Antennas For Smart Watches

Wearable wireless communication devices need to be worn directly on human body orintegrated into a user’s clothing or accessories. Nowadays, the study of wearable smartdevices has turned to commercial applications other than concepts, e.g., Google glasses,navigation shoes, smart wristbands, smart watches, etc. The smart watches can be connectedto the Internet through mobile phones. In this way, the messages can be input to the smartwatches. Moreover, the portability and wearable properties of the smart watches attract peopleto increase the functions of smart watches. For example, the smart watches are required toconnect to wireless networks directly without a mobile phone, even replace the mobile phonesin some special situations. Antenna is one of the key components for a smart phone. Thisthesis investigates some new antenna structures for smart watch applications.In Chapter2, we explore the dielectric substrate suitable for wearable antennas, theelectromagnetic properties of human body and the related performance of the antenna when itis placed on the human body. The key technologies for antenna miniaturization andmulti-band or broadband operations are introduced, which are helpful for the design of anantenna based on watch strap.In Chapter3, a small antenna composed of a number of meander strips is proposed forsmart watch. The antenna has a miniaturized structure, the size of the antenna is40mm136mm, which is similar to an ordinary watch. The antenna can achievemulti-broadband operation. Five operating bands for VSWR3(return loss6dB) cover870-990MHz (12.9%),1530-1610MHz (2.5%),2050-3230MHz (44.7%),3350-3770MHz(11.8%) and4090-6850MHz (50.5%).In Chapter4, the performance of the smart watch antenna proposed in Chapter3isinvestigated when it is conformal to a wrist. The shape of a human wrist and the shape of thewatch worn on the wrist are modeled using a ring of nine rectangular planes. The conformalantenna is printed on three rectangular planes at one side of the ring. The antenna achieves sixfrequency bands:0.93-0.94GHz,1.48-1.61GHz,1.93-3.23GHz,3.4-3.76GHz,4.02-6.17GHzand6.36-6.69GHz for VSWR3, which cover the GPS (1.575-GHz), WiMAX and WiFibands. The influences of the different curvatures of the substrate on the conformal antenna arealso investigated, providing a technique support for the practical applications of the smartwatch antennas. In Chapter5, the performance of the watch-strap-based smart antenna is investigatedwhen it is worn on human wrist. The simulation model of the human wrist is a simplifiedstructure, which consists of skins, fats, muscles and bones. In order to avoid the direct contactof the ground plane of the antenna with the human body, a layer of foam between the antennaand the human wrist is introduced. The simulated results of the proposed antenna worn on thehuman wrist are presented. Six frequency bands for VSWR3are achieved, covering0.78-0.89GHz,1.42-3.22GHz,3.35-3.85GHz,4.05-4.36GHz,4.55-6.15GHz and6.25-6.61GHz. It is confirmed that the proposed antenna is suitable for use as a smart watchantenna for wireless communications.