize the performance of the power transistor. With the proposed split layout of the external capacitor, gain, output power, and power-added efficiency (PAE) were improved. Additionally, a capacitive neutralization technique was applied to the power and driver stages to ensure the stability and enhance the gain of the PA. The measured P1dB and the saturation power were 22.0 dBm and 23.3 dBm, respectively, while the peak PAE was 27.8% at 28.5 GHz. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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18 pages, 7199 KiB  
Article
Design and Analysis of Novel Reconfigurable Monopole Antenna Using Dip Switch and Covering 5G-Sub-6-GHz and C-Band Applications
by Ali Kadhum Abd, Jamal Mohammed Rasool, Zain-Aldeen S. A. Rahman and Yasir I. A. Al-Yasir
Electronics 2022, 11(20), 3368; https://doi.org/10.3390/electronics11203368 - 19 Oct 2022
Cited by 7 | Viewed by 2236
Abstract
This study presents a unique frequency-reconfigurable antenna that may be the first to use a dip switch and a bias circuit integrated on the same substrate as the antenna. Such an antenna may be used for many wireless applications, since it is small [...] Read more.
This study presents a unique frequency-reconfigurable antenna that may be the first to use a dip switch and a bias circuit integrated on the same substrate as the antenna. Such an antenna may be used for many wireless applications, since it is small and versatile enough to operate in several frequency bands with different modes. Printed on a Rogers RT5880 substrate, the suggested structure has a relative permittivity of 2.2, a tangent loss of 0.0009, and a size of 28 × 26.35 × 1.6 mm3. Three-PIN diode switches are inserted between radiating patches. The proposed antenna operates in four modes, covering nine different bands by using three dual bands (i.e., 4.36 and 7.78 GHz, 3.56 and 6.89 GHz, 3 and 6.2 GHz) in MODE 1, MODE 2, and MODE three, respectively, and triple band in MODE 4 (i.e., 2.88, 5.87, and 8.17 GHz). The efficiency of the planned antenna is 97.66%, and the gain varies from 1.38 to 4.89 dBi. The obtained bandwidths at corresponding frequencies range from 5.5 to 31.17%. The suggested structure is modeled in the CSTMWS and the simulated findings are experimentally confirmed. The suggested antenna may be employed in current portable (5G) devices and the IoT. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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13 pages, 6183 KiB  
Article
Design and Implementation of a Miniaturized Filtering Antenna for 5G Mid-Band Applications
by Fatimah K. Juma’a, Alaa I. Al-Mayoof, Abdulghafor A. Abdulhameed, Falih M. Alnahwi, Yasir I. A. Al-Yasir and Raed A. Abd-Alhameed
Electronics 2022, 11(19), 2979; https://doi.org/10.3390/electronics11192979 - 20 Sep 2022
Cited by 6 | Viewed by 1728
Abstract
Combining a microwave filter with an antenna results in a low-cost, efficient, and small-size selective radiator called a filtering antenna or filtenna. In this work, a compact filtering antenna is presented to radiate within the 5G mid-band frequencies along (3.6–3.8 GHz) with strong [...] Read more.
