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A compact planar ultra-wideband (UWB) multiple-input–multiple-output antenna array with two radiating elements is proposed in this work. Elements separation is kept at 5.5 mm and the isolation is achieved with a floating parasitic decoupling structure not known for UWB diversity antennas previously. The antenna system performs very well over the entire UWB frequency range of 3.1–10.6 GHz. The mutual coupling between the radiating elements is below −20 dB in most of the band. The decoupling structure is investigated in detail and the diversity analysis of the antenna in Rayleigh fading environment for indoor and outdoor propagations is also presented by computing envelope correlation coefficients. The proposed antenna array measures 33 × 45.5 mm2 only and it is suitable for handheld devices, personal digital assistant (PDA)s, next generation home entertainment systems and robots.

This book covers all areas of smart antennas, electromagnetic interference, and microwave antennas for wireless communications. Smart antennas or adaptive antennas are multi-antenna components on one or both sides of a radio communication connection, combined with advanced signal processing algorithms. They've evolved into a critical technology for third-generation and beyond mobile communication systems to meet their lofty capacity and performance targets. It seems that a significant capacity gain is achievable, particularly if they are employed on both sides of the connection. There are several essential characteristics of these systems that need scientific and technical investigation. Included in the book are beamforming, massive MIMO, network MIMO, mmwave transmission, compressive sensing, MIMO radar, sensor networks, vehicle-to-vehicle communication, location, and machine learning.

This study proposes a pattern–diversity antenna with different radiation patterns at two different frequency bands (f1 and f2; f1: broadside radiation pattern, f2: conical radiation pattern). The proposed structure consists of a central circular antenna and two annular ring antennas, with each of the antennas having individual ports. Two of the ports (port 1 and port 3) exhibit orthogonal broadside radiation patterns at low bands, and the other two ports (port 1 and port 2) exhibit orthogonal conical radiation patterns at high bands. Thus, they have polarization diversity characteristics. To improve isolation between the ports, the inner part of the annular ring antennas is shorted by an array, and the outermost port is positioned orthogonal to the other ports. Using this configuration, the isolation values between the ports are −26.7 and −30.1 dB at the two frequency bands, respectively. Using the fabricated prototype, experimental results show that the proposed antenna achieves −10 dB bandwidths of 240 MHz (5.71–5.95 GHz) and 210 MHz (7.69–7.9 GHz) at f1 and f2, respectively.

Interference has been a key roadblock against the effectively deployment of applications for end-users in wireless networks including fifth-generation (5G) and beyond fifth-generation (B5G) networks. Protocols and standards for various communication types have been established and utilised by the community in the last few years. However, interference remains a key challenge, preventing end-users from receiving the quality of service (QoS) expected for many 5G applications. The increased need for better data rates and more exposure to multimedia information lead to a non-orthogonal multiple access (NOMA) scheme that aims to enhance spectral efficiency and link additional applications employing successive interference cancellation and superposition coding mechanisms. Recent work suggests that the NOMA scheme performs better when combined with suitable wireless technologies specifically by incorporating antenna diversity including massive multiple-input multiple-output architecture, data rate fairness, energy efficiency, cooperative relaying, beamforming and equalization, network coding, and space–time coding. In this paper, we discuss several cooperative NOMA systems operating under the decode-and-forward and amplify-and-forward protocols. The paper provides an overview of power-domain NOMA-based cooperative communication, and also provides an outlook of future research directions of this area.

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.

In this paper a multi-band/Ultra- Wideband (UWB) Multiple Input Multiple Output (MIMO) antenna, which is composed of two identical microstrip fed triple notch band UWB antennas and a Radial Stub Loaded Resonator (RSLR), is proposed and verified numerically and experimentally. The antenna is designed to meet the requirement of multi-band/UWB communication applications. A Defected Microstrip Structure (DMS) Band-Stop Filter (BSF) and an invert ?-shaped slot are employed to design the triple notch band UWB antenna. The resonance characteristics of the DMS-BSF and the band notch functions are presented to realize the proposed triple notch band UWB antenna. The isolation of the multi-band/UWB-MIMO antenna has been enhanced by inserting an RSLR loaded T-shaped stub between two identical triple notch band antennas. Both simulation and measurement results are presented to illustrate the performances of the proposed multi-band/UWB-MIMO antenna.

