A Triangular-shaped Quarter-mode Substrate Integrated Waveguide based Antenna for WBAN Applications

In this study, a compact quarter-mode substrate integrated waveguide (QMSIW) based dual-band antenna is proposed for wireless body area network applications. A QMSIW resonator is realised by splitting the full-mode substrate integrated waveguide cavity along the perfect magnetic conductor walls. The proposed antenna preserves the fundamental mode TE110 and the third order mode TE220 of the square SIW cavity. The proposed antenna is linearly polarised in the lower band at 2.45 GHz and circularly polarised in the higher frequency band at 5.8 GHz. The on-body performance of the antenna is validated on a piece of pork muscle tissue and it has been found to be stable with respect to surroundings. The proposed antenna covers the ISM bands 44 MHz (2.445 GHz - 2.489 GHz) and 225 MHz (5.730 GHz - 5.955 GHz) at 2.45 GHz and 5.8 GHz, respectively. The measured gain of the antenna on pork tissue is 1.87 dBi and 5.5 dBi at two bands. In addition, the specific absorption rate is obtained of 0.65 mW/g and 1.51 mW/g at two bands (wext = 2 mm), averaged over 1 g of muscle with 100mW input power. Moreover, the simulated and experimental results demonstrate a good agreement

Statistical Review Evaluation of 5G Antenna Design Models from a Pragmatic Perspective under Multi-Domain Application Scenarios

Antenna design for the 5G spectrum requires analysis of contextual frequency bands, design of miniaturization techniques, gain improvement models, polarization techniques, standard radiation pattern designs, metamaterial integration, and substrate selection. Most of these models also vary in terms of qualitative & and quantitative parameters, which include forward gain levels, reverse gain, frequency response, substrate types, antenna shape, feeding levels, etc. Due to such a wide variety in performance, it is ambiguous for researchers to identify the optimum models for their application-specific use cases. This ambiguity results in validating these models on multiple simulation tools, which increases design delays and the cost of deployments. To reduce this ambiguity, a survey of recently proposed antenna design models is discussed in this text. This discussion recommended that polarization optimization and gain maximization are the major impact factors that must be considered while designing antennas. It is also recommended that collocated microstrip slot antennas, fully planar dual-polarized broadband antennas, and real-time deployments of combined slot antenna pairs with wide-band decoupling are very advantageous. Based on this discussion, researchers will be able to identify optimal performance-specific models for different applications. This discussion also compares underlying models in terms of their quantitative parameters, which include forward gain levels, bandwidth, complexity of deployment, scalability, and cost metrics. Upon referring to this comparison, researchers will be able to identify the optimum models for their performance-specific use cases. This review also formulates a novel Antenna Design Rank Metric (ADRM) that combines the evaluated parameters, thereby allowing readers to identify antenna design models that are optimized for multiple parameters and can be used for large-scale 5G communication scenarios

