Showing papers on "Antenna (radio) published in 2021"

Ultra-Wideband Antennas and Propagation: For Communications, Radar and Imaging

Abstract: Editors. Prime Contributors. Preface. Acknowledgments. Abbreviations & Acronyms. 1 Introduction to UWB Signals and Systems (Andreas F. Molisch). 1.1 History of UWB. 1.2 Motivation. 1.3 UWB Signals and Systems. 1.4 Frequency Regulation. 1.5 Applications, Operating Scenarios and Standardisation. 1.6 System Outlook. References. Part I Fundamentals. Introduction to Part I (Wasim Q. Malik and David J. Edwards). 2 Fundamental Electromagnetic Theory (Mischa Dohler). 2.1 Introduction. 2.2 Maxwell's Equations. 2.3 Resulting Principles. References. 3 Basic Antenna Elements (Mischa Dohler). 3.1 Introduction. 3.2 Hertzian Dipole. 3.3 Antenna Parameters and Terminology. 3.4 Basic Antenna Elements. References. 4 Antenna Arrays (Ernest E. Okon). 4.1 Introduction. 4.2 Point Sources. 4.3 The Principle of Pattern Multiplication. 4.4 Linear Arrays of n Elements. 4.5 Linear Broadside Arrays with Nonuniform Amplitude Distributions. 4.6 Planar Arrays. 4.7 Design Considerations. 4.8 Summary. References. 5 Beamforming (Ben Allen). 5.1 Introduction. 5.2 Antenna Arrays. 5.3 Adaptive Array Systems. 5.4 Beamforming. 5.5 Summary. References. 6 Antenna Diversity Techniques (Junsheng Liu, Wasim Q. Malik, David J. Edwards and Mohammad Ghavami). 6.1 Introduction. 6.2 A Review of Fading. 6.3 Receive Diversity. 6.4 Transmit Diversity. 6.5 MIMO Diversity Systems. References. Part II Antennas for UWB Communications. Introduction to Part II (Ernest E. Okon). 7 Theory of UWB Antenna Elements (Xiaodong Chen). 7.1 Introduction. 7.2 Mechanism of UWB Monopole Antennas. 7.3 Planar UWB Monopole Antennas. 7.4 Planar UWB Slot Antennas. 7.5 Time-Domain Characteristics of Monopoles 7.6 Summary. Acknowledgements. References. 8 Antenna Elements for Impulse Radio (Zhi Ning Chen). 8.1 Introduction. 8.2 UWB Antenna Classification and Design Considerations. 8.3 Omnidirectional and Directional Designs. 8.4 Summary. References. 9 Planar Dipole-like Antennas for Consumer Products (Peter Massey). 9.1 Introduction. 9.2 Computer Modelling and Measurement Techniques. 9.3 Bicone Antennas and the Lossy Transmission Line Model. 9.4 Planar Dipoles. 9.5 Practical Antenna. 9.6 Summary. Acknowledgements. References. 10 UWB Antenna Elements for Consumer Electronic Applications (Dirk Manteuffel). 10.1 Introduction. 10.2 Numerical Modelling and Extraction of the UWB Characterisation. 10.3 Antenna Design and Integration. 10.4 Propagation Modelling. 10.5 System Analysis. 10.6 Conclusions. References. 11 Ultra-wideband Arrays (Ernest E. Okon). 11.1 Introduction. 11.2 Linear Arrays. 11.3 Null and Maximum Directions for Uniform Arrays. 11.4 Phased Arrays. 11.5 Elements for UWB Array Design. 11.6 Modelling Considerations. 11.7 Feed Configurations. 11.8 Design Considerations. 11.9 Summary. References. 12 UWB Beamforming (Mohammad Ghavami and Kaveh Heidary). 12.1 Introduction. 12.2 Basic Concept. 12.3 A Simple Delay-line Transmitter Wideband Array. 12.4 UWB Mono-pulse Arrays. 12.5 Summary. References. Part III Propagation Measurements and Modelling for UWB Communications. Introduction to Part III (Mischa Dohler and Ben Allen). 13 Analysis of UWB Signal Attenuation Through Typical Building Materials (Domenico Porcino). 13.1 Introduction. 13.2 A Brief Overview of Channel Characteristics. 13.3 The Materials Under Test. 13.4 Experimental Campaign. 13.5 Conclusions. References. 14 Large- and Medium-scale Propagation Modelling (Mischa Dohler, Junsheng Liu, R. Michael Buehrer, Swaroop Venkatesh and Ben Allen). 14.1 Introduction. 14.2 Deterministic Models. 14.3 Statistical-Empirical Models. 14.4 Standardised Reference Models. 14.5 Conclusions. References. 15 Small-scale Ultra-wideband Propagation Modelling (Swaroop Venkatesh, R. Michael Buehrer, Junsheng Liu and Mischa Dohler). 15.1 Introduction. 15.2 Small-scale Channel Modelling. 15.3 Spatial Modelling. 15.4 IEEE 802.15.3a Standard Model. 15.5 IEEE 802.15.4a Standard Model. 15.6 Summary. References. 16 Antenna Design and Propagation Measurements and Modelling for UWBWireless BAN (Yang Hao, Akram Alomainy and Yan Zhao). 16.1 Introduction. 16.2 Propagation Channel Measurements and Characteristics. 16.3 WBAN Channel Modelling. 16.4 UWB System-Level Modelling of Potential Body-Centric Networks. 16.5 Summary. References. 17 Ultra-wideband Spatial Channel Characteristics (Wasim Q. Malik, Junsheng Liu, Ben Allen and David J. Edwards). 17.1 Introduction. 17.2 Preliminaries. 17.3 UWB Spatial Channel Representation. 17.4 Characterisation Techniques. 17.5 Increase in the Communication Rate. 17.6 Signal Quality Improvement. 17.7 Performance Parameters. 17.8 Summary. References. Part IV UWB Radar, Imaging and Ranging. Introduction to Part IV (Anthony K. Brown). 18 Localisation in NLOS Scenarios with UWB Antenna Arrays (Thomas Kaiser, Christiane Senger, Amr Eltaher and Bamrung Tau Sieskul). 18.1 Introduction. 18.2 Underlying Mathematical Framework. 18.3 Properties of UWB Beamforming. 18.4 Beamloc Approach. 18.5 Algorithmic Framework. 18.6 Time-delay Estimation. 18.7 Simulation Results. 18.8 Conclusions. References. 19 Antennas for Ground-penetrating Radar (Ian Craddock). 19.1 Introduction. 19.2 GPR Example Applications. 19.3 Analysis and GPR Design. 19.4 Antenna Elements. 19.5 Antenna Measurements, Analysis and Simulation. 19.6 Conclusions. Acknowledgements. References. 20 Wideband Antennas for Biomedical Imaging (Ian Craddock). 20.1 Introduction. 20.2 Detection and Imaging. 20.3 Waveform Choice and Antenna Design Criteria. 20.4 Antenna Elements. 20.5 Measurements, Analysis and Simulation. 20.6 Conclusions. Acknowledgements. References. 21 UWB Antennas for Radar and Related Applications (Anthony K. Brown). 21.1 Introduction. 21.2 Medium- and Long-Range Radar. 21.3 UWB Reflector Antennas. 21.4 UWB Feed Designs. 21.5 Feeds with Low Dispersion. 21.6 Summary. References. Index.

Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers.

Abstract: Although advances in wireless technologies such as miniature and wearable electronics have improved the quality of our lives, the ubiquitous use of electronics comes at the expense of increased exposure to electromagnetic (EM) radiation. Up to date, extensive efforts have been made to develop high-performance EM absorbers based on synthetic materials. However, the design of an EM absorber with both exceptional EM dissipation ability and good environmental adaptability remains a substantial challenge. Here, we report the design of a class of carbon heterostructures via hierarchical assembly of graphitized lignocellulose derived from bamboo. Specifically, the assemblies of nanofibers and nanosheets behave as a nanometer-sized antenna, which results in an enhancement of the conductive loss. In addition, we show that the composition of cellulose and lignin in the precursor significantly influences the shape of the assembly and the formation of covalent bonds, which affect the dielectric response-ability and the surface hydrophobicity (the apparent contact angle of water can reach 135°). Finally, we demonstrate that the obtained carbon heterostructure maintains its wideband EM absorption with an effective absorption frequency ranging from 12.5 to 16.7 GHz under conditions that simulate the real-world environment, including exposure to rainwater with slightly acidic/alkaline pH values. Overall, the advances reported in this work provide new design principles for the synthesis of high-performance EM absorbers that can find practical applications in real-world environments.

Design of a High-Efficiency and -Gain Antenna Using Novel Low-Loss, Temperature-Stable Li2Ti1–x(Cu1/3Nb2/3)xO3 Microwave Dielectric Ceramics

Abstract: Microwave dielectric ceramics are vital for filters, dielectric resonators, and dielectric antennas in the 5G era. It was found that the (Cu1/3Nb2/3)4+ substitution can effectively adjust the TCF (...

A Novel Approach of Design and Analysis of a Hexagonal Fractal Antenna Array (HFAA) for Next-Generation Wireless Communication

Abstract: The study and exploration of massive multiple-input multiple-output (MMIMO) and millimeter-wave wireless access technology has been spurred by a shortage of bandwidth in the wireless communication sector. Massive MIMO, which combines antennas at the transmitter and receiver, is a key enabler technology for next-generation networks to enable exceptional spectrum and energy efficiency with simple processing techniques. For massive MIMOs, the lower band microwave or millimeter-wave band and the antenna are impeccably combined with RF transceivers. As a result, the 5G wireless communication antenna differs from traditional antennas in many ways. A new concept of the MIMO tri-band hexagonal antenna array is being introduced for next-generation cellular networks. With a total scaling dimension of 150 × 75 mm2, the structure consists of multiple hexagonal fractal antenna components at different corners of the patch. The radiating patch resonates at 2.55–2.75, 3.45–3.7, and 5.65–6.05 GHz (FR1 band) for better return loss (S11) of more than 15 dB in all three operating bands. The coplanar waveguide (CPW) feeding technique and defective ground structure in the ground plane have been employed for effective impedance matching. The deviation of the main lobe of the radiation pattern is achieved using a two-element microstrip Taylor antenna array with series feeding, which also boosts the antenna array’s bandwidth and minimizes sidelobe. The proposed antenna is designed, simulated, and tested in far-field radiating conditions and generates tri-band S-parameters with sufficient separation and high-quality double-polarized radiation. The fabrication and testing of MIMO antennas were completed, where the measurement results matched the simulation results. In addition, the 5G smartphone antenna system requires a new, lightweight phased microwave antenna (μ-wave) with wide bandwidth and a fire extender. Because of its decent performance and compact architectures, the proposed smartphone antenna array architecture is a better entrant for upcoming 5G cellular implementations.

