Research and design of broadband circularly polarized rectenna

A broadband circularly polarized rectifying antenna (rectenna) for the micro-radio energy harvesting in space, which consists of a radio frequency (RF) energy receiving antenna and a multi-band rectifying circuit is proposed in this paper. The log periodic cross dipole is used to obtain wideband characteristics on the radiation patch of the receiving antenna. At the same time, two pairs of orthogonal crossed dipoles are connected by a curved 90 degree phase delay line, which is aim to achieve the circular polarization characteristics of the antenna. The multi-band rectifying circuit is composed of two single-stage voltage doubler rectifying circuit. A new impedance matching circuit with two branches is introduced to improve the performance and efficiency of the rectifying circuit in parallel. The simulation results show that the impedance bandwidth and the 3 dB axial ratio bandwidth of the receiving antenna are 1100 MHz and 350 MHz respectively. The power sensitivity of multi-band rectifying circuit reaches-35 dBm, and the maximum RF-DC conversion efficiency is up to 76.5%. The measured output voltage of the rectenna is about 139 mV when the radiation intensity is 6.02 μT and the value of load resistor is 700 Ω, so it is suitable for low power RF energy harvesting applications.