Antenna Design for 5G and Beyond

With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas

Study of mm-wave Fixed Beam and Frequency Beam-Scanning Antenna Arrays

Millimeter-wave frequencies are anticipated to be widely adapted for future wireless communication systems to resolve the demand of high data-rate and capacity issues. The millimeter-wave frequency range offers wide spectrum and a shift for most newly developing technologies as the microwave and lower frequency bands are becoming overcrowded and congested. These high frequency bands offer short wavelengths which has enabled the researchers to design and implement compact and adaptable antenna solutions. This research focuses on the implementation, transformation and modification of antenna structures used in lower frequency bands to millimeter-wave applications with high gain and multi-band and wideband performances. The first part of the thesis presents a microstrip patch array antenna with high gain in the upper 26 GHz range for 5G applications. The tolerance of the antenna, on widely used Rogers RT/duroid 5880 substrate, is observed with the edge-fed structure when curved in both concave and convex directions. In the second part of the thesis, 20 rectangular loops are arranged in a quasi-rhombic shaped planar microstrip grid array antenna configuration with dual-band millimeter-wave performance. A comparison with equal sized microstrip patch array is also presented to analyse the performance. The antenna operates in the upper 26 GHz band and has two frequency bands in close proximity. The third part of the thesis discusses the transition from wire Bruce array antenna to planar technology. Having been around for nearly a century and despite the simplicity of structure, the research community has not extended the concept of Bruce array antenna for further research. The proposed planar Bruce array antenna operates in three frequency v bands with optimization focus on 28.0 GHz band that has a directive fan-beam radiation pattern at broadside whereas the other two frequency ranges, above 30 GHz, have dual-beam radiation patterns which provide radiation diversity in narrow passages. The final part of the thesis deals with the transformation and modification of wire Bruce array antenna geometry to edge-fed printed leaky-wave antennas for millimeter-wave frequency scanning applications. In the first approach, the lengths of the unit-cell are optimised, without any additional circuitry, to enable two scanning ranges and mitigate the Open-Stopband, at broadside, for seamless scanning in the first range. A Klopfen-stein tapered divider is then deployed to make a linear array of the proposed antenna to achieve high gain. In the second approach, the horizontal and vertical lengths of the meandered unit-cell are replaced with semi-circular and novel bowtie elements, respectively, to obtain wide scanning range. The numerical results and optimizations have been performed using CST Micro-wave Studio where the effects of metallization and dielectric losses are properly consid-ered. The prototypes of the proposed antennas have been fabricated and experimentally validated

High Gain Planar Antenna Structures for Ka-band Applications

Antennas are an essential part of a communication system as they control a coverage area of the signal. The millimeter wave band has the potential to offer numerous radio applications which require the large bandwidth channels. Due to the current cellular subscribers’ demand of higher data rates, even cellular communication is expected to move in millimeter wave communications at Ka band of 26.5 GHz to 40 GHz. However, millimeter waves are sensitive to the high degree of atmospheric and oxygen absorption losses. This challenge of the millimeter wave communication can be tackled by employing high gain antennas. In addition, modern electronic products require compact handheld devices to offer the user-friendly system as well as capture the market. Therefore, planar antenna structures are apt for these communication systems. In this thesis, two antenna structures are presented at the Ka band for millimeter wave communications. Initially, four element patch antenna is presented for high gain in the broadside direction. Patch elements are excited using an aperture coupling from 50Ω microstrip line. Air-gap cavity is used to improve the impedance bandwidth of the design. This structure obtains a relatively moderate impedance bandwidth of 4.6%. The proposed four-element patch antenna exhibits a flat gain over an operating band with 13.8 dB gain at the design frequency. The antenna achieves a wide beamwidth of 700 in H plane. In addition, side lobe levels in E and H planes are -14.5 dB and 23 dB respectively. For the second prototype, an Antipodal Fermi-Linear Tapered Slot Antenna (AFLTSA) is presented to achieve the wide impedance bandwidth with high flat gain for endfire radiation. Substrate Integrated waveguide (SIW) technique is utilized to feed the AFLTSA which reduces insertion losses of the structure. Fermi-Dirac distributed curve in conjunction with a linear curve for a tapered slot increases the coupling of the electric field from a substrate integrated waveguide to the tapered slot. Knife edge rectangular corrugation profile is used at edges of AFLTSA in order to reduce the side lobes and cross polarization levels of radiation pattern. The proposed structure achieves the wide impedance bandwidth to support requirements for high data rate channels. Measurement results from a fabricated prototype exhibit a flat gain over an entire operating frequency band with 16.4 dB gain at 28 GHz. The wide impedance bandwidth is achieved with return loss below 15 dB. Proposed structure has low side lobe levels of -13.9 dB in H plane and -19.5 dB in E plane. In addition, it offers a low cross polarization level of -22 dB

Design and analysis of miniaturized substrate integrated waveguide reconfigurable filters for mm-wave applications.

