Research On Novel Implantable Antennas For Biomedical Applications

Implantable antennas are located inside human body and used in biomedical field for wireless communication with the devices outside human body. Compared with traditional antennas, due to the complexity and limitation of the implantation environment, implantable antennas have more critical restriction on the properties of miniaturization, multiband, wideband, circular polarization, biocompatiblity and safety. This dissertation mainly focuses on the study of novel implantable antenna design to meet various needs of implantable antennas for biomedical applications. Methods such as using different materials and technologies, proposing novel structures, introducing human models, calculating communication link, and etc. are adopted for the research on novel implantable antenna.The sections included are as follows:1. Based on the most traditional printed circuit board (PCB) processing technology, a novel miniaturized implantable antenna is proposed, working at Medical Implant Communication Services (MICS,402-405MHz) band. It is designed on PCB with high dielectric coefficient with a novel meandered slot structure, and excited by a microstrip line with a shorting pin connected. In addition, two U-shaped stubs are adopted to match the feeding impedance to 50Ω. Finally, a miniaturized antenna with a size of 11×10 mm2 is achieved and can be implanted into human arm for communication with relative long distance.2. Based on the most traditional PCB processing technology, both single-band and dual-band antennas are studied with wideband performance at MICS band for implantable applications. For antenna with single-band performance at MICS band, it is designed for ingestible capsule system.With the introducing of a strip connected to the centre of a simple dipole, a new resonance is introduced besides its fundamental resonance and therefore bandwidth enhancement can be achieved. Besides, for antenna with dual-band performance at both MICS band and Industrial Scientific Medical (ISM) band, it is designed based on a dual-band planar inverted-F antenna (PIFA) with II structure, and open-end slot is introduced on its ground plane so that bandwidth can be enhanced significantly at lower frequency band.3. Loop antenna with LC loadings is proposed and its miniaturization can be achieved using slow wave effect. The antenna is designed at ISM band with a centre frequency of 915 MHz and the property can be switched between left-hand circular polarization (LHCP) and left-hand circular polarization (RHCP) by changing the positions of its feeding and shorts.4. A miniaturized dual-band implantable antenna, working at both 402 MHz MICS band and 2.45 GHz ISM band, is designed using sprial dipole structure printed on two sides of PCB material. During the research, a inductive loop is loaded on the antenna to achieve better impedance matching to 50-Ω at two woring bands. Moreover, biocompatible insulating material Parylene-C is coated around the proposed antenna to realize biocompatiblity. Besides, human model is introduced for simulation to analyze the stability of the antenna performance.