Antenna Decoupling by Common and Differential Modes Cancellation

Abstract: In this article, a general decoupling method based on a new perspective of common mode (CM) and differential mode (DM) cancellation is proposed. For two closely spaced antennas, the mutual coupling effect can be analyzed and solved by exciting them simultaneously with in-phase (CM) and out-of-phase (DM) signals. It is theoretically proved that, if CM and DM impedances are the same, the mutual coupling effect between two separated antennas can be totally eliminated. Therefore, we can solve the coupling problem by CM and DM impedance analysis and exploit the unique field properties of characteristic modes to assist in antenna decoupling in a physical intuitive way. To validate the feasibility of this method, two practical design examples, including the decoupling between closely spaced dipole antennas and planar inverted-F antennas, are proposed. Both design examples have demonstrated that the proposed method can provide a systemic design guideline for antenna decoupling and achieve better decoupling performance compared to the conventional decoupling techniques. We forecast the proposed decoupling scheme, with a simplified decoupling procedure, has great potential for the applications of antenna arrays and multi-input multi-output (MIMO) systems.

Reconfigurable Intelligent Surfaces: A Signal Processing Perspective With Wireless Applications.

Abstract: A reconfigurable intelligent surface (RIS) is a two-dimensional surface of engineered material whose properties are reconfigurable rather than static [4]. For example, the scattering, absorption, reflection, and diffraction properties can be changed with time and controlled by software. In principle, the surface can be used to synthesize an arbitrarily-shaped object of the same size, when it comes to how electromagnetic waves interact with it [5]. The long-term vision of the RIS technology is to create smart radio environments [9], where the wireless propagation conditions are co-engineered with the physical-layer signaling, and investigate how to utilize this new capability. The common protocol stack consists of seven layers and wireless technology is chiefly focused on the first three layers (physical, link, and network) [10]. An RIS operates at what can be referred to as Layer 0, where the traditional design issue is the antennas of the transmitter/receivers; one can think of RIS as extending the antenna design towards the environment, commonly seen as uncontrollable and decided by "nature". This approach can profoundly change the wireless design beyond 5G. This article provides a tutorial on the fundamental properties of the RIS technology from a signal processing perspective, to complement the recent surveys of electromagnetic and hardware aspects [4], [7], communication theory [11], and localization [8]. We will provide the formulas and derivations that are required to understand and analyze RIS-aided systems, and exemplify how they can be utilized for improved communication, localization, and sensing. We will also elaborate on the fundamentally new possibilities enabled by Layer 0 engineering and electromagnetic phenomena that remain to be modeled and utilized for improved signal processing.

Position Location for Futuristic Cellular Communications: 5G and Beyond

Abstract: With vast mmWave spectrum and narrow beam antenna technology, precise position location is now possible in 5G and future mobile communication systems. In this article, we describe how centimeter-level localization accuracy can be achieved, particularly through the use of map-based techniques. We show how data fusion of parallel information streams, machine learning, and cooperative localization techniques further improve positioning accuracy.

Wideband Four-Port MIMO antenna array with high isolation for future wireless systems

Abstract: A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed. Each array antenna element is a microstrip-line fed monopole type. The novelty of the antenna lies in loading an “EL” slot into the radiating element along with two identical stubs coupled to the partial ground in order to improve the impedance matching and radiation characteristics across the bands of interest. To further attain high port isolation without affecting the compactness and radiation performance of each antenna element, the technique of introducing an innovative un-protruded multi-slot (UPMS) isolating element (of low-profile 2 × 19 mm2) between two closely spaced antenna elements (with an edge-to-edge distance of approx. 0.03λ at 4.6 GHz) is also presented. Besides demonstrating a small footprint of 30 × 40 × 1.6 mm3, the proposed four-port MIMO antenna array has also shown wide 10-dB impedance bandwidth of 58.56% (3.20–5.85 GHz), high isolation of more than 17.5 dB, and good gain and efficiency of around 3.5 dBi and 85%, respectively, across the bands of interest. Finally, the MIMO performance metrics of the proposed antenna are also analyzed.

Study on on-Chip Antenna Design Based on Metamaterial-Inspired and Substrate-Integrated Waveguide Properties for Millimetre-Wave and THz Integrated-Circuit Applications

Abstract: This paper presents the results of a study on improving the performance parameters such as the impedance bandwidth, radiation gain and efficiency, as well as suppressing substrate loss of an innovative antenna for on-chip implementation for millimetre-wave and terahertz integrated-circuits. This was achieved by using the metamaterial and the substrate-integrated waveguide (SIW) technologies. The on-chip antenna structure comprises five alternating layers of metallization and silicon. An array of circular radiation patches with metamaterial-inspired crossed-shaped slots are etched on the top metallization layer below which is a silicon layer whose bottom surface is metalized to create a ground plane. Implemented in the silicon layer below is a cavity above which is no ground plane. Underneath this silicon layer is where an open-ended microstrip feedline is located which is used to excite the antenna. The feed mechanism is based on the coupling of the electromagnetic energy from the bottom silicon layer to the top circular patches through the cavity. To suppress surface waves and reduce substrate loss, the SIW concept is applied at the top silicon layer by implementing the metallic via holes at the periphery of the structure that connect the top layer to the ground plane. The proposed on-chip antenna has an average measured radiation gain and efficiency of 6.9 dBi and 53%, respectively, over its operational frequency range from 0.285–0.325 THz. The proposed on-chip antenna has dimensions of 1.35 × 1 × 0.06 mm3. The antenna is shown to be viable for applications in millimetre-waves and terahertz integrated-circuits.

