A Novel End-shorted Printed Open Loop Antenna for IEEE 802.15 2.4 GHz Wireless Sensor Network Platform Applications

摘要

In this paper, a novel antenna design with a coupling feeding mechanism for WSN applications at IEEE 802.15 2.4 GHz operation has presented and implemented. By adjusting coupling element, impedance matching for RF input 50 ohm can be obtained. By tuning the length of the resonant strip, resonant frequency at 2.4 GHz can be easily controlled. In addition, a novel end-shorting between the end of the resonant strip and the ground plane provide a half wavelength current loop for EM compatibility and small clearance area on main circuit board. The whole dimension of the proposed antenna occupied just only a small area of 16.5 × 2 mm2. The proposed antenna design has excellent performances in bandwidth of 140 MHz @ 10 dB, radiation efficiency of > 50% and omni-like radiation patterns. For the viewpoints in practical WSN application, user’s effects including user’s head and body tissue were discussed and explained. For radiation power absorption, user’s head plays a key role to affect the EM power distribution in radiation efficiency and front/back ratio in free space. As for impedance detuning, body tissue and user’s head both lead to resonant frequency shifting. Further detailed discussions and explanations for the proposed antenna will be explained in Sects. 2 and 3.