Design Of Miniaturized And Wearable Satellite Navigation Antenna

With the arrival of 5G era,various applications including intelligent home,intelligent manufacturing,unmanned driving etc.require accurate simulations of the objects and the environments for efficient and safe applications.Meanwhile,more stringent requirements are put forward for the accuracy of navigation and positioning in these applications.However,the operating frequency band of the navigation system is relatively low,which leads to the large size of the corresponding antenna.Therefore,the realization of antenna miniaturization becomes a major difficulty in the current research.In addition,under the background of 5G,it is difficult for the traditional antennas f to meet the practical requirements in the modern applications.The wide use of wearable devices has attracted the much attentions among the scholars on the research of wearable antennas.This kind of special application scenario also put forward higher requirement on the antenna designs.The current research in this field is mainly focused on the flexible antennas or small-size button antennas.In this thesis,two different types of antennas are designed according to the working frequency band of the satellite navigation system.The main work of this thesis is summarized as follows:A small circularly polarized microstrip patch antenna is designed for the application of GPS and BD navigation.The antenna consists of top patch and bottom patch fed by a Wilkinson power divider.The left-handed polarized waves radiated by the top and bottom patches are cancelled out each other,thus reducing the backward radiation of the antenna.The right-handed polarized waves radiated by the top and bottom patches h are superposed to improve the broadside gain of the antenna.The designed antenna works in the circularly polarized mode in the bands of GPS L1 and BD B1,with a front-to-rear ratio of about 14d B.The overall size of the proposed antenna is50×50×12mm~3.A dual-band dual-polarization coplanar waveguide(CPW)antenna fabricated on fabric is developed to operate in both GPS and WLAN frequency bands for the applications of navigation and communication.Firstly,an antenna with dual-band characteristics is designed,and then the circular polarization performance of the antenna in the GPS L1 band is realized by adding perturbation branches.Then,the antenna with circular polarization is simulated and optimized.Finally,the designed antenna in this thesis can realize the circular polarization characteristic in the GPS L1 band and the linear polarization characteristic in the WLAN band.The robustness of the antenna was analyzed,and the results show that the performance of the antenna is hardly changed by bending the antenna along the different directions,which verifies the reliability of the antenna.Because of the strong backward radiation of the CPW antenna,the resulting effect on the human body is very strong,thus resulting in exceeding the requirements on the Specific Absorption Ratio(SAR).To ensure that it can be safely worn on the human body,an artificial magnetic conductor(AMC)structure with the characteristics of in-phase reflection is designed to be placed at the bottom of the antenna for the reduction of the backward radiation of the antenna.In this thesis,three kinds of the AMC units working in different frequency bands are designed and located below the antenna,respectively.By adjusting the distance between the AMC structure and the antenna,the impedance matching characteristics of the AMC-based antennas are guaranteed.The AMC-based antenna is placed above the human body,and the SAR value is simulated.The resulting SAR meets the requirements.Therefore,the designed antenna loaded with AMC structure can be safely applied in the wearable application.