Combining a microwave filter with an antenna results in a low-cost, efficient, and small-size selective radiator called a filtering antenna or filtenna. In this work, a compact filtering antenna is presented to radiate within the 5G mid-band frequencies along (3.6–3.8 GHz) with strong rejection for the frequencies outside this range. The proposed filtering antenna consists of a crescent-shaped planar monopole antenna that is electromagnetically coupled with a reduced-size capacitively loaded loop (CLL) microwave band-pass filter. The miniaturization of CLL is achieved by utilizing a single ring CLL structure instead of two rings to reduce the filter size to half without affecting the filter performance. The filtering antenna in this work is fabricated on a Rogers RT5880 substrate with dimensions equal to 24.2 × 27 × 0.8 mm3. Good congruence between the measurements and the simulation results, and both verify the antenna’s perfect operation along the 5G mid-band frequency range. The simulated and measured peak realized gain values of the proposed structure are 2.24 dB and 2.2 dB, respectively. Furthermore, the power pattern of the designed filtering antenna is omnidirectional, which is very convenient for portable 5G mid-band devices. Compared to other works, it is found that in spite of the small dimensions of the filtering antenna (24.2 × 27 × 0.8 mm3), the antenna has a bandwidth that covers the range 3.6–3.82 GHz with a maximum gain value equal to 2.2 GHz and omnidirectional pattern which makes the antenna very suitable for 5G mid-band applications. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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20 pages, 8025 KiB  
Article
Design a Compact Printed Log-Periodic Biconical Dipole Array Antenna for EMC Measurements
by Abdulghafor A. Abdulhameed and Zdeněk Kubík
Electronics 2022, 11(18), 2877; https://doi.org/10.3390/electronics11182877 - 11 Sep 2022
Cited by 7 | Viewed by 3044
Abstract
This article presents the design, modeling, and fabrication of a printed log-periodic biconical dipole array antenna (PLPBDA) for electromagnetic compatibility (EMC) measurements. The proposed structure used bow tie-shaped dipoles instead of typical dipoles to achieve a size reduction of 50% and bandwidth enhancement [...] Read more.
This article presents the design, modeling, and fabrication of a printed log-periodic biconical dipole array antenna (PLPBDA) for electromagnetic compatibility (EMC) measurements. The proposed structure used bow tie-shaped dipoles instead of typical dipoles to achieve a size reduction of 50% and bandwidth enhancement of 170% with the help of PCB technology. Furthermore, the balanced feeding method and the modifications in bow tie-shaped dipole dimensions were utilized to obtain broad bandwidth of 5.5 GHz (from 0.5 GHz to 6 GHz). This structure comprises 12 dipole elements with a compact size of 170 × 160 × 1.6 mm, reflecting low fluctuations gain of about (4.6–7) dBi with the help of an extra dipole. Moreover, the achieved frequency and radiation characteristics (simulated and measured) agree with each other and are compatible with the results of classical EMC antennas. The achievements of this structure showed promising results compared to both literature reviews and reference antenna Hyper LOG® 7060 offered for sale. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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14 pages, 3380 KiB  
Article
A Miniaturized Triple-Band Antenna Based on Square Split Ring for IoT Applications
by Duaa H. Abdulzahra, Falih Alnahwi, Abdulkareem S. Abdullah, Yasir I. A. Al-Yasir and Raed A. Abd-Alhameed
Electronics 2022, 11(18), 2818; https://doi.org/10.3390/electronics11182818 - 7 Sep 2022
Cited by 10 | Viewed by 1573
Abstract
This article presents a miniaturized triple-band antenna for Internet of Things (IoT) applications. The miniaturization is achieved by using a split square ring resonator and half ring resonator. The antenna is fabricated on an FR4 substrate with dimensions of (33 × 22 × [...] Read more.
This article presents a miniaturized triple-band antenna for Internet of Things (IoT) applications. The miniaturization is achieved by using a split square ring resonator and half ring resonator. The antenna is fabricated on an FR4 substrate with dimensions of (33 × 22 × 1.6) mm3. The proposed antenna resonates at the frequencies 2.4 GHz, 3.7 GHz, and 5.8 GHz for WLAN and WiMax applications. The obtained −10 dB bandwidth for the three bands of the proposed antenna are 300 MHz, 360 MHz, and 900 MHz, respectively. The measured reflection coefficient values of the proposed antenna corresponding to each resonant frequency are equal to −14.772 dB, −20.971 dB, and −28.1755 dB, respectively. The measured gain values are 1.43 dBi, 0.89 dBi, and 1 dBi, respectively, at each resonant frequency. There is a good agreement between the measured and simulated results, and both show an omnidirectional radiation pattern at each of the antenna resonant frequencies that is suitable for IoT portable devices. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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14 pages, 6395 KiB  
Article
A 26–30 GHz GaN HEMT Low-Noise Amplifier Employing a Series Inductor-Based Stability Enhancement Technique
by Hyunbae Ahn, Honggu Ji, Dongmin Kang, Sung-Min Son, Sanghun Lee and Junghwan Han
Electronics 2022, 11(17), 2716; https://doi.org/10.3390/electronics11172716 - 30 Aug 2022
Cited by 7 | Viewed by 2362
Abstract
This article presents a 26–30 GHz gallium nitride (GaN) high electron mobility transistor (HEMT) low-noise amplifier (LNA) for fifth-generation base station applications. In the proposed design, a series inductor-based stability enhancement technique was utilized to improve the reverse isolation and stability performance of [...] Read more.
