Differentially-fed Omnidirectional Circularly Polarized Patch Antenna for RF Energy Harvesting

A differentially-fed omnidirectional circularly-polarized antenna is investigated for application in RF energy harvesting. The antenna is composed of a two-layer substrate and back-to-back printed square patches which have two diagonal stubs and one truncation. The patches share a common ground plane. Both patches generate circular polarization (CP) and omnidirectional CP is provided. The antenna provides an axial-ratio bandwidth of 20 MHz from 2.43 GHz to 2.45 GHz. In order to measure the proposed differentially-fed antenna, a feed network connected between the SMA port and differential port is designed. Furthermore, the combined configurations with the proposed antenna, bandpass filter and rectifier can be built and convert the electromagnetic field to DC. The measured output voltage is 255mV at 2.40GHz.