Special Issue "Recent Technical Developments in Energy-Efficient 5G Mobile Cells"

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

Deadline for manuscript submissions: closed (31 December 2019).

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A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Raed A Abd-Alhameed
Website
Guest Editor

Special Issue Information

Dear Colleagues,

At present, 4G systems provide a universal platform for broadband mobile services. However, mobile traffic is still growing at an unprecedented rate, and the need for more sophisticated broadband services is pushing the limits of the current standards to provide an even tighter integration between wireless technologies and higher speeds. The change in the nature of services and devices, along with pressures on the operation and capital costs put stringent limits on the design of mobile networks. Moreover, energy efficiency is now at the forefront of the socio-economic agenda, creating market drivers towards energy compliant handsets and networking devices.

This has led to the need for a new generation of mobile communications, the so-called 5G. Although 5G systems are not expected to penetrate the market until 2020, the evolution towards 5G is widely accepted to be the logical convergence of internet services with existing mobile networking standards, leading to the commonly used term “mobile internet” over heterogeneous networks, with very high connectivity speeds.

This Special Issue aims to narrow the gap between the current networking technologies and the foreseen requirements that are targeted at the future development of the 5G mobile and wireless communications networks in terms of the following:

  • higher networking capacity
  • ability to support more users
  • lower cost per bit
  • enhanced energy efficiency
  • adaptability to new services and devices (examples, smart cities, and the Internet of things (IoT)).

Specific Topics

It is expected that the future mobile networks will be built using small cells (such as femto, pico, and relay) and heterogeneous cells, which include WiFi hotspots, among others. The dense deployment of these cells and their coexistence are all new and important research challenges for future 5G and beyond. Submissions can focus on the conceptual and applied research in topics including, but not limited to, the following:

  • Energy efficient and multi-standard RF front-end
  • Network coded cooperation for mobile cells
  • Reconfigurable or multimode RF spectrum operation
  • MIMO/mMIMO for 5G mobile networks
  • Reconfigurable antenna array for 4G/5G handsets and base stations
  • High-speed and energy-efficient connectivity on demand
  • Secure networking coding for mobile small cells
  • Enabling mobile small cells and network virtualization
  • 5G small cells technologies and applications
  • Emerging the IoT applications with the new 5G developments.

Submissions should be of high enough quality for an international journal, and should not be submitted or published elsewhere. However, the extended versions of conference papers that show significant improvement (minimal of over 30%) can be considered for review in this Special Issue.  In addition, we welcome review papers covering the subjects of this Special Issue.

Technical Program Committee Members:

  1. Professor Peter Excell  Wrexham University
  2. Professor Jonathan Rodriguez  South Wales University
  3. Professor Simon Shepherd  University of Bradford
  4. Professor Irfan Awan  University of Bradford
  5. Professor Rami Qahwaji  University of Bradford
  6. Doctor Issa Elfergani  Instituto de Telecomunicações, Averio, Portugal
  7. Doctor James M Noras  University of Bradford
  8. Doctor Chan H See  University of Bolton

Prof. Dr. Raed Abd-Alhameed
Guest Editor

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 papers will be 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. Electronics 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 1500 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

  • 5G
  • Antennas and Propagation
  • Energy Efficient
  • Internet of Things (IoT)
  • MIMO
  • Network Coded Cooperation
  • Network Security
  • Network Virtualization
  • Radio Frequency and Reconfigurable Spectrum
  • Small Cell Technology

Published Papers (16 papers)

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Editorial

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Open AccessEditorial
Recent Technical Developments in Energy-Efficient 5G Mobile Cells: Present and Future
Electronics 2020, 9(4), 664; https://doi.org/10.3390/electronics9040664 - 20 Apr 2020
Abstract
The chapter of 4G (4th Generation) mobile systems is finally coming to an end, with waves of 4G systems having been deployed throughout Europe and worldwide [...] Full article

