A Multiple Antenna System Design for Wearable Device Using Theory of Characteristic Mode

Abstract

In this paper, a wearable three-antenna system aiming for cellular Internet of Things (IoT) applications is proposed. The presented antenna system consists of two cellular antennas (LTE low-and mid-band antennas) and one GPS antenna designed by using the Theory of Characteristic Mode (TCM). Both the simulated and measured results with good agreements are provided in this work. As a result of successful excitation of chassis modes, the proposed cellular antennas can cover the desired cellular bands between 699-862 MHz and 1710-2155 MHz with corresponding wideband matching circuits. Meanwhile, the proposed GPS antenna operates with a good right hand circular polarization (RHCP) performance (at least 5 dB higher gain than left hand circular polarization (LHCP)). Reasonable isolation performances among three antennas are also gained due to utilization of orthogonal modes. The results also show that with the proximity of human body (wrist phantom), over the wideband operation bands all antennas can achieve good efficiency. The averaged levels of-10 dB,-6 dB, and-4 dB, respectively for LTE low band, mid band and GPS band are achieved, indicating its potential in future wearable cellular IoT applications. Index Terms-wearable antenna, Theory of Characteristic Mode (TCM), small mobile terminal antenna, wristband antenna I.

Printed GNSS and Bluetooth Antennas Embedded on Flexible Low Loss Substrates for Wearable Applications

“…In addition, the antenna pattern in the phi90 cut changed away from the hand towards 0 degrees, but the pattern is not as symmetric as the phi0 cut due to the position of the hand. A common location for a GNSS antenna is the device itself, which provided −4 dB gain in [7]. The radiation patterns on the body are similar to what is measured here.…”

“…The SEBS (TC9) flexible substrate material improves the efficiencies of both the GNSS antenna by 1.6 dB and Bluetooth antenna by 2.2 dB. Compared to [4][5][6][7][8][9][10][11], the current improvements are remarkable for replacing previous printed circuit board materials with molded polymers in which the loss levels are very competitive. Antenna radiation patterns were measured in a Satimo Starlab system in free space and the axis cuts are presented in Fig.…”

“…Typical antenna systems in wearable devices consist of dual or multiple band antennas. Two cellular antennas, LTE low and mid-band antennas and one GNSS antenna operating at 699-862 MHz and 1710-2155 MHz are presented in [7]. The polarization performance of the GNSS antenna was 5 dB higher for the right-hand circular polarization (RHCP) than the left-hand circular polarization (LHCP).…”

“…The device had a reasonable isolation between antennas and efficiencies of −10 dB, −6 dB, and −4 dB for the LTE low band, mid-band, and GNSS band [7]. In addition, four-band antenna structures were presented providing radiation efficiencies of −6 dB at 810-960 MHz, −2 dB at 1370-1450 MHz, and −2 dB at 1710-1630 MHz for LTE/WCDMA bands and −1 dB for the ISM band in the free space environment.…”

A Compact Four-Port Coplanar Antenna Based on an Excitation Switching Reconfigurable Mechanism for Cognitive Radio Applications

“…The high isolation characteristics of the proposed antenna are realized by designing the UWB antenna as an electric source and the NB antennas as magnetic sources. This results in a fundamentally orthogonal design [27][28][29][30][31] (orthogonal characteristic mode).…”