Rectenna Arrays for Recycling Statistical Broadband Radiation

This paper discusses a study of rectification of broadband statistically time-varying low-power microwave radiation. Polarization, spectral content and power levels of incident radiation of the array are allowed to vary randomly over a broad range. The applications for this work are in wireless powering of indoor industrial sensors, sensor arrays in areas of low solar radiation, and recycling of ambient RF energy. A 64-element dual-polarized spiral rectenna array is designed and characterized over a frequency range of 2-18GHz. In the design, nonlinear harmonic balance simulations are combined with full-wave field analysis. The nonlinear simulations are compared with source-pull diode nonlinear measurements in order to establish a reliable design methodology. The rectifier diodes are directly matched to the antenna over a broad frequency range and a large range of input power density levels from 10-5 to 10-1 mWcm2. This eliminates matching and filtering circuits, thereby maximizing effective area. The rectified DC power and efficiency are characterized as a function of DC load impedance and DC circuit topology, polarization, incident power density, and incidence angle.