This article presents a 26–30 GHz gallium nitride (GaN) high electron mobility transistor (HEMT) low-noise amplifier (LNA) for fifth-generation base station applications. In the proposed design, a series inductor-based stability enhancement technique was utilized to improve the reverse isolation and stability performance of the amplifier and to mitigate the effect of the parasitic capacitance of the GaN HEMT device. To validate the concept of the design, a three-stage GaN HEMT LNA was designed and fabricated in a 0.15-um GaN on silicon carbide technology. The demonstrated design achieved a gain of 20.2 dB, a noise figure of 2.4–2.5 dB, an output 1-dB compression point of 17.2 dBm, and an output third-order intercept point of 32.2 dBm. The design also attained stability (μ criterion) up to 7.7 at the operating frequency. The implemented design consumed power of 320 mW with a nominal supply of 10 V. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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17 pages, 5076 KiB  
Article
Substrate-Induced Dissipative and Non-Linear Effects in RF Switches: Probing Ultimate Performance Based on Laser-Machined Membrane Suspension
by Arun Bhaskar, Justine Philippe, Etienne Okada, Flavie Braud, Jean-François Robillard, Cédric Durand, Frédéric Gianesello, Daniel Gloria, Christophe Gaquière and Emmanuel Dubois
Electronics 2022, 11(15), 2333; https://doi.org/10.3390/electronics11152333 - 27 Jul 2022
Cited by 2 | Viewed by 1635
Abstract
With the evolution of radio frequency (RF)/microwave technology, there is a demand for circuits that are able to meet highly challenging RF front end specifications. Silicon-on-insulator (SOI) technology is one of the leading platforms for upcoming wireless generation. The degradation of performance due [...] Read more.
With the evolution of radio frequency (RF)/microwave technology, there is a demand for circuits that are able to meet highly challenging RF front end specifications. Silicon-on-insulator (SOI) technology is one of the leading platforms for upcoming wireless generation. The degradation of performance due to substrate coupling is a key problem to address for telecommunication circuits, especially for the high throw count switches in RF front ends. In this context, a fast, flexible and local laser ablation technique of the silicon handler allows for the membrane suspension of large millimeter-scale circuits. This approach enables the evaluation of the ultimate performance in the absence of the substrate, i.e., without dissipative losses and substrate-induced non-linear effects, on capacitive comb coupling structures and RF switches. Compared to high-resistivity SOI substrates, the high frequency characterization of RF membrane switches reveals a superior linearity performance with a reduction in second and third harmonics by 17.7 dB and 7.8 dB, respectively. S-parameter analysis also reveals that membrane suspension entails insertion losses that are improved by 0.38 dB and signal reflection lowered by 4 dB due to a reduced off-state capacitance. With reference to a trap-rich substrate, the membrane suspension also achieves an additional 7.8 dB reduction in the second harmonic, indicating that there is still scope for improvement in this figure of merit. The obtained results demonstrate a new way to evaluate optimized circuit performance using post-fabrication substrate engineering. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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17 pages, 8423 KiB  
Article
A New Compact Dual-Polarized MIMO Antenna Using Slot and Parasitic Element Decoupling for 5G and WLAN Applications
by Samuel B. Paiva, Adaildo G. D’Assunção Junior, Valdemir P. Silva Neto and Adaildo Gomes D’Assunção
Electronics 2022, 11(13), 1943; https://doi.org/10.3390/electronics11131943 - 21 Jun 2022
Cited by 9 | Viewed by 2021
Abstract
This paper presents a compact dual-polarized multiple-input multiple-output (MIMO) antenna for fifth generation (5G) and wireless local area network (WLAN) applications. At first, a compact two-element dual-polarized MIMO antenna designed to operate at 3.5 GHz was developed. After that, some modifications were performed [...] Read more.
