The Design Of Antennas For Smart Watch Applications

Wearable computer,as the new generational electronic instrument,had an explosive development form 2012 when Google released Google glasses,and more and more companies and researchers devote themselves to the exploitation and research of the smart wearable device.Kinds of wearable device come into the view of people like VR glasses,smart watch,smart wristband and so on.Smart watch,as the outstanding one of the wearable device,attracts attentions of most people because of its novel and individual functions.In the smart watch,normally has a powerful CPU and the system is very perfect also,these make it has the ability of communicate with the network and the real person.So the antennas as the bridge of communication play a key role to the functions of the smart watch to come true.As we all know,the size of the smart watch is much smaller than the smart phone,it makes the antennas design difficult and challenging.In this dissertation,for wireless communication and mobile communication,a frame-integrated loop MIMO antennas and a PIFA-based GSM antenna for smart watch applications are designed respectively based on the basic theory of antenna and the key technology of the antennas design.The specific research contents are summarized as follows:For wireless communication system,mainly design a Wi-Fi MIMO antenna for smart watch applications.First,a frame-integrated MIMO antenna based on a simple loop antenna is designed.The antenna has a compact structure for fabrication and integration.After optimization,we can see the-10dB impedance bandwidth can cover the 2.4G UHF ISM band and the isolation coefficient is below-20dB in the 2.4G band.Taking into account the 802.1 In protocol,a dual band MIMO loop antenna is designed.The antenna has three resonances through modifying the direct feed to a coupling feed.We found the 10dB impedance bandwidth can cover the 2.4G and 5G ISM bands and the isolation coefficient is below-15dB.For mobile communication system,mainly design a dual band PIFA antenna for GSM operation and a single band antenna for GSM 900 application.In the beginning,there is a short introduction of the PIFA antenna,and then design a dual band antenna for smart watch applications.The antenna has a simple structure and can be summarized as a couple of twoPIFAs.In order to present a good feeling to the readers,it introduces the design procedure of the antenna in detail.Through the parameter analysis,the principle and structure of the design are given step by step.According to the results given by the simulation software,the physical model of the design is fabricated and tested in the anechoic chamber,and the measurement results are found anastomotic of the simulation results.The results show the-6dB impedance bandwidth can cover the GSM 1800 band as expected,but the bandwidth is not enough in the GSM 900 band and is only 15MHz approximately.In addition,the SAR values of the antenna shown in the simulation software are below the limiting value.In the end,a tunable technology using the capacitor loaded in the structure of the antenna is provided to resolve the problem of the band insufficient.The tunable technology is realized by a continuous adjustment of the capacitor to make the low band of the antenna continuous changed without influence the high band.Because of the narrow band of the PIFA antenna and the abuse of the tunable band,we design a GSM 900 band antenna for smart watch applications.This antenna use the reaction of two metal patches to excite a new mode,this new mode can effectively cover GSM 900 band.For adjust the input impedance of the antenna,we use a match network to make the antenna bandwidth to attain 88MHz,this make the antenna cover the GSM 900 band easily.