Effect of small wearable device antenna location on its impedance, bandwidth potential and radiation efficiency

Abstract

In this paper, a simulation study of the effect of antenna locations on antenna matching, bandwidth potential and radiation efficiency performance operating in 3GPP Long Term Evolution (LTE) Band 3 (1710-1880 MHz), Band 20 UL (832-862 MHz) and 2.4 GHz WLAN band (2.4-2.5 GHz), in free space and with phantom, is presented. An inverted F antenna (IFA) is utilized in this study and mounted on a small cellular wrist device. The results indicate that for each band, with efficient excitation of its fundamental mode, an antenna whose electrical field maxima located at short edge of the chassis always has higher bandwidth potential and its radiation efficiency will have less reduction when introducing phantom. Moreover, changes in matching characteristic of different antenna positions vary from each band, indicating the optimal antenna placement to obtain robust matching feature. Therefore, by comparing the variations on antenna behaviors, it provides useful insights into how to select the optimal antenna locations on the device with reduced a user effect for a specific operation band.

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

“…In addition, the bandwidth of a radiator is limited by high quality factor Q of the small physical dimension according to [7] and [8]. Although in our unpublished paper [9], a narrow band IFA mounted on the casing is proposed for LTE Band 20 UL (832-862 MHz), an active component, namely RF switch, is further needed to make the antenna tunable so that it can cover all other low operation bands. In turn, the total efficiency performance will be degraded by the insertion loss of the active component.…”

Sub-GHz Wrist-Worn Antennas for Wireless Sensing Applications: A Review

“…One of the earliest Sub-GHz wrist worn antennas was reported in 1984 [71], which was a loop antenna embedded in a wristwatch strap for FM radio reception (88 -108 MHz) [72]. In the past years, this has evolved into diverse forms of antenna topologies, including planar Inverted-F antennas (PIFA) [15], [37], [39], [70], [73]- [80], Inverted-F antennas (IFA) [81], [82], dipoles [83]- [87], monopoles [88]- [90], loops [38], [91], [92], helical antennas [93], [94], spiral antennas [95], and microstrip patch antennas [96]- [99]. In the literature, various Sub-GHz wrist-worn antennas have been reported, with the majority of them accounting for the effects of the human body on antenna performance.…”

“…As summarized in Column C of Table 2, various antenna topologies have been explored for Sub-GHz wristwatch applications, including patch antennas [96]- [99], loop antennas [38], [91], [92], PIFA antennas [15], [37], [39], [70], [73]- [80], IFA antennas [81], [82], dipole antennas [84]- [87], [112], monopole antennas [83], [88]- [90], helical antennas [93], [94], and spiral antennas [95]. Among these, PIFA and IFA topologies are particularly favoured (see Fig.…”

“…Low-loss materials are preferred for optimal performance [117]. • Presence of internal smartwatch components: Many antennas, such as those in [15], [37], [39], [70], [73], [75], [81], [82], [91] are integrated into practical wristwatch devices. The close proximity of internal components to the radiating element can introduce losses and influence the antenna's gain performance.…”