This paper presents a compact dual-polarized multiple-input multiple-output (MIMO) antenna for fifth generation (5G) and wireless local area network (WLAN) applications. At first, a compact two-element dual-polarized MIMO antenna designed to operate at 3.5 GHz was developed. After that, some modifications were performed in the initial configuration, and a compact two-element dual-polarized MIMO was designed to operate at 3.5 and 5.35 GHz. A simple decoupling technique using parasitic element and slot was used to enhance the isolation between the radiating elements and to achieve an isolation above 18 dB over the band ranging from 3.4 to 3.6 GHz for the first antenna, and to achieve isolations above 19.8 dB over the first band ranging from 3.4 to 3.6 GHz and above 16.75 dB over the second band ranging from 5.15 to 5.85 GHz for the second antenna. Simulations were performed in the Ansoft HFSS software for numerical characterization and the prototype was fabricated with FR-4 dielectric and measured, presenting a good agreement between simulated and measured results. Furthermore, the envelope correlation coefficient (ECC) and the diversity gain (DG) were analyzed and present good results. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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13 pages, 4031 KiB  
Article
A Compact CSRR-Based Sensor for Characterization of the Complex Permittivity of Dielectric Materials
by Jurgen K. A. Nogueira, João G. D. Oliveira, Samuel B. Paiva, Valdemir P. Silva Neto and Adaildo G. D’Assunção
Electronics 2022, 11(11), 1787; https://doi.org/10.3390/electronics11111787 - 4 Jun 2022
Cited by 5 | Viewed by 1973
Abstract
A sensor is proposed to characterize the complex permittivity of dielectric materials in a non-destructive and non-invasive way. The proposed sensor is based on a rectangular patch microstrip two-port circuit with a complementary split-ring resonator (CSRR) element. The slotted CSRR element of the [...] Read more.
A sensor is proposed to characterize the complex permittivity of dielectric materials in a non-destructive and non-invasive way. The proposed sensor is based on a rectangular patch microstrip two-port circuit with a complementary split-ring resonator (CSRR) element. The slotted CSRR element of the sensor plays a key role in determining the electrical properties of the materials under test (MUT). The sensitivity analysis is determined by varying the permittivity of the MUT. The proposed sensor is simulated and analyzed using Ansoft HFSS software. A prototype was fabricated and measurements were made on two different samples of dielectric materials with complex permittivity values available in the literature. The simulated and measured results showed good agreement. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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30 pages, 13065 KiB  
Article
Efficient Colour Image Encryption Algorithm Using a New Fractional-Order Memcapacitive Hyperchaotic System
by Zain-Aldeen S. A. Rahman, Basil H. Jasim, Yasir I. A. Al-Yasir and Raed A. Abd-Alhameed
Electronics 2022, 11(9), 1505; https://doi.org/10.3390/electronics11091505 - 7 May 2022
Cited by 10 | Viewed by 1790
Abstract
In comparison with integer-order chaotic systems, fractional-order chaotic systems exhibit more complex dynamics. In recent years, research into fractional chaotic systems for the utilization of image cryptosystems has become increasingly highlighted. This paper describes the development, testing, numerical analysis, and electronic realization of [...] Read more.
