Design of a 2×2 antenna-array RF power emitter with object detection function for sensor location identification

In this paper, we propose a 915 MHz RF power emitter integrated with a 2×2 patch antenna array and four switchable reflection-type phase shifters with nominal phase delay of −90°, 0°, or +90°. For achieving the object detection function, a centered harmonic antenna at 1830 MHz is also integrated to identify the location of sensor by receiving the harmonic wave reflected from the sensor. In our experiment, a harmonic tag formed by a dual-band Yagi-Uda antenna and a loaded diode is developed to emulate a sensor with rectification for energy harvest. By beam scanning and detecting the maximum reflected power increment, the location of the harmonic tag can be identified successfully at a distance within an angle of+25°.