Quasi-Optical Multi-Beam Antenna Technologies for B5G and 6G mmWave and THz Networks: A Review

Abstract: Multi-beam antennas are critical components in future terrestrial and non-terrestrial wireless communications networks. The multiple beams produced by these antennas will enable dynamic interconnection of various terrestrial, airborne and space-borne network nodes. As the operating frequency increases to the high millimeter wave (mmWave) and terahertz (THz) bands for beyond 5G (B5G) and sixth-generation (6G) systems, quasi-optical techniques are expected to become dominant in the design of high gain multi-beam antennas. This paper presents a timely overview of the mainstream quasi-optical techniques employed in current and future multi-beam antennas. Their operating principles and design techniques along with those of various quasi-optical beamformers are presented. These include both conventional and advanced lens and reflector based configurations to realize high gain multiple beams at low cost and in small form factors. New research challenges and industry trends in the field, such as planar lenses based on transformation optics and metasurface-based transmitarrays, are discussed to foster further innovations in the microwave and antenna research community.

Intelligent Surface-Aided Transmitter Architectures for Millimeter-Wave Ultra Massive MIMO Systems

Abstract: In this article, we study two novel massive multiple-input multiple-output (MIMO) transmitter architectures for millimeter wave (mmWave) communications which comprise few active antennas, each equipped with a dedicated radio frequency (RF) chain, that illuminate a nearby large intelligent reflecting/transmitting surface (IRS/ITS). The IRS (ITS) consists of a large number of low-cost and energy-efficient passive antenna elements which are able to reflect (transmit) a phase-shifted version of the incident electromagnetic field. Similar to lens array (LA) antennas, IRS/ITS-aided antenna architectures are energy efficient due to the almost lossless over-the-air connection between the active antennas and the intelligent surface. However, unlike for LA antennas, for which the number of active antennas has to linearly grow with the number of passive elements (i.e., the lens aperture) due to the non-reconfigurablility (i.e., non-intelligence) of the lens, for IRS/ITS-aided antennas, the reconfigurablility of the IRS/ITS facilitates scaling up the number of radiating passive elements without increasing the number of costly and bulky active antennas. We show that the constraints that the precoders for IRS/ITS-aided antennas have to meet differ from those of conventional MIMO architectures. Taking these constraints into account and exploiting the sparsity of mmWave channels, we design two efficient precoders; one based on maximizing the mutual information and one based on approximating the optimal unconstrained fully digital (FD) precoder via the orthogonal matching pursuit algorithm. Furthermore, we develop a power consumption model for IRS/ITS-aided antennas that takes into account the impacts of the IRS/ITS imperfections, namely the spillover loss, taper loss, aperture loss, and phase shifter loss. Moreover, we study the effect that the various system parameters have on the achievable rate and show that a proper positioning of the active antennas with respect to the IRS/ITS leads to a considerable performance improvement. Our simulation results reveal that unlike conventional MIMO architectures, IRS/ITS-aided antennas are both highly energy efficient and fully scalable in terms of the number of transmitting (passive) antennas. Therefore, IRS/ITS-aided antennas are promising candidates for realizing the potential of mmWave ultra massive MIMO communications in practice.

Terahertz-Band Joint Ultra-Massive MIMO Radar-Communications: Model-Based and Model-Free Hybrid Beamforming

Abstract: Wireless communications and sensing at terahertz (THz) band are increasingly investigated as promising short-range technologies because of the availability of high operational bandwidth at THz. In order to address the extremely high attenuation at THz, ultra-massive multiple-input multiple-output (MIMO) antenna systems have been proposed for THz communications to compensate propagation losses. However, the cost and power associated with fully digital beamformers of these huge antenna arrays are prohibitive. In this paper, we develop wideband hybrid beamformers based on both model-based and model-free techniques for a new group-of-subarrays (GoSA) ultra-massive MIMO structure in low-THz band. Further, driven by the recent developments to save the spectrum, we propose beamformers for a joint ultra-massive MIMO radar-communications system, wherein the base station serves multi-antenna user equipment (RX), and tracks radar targets by generating multiple beams toward both RX and the targets. We formulate the GoSA beamformer design as an optimization problem to provide a trade-off between the unconstrained communications beamform-ers and the desired radar beamformers. To mitigate the beam split effect at THz band arising from frequency-independent analog beamformers, we propose a phase correction technique to align the beams of multiple subcarriers toward a single physical direction. Additionally, our design also exploits second-order channel statistics so that an infrequent channel feedback from the RX is achieved with less channel overhead. To further decrease the ultra-massive MIMO computational complexity and enhance robustness, we also implement deep learning solutions to the proposed model-based hybrid beamformers. Numerical experiments demonstrate that both techniques outperform the conventional approaches in terms of spectral efficiency and radar beampatterns, as well as exhibiting less hardware cost and computation time.

