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Remote power transmission is very challenging in many areas such as space applications, information technology devices, smart sensor units for remote sensing, smart actuators, micro-aerial vehicles (MAV), flying robots, and space vehicles applications which require autonomous operations. On the contrary of many researches on smart materials, such as piezoelectric, electro active polymers, and many others, the power feeding and control system for smart actuators has not been actively investigated. Most smart material devices and systems use a hard-wire networked control circuit that was the main resource system for power feed and control. Such a power network system imposes a limitation on the devices’ maneuverability under the scenario of mission-oriented moving smart system. In addition, the hard wiring may not be a suitable solution for a multi-nodal system due to the unavoidable network complexity which gives rise to the weight increase by the weight of wired network, the need of complex gate switching of power and control networks, and the needed interdependency of power and control routines.
Rectenna (rectifying antenna) is a combination of an antenna and a rectifier consisting of a Schottky barrier diode, inductor, and a capacitor, which converts microwave power into a DC power. In microwave power transmission, the power delivery method must provide not only sufficient power, but also other relevant issues, such as adaptability on complex structures, flexible configuration, and higher power density for vehicle operation. For the most of motors for MAVs and robots, the high power required for their actuations. Therefore, devices that use wirelessly controlled smart membrane actuators must determine the power modes on top of the requirements for being structurally lightweight, thin and flexible.
Various flexible dipole rectennas and arrays have been designed, fabricated, and characterized over a frequency range of 9 -12 GHz through laboratory testing. The maximum power of 0.45 mW was obtained from a parallel-serial connected rectenna array (10x9). The efficiency of dipole rectenna arrays ranges from 20 % to 50 % depending on the input power and the pole configuration.
Microwave measurement setup (NASA)