A new compact, uniplanar, polarisation-diversity, monopole-like slot antenna for ultra-wideband (UWB) systems is presented. The proposed design effectively integrates orthogonally fed slot antennas, utilising the uniplanar nature of coplanar waveguide without degrading the time-domain characteristics and diversity performance. To achieve high isolation between the ports, a strip is integrated diagonally in the ground plane. Furthermore, by loading arc shaped slot resonators on the feeding structures, the proposed antenna successfully rejects the undesired subband, assigned for IEEE 802.11a and HIPERLAN/2. The measured results demonstrate that the antenna provides a 2:1 voltage standing wave ratio (VSWR) band from 2.76 to 10.75 GHz whereas showing rejection in the frequency band 4.75–6.12 GHz, along with an inter-port isolation better than 15 dB. The proposed radiator displays a nearly omnidirectional radiation pattern, along with a moderate gain and efficiency. The envelope correlation coefficient discloses a good diversity performance across the UWB spectrum. Furthermore, the time-domain analysis shows minimum dispersion to the radiated pulse. In addition, the experimental analysis indicates that the proposed design is less disposed to the housing effects when mounted in metallic casing. All these features make the proposed antenna a viable candidate for UWB dual-polarised multiple-input–multiple-output applications.

A holistic performance analysis and classification of multiport antennas (MPAs) is conducted in this paper. We focus on 5.9 GHz vehicle-to-vehicle communications suited to the emerging technology of intelligent transportation systems. Three-dimensional (3-D) uniform/isotropic, directional, and omnidirectional propagation scenarios are considered to account for any wireless environment. The presented analysis can be adapted to any MPA with an arbitrary number of ports, operating in any frequency band, or used in other emerging technologies such as in 5G and beyond 5G communications. On top of the classical key performance metrics (KPMs) in communication theory, i.e., the diversity antenna gain (DAG) and channel capacity (CC), we employ for the first time the energy efficiency as one more KPM capable to characterize performance and classify MPAs, particularly when DAG and CC fail to do so. Computation of the aforementioned KPMs departs from a covariance matrix formulation incorporating all intrinsic features that affect MPA performance, namely, MPA radiation characteristics, MPA termination conditions, and wireless propagation channel attributes. Accordingly, we derive the ideal form of the covariance matrix under the standardized and widely adopted 3-D uniform/isotropic wireless propagation scenario. A good MPA design should be one with a covariance matrix as close as possible to this ideal one. The adopted performance analysis methodology can thus inform the design of optimum MPAs and accordingly, we designed a proof-of-concept box-shaped MPA which shows outstanding performance across all propagation scenarios. It would be wise to conduct similar performance analyses as in this paper before releasing an MPA design.

The utilization of additively manufactured (AM) or 3D printing technology is a revolutionary technique that is widely used for antenna fabrication, driven by its cost effectiveness, rapid prototyping capabilities, and the potential for customized antenna designs. particularly conducive to Wireless Local Area Network (WLAN) applications. In this study, a two port pattern diversity antenna was developed with modified dimensions aimed at improving gain, radiation pattern and bandwidth specifically at 5.8 GHz frequency. The designed antenna was analysed using substrates of thicknesses 0.5 mm and 5 mm, wherein polylactic acid was used. The antenna featuring a 0.5 mm substrate exhibited a bandwidth of 100 MHz, spanning from 5.16 to 5.26 GHz, representing a bandwidth efficiency of 1.91%. Conversely, the antenna constructed with a 5 mm substrate exhibited a significantly broader bandwidth of 450 MHz, ranging from 5.53 to 5.98 GHz, with a bandwidth efficiency of 7.81%. Addressing the challenges posed by higher substrate thickness and potential dielectric losses, a square-structured narrow-band cavity antenna was engineered with an operating frequency range of 5.5–6 GHz, characterized by an edge length of 32 mm. Subsequently, a wideband antenna was devised to mitigate return losses associated with the cavity antenna. By incorporating modifications, a pattern diversity antenna was synthesized, boasting dimensions of 1.15λ × 1.15λ × 1.15λ at 5.8 GHz, offering an operational range from 5.16 to 6.18 GHz, with a substantial bandwidth of 1.02 GHz, while ensuring an isolation of 39.4 dB, a gain of 7.36 dBi, and beam tilting capabilities of 60° and 300°. In order to validate the performance of the designed antenna, radiation pattern computations were conducted utilizing the Anritsu MS2028C Vector Network Analyzer (VNA), complemented by far-field radiation analyses conducted within an anechoic chamber. The proposed antenna surpassed its counterparts in terms of isolation, gain, and bandwidth, positioning it as an optimal choice for upper WLAN applications pertinent to the forthcoming 5G/6G advancements.

The research presents mutual coupling reduction between UWB-MIMO antenna elements using stub loading technique. The proposed 2 × 2 UWB antenna geometry consists of two circular-shaped monopole radiators with a partial ground for perfect impedance matching. Stubs of 20 mm × 0.2 mm are inserted between the two antenna elements in the ground plane to improve the isolation. The decoupling stub leads to a mutual coupling reduction of less than 20 dB. The farfield measurement at a selected frequency of 10 GHz confirms an omnidirectional radiation pattern. Different MIMO antenna metric such as channel capacity loss (CCL), mean effective gain (MEG), total active reflection coefficient (TARC), envelope correlation coefficient (ECC), and surface current are presented. Details of the design considerations and the simulation and measurement results are presented and discussed. The proposed MIMO antenna array can be well suited for UWB applications.