Full Duplex Radio/Radar Technology: The Enabler for Advanced Joint Communication and Sensing

Abstract: The use of joint communication and sensing (JCAS) systems in efficiently utilizing the scarce RF spectrum has received increased interest in recent years. Due to the (re)use of the same resources by both functions (e.g., frequency of operation, waveforms, and hardware), various design challenges are evident in integrating communication and sensing/radar systems, and novel techniques are required to overcome them to provide both subsystems with optimal performance. We have identified full duplex operation as the key enabler for JCAS systems as discussed in this article. Furthermore, since JCAS systems usually employ large antenna arrays, novel beamforming techniques are required to efficiently manage the sensing and communication beams in addition to self-interference suppression, whereas their joint waveforms need to be optimized considering the performance metrics of both subsystems. These requirements yield design trade-offs to address; existing and novel solutions to these aspects are explored herein from a signal processing perspective. This article also presents experimental full duplex sensing results through over-the-air RF measurements, showcasing the feasibility of integrating sensing systems with communication systems.

Dual-Band Shared-Aperture Base Station Antenna Array With Electromagnetic Transparent Antenna Elements

Abstract: An electromagnetic transparent antenna element is proposed for dual-band shared-aperture fifth-generation (5G) MIMO base station antenna array developments. The antenna element that operates in the low-frequency band (LB) of 1.8–2.7 GHz is placed above the aperture of the antenna array that operates in the high-frequency band (HB) of 3.3–3.8 GHz. Because of this antenna array configuration, the antenna elements in the LB have to be transparent to the electromagnetic waves radiated by the HB antenna array. This kind of electromagnetic transparent antenna element allows the HB antenna array working properly in the dual-band shared-aperture antenna array configuration. In this work, the electromagnetic transparent antenna element is inspired by the element of a typical wide-angle bandpass frequency selective surface (FSS). The radiation performance of the electromagnetic transparent antenna element at the LB is realized by properly combining the wide-angle bandpass FSS elements. A dual-band dual-polarized shared-aperture antenna array is then developed to demonstrate the concept and design. The experimental result validates the stable radiation patterns of each antenna element in both LB and HB. It indicates the proposed approach is promising for 5G MIMO base station antenna array developments.

Channel Measurement and Ray-Tracing-Statistical Hybrid Modeling for Low-Terahertz Indoor Communications

Abstract: TeraHertz (THz) communications are envisioned as a promising technology, owing to its unprecedented multi-GHz bandwidth. One fundamental challenge when moving to new spectrum is to understand the science of radio propagation and develop an accurate channel model. In this paper, a wideband channel measurement campaign between 130 GHz and 143 GHz is investigated in a typical meeting room. Directional antennas are utilized and rotated for resolving the multi-path components (MPCs) in the angular domain. With careful system calibration that eliminates system errors and antenna effects, a realistic power delay profile is developed. Furthermore, a combined MPC clustering and matching procedure with ray-tracing techniques is proposed to investigate the cluster behavior and wave propagation of THz signals. In light of the measurement results, physical parameters and insights in the THz indoor channel are comprehensively analyzed, including the line-of-sight path loss, power distributions, temporal and spatial features, and correlations among THz multi-path characteristics. Finally, a hybrid channel model that combines ray-tracing and statistical methods is developed for THz indoor communications. Numerical results demonstrate that the proposed hybrid channel model shows good agreement with the measurement and outperforms the conventional statistical and geometric-based stochastic channel model in terms of the temporal-spatial characteristics.

Folded Transmitarray Antenna With Circular Polarization Based on Metasurface

Abstract: We propose a low-profile broadband planar circularly polarized folded transmitarray antenna (CPFTA) based on well-designed top and bottom metasurfaces (MSs). The top MS is employed to reflect the $x$ -polarized wave as a ground and, at the same time, to convert the $y$ -polarized wave into circularly polarized waves with arbitrary phase shifts in the operation band. A bottom MS is applied to reflect the incident wave and twist its polarization by 90°. The whole CPFTA, including the feeding source of microstrip antenna, and the top and bottom MSs can be fully integrated and fabricated using low-cost printed circuit board technology. Both simulated and measured results demonstrate significant advantages of the proposed antenna, including broad bandwidth, high gain, lower profile, planar geometry, and easy integration. The fabricated sample shows 3 dB axial ratio (AR) bandwidth of 23.2%, 3 dBi gain bandwidth of 11.6%, and the maximum gain of 22.8 dBi at 10.3 GHz with the antenna efficiency of 21.8%. The proposed CPFTA is promising for applications in satellite communications with circularly polarized antennas.

