Mälardalen University Press Dissertations No. 157 MEASUREMENT SYSTEM FOR MICROWAVE IMAGING TOWARDS A BIOMEDICAL APPLICATION Nikola Petrović 2014 School of Innovation, Design and Engineering Mälardalen University Press Dissertations No. 157 MEASUREMENT SYSTEM FOR MICROWAVE IMAGING TOWARDS A BIOMEDICAL APPLICATION Nikola Petrović Akademisk avhandling som för avläggande av teknologie doktorsexamen i elektronik vid Akademin för innovation, design och teknik kommer att offentligen försvaras onsdagen den 28 maj 2014, 10.00 i Paros, Mälardalens högskola, Västerås. Fakultetsopponent: Professor Christian Pichot, University of Nice Copyright © Nikola Petrović, 2014 ISBN 978-91-7485-146-5 ISSN 1651-4238 Printed by Arkitektkopia, Västerås, Sweden Akademin för innovation, design och teknik Mälardalen University Press Dissertations No. 157 Mälardalen University Press Dissertations No. 157 MEASUREMENT SYSTEM FOR MICROWAVE IMAGING TOWARDS A BIOMEDICAL APPLICATION MEASUREMENTNikola SYSTEM Petrović FOR MICROWAVE IMAGING TOWARDS A BIOMEDICAL APPLICATION Nikola Petrović Akademisk avhandling som för avläggande av teknologie doktorsexamen i elektronik vid Akademin för innovation, design och teknik kommer att offentligen försvaras onsdagen den 28 maj 2014, 10.00 i Paros, Mälardalens högskola, Västerås. Akademisk avhandling Fakultetsopponent: Professor Christian Pichot, University of Nice som för avläggande av teknologie doktorsexamen i elektronik vid Akademin för innovation, design och teknik kommer att offentligen försvaras onsdagen den 28 maj 2014, 10.00 i Paros, Mälardalens högskola, Västerås. Fakultetsopponent: Professor Christian Pichot, University of Nice Akademin för innovation, design och teknik Akademin för innovation, design och teknik Abstract Microwave imaging techniques have shown excellent capabilities in various fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups throughout the world work on prototype systems for producing images of human tissues in different biomedical applications, In loving memory of my brother Ljubiˇsa particularly breast tumor detection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabrication of suitable antennas, are essential to the development of efficient microwave imaging systems. The first part of this thesis focuses on measurement systems for microwave imaging in terms of antenna design and development, robot controlled synthetic array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The presented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom. The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and constructed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numerical simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the performance goals, demonstrating the potential for the future microwave imaging system called Mamacell. ISBN 978-91-7485-146-5 ISSN 1651-4238 In loving memory of my brother Ljubiˇsa Abstract Microwave imaging techniques have shown excellent capabilities in var- ious fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups through- out the world work on prototype systems for producing images of human tissues in different biomedical applications, particularly breast tumor de- tection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabri- cation of suitable antennas, are essential to the development of efficient microwave imaging systems. The first part of this thesis focuses on measurement systems for mi- crowave imaging in terms of antenna design and development, robot con- trolled synthetic antenna array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The pre- sented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom. The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and con- structed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numeri- cal simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the per- formance goals, demonstrating the potential for the future microwave imaging system called Mamacell. Abstract Microwave imaging techniques have shown excellent capabilities in var- ious fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups through- out the world work on prototype systems for producing images of human tissues in different biomedical applications, particularly breast tumor de- tection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabri- cation of suitable antennas, are essential to the development of efficient microwave imaging systems. The first part of this thesis focuses on measurement systems for mi- crowave imaging in terms of antenna design and development, robot con- trolled synthetic antenna array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The pre- sented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom. The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and con- structed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numeri- cal simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the per- formance goals, demonstrating the potential for the future microwave imaging system called Mamacell. Sammandrag Mikrov˚agsavbildningstekniker har p˚avisat utm¨arkta m¨ojligheter inom olika omr˚aden s˚asom anl¨aggningsarbeten, of¨orst¨orande provning, indus- triella till¨ampningar, och har under de senaste decennierna haft en stark tillv¨axt som ett forsknings¨amne inom biomedicinsk diagnostik. M˚anga forskargrupper runt om i v¨arlden jobbar p˚aprototypsystem f¨or att fram- st¨alla bilder av m¨ansklig v¨avnad i olika biomedicinska till¨ampningar, s¨arskilt f¨or br¨osttum¨ordetektion. Dock st˚ar forskarv¨arlden inf¨or m˚anga utmaningar och f¨or att vara konkurrenskraftiga bland andra avbild- ningsmetoder s˚a¨arett av medlen att l¨aggatonvikten p˚aexperimentellt arbete. F¨oljaktligen ¨ar anv¨andningen av flexibla och