In comparison with integer-order chaotic systems, fractional-order chaotic systems exhibit more complex dynamics. In recent years, research into fractional chaotic systems for the utilization of image cryptosystems has become increasingly highlighted. This paper describes the development, testing, numerical analysis, and electronic realization of a fractional-order memcapacitor. Then, a new four-dimensional (4D) fractional-order memcapacitive hyperchaotic system is suggested based on this memcapacitor. Analytically and numerically, the nonlinear dynamic properties of the hyperchaotic system have been explored, where various methods, including equilibrium points, phase portraits of chaotic attractors, bifurcation diagrams, and the Lyapunov exponent, are considered to demonstrate the chaos behaviour of this new hyperchaotic system. Consequently, an encryption cryptosystem algorithm is used for colour image encryption based on the chaotic behaviour of the memcapacitive model, where every pixel value of the original image is incorporated in the secret key to strengthen the encryption algorithm pirate anti-attack robustness. For generating the keyspace of that employed cryptosystem, the initial condition values, parameters, and fractional-order derivative value(s) (q) of the memcapacitive chaotic system are utilized. The common cryptanalysis metrics are verified in detail by histogram, keyspace, key sensitivity, correlation coefficient values, entropy, time efficiency, and comparisons with other recent related fieldwork in order to demonstrate the security level of the proposed cryptosystem approach. Finally, images of various sizes were encrypted and recovered to ensure that the utilized cryptosystem approach is capable of encrypting/decrypting images of various sizes. The obtained experimental results and security metrics analyses illustrate the excellent accuracy, high security, and perfect time efficiency of the utilized cryptosystem, which is highly resistant to various forms of pirate attacks. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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27 pages, 12613 KiB  
Article
High-Security Image Encryption Based on a Novel Simple Fractional-Order Memristive Chaotic System with a Single Unstable Equilibrium Point
by Zain-Aldeen S. A. Rahman, Basil H. Jasim, Yasir I. A. Al-Yasir and Raed A. Abd-Alhameed
Electronics 2021, 10(24), 3130; https://doi.org/10.3390/electronics10243130 - 16 Dec 2021
Cited by 11 | Viewed by 2170
Abstract
Fractional-order chaotic systems have more complex dynamics than integer-order chaotic systems. Thus, investigating fractional chaotic systems for the creation of image cryptosystems has been popular recently. In this article, a fractional-order memristor has been developed, tested, numerically analyzed, electronically realized, and digitally implemented. [...] Read more.
Fractional-order chaotic systems have more complex dynamics than integer-order chaotic systems. Thus, investigating fractional chaotic systems for the creation of image cryptosystems has been popular recently. In this article, a fractional-order memristor has been developed, tested, numerically analyzed, electronically realized, and digitally implemented. Consequently, a novel simple three-dimensional (3D) fractional-order memristive chaotic system with a single unstable equilibrium point is proposed based on this memristor. This fractional-order memristor is connected in parallel with a parallel capacitor and inductor for constructing the novel fractional-order memristive chaotic system. The system’s nonlinear dynamic characteristics have been studied both analytically and numerically. To demonstrate the chaos behavior in this new system, various methods such as equilibrium points, phase portraits of chaotic attractor, bifurcation diagrams, and Lyapunov exponent are investigated. Furthermore, the proposed fractional-order memristive chaotic system was implemented using a microcontroller (Arduino Due) to demonstrate its digital applicability in real-world applications. Then, in the application field of these systems, based on the chaotic behavior of the memristive model, an encryption approach is applied for grayscale original image encryption. To increase the encryption algorithm pirate anti-attack robustness, every pixel value is included in the secret key. The state variable’s initial conditions, the parameters, and the fractional-order derivative values of the memristive chaotic system are used for contracting the keyspace of that applied cryptosystem. In order to prove the security strength of the employed encryption approach, the cryptanalysis metric tests are shown in detail through histogram analysis, keyspace analysis, key sensitivity, correlation coefficients, entropy analysis, time efficiency analysis, and comparisons with the same fieldwork. Finally, images with different sizes have been encrypted and decrypted, in order to verify the capability of the employed encryption approach for encrypting different sizes of images. The common cryptanalysis metrics values are obtained as keyspace = 2648, NPCR = 0.99866, UACI = 0.49963, H(s) = 7.9993, and time efficiency = 0.3 s. The obtained numerical simulation results and the security metrics investigations demonstrate the accuracy, high-level security, and time efficiency of the used cryptosystem which exhibits high robustness against different types of pirate attacks. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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14 pages, 4281 KiB  
Article
Design and Optimization of Microwave Sensor for the Non-Contact Measurement of Pure Dielectric Materials
by Luqman Ali, Cong Wang, Inam Ullah, Adnan Yousaf, Wali Ullah Khan, Shafi Ullah, Rahim Khan, Fawaz Alassery, Habib Hamam and Muhammad Shafiq
Electronics 2021, 10(24), 3057; https://doi.org/10.3390/electronics10243057 - 8 Dec 2021
Cited by 11 | Viewed by 3307
Abstract
This article presents an optimized microwave sensor for the non-contact measurement of complex permittivity and material thickness. The layout of the proposed sensor comprises the parallel combination of an interdigital capacitor (IDC) loaded at the center of the symmetrical differential bridge-type inductor fabricated [...] Read more.