Research

Jump to: Editorial, Review

Open AccessFeature PaperArticle
A New CPW-Fed Diversity Antenna for MIMO 5G Smartphones
Electronics 2020, 9(2), 261; https://doi.org/10.3390/electronics9020261 - 04 Feb 2020
Cited by 4
Abstract
In this study, a new coplanar waveguide (CPW)-fed diversity antenna design is introduced for multiple-input–multiple-output (MIMO) smartphone applications. The diversity antenna is composed of a double-fed CPW-fed antenna with a pair of modified T-ring radiators. The antenna is designed to cover the frequency [...] Read more.
In this study, a new coplanar waveguide (CPW)-fed diversity antenna design is introduced for multiple-input–multiple-output (MIMO) smartphone applications. The diversity antenna is composed of a double-fed CPW-fed antenna with a pair of modified T-ring radiators. The antenna is designed to cover the frequency spectrum of commercial sub-6 GHz 5G communication (3.4–3.8 and 3.8–4.2 GHz). It also provides high isolation, better than −16 dB, without an additional decoupling structure. It offers good potential to be deployed in future smartphones. Therefore, the characteristics and performance of an 8-port 5G smartphone antenna were investigated using four pairs of the proposed diversity antennas. Due to the compact size and also the placement of the elements, the presented CPW-fed smartphone antenna array design occupies a very small part of the smartphone board. Its operation band spans from 3.4 to 4.4 GHz. The simulated results agree well with measured results, and the performance of the smartphone antenna design in the presence of a user is given in this paper as well. The proposed MIMO design provides not only sufficient radiation coverage supporting different sides of the mainboard but also polarization diversity. Full article
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Open AccessArticle
Low-Profile and Closely Spaced Four-Element MIMO Antenna for Wireless Body Area Networks
Electronics 2020, 9(2), 258; https://doi.org/10.3390/electronics9020258 - 04 Feb 2020
Cited by 3
Abstract
A compact four-element multiple-input multiple output (MIMO) antenna is proposed for medical applications operating at a 2.4 GHz ISM band. The proposed MIMO design occupies an overall volume of 26 mm × 26 mm × 0.8 mm. This antenna exhibits a good impedance [...] Read more.
A compact four-element multiple-input multiple output (MIMO) antenna is proposed for medical applications operating at a 2.4 GHz ISM band. The proposed MIMO design occupies an overall volume of 26 mm × 26 mm × 0.8 mm. This antenna exhibits a good impedance matching at the operating frequency of the ISM band, whose performance attributes include: isolation around 25 dB, envelope correlation coefficient (ECC) less than 0.02, average channel capacity loss (CCL) less than 0.3 bits/s/Hz and diversity gain (DG) of around 10 dB. The average peak realized gain of the four-element MIMO antenna is 2.4 dBi with more than 77 % radiation efficiency at the frequency of interest (ISM 2.4 GHz). The compact volume and adequate bandwidth, as well as the good achieved gain, make this antenna a strong candidate for bio-medical wearable applications. Full article
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Open AccessFeature PaperEditor’s ChoiceArticle
Complex Bianisotropy Effect on the Propagation Constant of a Shielded Multilayered Coplanar Waveguide Using Improved Full Generalized Exponential Matrix Technique
Electronics 2020, 9(2), 243; https://doi.org/10.3390/electronics9020243 - 02 Feb 2020
Cited by 2
Abstract
A theoretical study of the electromagnetic propagation in a complex medium suspended multilayer coplanar waveguide (CPW) is presented. The study is based on the generalized exponential matrix technique (GEMT) combined with Galerkin’s spectral method of moments applied to a CPW printed on a [...] Read more.
