Self-harmonics suppression rectenna for wireless power harvesting

Abstract

The development and analysis of several designs of self-harmonic suppression rectenna for the wireless power harvesting system are presented. The purpose of self-harmonic suppression rectenna is to eliminate the using of a harmonic filter circuit in filtering the harmonic radiation and electromagnetic interference (EMI) in rectenna system. The motivation for this work has been inspired by the need for compact size, low cost, high efficient rectenna system and also very important is the design structure is simple in order to reduce the error during the fabrication process. In the response to these challenging demands, four designs of self-harmonic suppression microstrip patch antenna have been simulated, fabricated, measured and analysed. Two designs can be classified in linear polarization while the other two designs exhibit the circular polarization properties. The technique to suppress the harmonics which have been introduced are the slits, slot and notch at the patch structure and an open stub at the microstrip feeding line. Also, a defected ground structure technique is applied to reduce the size of the patch antenna. The perturbation technique has been introduced to the basic rectangular and circular shapes microstrip patch antenna to produce circular polarization property. As a result, the rectangular shape becomes a nearly-square shape, while the circular shape becomes an elliptical-shape. Subsequently, a dual polarization of circularly polarized property is also proposed. To obtain high output voltage, a self-harmonic suppression microstrip patch array antenna is developed. For conversion of RF-to-DC signal, a few designs of rectifier circuits are proposed. The proposed rectifier matching networks are capable to provide a good impedance matching with a wide range of incident power. All the simulation has been done by using CST Microwave Simulator and Advanced Design System (ADS). To validate the theory and simulation, the prototypes of all designs have been fabricated and measured. For the comparison, the prototype of the conventional linear polarization (LP) rectangular and circular microstrip patch antenna are also have been designed and fabricated. The measurements show an excellent result and is in line with the simulated result. The measured of the return loss of the antennas show it resonate at the fundamental frequency, while at the harmonic frequencies, the magnitude of the return loss were suppressed successfully. In the wireless power harvesting system experimental work, it is seen that a significant improvement of the output power is achieved compared to the reference antenna without harmonic suppression. All design has been realized by using a standard PCB process. Therefore, the fabrication technique is very simple with a very cheap cost, thus it can be conveniently mass-produced.