This article presents an optimized microwave sensor for the non-contact measurement of complex permittivity and material thickness. The layout of the proposed sensor comprises the parallel combination of an interdigital capacitor (IDC) loaded at the center of the symmetrical differential bridge-type inductor fabricated on an RF-35 substrate (εr = 3.5 and tanδ = 0.0018). The bridge-type differential inductor is introduced to obtain a maximum inductance value with high quality (Q) factor and low tunable resonant frequency. The central IDC structure is configured as a spur-line structure to create a high-intensity coupled electric field (e-field) zone, which significantly interacts with the materials under test (MUTs), resulting in an increased sensitivity. The proposed sensor prototype with optimized parameters generates a resonant frequency at 1.38 GHz for measuring the complex permittivity and material thickness. The experimental results indicated that the resonant frequency of the designed sensor revealed high sensitivities of 41 MHz/mm for thickness with a linear response (r2 = 0.91567), and 53 MHz/Δεr for permittivity with a linear response (r2 = 0.98903). The maximum error ratio for measuring MUTs with a high gap of 0.3 mm between the testing sample and resonator is 6.52%. The presented performance of the proposed sensor authenticates its application in the non-contact measurement of samples based on complex permittivity and thickness. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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16 pages, 8838 KiB  
Article
Design of Low-Profile Single- and Dual-Band Antennas for IoT Applications
by Wazie M. Abdulkawi, Abdel Fattah A. Sheta, Ibrahim Elshafiey and Majeed A. Alkanhal
Electronics 2021, 10(22), 2766; https://doi.org/10.3390/electronics10222766 - 12 Nov 2021
Cited by 22 | Viewed by 3359
Abstract
This paper presents novel low-cost single- and dual-band microstrip patch antennas. The proposed antennas are realized on a square microstrip patch etched symmetrically with four slots. The antenna is designed to have low cost and reduced size to use in Internet of things [...] Read more.
This paper presents novel low-cost single- and dual-band microstrip patch antennas. The proposed antennas are realized on a square microstrip patch etched symmetrically with four slots. The antenna is designed to have low cost and reduced size to use in Internet of things (IoT) applications. The antennas provide a reconfigurable architecture that allows operation in different wireless communication bands. The proposed structure can be adjusted to operate either in single band or in dual-band operation. Two prototypes are implemented and evaluated. The first structure works at a single resonance frequency (f1 = 2.4 GHz); however, the second configuration works at two resonance frequencies (f1 = 2.4 GHz and f2 = 2.8 GHz) within the same size. These antennas use a low-cost FR-4 dielectric substrate. The 2.4 GHz is allotted for the industrial, scientific, and medical (ISM) band, and the 2.8 GHz is allocated to verify the concept and can be adjusted to meet the user’s requirements. The measurement of the fabricated antennas closely matches the simulated results. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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18 pages, 2898 KiB  
Article
A New Optimization Algorithm Based on the Fungi Kingdom Expansion Behavior for Antenna Applications
by Falih M. Alnahwi, Yasir I. A. Al-Yasir, Dunia Sattar, Ramzy S. Ali, Chan Hwang See and Raed A. Abd-Alhameed
Electronics 2021, 10(17), 2057; https://doi.org/10.3390/electronics10172057 - 26 Aug 2021
Cited by 2 | Viewed by 3607
Abstract
This paper presents a new optimization algorithm based on the behavior of the fungi kingdom expansion (FKE) to optimize the radiation pattern of the array antenna. The immobile mass expansion of the fungi is mimicked in this work as a chaotic behavior with [...] Read more.