A theoretical study of the electromagnetic propagation in a complex medium suspended multilayer coplanar waveguide (CPW) is presented. The study is based on the generalized exponential matrix technique (GEMT) combined with Galerkin’s spectral method of moments applied to a CPW printed on a bianisotropic medium. The analytical formulation is based on a Full-GEMT, a method that avoids usual procedures of heavy and tedious mathematical expressions in the development of calculations and uses matrix-based mathematical expressions instead. These particularities are exploited to develop a mathematical model for the characterization of wave propagation in a three-layer shielded suspended CPW structure. This study is based on the development of mathematical formulations in full compact matrix-based expressions resulting in Green’s functions in a matrix form. The implemented method incorporates a new accelerating procedure developed in the GEMT which provides an initial value used to speed up searching for the exact solution in the principal computation code. This helped us to obtain accurate solutions with tolerable computing time. Good agreements have been achieved with the literature in terms of accuracy and rapid convergence. The results for different cases of bianisotropy have been investigated, and particularly, the effect on the dispersion characteristics is presented and compared with the isotropic case. Full article
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Open AccessFeature PaperArticle
A Compact Semi-Circular and Arc-Shaped Slot Antenna for Heterogeneous RF Front-Ends
Electronics 2019, 8(10), 1123; https://doi.org/10.3390/electronics8101123 - 06 Oct 2019
Cited by 8
Abstract
In this paper, a new miniaturized compact dual-band microstrip slot antenna is presented. To achieve the dual-band characteristics, two adjunct partial arc-shaped small slots are joined to two main circular slots embedded in the ground of the antenna structure. With a reduced size [...] Read more.
In this paper, a new miniaturized compact dual-band microstrip slot antenna is presented. To achieve the dual-band characteristics, two adjunct partial arc-shaped small slots are joined to two main circular slots embedded in the ground of the antenna structure. With a reduced size of 30 × 28.5 × 0.8 mm3, the proposed antenna presents a dual-band characteristic. The design is optimized using a High Frequency Structure Simulator (HFSS) followed by experimental verifications. An impedance bandwidth, for S11 ≤ 10 dB, that covers the 1.8 GHz and 2.4 GHz bands is accomplished, which makes the proposed antenna basically suitable for hand-held devices and medical applications. More applications such as digital communication system (DCS) 1.71–1.88 GHz, personal communication services (PCS) 1.85–1.99 GHz, Universal and mobile telecommunications system UMTS 1.92–2.17 GHz, Bluetooth 2.4–2.5 GHz, and Wi-Fi 2.4–2.454 GHz, Industrial Scientific and Medical radio frequency (RF) band ISM-2.4 GHz, Wireless Local Area Network (WLAN-2.4) are possible by simply changing one of the geometrical antenna dimensions. The antenna is characterized by stable radiation patterns as well. Full article
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Open AccessArticle
High-Performance Multiple-Input Multiple-Output Antenna System For 5G Mobile Terminals
Electronics 2019, 8(10), 1090; https://doi.org/10.3390/electronics8101090 - 25 Sep 2019
Cited by 12
Abstract
In this paper, the systematic design of a multiple antenna system for 5G smartphone operating at 3.5 GHz for multiple-input multiple-output (MIMO) operation in smartphones is proposed. The smartphone is preferred to be lightweight, thin, and attractive, and as a result metal casings [...] Read more.
In this paper, the systematic design of a multiple antenna system for 5G smartphone operating at 3.5 GHz for multiple-input multiple-output (MIMO) operation in smartphones is proposed. The smartphone is preferred to be lightweight, thin, and attractive, and as a result metal casings have become popular. Using conventional antennas, such as a patch antenna, Inverted-F antennas, or monopole, in proximity to metal casing leads to decreasing its total efficiency and bandwidth. Therefore, a slot antenna embedded in the metal casing can be helpful, with good performance regarding bandwidth and total efficiency. The proposed multiple antenna system adopted the unit open-end slot antenna fed by Inverted-L microstrip with tuning stub. The measured S-parameters results agree fairly with the numerical results. It attains 200 MHz bandwidth at 3.5 GHz with ports isolation of (≤−13 dB) for any two antennas of the system. The influence of the customer’s hand for the proposed multiple antenna system is also considered, and the MIMO channel capacity is computed. The maximum achievable MIMO channel capacity based on the measured result is 31.25 bps/Hz and is about 2.7 times of 2 × 2 MIMO operation. Full article
