A 915 MHz Wristwatch-Integrated Antenna for Wireless Health Monitoring

A compact 915 MHz antenna integrated within a wristwatch wireless sensor device is presented. The antenna is a variant of a planar inverted-F antenna (PIFA) and uses a dual-resonator configuration. The results of simulation and measurement are shown to be in good agreement with the antenna exhibiting desirable impedance and radiation characteristics together with low Specific Absorption Rate (SAR) performance. The antenna is fabricated using a low cost flexible printed circuit and is fully integrated into the watch device. Measurements on the prototype antenna show a –10 dB impedance bandwidth of 30 MHz, a peak realized gain of –4.9 dBi and a peak radiation efficiency of 15.9% at 915 MHz. The antenna also has a low SAR value of 0.003 W/kg making it suitable for a wide range of wrist-worn wireless applications.