Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Modelling and characterisation of antennas and propagation for body-centric wireless communication

PhDBody-Centric Wireless Communication (BCWC) is a central point in the development of fourth generation mobile communications. The continuous miniaturisation of sensors, in addition to the advancement in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to a new concept of usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body or even implanted. Body-centric wireless networks take their place within the personal area networks, body area networks and body sensor networks which are all emerging technologies that have a broad range of applications such as healthcare and personal entertainment. The major difference between BCWC and conventional wireless systems is the radio channel over which the communication takes place. The human body is a hostile environment from radio propagation perspective and it is therefore important to understand and characterise the effect of the human body on the antenna elements, the radio channel parameters and hence the system performance. This is presented and highlighted in the thesis through a combination of experimental and electromagnetic numerical investigations, with a particular emphasis to the numerical analysis based on the finite-difference time-domain technique. The presented research work encapsulates the characteristics of the narrowband (2.4 GHz) and ultra wide-band (3-10 GHz) on-body radio channels with respect to different digital phantoms, body postures, and antenna types hence highlighting the effect of subject-specific modelling, static and dynamic environments and antenna performance on the overall body-centric network. The investigations covered extend further to include in-body communications where the radio channel for telemetry with medical implants is also analysed by considering the effect of different digital phantoms on the radio channel characteristics. The study supports the significance of developing powerful and reliable numerical modelling to be used in conjunction with measurement campaigns for a comprehensive understanding of the radio channel in body-centric wireless communication. It also emphasises the importance of considering subject-specific electromagnetic modelling to provide a reliable prediction of the network performance

Analysis and Design of Footwear Antennas

Wearable technologies are found in an increasing number of applications including sport and medical monitoring, gaming and consumer electronics. Sensors are used to monitor vital signs and are located on various parts of the body. Footwear sensors permit the collection of data relating to gait, running style, physiotherapy and research. The data is sent from sensors to on-body hubs, often using wired technology, which can impact gait characteristics. This thesis describes the design of footwear antennas for wireless sensor telemetry. The work addresses the challenges of placing antennas close to the foot as well as the proximity to the ground. Guidelines for polarization are presented. The channel link between footwear and wrist is investigated for both narrowband and wideband channels across different frequencies. The effects of the body proximity and movement were gauged for walking subjects and are described in terms of the Rician Distribution K-factor. Different antenna solutions are presented including UWB antennas on various footwear locations as well as 433 MHz integrated antennas in the insole. Both directional and omnidirectional antennas were considered for UWB and the evaluation was for both time-domain and frequencydomain. The research established new ideas that challenge the old paradigm of the waist as the best hub position, demonstrating that a hub on the footwear using directional antennas outperforms a hub on the waist using an omnidirectional antenna. The cumulative distribution functions of measured path gains are evaluated and the results are described in terms of the achievable minimum data rate considering the Body Area Network standard

Insole Antenna for On-Body Telemetry

A 433 MHz antenna is proposed for integration with the insole of footwear for a body area network. The folded dipole design with an asymmetric groundplane radiates from its edges and considers the close proximity of the human foot and ground surfaces. It functions for different ground conductivity conditions and an on-body communication link with an Inverted F Antenna in the upper body area was evaluated on a static and dynamic human subject. The antenna solution was compliant with Specific Absorption Rate requirements, remains matched and links with upper-body nodes regardless of the body posture and node location

A novel, low-profile, vertically-polarized UWB antenna for WBAN

This paper proposes a novel, low-profile UWB antenna for wireless body area network (WBAN) applications. The antenna has a polarization perpendicular to the body-free-space interface, which is interesting in order to minimize the coupling into the body. Its structure comprises a modified mono-cone with a top-cross-plate and is coaxially fed through the ground plane. The higher frequency band |S11| performance is due to the mono-cone while the top-cross-plate is responsible for the lower frequency band. This plate also leads to a height reduction when compared to conventional mono-cone antennas. A comprehensive parametric study is done to provide design guidelines. Both frequency- and time-domain results have been measured and presented to validate the design. Results show that the antenna operates from 3.06 to beyond 12 GHz based on |S11| ≤ -10 dB, radiates omni-directionally in the H-plane, and has a radiation efficiency over 95%. The system-fidelity factor for UWB signals is adequate for pulse transmission. Finally, the influence of the human proximity on the antenna matching was tested. Results show that its impedance is nearly unchanged as compared to free-space