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Open AccessArticle
Low-Profile Frequency Reconfigurable Antenna for Heterogeneous Wireless Systems
Electronics 2019, 8(9), 976; https://doi.org/10.3390/electronics8090976 - 31 Aug 2019
Cited by 6
Abstract
A low-profile (0.21λg × 0.35λg × 0.02λg) and a simply-structured frequency-switchable antenna with eight frequency choices is presented in this paper. The radiating structure (monopole) is printed on a 1.6-mm thicker, commercially-available substrate of FR-4 ( [...] Read more.
A low-profile (0.21 λ g × 0.35 λ g × 0.02 λ g ) and a simply-structured frequency-switchable antenna with eight frequency choices is presented in this paper. The radiating structure (monopole) is printed on a 1.6-mm thicker, commercially-available substrate of FR-4 ( ϵ r = 4.4, tan δ = 0.020). Specifically, it uses three PIN diodes in the designated places to shift the resonant bands of the antenna. The antenna operates at four different modes depending on the ON and OFF states of the PIN diodes. While in each mode, the antenna covers two unique frequencies (Mode 1 = 1.8 and 3.29 GHz, Mode 2 = 2.23 and 3.9 GHz, Mode 3 = 2.4 and 4.55 GHz, and Mode 4 = 2.78 and 5.54 GHz). The performance results show that the proposed antenna scheme explores significant gain (>1.5 dBi in all modes) and reasonable efficiency (>82% in all modes) for each mode. Using a high-frequency structure simulator (HFSS), the switchable antenna is designed and optimized. The fabricated model along with the PIN diode and biasing network is tested experimentally to validate the simulation results. The proposed antenna may also be combined in compact and heterogeneous radio frequency (RF) front-ends because of its small geometry and efficient utilization of the frequency spectrum. Full article
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Open AccessArticle
Enabling Non-Linear Energy Harvesting in Power Domain Based Multiple Access in Relaying Networks: Outage and Ergodic Capacity Performance Analysis
Electronics 2019, 8(7), 817; https://doi.org/10.3390/electronics8070817 - 22 Jul 2019
Cited by 4
Abstract
The Power Domain-based Multiple Access (PDMA) scheme is considered as one kind of Non-Orthogonal Multiple Access (NOMA) in green communications and can support energy-limited devices by employing wireless power transfer. Such a technique is known as a lifetime-expanding solution for operations in future [...] Read more.
The Power Domain-based Multiple Access (PDMA) scheme is considered as one kind of Non-Orthogonal Multiple Access (NOMA) in green communications and can support energy-limited devices by employing wireless power transfer. Such a technique is known as a lifetime-expanding solution for operations in future access policy, especially in the deployment of power-constrained relays for a three-node dual-hop system. In particular, PDMA and energy harvesting are considered as two communication concepts, which are jointly investigated in this paper. However, the dual-hop relaying network system is a popular model assuming an ideal linear energy harvesting circuit, as in recent works, while the practical system situation motivates us to concentrate on another protocol, namely non-linear energy harvesting. As important results, a closed-form formula of outage probability and ergodic capacity is studied under a practical non-linear energy harvesting model. To explore the optimal system performance in terms of outage probability and ergodic capacity, several main parameters including the energy harvesting coefficients, position allocation of each node, power allocation factors, and transmit signal-to-noise ratio (SNR) are jointly considered. To provide insights into the performance, the approximate expressions for the ergodic capacity are given. By matching analytical and Monte Carlo simulations, the correctness of this framework can be examined. With the observation of the simulation results, the figures also show that the performance of energy harvesting-aware PDMA systems under the proposed model can satisfy the requirements in real PDMA applications. Full article
