Abstract
Flexible wearable wireless devices have found practical uses as their cost has fallen and Internet of Things applications have gained further acceptance. These devices are gaining further use and acceptance in the consumer and wearable space for applications such as logistical tracking and maintaining sensor information, including temperature, humidity, and location. In such applications, antennas are exposed to bending and crumbling. Therefore, flexible substrate antennas for use with polymer-based flexible devices are an important area of research that needs to be addressed. In this study, the bending capabilities of flexible polymer substrate antennas for general IoT applications were practically analyzed by fabricating flexible antennas on Polyethylene Terephthalate (PET), Polytetrafluoroethylene (PTFE) Teflon, and Polyvinylchloride (PVC) substrates operating at 2.45, 4.45, and 7.25 GHz frequencies. The basic premise was to investigate the flexibility and bending ability of polymer materials, and their tendency to withstand deformation. In the current paper, we start by providing an equivalent model for the flexible microstrip patch antenna under bent conditions, followed by outlining the process of designing flexible antennas on polymer substrates. Finally, the fabricated flexible antennas were tested in an anechoic chamber for various radiation characteristics such as reflection coefficients, operating frequency shifts, and impedance mismatch with the transmission line, under bending conditions up to 7 mm. The practical outcomes were then compared with our recent investigation on flexible polymer substrate antennas for wearable applications. This study provides a means to select a suitable polymer substrate for future wearable sensors and antennas with high bendability.
Highlights
Flexible wearable wireless devices are gaining significant attention because of their characteristics of light weight and low cost, low power consumption, high flexibility combined with robustness, and compact size. These wearable devices have become essential for many wireless applications. Flexible sensors such as antennas and RFID tags have been designed for WLAN, GPS, military, and biomedical related applications [1,2,3,4,5]
To conduct the measurements, testing was performed in a Frankonia anechoic chamwith a frequency range of 30 MHz to 40 GHz at a measuring distance of 3.0 m
The chamber provides excellent RF-Shielding, of less than 90 frequency range of 1–40 GHz, which is typical for the pan-type module made of 2.0 mm dB for the frequency range of 1–40 GHz, which is typical for the pan-type module made galvanized steel; see Figure 8 Vector Network Analyzer (VNA) was used inside the Frankonia anechoic chamber
Summary
Flexible wearable wireless devices are gaining significant attention because of their characteristics of light weight and low cost, low power consumption, high flexibility combined with robustness, and compact size. When subjected to stretching, folding, or twisting, these types of antennas become permanently deformed, if not broken, which renders them incompatible for applications that require high flexibility/bendability and are subject to this continuous deformation It is very important for the flexible sensors to be lightweight, small, 4.0/). To conduct the measurements, testing was performed in a Frankonia anechoic chamwith a frequency range of 30 MHz to 40 GHz at a measuring distance of 3.0 m. The chamber provides excellent RF-Shielding, of less than 90 frequency range of 1–40 GHz, which is typical for the pan-type module made of 2.0 mm dB for the frequency range of 1–40 GHz, which is typical for the pan-type module made galvanized steel; see Figure 8 VNA was used inside the Frankonia anechoic chamber.
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