Antennas And Wave Propagation In Wireless Body Area Networks: Design And Evaluation Techniques

Recently, fabrication of miniature electronic devices that can be used for wireless connectivity becomes of great interest in many applications. This has resulted in many small and compact wireless devices that are either implantable or wearable. As these devices are small, the space for the antenna is limited. An antenna is the part of the wireless device that receives and transmits a wireless signal. Implantable and wearable antennas are very susceptible to harmful performance degradation caused by the human body and very difficult to integrate, if not designed properly. A designer need to minimize unwanted radiation absorption by the human body to avoid potential health issues. Moreover, a wearable antenna will be inevitably exposed to user movements and has to deal with influences such as crumpling and bending. These deformations can cause degraded performance or a shifted frequency response, which might render the antenna less effective. The existing wearable and implantable antennas’ topologies and designs under discussion still suffer from many challenges such as unstable antenna behavior, low bandwidth, considerable power generation, less biocompatibility, and comparatively bigger size. The work presented in this thesis focused on two main aspects. Part one of the work presents the design, realization, and performance evaluation of two wearable antennas based on flexible and textile materials. In order to achieve high body-antenna isolation, hence, minimal coupling between human body and antenna and to achieve performance enhancement artificial magnetic conductor is integrated with the antenna. The proposed wearable antennas feature a small footprint and low profile characteristics and achieved a wider -10 dB input impedance bandwidth compared to wearable antennas reported in literature. In addition, using new materials in wearable antenna design such as flexible magneto-dielectric and dielectric/magnetic layered substrates is investigated. Effectiveness of using such materials revealed to achieve further improvements in antenna radiation characteristics and bandwidth and to stabilize antenna performance under bending and on body conditions compared to artificial magnetic conductor based antenna. The design of a wideband biocompatible implantable antenna is presented. The antenna features small size (i.e., the antenna size in planar form is 2.52 mm3), wide -10 dB input impedance bandwidth of 7.31 GHz, and low coupling to human tissues. In part two, an overview of investigations done for two wireless body area network applications is presented. The applications are: (a) respiratory rate measurement using ultra-wide band radar system and (b) an accurate phase-based localization method of radio frequency identification tag. The ultimate goal is to study how the antenna design can affect the overall system performance and define its limitations and capabilities. In the first studied application, results indicate that the proposed sensing system is less affected and shows less error when an antenna with directive radiation pattern, low cross-polarization, and stable phase center is used. In the second studied application, results indicate that effects of mutual coupling between the array elements on the phase values are negligible. Thus, the phase of the reflected waves from the tag is mainly determined by the distance between the tag and each antenna element, and is not affected by the induced currents on the other elements