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Open AccessFeature PaperArticle
Maximum Transmit Power for UE in an LTE Small Cell Uplink
Electronics 2019, 8(7), 796; https://doi.org/10.3390/electronics8070796 - 16 Jul 2019
Cited by 3
Abstract
To furnish the network with small cells, it is vital to consider parameters like cell size, interference in the network, and deployment strategies to maximize the network’s performance gains expected from small cells. With a small cell network, it is critical to analyze [...] Read more.
To furnish the network with small cells, it is vital to consider parameters like cell size, interference in the network, and deployment strategies to maximize the network’s performance gains expected from small cells. With a small cell network, it is critical to analyze the impact of the uplink power control parameters on the network’s performance. In particular, the maximum transmit power (Pmax) for user equipment (UE) needs to be revisited for small cells, since it is a major contributor towards interference. In this work, the network performance was evaluated for different Pmax values for the small cell uplink. Various deployment scenarios for furnishing the existing macro layer in LTE networks with small cells were considered. The Pmax limit for a small cell uplink was evaluated for both homogenous small cell and heterogeneous networks (HetNet). The numerical results showed that it would be appropriate to adopt Pmax = 18 dBm in uniformly distributed small cells rather than Pmax = 23 dBm, as in macro environments. The choice of Pmax = 18 dBm was further validated for three HetNet deployment scenarios. A decrease of 0.52 dBm and an increase of 0.03 dBm and 3.29 dBm in the proposed Pmax = 18 dBm were observed for the three HetNet deployments, respectively. Furthermore, we propose that the fractional power control mode can be employed instead of the full compensation mode in small cell uplinks. Full article
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Open AccessArticle
Frequency and Pattern Reconfigurable Antenna for Emerging Wireless Communication Systems
Electronics 2019, 8(4), 407; https://doi.org/10.3390/electronics8040407 - 07 Apr 2019
Cited by 15
Abstract
A printed and minimal size antenna having the functionality of frequency shifting as well as pattern reconfigurability is presented in this work. The antenna proposed in this work consists of three switches. Switch 1 is a lumped switch that controls the operating bands [...] Read more.
A printed and minimal size antenna having the functionality of frequency shifting as well as pattern reconfigurability is presented in this work. The antenna proposed in this work consists of three switches. Switch 1 is a lumped switch that controls the operating bands of the antenna. Switch 2 and Switch 3 controls the beam switching of the antenna. When the Switch 1 is ON, the proposed antenna operates at 3.1 GHz and 6.8 GHz, covering the 2.5–4.2 GHz and 6.2–7.4 GHz bands, respectively. When Switch 1 is OFF, the antenna operates only at 3.1 GHz covering the 2.5–4.2 GHz band. The desired beam from the antenna can be obtained by adjusting the ON and OFF states of Switches 2 and 3. Unique beams can be obtained by different combination of ON and OFF states of the Switches 2 and 3. A gain greater than 3.7 dBi is obtained for all four cases. Full article
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Open AccessArticle
Wireless-Powered Cooperative MIMO NOMA Networks: Design and Performance Improvement for Cell-Edge Users
Electronics 2019, 8(3), 328; https://doi.org/10.3390/electronics8030328 - 16 Mar 2019
Cited by 6
Abstract
