A passive harmonic reradiator tag for animal tracking

Abstract

Low power sensor nodes distributed over a large geographical area provide an economical way to collect environmental information. The sensors can utilize backscatter signals to communicate with a central node without significant power consumption. Each sensor can modulate its reflected backscatter signal by switching a load on the sensor antenna. This allows design of low power sensor nodes with longer lasting battery life. The nodes can be built to reradiate a harmonic of the received signal. This helps to avoid interference at the central node from reflection from unwanted objects. A passive harmonic reradiator is designed in this project to receive a 915 MHz electromagnetic wave and reradiate at 1.83 GHz. The design consists of receiver antenna, transmitter antenna, a Schottky diode, and matching network. Simulation and measurement results are provided. The results show promising characteristics for the use of the device to track animals in wild life.