Research And Design Of Broadband Implantable Antennas

Implantable medical devices can get real-time detection of people's physiological parameters inside body.By using wireless communication,information collected by an implantable device can be transmitted from inner body to outside body.The antenna is an important component of an implantable wireless devices which is required with low profile and wide bandwidth.It is not easy to obtain antenna miniaturization with wide bandwidth.This dissertation focuses on the design of antenna working at Medical implant communication services(MICS)and Human Body Communication(HBC).The following gives work involved in this dissertation.(1)Novel implantable antenna working at MICS band has been proposed.The antenna is printed on flexible substrate with 24 ?m thickness and fed by coplanar waveguide(CPW).The radiation part is composed with folded strip to maintain small size.The proposed antenna has a symmetric geometry with size of 12mm×13mm.The measured bandwidth of the proposed antenna is 270-420 MHz.The symmetric antenna is cut half at the symmetric plane resulting in size decreased to 12mm×7mm.The half-cut antenna still has wide bandwidth.Its measured bandwidth is 260-600 MHz.(2)The factors which may have influence on the MICS antennas have been studied including the thickness of insulation film,gap width between insulation film and antenna,and different body tissues.Antenna resonant frequency shifts to the right with the increase of insulation film's thickness.The air gap also causes antenna resonant frequency shifts to the right.In this dissertation,we first present the relationship of resonant frequency with antenna in free space compared with the one inside body.The antenna resonant has a 350 MHz low shift from free space to inner body.(3)Three novel antennas at HBC band have been proposed.The antennas are composed of helixes wound around hollow cylinder filled with magnetic material with radius of 7 mm and height of 20 mm.By using multiple helix and shorted wires,the proposed antennas have wide bandwidth covering 21-23 and 28-31 MHz,16-20 and 27-31 MHz,38-55 MHz,respectively.Compared with published antennas,the proposed antennas have wide bandwidth.(4)For antenna at HBC band,the effects of waterproof material thickness,gap width between waterproof material and air,different human tissues on the antenna frequency characteristics are simulated.It is found that these factors have little effect on the antenna S11.For the first time,the relationship between the resonant frequency of HBC band antenna in human body and in free space is given.When the antenna is put into muscle from air,the resonant frequency shifts slightly to the low and the offset is 1 MHz.The antenna proposed in this thesis has the characteristics of small size,wide bandwidth,low price,easy processing and so on.It has good application prospects in implantable medical equipment.The antenna design method and the antenna performance rule given in this thesis can provide reference for the design of implanted antenna.