Study And Application Of Receiver Rectifier Antennas

The wireless network of telecommunication has been well developed. People have searched for some ways to obtain the energy from nature resources, such as thermal effect, mechanical vibration, photovoltaic cells, and electromagnetic energy receiver. These methods have provided efficient and practical solutions to consumer, industrial and military needs. Taking into account the impact of external environments and the constraint on natural conditions, the reception of the microwave energy has been introduced by the usefulness of wireless devices as well as the potential range of applications.In recent years, the current trend in commercial and military communication systems has been to develop low cost, light weight rectennas (rectifier antenna) which are capable of capturing the microwave energy from surrounding environments and converting the power into DC energy with a high performance over a large spectrum of frequencies. Then wireless devices are supplied by relatively advancements in the rechargeable battery technology. With a simple configuration, the microstrip circuit is fabricated by the printed circuit board technology. Moreover, the shape and the operating mode of antennas are determined in terms of operating frequency, polarization, radiation patterns and equivalent impedance. The first rectenna consisted of a half-wavelength aluminum coupling pole antenna and a bridge Schottky barrier diode rectifier. It obtained a good conversion efficiency at 2.45GHz. The research of rectennas has been done in both domestic field and foreign countries.By using the simulation softwares Agilent ADS and Ansoft HFSS, this study is to design a microwave rectenna system able to support low and high power levels at an ISM frequency of 2.45GHz with a good efficiency of rectifying operation. And the performance of rectennas has been tested by a vector network analyzer and optimized by mechanical methods. We present an approach of "multiple parameter sweeps" for the matching circuit design at multiband frequencies and a wide span of the input power. This method is based on S parameter simulation at the operating frequencies. The sweeps of several parameters are combined into a hierarchical sweep plan. Due to the nonlinear performance of diodes, the input impedance changes with the variation of input power levels. Then the input impedance matching depends on both the nonlinear behavior of diodes against the input power and the operational frequency affecting the electromagnetic field distribution on transmission lines. However, the analyses on a variety of matching circuit configurations bring more evidence to improve the overall performance of rectifiers. This method has applied in a low cost, zero-bias Schottky diode rectifier having a RF-DC conversion efficiency of 55% with the output DC voltage (11V) and the output DC power (148mW). A hierarchical simulation of the rectifier circuit and an analytic description of multiple dimensional parameters are the key to study the relationship between the nonlinear performance of a rectifier and its matching circuit. This study should be useful for further microwave energy harvesting designs.