Design,Implementation And Performance Analysis Of UWB Antennas For Biomedical Applications

Antenna innovation has drawn great deal of attention both in industry and academia.They serve as the vital front-end components in a communication system and can be viewed as its eyes and ears.The research interest in antennas has significantly grown over the decades,as they are potentially improving a diverse range of medical,military and commercial applications.The good functionality of a right antenna can positively influence the dynamic performance and maximize the overall efficiency of a system.However,it is difficult to select the right antenna that matches the capabilities and specifications,as well as meets the size,weight,environment and mechanical operational requirements of the intended application completely.Therefore,many research efforts are dedicated to this area.The main objective of the research work in this thesis focuses on the design and construction,performance observation and analysis,testing and measurement of antennas applicable for use in biomedical applications.The first is in microwave-based medical diagnostic systems via sensing and imaging,and the second is in wireless body area network?WBAN?devices for medical monitoring in off-body communication mode.?1?For this purpose,a compact antenna?called as the microwave bodyscope?is presented for biomedical measurements of the human body in microwave-based diagnostic systems.The microwave bodyscope proves its capability as a pass-through propagation sensor for different parts of the human body and as a sensor detecting a 1 cm diameter object placed inside an artificial human head phantom.To achieve this,formerly an initial study is conducted that investigates two double-ridged horn?DRH?antennas operating in three different mediums–air,a medium close to human head tissues and water.Then,based on dimension,medium permittivity and operational bandwidth,the initial study predicts the most suitable antenna design that can serve as the basis for the development of a physically small size antenna.An idea resembling to a microwave biomedical probe that can come in direct contact with a human body without using immersive medium and can be used independently or in an array format.The initial study also investigates a cost effective and robust antenna fabrication methodology side by side.The operational frequency of the microwave bodyscope covers the microwave frequency band of interest from 0.5–3.0 GHz(for a S₁₁ under-7 dB).It is dielectrically matched to the permittivity of the human body,and because of its compactness,it can be visualized as a general purpose microwave probe among the RF biomedical community.Secondly,two types of antenna profiles are optimized as improved radiators for microwave imaging systems.It is realized that although medical microwave imaging in the0.5–3.0 GHz of the human body is able to give low-cost functional and pathological images as a non-invasive technique,still the capability of getting realistic experimental images is one of the remaining big challenges.One of the limiting reasons may be the incapability of the antennas to penetrate the tomographic sections of the biological targets with an appropriate illuminating profile.For this purpose,different aperture profiles of an E-plane sectoral horn antenna are studied in order to obtain the best optimal profile that may result in the better uniformity of the electric fields taking into account the diffraction and medium losses.The antenna profiles have been optimized to guarantee both the necessary bandwidth and the proper illumination of a brain cross-section.The electric field distributions along the vertical antenna aperture are first studied and then the fields on the cross-section are obtained.For the second profile,a tapered slot antenna?TSA?operating is examined in the far-field region with directive radiation characteristics.The TSA is excited by a stepped transmission line through slotline transition and corrugations are added to reduce the size of TSA and also improve its radiation performance.Simulated and measured results demonstrate that the proposed antenna operates with directive radiation patterns across a bandwidth spanning in the low microwave frequency range from 0.5–4GHz which is well known for good microwave signal penetration and acceptable image resolution.?2?The thesis presents a flexible,light-weight,low-profile ultrawideband wearable antenna for the purpose of integration into WBAN systems.The antenna operates across the 7.5 GHz ultrawideband?UWB?frequency spectrum ranging from 3.1–10.6 GHz.For flexibility,the antenna makes use of polyimide material as its substrate which has good combination of both physical and chemical properties.The antenna structure with an overall size of 35×30×0.18 mm³ consists of a mirrored-L monopole radiator and a modified coplanar waveguide?CPW?feed transmission line.The antenna radiation performance characteristics are examined in–free space,against bending effects to carry out the flexibility analysis test,then near the influence of human body proximity and lastly under harsh weather conditions to check adversarial effect on its substrate.A good agreement between the simulated and measured results is observed in all the cases.In terms of volume,comfortable degree and good radiation performance suggest the feasibility that the proposed wearable antenna can be applied in off-body communication mode for wearable WBAN devices particularly in medical monitoring.In the dissertation,an indebt study,parametric analysis and experimental validation of the antennas are carried out in order to fulfill the requirements and constraints and achieve desired results satisfying commendable criteria.The obtained results were found to be impressive and their comparison with the existing work proved to be satisfactory,also suggesting further advancement in the specified area.