인체통신용 안테나에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 2. 남상욱.This thesis presents the antennas for in-body, on-body communication. The antennas in body communication are severely affected by human body which has a high relative permittivity and conductivity. The high relative permittivity and conductivity degrades the antenna bandwidth and efficiency. Therefore, it is a main challenge that enhancing the bandwidth and the efficiency of the antenna maintaining the small size. In order to enhance the performance of the antennas several techniques are proposed in body communication antennas. Firstly, the Q value and the efficiency of the in-body antenna are investigated. Using the proposed equations, the optimum frequency of the in-body antenna will be given. To maximize the antenna dimensions in the endoscopy antenna, the outer wall loop antennas is proposed. The measurement results are given to show the performance of the proposed antenna. Secondly, the several techniques for on-body antenna are proposed. The conventional antennas without the ground plane like dipole and slot antennas are not appropriate for on-body environment because the body has low intrinsic impedance and high conductivity compared to that of the free space. Therefore, antennas with ground plane like patch and cavity-backed slot antennas are proposed for on-body communication. The cavity-backed slot antenna with via-hole above the slot is proposed for bandwidth enhancement of the antenna. As the place of the via-hole introduces the additional resonance, wider bandwidth is achieved. The substrate removal technique for cavity-backed slot antenna is also proposed for the bandwidth and the efficiency enhancement. The removal of the substrate across the slot decreases the Q of the antenna, increasing the bandwidth and efficiency. In addition, the folded-cavity-backed slot antenna is given for size miniaturization of the cavity-backed slot antenna. The folded structure of the proposed antenna increases the effective length of the antenna, decreasing the antenna resonance frequency. Furthermore, the reconfigurable shorted patch antenna is given for wide bandwidth. Lastly, the dual-band and dual-impedance cavity-backed slot antennas are given for the efficient on-body systems1. Introduction 1 1.1 WBAN (Wireless Body Area Network) Applications 1 1.2 Electrical Properties of Human Body 5 1.3 Challenges in Designing Body Communication Antenna 7 2. Antennas in Human Body 10 2.1 Properties of the Antenna in Human Body 10 2.1.1 Radiation efficiency of the Antenna in Human Body 11 2.1.2 Q of the Antenna in Human Body 14 2.1.3 Numerical Results and Conclusion 15 2.2 Outer-Wall Loop Antenna for Capsule Endoscope System 18 2.2.1 Introduction 18 2.2.2 Antenna Design 20 2.2.3 Simulation and Measurement results 23 2.2.4 Conclusion 31 3. Antennas on human body 32 3.1 Properties of the Antenna on Human Body 32 3.1.1 Model of the Human Body 32 3.1.2 Antennas without Ground on Human Body 34 3.1.3 Antennas with Ground Plane on Human Body 36 3.2 Cavity-backed slot Antenna on Human Body 38 3.2.1 Operation of Cavity-backled Slot Antenna 38 3.2.2 Bandwidth and Efficiency Enhancement using Substrate Removal 40 3.2.3 Bandwidth Increase using Via-hole above the Slot 54 3.2.4 Miniaturization using Folded Cavity Structure 66 3.2.5 Dual-band Technique for Slot Antennas 81 3.2.6 Dual Impedance Cavity-backed Slot Antenna 86 3.3 Shorted Patch Antenna on Human Body 97 3.3.1 Operation of Shorted Patch Antenna 98 3.3.2 Reconfigurable Shorted Patch Antenna 100Docto

Antenna and radio channel characterisation for low‐power personal and body area networks

PhDThe continuous miniaturisation of sensors, as well as the progression in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to new usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body. Body-centric wireless communications (BCWCs) is a central point in the development of fourth generation mobile communications. Body-centric wireless networks take their place within the personal area networks, body area networks and sensor networks which are all emerging technologies that have a wide range of applications (such as, healthcare, entertainment, surveillance, emergency, sports and military). The major difference between BCWC and conventional wireless systems is the radio channels over which the communication takes place. The human body is a hostile environment from a radio propagation perspective and it is therefore important to understand and characterise the effects of the human body on the antenna elements, the radio channel parameters and, hence, system performance. This thesis focuses on the study of body-worn antennas and on-body radio propagation channels. The performance parameters of five different narrowband (2.45 GHz) and four UWB (3.1- 10.6 GHz) body-worn antennas in the presence of human body are investigated and compared. This was performed through a combination of numerical simulations and measurement campaigns. Parametric studies and statistical analysis, addressing the human body effects on the performance parameters of different types of narrowband and UWB antennas have been presented. The aim of this study is to understand the human body effects on the antenna parameters and specify the suitable antenna in BCWCs at both 2.45 GHz and UWB frequencies. Extensive experimental investigations are carried out to study the effects of various antenna types on the on-body radio propagation channels as well. Results and analysis emphasize the best body-worn antenna for reliable and power-efficient on-body communications. Based on the results and analysis, a novel dual-band and dual-mode antenna is proposed for power-efficient and reliable on-body and off-body communications. The on-body performance of the DBDM antenna at 2.45 GHz is compared with other five narrowband antennas. Based on the results and analysis of six narrowband and four UWB antennas, antenna specifications and design guidelines are provided that will help in selecting the best body-worn antenna for both narrowband and UWB systems to be applied in body-centric wireless networks (BCWNs). A comparison between IV the narrowband and UWB antenna parameters are also provided. At the end of the thesis, the subject-specificity of the on-body radio propagation channel at 2.45 GHz and 3-10 GHz was experimentally investigated by considering eight real human test subjects of different shapes, heights and sizes. The subject-specificity of the on-body radio propagation channels was compared between the narrowband and UWB systems as well