| Compared with traditional medical devices,the implantable ones can obtain more accurate human pathological information which makes it focus in medical electric area.With the development of microelectronic technology,implantable devices tend to be more compact which requires more for miniaturization of implantable antenna.An implantable antenna is also required with wide bandwidth to suit for various human tissues with different electromagnetic parameters.This thesis aims to design miniaturized implantable antennas with wide bandwidth at Industrial,Scientific,and Medical(ISM)band and Human Body Communication(HBC)band.The following gives work involved in this thesis.(1)A novel flexible implantable antenna operating at ISM band has been proposed:The proposed antenna is printed on a 20μm-thick polyimide substrate with a symmetrical geometry.Coplanar waveguide feeding and step-shaped radiation patch are adopted to obtain antenna miniaturization and wide bandwidth.The propose antenna has a compact profile of 2 mm×10 mm.To further reduce the antenna footprint,the symmetrical antenna is cut in half along the symmetrical line.The half-cut antenna has a very compact size of 2mm×10 mm with maintaining wide bandwidth.The proposed antenna has been measured in liquid muscle phantom with its-10d B bandwidth covering 1.96 GHz-2.88 GHz.Compared with published implantable antennas,the width of proposed antenna is 2mm,which is less than the diameter of needle tube,and its length is only 10 mm,which is less than the total length of needle tube.The proposed antenna has a smaller footprint and thinner thickness suitable to be arranged inside a syringe for injection implant.(2)An ISM band antenna implanted in fat has been proposed:An antenna designed in muscle,skin,or digestion organs often has high return loss in fat due to the fact of that the dielectric constant of fat varies much with the forementioned ones.The proposed antenna can work both in fat and muscle with a low profile 2 mm×10 mm×20μm.Meandering line and C-shaped geometry is adopted to reduce antenna size.The proposed antenna excites two resonances in muscle at 1.37 GHz and 2.33 GHz,respectively.At the second resonance,the bandwidth of 2 GHz-2.96 GHz is obtained covering ISM band.In fat,only one resonance is excited,and the bandwidth of 2.4 GHz-2.59 GHz is obtained.(3)Two planar spiral antennas operating at HBC band have been proposed.Miniaturization is the challenge of HBC band antenna owing to low frequency and long wavelength.The proposed antennas are both of planar spiral type with size of 23.04π×0.3mm~3 and 22.5×16×0.3 mm~3,respectively Magnetic material with high dielectric constant and permeability is adopted to decrease resonant frequency and antenna size.Copper line is wound on the magnetic sheet as spiral shape to reduce antenna size further.The proposed antennas are measured in liquid muscle phantom and their bandwidth covers 41 MHz-44MHz and 23 MHz-28.5 MHz,which is miniaturized in the HBC band.Compared with published HBC antenna,the proposed antenna has the advantages of low profile and small size,which can be applied to small implantable medical methods.Compared with the existing implantable antennas,the antennas proposed in this thesis have the advantages of smaller size,wider bandwidth and easy fabrication,which meet the miniaturization requirements of implantable devices. |
PDF Full Text Request