Medical devices have made a big step forward in the past decades. One of the most noticeable medical events of the twenties century was the development of long-lasting, wireless electronic implants such as identification tags, pacemakers and neuronal stimulators. These devices were only made possible after the development of small scale radio frequency electronics. Small radio electronic circuits provided a way to operate in both transmission and reception mode allowing an implant to communicate with an external world from inside a living organism. Bidirectional communication is a vital feature that has been increasingly implemented in similar systems to continuously record biological parameters, to remotely configure the implant, or to wirelessly stimulate internal organs. Further miniaturisation of implantable devices to make the operation of the device more comfortable for the patient requires rethinking of the whole radio system concept making it both power efficient and of high performance. Nowadays, high data throughput, large bandwidth, and long term operation requires new radio systems to operate at UHF (ultra-high frequency) bands as this is the most suitable for implantable applications. For instance, the MICS (Medical Implant Communication System) band was introduced for the communication with implantable devices. However, this band could only enable communication at low data rates. This was acceptable for the transmission of telemetry data such as heart beat rate, respiratory and temperature with sub Mbps rates. Novel developments such as neuronal and prosthetic implants require significantly higher data rates more than 10 Mbps that can be achieved with large bandwidth communicating systems operating at higher frequencies in a GHz range. Higher operating frequency would also resolve a strong issue of MICS devices, namely the scale of implants defined by dimensions of antennas used at this band. Operation at 2.4 GHz ISM band was recognized to be the most adequate as it has a moderate absorption in the human body providing a compromise between an antenna/implant scale and a total power efficiency of the communicating system. This thesis addresses a key challenge of implantable radio communicating systems namely an efficient and small scale antenna design which allows a high yield fabrication in a microelectronic fashion. It was demonstrated that a helical antenna design allows the designer to precisely tune the operating frequency, input impedance, and bandwidth by changing the geometry of a self-assembled 3D structure defined by an initial 2D planar layout. Novel stimuli responsive materials were synthesized, and the rolled-up technology was explored for fabrication of 5.5-mm-long helical antenna arrays operating in ISM bands at 5.8 and 2.4 GHz. Characterization and various applications of the fabricated antennas are successfully demonstrated in the thesis.

In this master work, we investigated the feasibility of a magnetic resonance measurement technique using magnetic nanoparticle dispersions in both liquid and solid form. The implementation is realised as a coplanar waveguide operating in the frequency range of 0.5 - 20 GHz and an electromagnet producing a static magnetic field of strength up to 1.2 T. The Gilbert magnetic damping factor is determined for polymer composites of magnetic nanoparticles and the gyromagnetic ratio is determined for both nanoparticle dispersions in liquid form and polymer composites.

In this thesis the major objective is the implementation of the inverse neural network concept in the design of printed lens (transmitarray) antenna. As it is computationally extensive to perform full-wave simulations for entire transmitarray structure and thereafter perform optimization, the idea is to generate a design database assuming that a unit cell of the transmitarray is situated inside a 2D infinite periodic structure. This way we generate a design database of transmission coefficient by varying the unit cell parameters. Since, for the actual design, we need dimensions for each cell on the transmitarray aperture and to do this we need to invert the design database. The major contribution of this thesis is the proposal and the implementation of database inversion methodology namely inverse neural network modelling. We provide the algorithms for carrying out the inversion process as well as provide check results to demonstrate the reliability of the proposed methodology. Finally, we apply this approach to design a transmitarray antenna, and measure its performance.

Medical devices have made a big step forward in the past decades. One of the most noticeable medical events of the twenties century was the development of long-lasting, wireless electronic implants such as identification tags, pacemakers and neuronal stimulators. These devices were only made possible after the development of small scale radio frequency electronics. Small radio electronic circuits provided a way to operate in both transmission and reception mode allowing an implant to communicate with an external world from inside a living organism. Bidirectional communication is a vital feature that has been increasingly implemented in similar systems to continuously record biological parameters, to remotely configure the implant, or to wirelessly stimulate internal organs. Further miniaturisation of implantable devices to make the operation of the device more comfortable for the patient requires rethinking of the whole radio system concept making it both power efficient and of high performance. Nowadays, high data throughput, large bandwidth, and long term operation requires new radio systems to operate at UHF (ultra-high frequency) bands as this is the most suitable for implantable applications. For instance, the MICS (Medical Implant Communication System) band was introduced for the communication with implantable devices. However, this band could only enable communication at low data rates. This was acceptable for the transmission of telemetry data such as heart beat rate, respiratory and temperature with sub Mbps rates. Novel developments such as neuronal and prosthetic implants require significantly higher data rates more than 10 Mbps that can be achieved with large bandwidth communicating systems operating at higher frequencies in a GHz range. Higher operating frequency would also resolve a strong issue of MICS devices, namely the scale of implants defined by dimensions of antennas used at this band. Operation at 2.4 GHz ISM band was recognized to be the most adequate as it has a moderate absorption in the human body providing a compromise between an antenna/implant scale and a total power efficiency of the communicating system. This thesis addresses a key challenge of implantable radio communicating systems namely an efficient and small scale antenna design which allows a high yield fabrication in a microelectronic fashion. It was demonstrated that a helical antenna design allows the designer to precisely tune the operating frequency, input impedance, and bandwidth by changing the geometry of a self-assembled 3D structure defined by an initial 2D planar layout. Novel stimuli responsive materials were synthesized, and the rolled-up technology was explored for fabrication of 5.5-mm-long helical antenna arrays operating in ISM bands at 5.8 and 2.4 GHz. Characterization and various applications of the fabricated antennas are successfully demonstrated in the thesis.