This paper presents a new optimization algorithm based on the behavior of the fungi kingdom expansion (FKE) to optimize the radiation pattern of the array antenna. The immobile mass expansion of the fungi is mimicked in this work as a chaotic behavior with a sinusoidal map function, while the mobile mass expansion is realized by a linear function. In addition, the random germination of the spores is utilized for randomly distributing the variables that are far away from the best solution. The proposed FKE algorithm is applied to optimize the radiation pattern of the antenna array, and then its performance is compared with that of some well-known algorithms. The MATLAB simulation results verify the superiority of the proposed algorithm in solving 20-element antenna array problems such as sidelobe reduction with sidelobe ratio (SLR = 25.6 dB), flat-top pattern with SLR = 23.5 dB, rectangular pattern with SLR = 19 dB, and anti-jamming systems. The algorithm also results in a 100% success rate for all of the mentioned antenna array problems. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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12 pages, 2208 KiB  
Article
Assessment of Various Window Functions in Spectral Identification of Passive Intermodulation
by Khaled Gharaibeh
Electronics 2021, 10(9), 1034; https://doi.org/10.3390/electronics10091034 - 27 Apr 2021
Cited by 5 | Viewed by 1937
Abstract
Passive Intermodulation (PIM) distortion is a major problem in wireless communications which limits cell coverage and data rates. Passive nonlinearities result in weak intermodulation (IMD) products that are very difficult to diagnose, troubleshoot and model. To predict PIM, behavioral models are used where [...] Read more.
Passive Intermodulation (PIM) distortion is a major problem in wireless communications which limits cell coverage and data rates. Passive nonlinearities result in weak intermodulation (IMD) products that are very difficult to diagnose, troubleshoot and model. To predict PIM, behavioral models are used where spectral components of PIM are estimated from the power spectral density at the output of the model. The primary goal of this paper is to study the effect of window functions on the capability of the power spectral density computed from the periodogram of signal realizations to predict low power PIM components in a wideband multichannel communication system. Different window functions are analyzed and it is shown that windows with high side-lobe level fail to predict PIM components which are close to the main channels due to their high spectral leakage; while window functions with low roll-off rate of the side lobes fail to predict low power higher order PIM components especially when the frequency separation between the main carriers is high. These results are supported by simulations of the power spectral density computed using signal realizations of an LTE carrier aggregated system. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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15 pages, 8062 KiB  
Article
A Low-Cost Microwave Filter with Improved Passband and Stopband Characteristics Using Stub Loaded Multiple Mode Resonator for 5G Mid-Band Applications
by Falih M. Alnahwi, Yasir I. A. Al-Yasir, Abdulghafor A. Abdulhameed, Abdulkareem S. Abdullah and Raed A. Abd-Alhameed
Electronics 2021, 10(4), 450; https://doi.org/10.3390/electronics10040450 - 11 Feb 2021
Cited by 13 | Viewed by 2758
Abstract
This paper presents the design and implementation of a printed circuit microwave band-pass filter for 5G mid-band applications, using a Stub Loaded Multiple Mode Resonator (SL-MMR) technique. The objective of this article is to introduce a low-cost microstrip filter with improved passband and [...] Read more.
This paper presents the design and implementation of a printed circuit microwave band-pass filter for 5G mid-band applications, using a Stub Loaded Multiple Mode Resonator (SL-MMR) technique. The objective of this article is to introduce a low-cost microstrip filter with improved passband and stopband characteristics, based on a mathematical analysis of stub loaded resonators. The filter cost is reduced by selecting the low-cost FR4 dielectric material as a substrate for the proposed filter. Based on the transmission line model of the filter, mathematical expressions are derived to predict the odd-mode and the even-mode resonant frequencies of the SL-MMR. The mathematical model also highlights the capability of controlling the position of the SL-MMR resonant frequencies, so that the 5G sub-band that extends along the range (3.7–4.2 GHz) can perfectly be covered with almost a flat passband. At the resonance frequency, a fractional bandwidth of 12.8% (500 MHz impedance bandwidth) has been obtained with a return loss of more than 18 dB and an insertion loss of less than 2.5 dB over the targeted bandwidth. Furthermore, a pair of parasitic elements is attached to the proposed filter to create an additional transmission zero in the lower stopband of the filter to enhance the suppression of the filter stopband. The measured and simulation results are well agreed, and both reveal the acceptable performance of the stopband and passband characteristics of the filter. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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Review

Jump to: Research

28 pages, 2037 KiB  
Review
A Study on Multi-Antenna and Pertinent Technologies with AI/ML Approaches for B5G/6G Networks
by Maraj Uddin Ahmed Siddiqui, Faizan Qamar, Syed Hussain Ali Kazmi, Rosilah Hassan, Asad Arfeen and Quang Ngoc Nguyen
Electronics 2023, 12(1), 189; https://doi.org/10.3390/electronics12010189 - 30 Dec 2022
Cited by 17 | Viewed by 3007
Abstract
The quantum leap in mobile data traffic and high density of wireless electronic devices, coupled with the advancements in industrial radio monitoring and autonomous systems, have created great challenges for smooth wireless network operations. The fifth-generation and beyond (B5G) (also being referred to [...] Read more.