Doctoral Degree. University of KwaZulu-Natal, Durban.Microwave filters are an integral part of communication systems. With the advent of new technologies, microwave devices, such as filters, need to have superior performance in terms of power handling, selectivity, size, insertion loss etc. During the past decade, many applications have been added to the communication networks, resulting in communication systems having to operate at high frequencies in the region of THz to achieve the stringent bandwidth requirements. To achieve the requirements of the modern communication system, tunability and reconfigurability have become fundamental requirements to reduce the footprint of communication devices. However, the communication systems that are more prevalent such as planar circuits have either a large footprint or are not able to handle large amounts of power due to radiation leakage. In this thesis, Substrate Integrated Waveguide (SIW) technology has been employed. The SIW has the same properties as the conventional rectangular waveguide; hence it benefits from the high quality (Q) factor and can handle large powers with small radiation loss. The Half-mode (HMSIW), Quarter-mode (QMSIW), and Eighth-mode (EMSIW) cavity resonators have been designed and used for the miniaturization of the microwave filters. The coupling matrix method was used to implement a filter that uses cross-coupled EMSIW and HMSIW cavity resonators to improve the selectivity of the filter. Balanced circuit techniques have been used to design the circuits that preserve communication systems integrity whereby the Common Mode (CM) signal was suppressed using Deformed Ground Structure (DGS) and a center conductor patch with meandered line. For the designed dual-band filter, the common mode signal was suppressed to -90 dB and - 40 dB for the first and second passband, respectively. The insertion loss observed is 2.8 dB and 1.6 dB for the first and second passband, respectively. For tunability of the filter, a dual-band filter utilizing triangular HMSIW resonators has been designed and reconfigurability is achieved by perturbing the substrate permittivity by dielectric rods. The dielectric rods’ permittivity was changed to achieve tunability in the first instance, and then the rods’ diameter changed in the second instance. For the lowerband, frequency is tunable from 8.1 GHz to 9.15 GHz, while the upper band is tuned from 14.61 GHz to 16.10 GHz. A second order SIW filter with a two layer substrate was then designed to operate in the THz region. For reconfigurability, Graphene was sandwiched between the Silicon Di-Oxide substrate and the top gold plate of the filter, and the chemical potential of Graphene was then varied by applying a dc bias voltage. With a change in dc voltage the chemical potential of Graphene changes accordingly. From the results, a chemical potential change of 0.1 eV to 0.6 eV brings about a frequency change from 1.289 THz to 1.297 THz

Antennas for Wireless Body Area Networks

Disertační práce je zaměřena na vytvoření návrhu antény operující v blízkosti lidského těla. Kritické parametry zahrnují impedanční přizpůsobení, polarizační vlastnosti a vyzařovací charakteristiky. Základní výzkum je proveden na zjednodušených modelech lidského těla, kde jsou striktně definovány materiálové vlastnosti. Pro pokročilejší analýzu jsou využity detailnější modely. Simulace jsou konfrontovány s měřením na reálných vzorcích. V práci zahrnujeme interakci mezi anténou a lidským tělem.The dissertation thesis is focused on the proposing a general synthesis approach to the design of the antenna operating in proximity of human body models. The critical parameters comprise the antenna impedance matching, polarization properties and radiation patterns. The elementary investigation is done on simplified human body models, where we strictly define material properties. For advanced simulations, we have to consider more details in the model. Simulations are confronted with the measurement on real saples. In This thesis we will include the problems of interaction between an antenna and a human body.