Within the military there is great need for reliable communication between vehicles. During the planning and construction of a military RIB, Rigid-hulled Inflatable Boat, it is important to design an efficient antenna system that does not deteriorate out of disorder. It must also be ensured that the antennas transmitted power does not stay in the RIB boat. We have been given assignment to model and simulate a proposed antenna system and assess which tool is best suitable for the task. To analyze the antenna system we will look at the radiated electrical field together with the reflectionand EMC properties. The tool that we choose to use is a software called EMPro produced by Keysight Technologies. In this program we will create 3Dstructures for each individual object, the boat, the three antennas and the seawater. It’s also important to include each objects properties concerning material, so that they correctly reflect the reality. We are covering a broad spectrum with our antennas reaching from 1.6-30MHz, 30-88MHz and 100512MHz. The resulting simulation verifies that electromagnetic field would be powerful enough and that the antennas would not affect each other with the proposed placement. We could also confirm that our antennas reflected an inordinate amount of power but with cause that our models were not an exact replica of the antenna. The software EMPro is a suitable tool for this kind of projects concerning modeling and simulating antenna systems.Within the military there is great need for reliable communication between vehicles. During the planning and construction of a military RIB, Rigid-hulled Inflatable Boat, it is important to design an efficient antenna system that does not deteriorate out of disorder. It must also be ensured that the antennas transmitted power does not stay in the RIB boat. We have been given assignment to model and simulate a proposed antenna system and assess which tool is best suitable for the task. To analyze the antenna system we will look at the radiated electrical field together with the reflectionand EMC properties. The tool that we choose to use is a software called EMPro produced by Keysight Technologies. In this program we will create 3Dstructures for each individual object, the boat, the three antennas and the seawater. It’s also important to include each objects properties concerning material, so that they correctly reflect the reality. We are covering a broad spectrum with our antennas reaching from 1.6-30MHz, 30-88MHz and 100512MHz. The resulting simulation verifies that electromagnetic field would be powerful enough and that the antennas would not affect each other with the proposed placement. We could also confirm that our antennas reflected an inordinate amount of power but with cause that our models were not an exact replica of the antenna. The software EMPro is a suitable tool for this kind of projects concerning modeling and simulating antenna systems. / Inom militären finns stort behov av pålitlig kommunikation mellan fordon. Vid konstruktion av ett småfartyg i militärtoch bevakningssyfte är det viktigt att designa ett välfungerande antennsystem som inte försämras utav störningar, det ska även ses till att antennernas utsända effekt inte fastnar i småfartyget. Vi har fått en ritning av hur antennplaceringen är planerad, denna rapport går ut på att verifiera dess funktionalitet samt hitta en mjukvara som kan användas för att verifiera olika antennsystem. För att bedöma antennsystemet kommer denna rapport att undersöka att dess elektriska fält samt reflektionsoch EMC egenskaper, en uppgift som kan lösas med programvaran EMPro (Keysight). I programvaran skapas en 3Dstruktur som innehåller småfartyget, dess 3 stycken antenner samt omfattande havsvatten. Här tas hänsyn till objektens materialegenskaper, antennernas jordning samt de frekvenser antennerna arbetar på, 1.6-30MHz, 30-88MHz samt 100-512MHz. Simulering av systemet gav positiva resultat kring antennsystemets elektromagnetiskafält, antennerna kommer inte heller att störa varandra. Antennerna som vi har modellerat reflekterar orimligt mycket effekt, detta bortser vi från då vi inte haft tillgång till exakt avbildning av antennerna. EMPro är ett verktyg som är lämpligt att använda i detta samt liknande projekt. Dock krävs det att en kraftig dator finns tillgänglig då simuleringar av stora antennsystem baseras på stora uträkningar, som generellt tar lång tid.