Antenna Designs for CubeSats: A Review

Abstract: Cube Satellites, aka CubeSats, are a class of nano satellites that have gained popularity recently, especially for those that consider CubeSats as an emerging alternative to conventional satellites for space programs. This is because they are cost-effective, and they can be built using commercial off-the-shelf components. Moreover, CubeSats can communicate with each other in space and ground stations to carry out many functions such as remote sensing (e.g., land imaging, education), space research, wide area measurements and deep space communications. Consequently, communications between CubeSats and ground stations is critical. Any antenna design for a CubeSat needs to meet size and weight restrictions while yielding good antenna radiation performance. To date, a limited number of works have surveyed, compared and categorised the proposed antenna designs for CubeSats based on their operating frequency bands. To this end, this paper contributes to the literature by focusing on different antenna types with different operating frequency bands that are proposed for CubeSat applications. This paper reviews 48 antenna designs, which include 18 patch antennas, 5 slot antennas, 4 dipole and monopole antennas, 3 reflector antennas, 3 reflectarray antennas, 5 helical antennas, 2 metasurface antennas and 3 millimeter and sub-millimeter wave antennas. The current CubeSat antenna design challenges and design techniques to address these challenges are discussed. In addition, we classify these antennas according to their operating frequency bands, e.g., VHF, UHF, L, S, C, X, Ku, K/Ka, W and mm/sub-mm wave bands and provide an extensive qualitative comparison in terms of their size, −10 dB bandwidths, gains, reflection coefficients, and deployability. The suitability of different antenna types for different applications as well as the future trends for CubeSat antennas are also presented.

Compact Co-Linearly Polarized Microstrip Antenna With Fence-Strip Resonator Loading for In-Band Full-Duplex Systems

Abstract: A compact co-linearly polarized microstrip antenna with identical radiation properties is proposed and validated for in-band full-duplex systems. By exploring a fence-strip resonator (FSR) in the central plane of a patch, good isolation is achieved between the transmitting and receiving ports. The proposed FSR consists of a metallic vias fence and a strip with a distance away from the ground, performing as a pair of distributed inductor and capacitor. When the FSR is resonating, the radiating current is concentrated in the half part of the patch, performing at its half-TM10 mode with high port isolation. To validate the proposed antenna, a prototype with the size of $0.25\lambda _{0} \times 0.25\lambda _{0} \times 0.04\lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength at center frequency) has been fabricated and characterized, with experiments consistent well with simulations. A measured port isolation higher than 20 dB is achieved over the operating bandwidth of 2.40–2.52 GHz with the maximum of 30 dB. The proposed antenna is with the merits of compact size, low profile, simple feed, and planar-integrated structure for in-band full-duplex systems.

4D Automotive Radar Sensing for Autonomous Vehicles: A Sparsity-Oriented Approach

Abstract: We propose a high-resolution imaging radar system to enable high-fidelity four-dimensional (4D) sensing for autonomous driving, i.e., range, Doppler, azimuth, and elevation, through a joint sparsity design in frequency spectrum and array configurations. To accommodate a high number of automotive radars operating at the same frequency band while avoiding mutual interference, random sparse step-frequency waveform (RSSFW) is proposed to synthesize a large effective bandwidth to achieve high range resolution profiles. To mitigate high range sidelobes in RSSFW radars, optimal weights are designed to minimize the peak sidelobe level such that targets with a relatively small radar cross section are detectable without introducing high probability of false alarm. We extend the RSSFW concept to multi-input multi-output (MIMO) radar by applying phase codes along slow time to synthesize a two-dimensional (2D) sparse array with hundreds of virtual array elements to enable high-resolution direction finding in both azimuth and elevation. The 2D sparse array acts as a sub-Nyquist sampler of the corresponding uniform rectangular array (URA) with half-wavelength interelement spacing, and the corresponding URA response is recovered by completing a low-rank block Hankel matrix. Consequently, the high sidelobes in the azimuth and elevation spectra are greatly suppressed so that weak targets can be reliably detected. The proposed imaging radar provides point clouds with a resolution comparable to LiDAR but with a much lower cost. Numerical simulations are conducted to demonstrate the performance of the proposed 4D imaging radar system with joint sparsity in frequency spectrum and antenna arrays.

Printed Chipless Antenna as Flexible Temperature Sensor

Abstract: The ever-increasing number of devices on wearable and portable systems comes with challenges such as integration complexity, higher power requirements, and less user comfort. In this regard, the development of multifunctional devices could help immensely as they will provide the same functionalities with lesser number of devices. Herein, we present a dual-function flexible loop antenna printed on polyvinyl chloride (PVC) substrate. With a poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS) section as part of the printed structure, the presented antenna can also serve as a temperature sensor by means of change in resistance. The antenna resonates at 1.2- and 5.8-GHz frequencies. The ohmic resistance of the temperature sensing part decreases by ~70% when the temperature increases from 25 °C to 90 °C. The developed antenna was characterized using a vector network analyzer (VNA) in the same temperature range and the S11 magnitude was found to change by ~3.5 dB. The induced current was also measured in the GSM frequency range and sensitivity of ~1.2%/°C was observed for the sensing antenna. The flexible antenna was also evaluated in lateral and cross-bending conditions and the response was found to be stable for the cross-bending. Due to these unique features, the presented antenna sensor could play a vital role in the drive toward ubiquitous sensing through wearables, smart labels, and the Internet of Things (IoT).