Antenna Design for 5G and Beyond

This book is a reprint of the Special Issue Antenna Design for 5G and Beyond that was published in Sensors

Folded waveguide resonator filter for communication and radar systems

In this thesis, a primary investigation into developing a compact and low-loss bandpass filter, using novel folded waveguide resonators with a footprint reduction, has been addressed. A slot coupling between adjacent resonators is introduced, which is characterized by using full-wave EM simulations and verified experimentally. Two designs of 2-pole folded waveguide resonator filters of this type have been considered, fabricated and tested. In this thesis, an even more compact FWG resonator filter using a novel slot technique is reported. The attainable size reduction is about 50%, and the filter design is based on theoretical and full-wave electromagnetic (EM) simulations. Based on FWG structure, two types of folded waveguide resonators have been studied and considered the half-wavelength resonator and the quarter-wavelength resonator. Moreover, both structures for the realization of microwave cavities with high-Q, with the result of a high spurious free range and reduced footprint, have been evaluated. Furthermore, a novel folded waveguide resonator with about a 75 % reduction of the volume from the conventional size has been described. For comparison, two types of folded waveguide resonators have been studied, i.e. the quarter-wavelength resonator of square shape and the newly proposed triangular shape. In addition, a demonstration of a filter application for miniature triangular folded waveguide resonators has been designed and simulated using an EM simulator. In addition, numbers of experiments have been conducted to develop cavity FWG and Substrate Integrated folded waveguide SIFW resonator filters using a folded structure, which is the main aim of this thesis. Furthermore, this thesis deals with the simulation and implementation for many designs and topologies of FWG and SIFW resonator filters and their frequency response. Simulation and experimental results were presented to validate the design and to show the advantages of these types of filters. In addition, a new type of filter with a compact multi-layer structure and low loss is attractive for implementation with advanced device technologies, such as micromachining, LTCC and LCP technologies

Substrate Integrated Waveguide Based Millimeter Wave Antennas

Antennas those operating at millimeter-wave (mm-wave) frequencies (30 - 300 GHz) are more advantageous than operating at less than 6 GHz, due to a reduction in antenna physical dimensions, an increase in the data transfer rate, and reduction in latency. However, the electromagnetic waves propagating in free space at mm-wave frequencies experience significant propagation path loss due to the atmospheric absorption and rain attenuation. Therefore, high-gain antennas are preferred to compensate for path loss and to increase the range of wireless communication. Also, transmission lines such as microstrip, and coplanar waveguides incur high radiation losses at mm-wave frequencies. Hence, to minimize losses, a planar waveguide known as a substrate integrated waveguide (SIW) is preferred. Besides, at mm-wave frequencies, circularly polarized (CP) waves are preferred over linearly polarized (LP) waves as these waves reduce multi-path effects at the receiver. The objectives of this thesis are to design high-gain linearly, and circularly polarized antennas based on SIW at the mm-wave frequency 30 GHz. The proposed antenna models were designed, simulated, and analyzed using CST software. The antenna prototypes were fabricated and measured for the reflection coefficient, gain, and principal plane radiation patterns. In this thesis, we are proposing two single element antennas, a linear to circular wave polarizer, and an array antenna. At first, we present, a planar, cylindrical sector-substrate integrated waveguide (CS-SIW) narrow slot antenna. The impedance bandwidth of this antenna is 10.87% which is approximately equivalent to 4 GHz of bandwidth at 30 GHz, and the antenna gain ranges from 8.33 to 8.84 dB within the impedance bandwidth. Further, to improve the gain, an engineered substrate is constructed on top of the CS-SIW slot antenna. The impedance bandwidth of the modified antenna is 10.42% - also, the gain ranges from 10.5 to 11.44 dB over the impedance bandwidth, which implies an increase in the gain from 2.1 to 2.7 dB when compared with the gain of CS-SIW slot antenna. Also, we propose a three-layered meander-line polarizer at 30 GHz which transforms linearly polarized waves to circularly polarized waves for the CS-SIW slot antenna. Lastly, we present, a 1 × 8 CS-SIW slot antenna array with a superstrate to achieve a high-gain LP antenna. The impedance bandwidth of the antenna is 10%. The gain of the array antenna integrated with a superstrate layer varies from 21.35 to 22.95 dB over the impedance bandwidth