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Wearable antennas have an enormous potential in future welfare, healthcare, and childcare applications. These applications require the antenna to be an integral and unnoticeable part of clothing and to be able to endure different environmental conditions and repeated washing. We manufactured UHF RFID tags by screen printing polymer thick film ink antennas on two different fabric substrates and tested...
Bodyworn tags are a challenging application for radio frequency identification (RFID) systems. The importance of this application will increase in the future due to emerging novel wireless identification and sensor systems. In this paper, a literature survey of wearable RFID tag antennas is presented. One-layer and multilayer tags are compared. The body effect on antenna parameters is analysed. Based...
Commercial snap-on buttons are used in a coaxial-to-microstrip transition. The reflection properties of the transition are examined in time and frequency domains. Snap-on buttons are usable in wearable antenna connections in a frequency range up to three gigahertz.
A plaster antenna for 2.45 GHz applications is presented. Measurement results for different use cases are given, and bending effects are examined. The proposed structure exhibits a 6 dBi on-body gain, and covers the 2.4-2.5 GHz ISM band in all use cases. The effect of bending the antenna on the SAR has been investigated by simulations. The antenna is suitable for medical applications.
Commercial plaster material (polyacrylate) is used as an antenna substrate. Two 2.45 GHz patch antennas are introduced, both designed to be attached directly to the skin. Measured efficiencies are 70 % in free space and 60 % on-body. Measured on-body gains of each antenna are 6.2 and 1.4 dBi. Simulated 1 g specific absorption rates (SAR) of the two antennas are 2.3 W/kg and 1.6 W/kg using 1 W input...
The effect of a human body near one-layer GPS antennas has been studied with the help of measurements. In general, to avoid changing the input impedance, the user and the antenna need to be separated by lambda/2pi. In contrast, antennas with a ground plane may be satisfied with a separation of 1 cm or few millimetres. The radiation efficiencies of the measured antennas at a 3-cm separation are only...
The effect of antenna bending on return loss, impedance bandwidth, and radiation pattern is studied, taking four antennas as examples. These include a patch, slot, inverted-F, and dipole antenna. Some of them exhibit circular polarization and one is broadband. Impedance is seen to be fairly constant regardless of bending, though if circular polarization is excited by careful antenna shaping, the circular...
The effect of human body on wearable 100 MHz antennas is studied by measurements. At that frequency, the body is very thin compared to the wavelength, but about half a wavelength tall. Antenna performance is most affected by the posture of the antenna wearer, second matter being antenna position on body. Physical traits of the wearer have only a slight effect on the antenna performance. A ??13 dBi...
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