Effects of a phantom hand on a non-resonant element for a 2.5 GHz smartwatch antenna

Abstract

Smartwatches with wireless connectivity are becoming widely used and therefore, antenna engineering efforts are addressed to obtain small and efficient antenna systems. Since the space in a smartwatch is considerably small compared to other wireless devices, a non-resonant element of 12.0 mm × 3.0 mm × 2.4 mm for 2.4–2.5 GHz antenna system operation is proposed herein on a 30 mm × 30 mm ground plane. The ground clearance area is 14 mm × 5 mm, which leaves more space for facilitating the integration of other electronic components in the reduced ground plane area available for this kind of applications. Since the element is non-resonant, a matching network is used to match the antenna system when regarding the presence of a phantom hand.Several distances between the ground plane and the phantom hand are analyzed, from touching position to 6 mm distance. For each case, a new matching has been designed without the need of modifying the geometry of the antenna element. Measured total efficiency is in average (2.4–2.5 GHz) 15.1% for the worst case (touching position) and increases up to 37.0% for the 6 mm case. These results are of practical interest to design smartwatch devices.