A Wideband Dual-Polarized Endfire Antenna Array With Overlapped Apertures and Small Clearance for 5G Millimeter-Wave Applications

Abstract: In this article, an endfire dual-polarized phased antenna array with small ground clearance is proposed for the fifth-generation (5G) millimeter-wave (mmW) applications with a wide bandwidth In this array, each antenna element consists of a dipole fed by a microstrip line for horizontal polarization and an H-plane horn using substrate-integrated waveguide (SIW) for vertical polarization To achieve a wide bandwidth for vertical polarization, two metal vias are added at the aperture of the horn antenna Then, a four-element antenna array is designed by partially overlapping the aperture of each horn element A prototype has been fabricated using multilayer printed circuit board (PCB) process The measured results agree well with the simulated ones The antenna is with an impedance bandwidth of $\vert \text{S}_{11}\vert dB from 244 to 295 GHz for both polarizations The maximum gains of vertical and horizontal polarizations are 916 and 927 dBi, with the scanning angle from −34° to 33° for both polarizations with gain deterioration less than 3 dB The proposed antenna is a promising solution for 5G mmW cellphones or antenna-in-package applications

Radio Positioning With EM Processing of the Spherical Wavefront

Abstract: Next 5G and beyond applications have attracted a tremendous interest towards systems using antenna arrays with an extremely large number of antennas where the technology conceived for communication might also be exploited for high-accuracy positioning applications. In this paper, we investigate the possibility to infer the position of a single antenna transmitter using a single asynchronous receiving node by retrieving information from the incident spherical wavefront. To this end, we consider the adoption of a suitable mix of processing at electromagnetic (EM) and signal levels, as a lower complexity alternative to classical massive array systems where the processing is done entirely at signal level. Thus, we first introduce a dedicated general model for different EM processing architectures, entailing the use or not of a lens that can have either a reconfigurable or a fixed phase profile, and successively we investigate their attainable positioning performance. The effect of the interference is also investigated to evaluate the robustness of the considered system to the presence of multiple simultaneous transmitting sources. Results, obtained for different apertures of the exploited lens/array, confirm the possibility to achieve interesting positioning performance using a single antenna array with a limited aperture.

Wideband Integrated Quad-Element MIMO Antennas Based on Complementary Antenna Pairs for 5G Smartphones

Abstract: In this article, a wideband and highly-integrated quad-element multiple-input multiple-output (MIMO) antenna is proposed for the first time, to adapt to the size-limited environment in fifth-generation (5G) smartphones. First, the wideband decoupling between two extremely closely-spaced open-slot antennas with face-to-face and back-to-back configurations are investigated. Then, based on the complementary antenna pairs, wideband integrated quad-element MIMO antennas are implemented by the ingenious combination of these antenna pairs. For validation, an $8 \times 8$ MIMO system, constituted by two sets of integrated quad-antenna configurations, is simulated, fabricated, and measured. Both the simulated and measured results show that the $8\times 8$ MIMO system can provide isolation of better than 10 dB between any two ports and a total antenna efficiency of 52.8%–70.8%/40.5%–75.0% across 3.3–5.0 GHz. Compared with the existing integrated quad-antenna design schemes, the proposed solution can expand the bandwidth from less than 200 to 1700 MHz, covering the entire 5G N77, N78, and N79 bands. In addition to the integrated quad-antenna design, further extension to integrated multiantenna configurations is also discussed by the flexible combination of complementary antenna pairs, which paves the way for future higher-order MIMO system in smartphones.

Packaging and Antenna Integration for Silicon-Based Millimeter-Wave Phased Arrays: 5G and Beyond

Abstract: This article reviews current research and development as well as future opportunities for packaging and antenna integration technologies for silicon-based millimeter-wave phased arrays in emerging communication applications. Implementations of state-of-the-art silicon-based phased arrays below 100 GHz are discussed, with emphasis on array architectures for scaling, antenna integration options, substrate materials and process, antenna design, and IC-package codesign. Opportunities and challenges to support phased array applications beyond 100 GHz are then presented, including emerging packaging architectures, interconnect characterization requirements, thermal management approaches, heterogeneous integration of multifunction chiplets, and novel antenna technologies.

Design and Analysis of Dual Polarized Broadband Microstrip Patch Antenna for 5G mmWave Antenna Module on FR4 Substrate

Abstract: This study presents a dual polarized broadband microstrip patch antenna for a 5G mmWave antenna module on an FR4 substrate. The proposed antenna was fabricated using a standard FR4 printed circuit board (PCB) process because of its low cost and ease of mass production. The electrical properties of the FR4 substrate in the 5G mmWave frequency band were also characterized. An air cavity structure was introduced to mitigate the high loss tangent of the FR4 substrate. Capacitive elements such as proximity L-probe feedings and parasitic patches are used to improve the impedance bandwidth of the patch antenna. For the polarization diversity of the massive multiple-input multiple-output (MIMO) capability, the antenna radiator was designed with a symmetrical structure, and the relative position of the L-probes excites the orthogonal resonant modes to enable dual linear polarization. The operation principle of the proposed antenna was thoroughly analyzed by characteristic mode analysis (CMA). The measured bandwidth of a single antenna was 23.1 % (23 ~ 29 GHz) and the gain value was 5 dBi. The measured cross-polarization suppression ratio of single antenna was 15 ~ 20 dB. The measured gain value of $1\times 4$ antenna array was 10 ~ 11 dBi and the cross-polarization suppression ratio was about 20 dB. The size of the proposed single antenna is $0.41\lambda _{0}\times 0.41\lambda _{0}\times 0.1\lambda _{0}$ , and that of a $1\times 4$ antenna array is $2.78\lambda _{0}\times 0.41\lambda _{0}\times 0.1\lambda _{0}$ . The envelope correlation coefficient (ECC) was calculated and was lower than 0.02 in the 5G mmWave frequency band.

