Research On Wearable Antennas Equipped With Artificial Magnetic Conductor

With the improvement of living standards and the deterioration of population ageing problem, medical treatment and health care have been paid more attention. Owing to low level of medical facilities,high cost of treatment and slow service, traditional medical model can’t satisfy people’s medical care needs. Body area network(BAN) is an effective technical method to solve these problems. As one key component for wireless signal transmission in BAN systems, antennas may affect the transmission of biomedical signals. At present, wearable antenna exists the problems of low gain, strong coupling with human body and large size. Therefore, antennas with good performance are of great value and significance for BAN applications.This dissertation was supported in part by the National Natural Science Foundation of China(61372008), the State Key Laboratory of Millimeter Waves(K201405), and the Fundamental Research Funds for the Central Universities(2014ZZ0031), and two wearable antennas based on artificial magnetic conductor(AMC) are proposed for BAN applications, as following.1) A dual-band monopole antenna based on annular AMC is designed, which includes a dual-band monopole antenna, and an annular AMC structure. The dual-band monopole antenna consists of upper and lower ring with different radius and an ellipse patch, which is fed by coplanar waveguide(CPW). To achieve high gain, low radiation and low profile, a dual-band annular AMC with the characteristic of in-phase reflection phase is integrated with the antenna, acting as a reflector. And the ± 90° reflection phase band-gap of the AMC is consistent with the working frequency of antenna. The AMC-integrated antenna covers the industrial, scientific, and medical(ISM) bands of 2.4-2.48 GHz and 5.725-5.85 GHz, and has an average gain of 11.8 d Bi in lower band, 8 d Bi in upper band, and a front-to-back ratio of 10 d B.Due to the limits of ± 90° reflection phase band-gap, the research of broadband wearable antenna based on AMC is slow. Thus, an windmill-like broadband antenna equipped with square-shaped AMC is studied in the paper.2) An windmill-like broadband antenna equipped with AMC is proposed, which consists a broadband dipole antenna, and a square-shaped AMC structure. The broadband dipole antenna is composed of four S-shaped strips in the direction of up, down, left, and right, respectively. S-shaped strips in the direction of up and left are interconnected and etched on the top side of substrate, while S-shaped strips in the direction of down and right are interconnected and sculptured on the bottom. Radiator on the top side of substrate is connected with an annular microstrip line, which is fed by a coaxial cable. Also, in order to reduce the coupling between the antenna and human body, improve the gain of antenna, a broadband square-shaped AMC is used as a reflector of the dipole antenna. The AMC-integrated antenna covers the upper ultra wideband of 5.7-11.0 GHz, has an average gain of 8 d Bi, and a front-to-back ratio greater than 15 d B. The distance for reliable communication can be guaranteed within 10 m in indoor LOS environment. Research on wearable antenna should not only consider the performance of antenna itself, but also its special application environment. Thus, bending effect on the antenna performance, antenna radiation intensity to human body, temperature increase in human tissues and reliable communication distance, namely, link budget, are studied in details.This article shows that AMC plays an important role in reducing the coupling between the antenna and human body, improving the gain of antenna, and keeping low profile. AMC with the characteristics of broadband and miniaturization can further improve the bandwidth and reduces the volume of the antenna.