The quantum leap in mobile data traffic and high density of wireless electronic devices, coupled with the advancements in industrial radio monitoring and autonomous systems, have created great challenges for smooth wireless network operations. The fifth-generation and beyond (B5G) (also being referred to as sixth-generation (6G)) wireless communication technologies, due to their compatibility with the previous generations, are expected to overcome these unparalleled challenges. Accompanied by traditional and new techniques, the massive multiple input multiple output (mMIMO) approach is one of the evolving technologies for B5G/6G systems used to control the ever-increasing user stipulations and the emergence of new cases efficiently. However, the major challenges in deploying mMIMO systems are their high computational intricacy and high computing time latencies, as well as difficulties in fully exploiting the multi-antenna multi-frequency channels. Therefore, to optimize the current and B5G/6G wireless network elements proficiently, the use of the mMIMO approach in a HetNet structure with artificial intelligence (AI) techniques, e.g., machine learning (ML), distributed learning, federated learning, deep learning, and neural networks, has been considered as the prospective efficient solution. This work analyzes the observed problems and their AI/ML-enabled mitigation techniques in different mMIMO deployment scenarios for 5G/B5G networks. To provide a complete insight into the mMIMO systems with emerging antenna and propagation precoding techniques, we address and identify various relevant topics in each section that may help to make the future wireless systems robust. Overall, this work is designed to guide all B5G/6G stakeholders, including researchers and operators, aiming to understand the functional behavior and associated techniques to make such systems more agile for future communication purposes. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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24 pages, 5479 KiB  
Review
A Review on Improved Design Techniques for High Performance Planar Waveguide Slot Arrays
by Giovanni Andrea Casula, Giuseppe Mazzarella, Giorgio Montisci and Giacomo Muntoni
Electronics 2021, 10(11), 1311; https://doi.org/10.3390/electronics10111311 - 30 May 2021
Cited by 8 | Viewed by 4192
Abstract
Planar waveguide slot arrays (WSAs) have been used since 1940 and are currently used as performing antennas for high frequencies, especially in applications such as communication and RADAR systems. We present in this work a review of the most typical waveguide slot array [...] Read more.
Planar waveguide slot arrays (WSAs) have been used since 1940 and are currently used as performing antennas for high frequencies, especially in applications such as communication and RADAR systems. We present in this work a review of the most typical waveguide slot array configurations proposed in the literature, describing their main limitations and drawbacks along with possible effective countermeasures. Our attention has been focused mainly on the improved available design techniques to obtain high performance WSAs. In particular, the addressed topics have been reported in the following. Partially filled WSAs, or WSAs covered with single or multilayer dielectric slabs, are discussed. The most prominent second-order effects in the planar array feeding network are introduced and accurately modeled. The attention is focused on the T-junction feeding the array, on the effect of interaction between each slot coupler of the feeding network and the radiating slots nearest to this coupler, and on the waveguide bends. All these effects can critically increase the first sidelobes if compared to the ideal case, causing a sensible worsening in the performance of the array. Full article
(This article belongs to the Special Issue RF/Microwave Circuits for 5G and Beyond)
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