In this paper, we study two transmission scenarios for the base station (BS) in cellular networks to serve the far user, who is located at the cell-edge area in such a network. In particular, we show that wireless-powered non-orthogonal multiple access (NOMA) and [...] Read more.
In this paper, we study two transmission scenarios for the base station (BS) in cellular networks to serve the far user, who is located at the cell-edge area in such a network. In particular, we show that wireless-powered non-orthogonal multiple access (NOMA) and the cell-center user in such a model can harvest energy from the BS. To overcome disadvantages of the cell-edge user due to its weak received signal, we fabricate a far NOMA user with multiple antennas to achieve performance improvement. In addition, the first scenario only considers a relay link deployed to forward signals to a far NOMA user, while both direct links and relay links are generally enabled to serve a far user in the second scenario. These situations, together with their outage performance, are analyzed and compared to provide insights in the design of a real-multiple-antenna NOMA network, in which the BS is also required to equip multiple antennas for robust quality of transmission. Higher complexity in computations is already known in consideration of outage metrics with respect to performance analysis, since the system model employs multiple antennas. To this end, we employ a transmit antenna selection (TAS) policy to formulate closed-form expressions of outage probability that satisfies the quality-of-service (QoS) requirements in the NOMA network. Our simulation results reveal that the performance of the considered system will be improved in cases of higher quantity of transmit antennas in dedicated devices. Finally, the proposed design in such a NOMA system cannot only ensure a downlink with higher quality to serve a far NOMA user, but also provide significant system performance improvement compared to a traditional NOMA networks using a single antenna. Full article
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Open AccessArticle
Multi-Points Cooperative Relay in NOMA System with N-1 DF Relaying Nodes in HD/FD Mode for N User Equipments with Energy Harvesting
Electronics 2019, 8(2), 167; https://doi.org/10.3390/electronics8020167 - 01 Feb 2019
Cited by 7
Abstract
Non-Orthogonal Multiple Access (NOMA) is the key technology promised to be applied in next-generation networks in the near future. In this study, we propose a multi-points cooperative relay (MPCR) NOMA model instead of just using a relay as in previous studies. Based on [...] Read more.
Non-Orthogonal Multiple Access (NOMA) is the key technology promised to be applied in next-generation networks in the near future. In this study, we propose a multi-points cooperative relay (MPCR) NOMA model instead of just using a relay as in previous studies. Based on the channel state information (CSI), the base station (BS) selects a closest user equipment (UE) and sends a superposed signal to this UE as a first relay node. We have assumed that there are N UEs in the network and the N-th UE, which is farthest from BS, has the poorest quality signal transmitted from the BS compared the other UEs. The N-th UE received a forwarded signal from N 1 relaying nodes that are the UEs with better signal quality. At the i-th relaying node, it detects its own symbol by using successive interference cancellation (SIC) and will forward the superimposed signal to the next closest user, namely the ( i + 1 ) -th UE, and include an excess power which will use for energy harvesting (EH) intention at the next UE. By these, the farthest UE in network can be significantly improved. In addition, closed-form expressions of outage probability for users over both the Rayleigh and Nakagami-m fading channels are also presented. Analysis and simulation results performed by Matlab software, which are presented accurately and clearly, show that the effectiveness of our proposed model and this model will be consistent with the multi-access wireless network in the future. Full article
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Review