Planar dual-band 27/39 GHz millimeter-wave MIMO antenna for 5G applications

Abstract: This research work presents another design of a multi-input multi-output (MIMO) antenna with dual wide operating bands at the millimeter-wave (MMW) region proposed for 5G applications. The design consists of two monopole elements with full size of 26 × 11 mm2. The two monopoles are designed to provide dual-band operation at the frequencies 27 GHz and 39 GHz. The mutual coupling between the two elements is studied and optimized to maximally reduce the effect of one element on the other. The S-parameters of the proposed MMW MIMO configuration are simulated using two software and measured using VNA. The results are well agreed with considerable shifting between the measured and the simulated, which can be due to the fabrication tolerance and cable losses. The radiation characteristics are investigated in terms of gain and efficiency. The proposed MIMO manifests acceptable gain that reaches 5 dBi and 5.7 dBi in the first and second bands, respectively, while the radiation efficiency reaches 99.5% and 98.6% over the first and the second bands, respectively. The MIMO performance is also studied where a very low envelope correlation of about 10–4 is obtained and a diversity gain of about 10 dB over the two operating bands is also achieved. The comparison between simulation and measurement shows the possible potential of the proposed MIMO antenna that makes it feasible for MMW 5G applications.

Metamaterial mechanical antenna for very low frequency wireless communication

Abstract: Very low frequency wireless communication (3–30 kHz) often is restricted by the antenna size and complex impedance matching network in practical applications. Mechanical antenna has recently stimulated much practical research interest due to the potential capacity for breaking the size limitation. However, mechanical antenna is barely investigated from the perspective of material science. Here, we demonstrate a compact piezoelectric metamaterial mechanical antenna with high radiation efficiency, multi-frequency bands, and small size. Three operating frequencies at 22 kHz, 24 kHz, and 26 kHz are independently adjusted by the structure parameters and material of a piezoelectric radiating unit cell, and the modulation range is beyond 15 kHz. The basic parameters studies reveal the detailed modulation mechanism and provide a theory base for the metamaterial antenna design. Except for the smaller than 1/1000 wavelength size, the radiated magnetic field intensity is also averagely increased by 3 × 104 fT. All the simulated results demonstrate the great potential of the proposed piezoelectric metamaterial antenna in the applications of portable, small, high-performance wireless communication devices. A compact piezoelectric metamaterial–based mechanical antenna is reported. Simulations of unit cell antenna and analyzes of characteristics reveal the influence of material parameters and structure parameters on the electromagnetic performance of the proposed antenna. The utilization of metamaterial structure brings multi-band properties for the mechanical antenna, and each resonant peak can be independently modulated.

Ultra-compact dual-band smart NEMS magnetoelectric antennas for simultaneous wireless energy harvesting and magnetic field sensing.

Abstract: Ultra-compact wireless implantable medical devices are in great demand for healthcare applications, in particular for neural recording and stimulation. Current implantable technologies based on miniaturized micro-coils suffer from low wireless power transfer efficiency (PTE) and are not always compliant with the specific absorption rate imposed by the Federal Communications Commission. Moreover, current implantable devices are reliant on differential recording of voltage or current across space and require direct contact between electrode and tissue. Here, we show an ultra-compact dual-band smart nanoelectromechanical systems magnetoelectric (ME) antenna with a size of 250 × 174 µm2 that can efficiently perform wireless energy harvesting and sense ultra-small magnetic fields. The proposed ME antenna has a wireless PTE 1–2 orders of magnitude higher than any other reported miniaturized micro-coil, allowing the wireless IMDs to be compliant with the SAR limit. Furthermore, the antenna’s magnetic field detectivity of 300–500 pT allows the IMDs to record neural magnetic fields. Wireless implantable medical devices (IMDs) are hamstrung by both size and efficiency required for wireless power transfer. Here, Zaeimbashi et al. present a magnetoelectric nano-electromechanical systems that can harvest energy and sense weak magnetic fields like those arising from neural activity.

Tunable Terahertz Dielectric Resonator Antenna

Abstract: An annular dielectric resonator (DR) antenna (DRA) is implemented for THz applications. A silicon made DR is loaded with graphene disk for obtaining the tunability in the frequency response. The physical parameters of silicon annular DR can be set to obtain the resonance at any frequency in the lower THz band and can be tuned by changing the chemical potential of graphene nano-disk placed at the top of the DR. The response of antenna is preserved after changing the chemical potential of graphene. The higher order hybrid electromagnetic mode is excited in the antenna structure. The proposed research work provides a way to implement the antenna for THz frequency with high gain around 3.8 dBi and radiation efficiency in the range 72 − 75%.

A High-Efficiency Conformal Transmitarray Antenna Employing Dual-Layer Ultrathin Huygens Element

Abstract: A high-efficiency conformal transmitarray with ultrathin dual-layer Huygens element is developed. The element consists of “I” shape patches for magnetic response and “T” shape stubs for electric response printed on two metal layers of a single substrate with only 0.5 mm thickness ( $\lambda _{0}$ /60 at 10 GHz). By tuning the magnetic and electric responses, the transmitting phase of the element can be changed. Eight elements are designed to cover quantized 360° phase range with a maximal 1.67 dB loss. Then, the proposed elements are employed in a small conformal transmitarray design. To improve the antenna efficiency, the elements’ dimensions are calculated by considering the oblique incidence effects. Finally, a cylindrically conformal transmitarray with a larger aperture size is simulated, fabricated, and measured. It can achieve a measured gain of 20.6 dBi with a 47% aperture efficiency.