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Open AccessFeature PaperReview
A Survey on RF and Microwave Doherty Power Amplifier for Mobile Handset Applications
Electronics 2019, 8(6), 717; https://doi.org/10.3390/electronics8060717 - 25 Jun 2019
Cited by 4
Abstract
This survey addresses the cutting-edge load modulation microwave and radio frequency power amplifiers for next-generation wireless communication standards. The basic operational principle of the Doherty amplifier and its defective behavior that has been originated by transistor characteristics will be presented. Moreover, advance design [...] Read more.
This survey addresses the cutting-edge load modulation microwave and radio frequency power amplifiers for next-generation wireless communication standards. The basic operational principle of the Doherty amplifier and its defective behavior that has been originated by transistor characteristics will be presented. Moreover, advance design architectures for enhancing the Doherty power amplifier’s performance in terms of higher efficiency and wider bandwidth characteristics, as well as the compact design techniques of Doherty amplifier that meets the requirements of legacy 5G handset applications, will be discussed. Full article
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Open AccessFeature PaperReview
Recent Developments of Dual-Band Doherty Power Amplifiers for Upcoming Mobile Communications Systems
Electronics 2019, 8(6), 638; https://doi.org/10.3390/electronics8060638 - 06 Jun 2019
Cited by 8
Abstract
Power amplifiers in modern and future communications should be able to handle different modulation standards at different frequency bands, and in addition, to be compatible with the previous generations. This paper reviews the recent design techniques that have been used to operate dual-band [...] Read more.
Power amplifiers in modern and future communications should be able to handle different modulation standards at different frequency bands, and in addition, to be compatible with the previous generations. This paper reviews the recent design techniques that have been used to operate dual-band amplifiers and in particular the Doherty amplifiers. Special attention is focused on the design methodologies used for power splitters, phase compensation networks, impedance inverter networks and impedance transformer networks of such power amplifier. The most important materials of the dual-band Doherty amplifier are highlighted and surveyed. The main problems and challenges covering dual-band design concepts are presented and discussed. In addition, improvement techniques to enhance such operations are also exploited. The study shows that the transistor parasitic has a great impact in the design of a dual-band amplifier, and reduction of the transforming ratio of the inverter simplifies the dual-band design. The offset line can be functionally replaced by a Π-network in dual-band design rather than T-network. Full article
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Open AccessFeature PaperReview
Recent Developments of Reconfigurable Antennas for Current and Future Wireless Communication Systems
Electronics 2019, 8(2), 128; https://doi.org/10.3390/electronics8020128 - 26 Jan 2019
Cited by 30
Abstract
Reconfigurable antennas play important roles in smart and adaptive systems and are the subject of many research studies. They offer several advantages such as multifunctional capabilities, minimized volume requirements, low front-end processing efforts with no need for a filtering element, good isolation, and [...] Read more.
Reconfigurable antennas play important roles in smart and adaptive systems and are the subject of many research studies. They offer several advantages such as multifunctional capabilities, minimized volume requirements, low front-end processing efforts with no need for a filtering element, good isolation, and sufficient out-of-band rejection; these make them well suited for use in wireless applications such as fourth generation (4G) and fifth generation (5G) mobile terminals. With the use of active materials such as microelectromechanical systems (MEMS), varactor or p-i-n (PIN) diodes, an antenna’s characteristics can be changed through altering the current flow on the antenna structure. If an antenna is to be reconfigurable into many different states, it needs to have an adequate number of active elements. However, a large number of high-quality active elements increases cost, and necessitates complex biasing networks and control circuitry. We review some recently proposed reconfigurable antenna designs suitable for use in wireless communications such as cognitive-ratio (CR), multiple-input multiple-output (MIMO), ultra-wideband (UWB), and 4G/5G mobile terminals. Several examples of antennas with different reconfigurability functions are analyzed and their performances are compared. Characteristics and fundamental properties of reconfigurable antennas with single and multiple reconfigurability modes are investigated. Full article
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Open AccessFeature PaperReview
Recent Progress in the Design of 4G/5G Reconfigurable Filters
Electronics 2019, 8(1), 114; https://doi.org/10.3390/electronics8010114 - 20 Jan 2019
Cited by 17
Abstract
Currently, several microwave filter designs contend for use in wireless communications. Among various microstrip filter designs, the reconfigurable planar filter presents more advantages and better prospects for communication applications, being compact in size, light-weight and cost-effective. Tuneable microwave filters can reduce the number [...] Read more.
Currently, several microwave filter designs contend for use in wireless communications. Among various microstrip filter designs, the reconfigurable planar filter presents more advantages and better prospects for communication applications, being compact in size, light-weight and cost-effective. Tuneable microwave filters can reduce the number of switches between electronic components. This paper presents a review of recent reconfigurable microwave filter designs, specifically on current advances in tuneable filters that involve high-quality factor resonator filters to control frequency, bandwidth and selectivity. The most important materials required for this field are also highlighted and surveyed. In addition, the main references for several types of tuneable microstrip filters are reported, especially related to new design technologies. Topics surveyed include microwave and millimetre wave designs for 4G and 5G applications, which use varactors and MEMSs technologies. Full article
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