The previous experimental results showed that 230 volts of output was obtained from a 6 x 6 array at a far-field exposure (1.8 meters away) with an x-band input power of 20 watts. This result showed a feasibility of using a microwave to power feed and control smart actuators. Based on the previous research reported, we have achieved 500 V output level for practical applications. However, the rectenna has rigid structures that may give a limitation of flexibility of the smart actuators’ system. In order to apply this concept into real applications, the rectennas have to be flexible, so that it could be patched on smart actuators. In this paper, a design concept of various flexible rectennas and their performances in terms of design parameters such as geometry of rectenna will be discussed as well as integration for a system. The performance of flexible designed rectennas as a preliminary experiment will be presented in terms of the input power, output power of the rectennas, various shapes of rectennas in an array for difference applications, and their efficiencies.
Microwave-driven smart material actuators were first envisioned and developed as the best option to simplify the complexity and weight of hard wired networked power and control for smart actuator arrays. A power allocation and distribution scheme (PAD) was originally devised to simplify the wiring of thousands of control cables. The original design was limited to 20 volts, the maximum drain-source voltage of a dual-gate MOSFET used in the circuit. The present research sought to extend the usable voltage range to 200 volts.
The concept of microwave driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard wired control circuitry for applications such as membrane actuators, insect-like flying objects, or micro-aero-vehicles. Accordingly, rectenna technology was adopted to convert power from microwave to DC and run actuator devices. Previous experimental results showed that 230 VDC output was obtained from a 6 x 6 rectenna array at a far-field exposure (1.8 meters away) with an x-band input power of 20 watts. This result showed the feasibility of using microwaves to power feed and control smart actuators. We have tested a 6 x 6 JPL array patch rectenna which was designed to generate theoretical voltages up to 540 volts. The test result indicated that the performance degradation of Shottky barrier diodes on the rectenna array caused the output voltage to drop. Thus, an estimation of output voltage was made to show the performance beyond the previous measurement by extrapolating and correlating the measured data with a 200 W TWT amplifier in a reverse process. The estimated peak output voltage was 515 volts. In this experiment, due to the degradation of the rectenna performance, we had to measure the output performance based on comparison of the previous result of the rectenna output of a 20W amplifier with the output from the 200 W amplifier. For the real applications, the degradation of Schottky diodes will be a critical issue to be resolved in the fabrication process.
The concept of microwave-driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry. Networked rectenna patch array receives and converts microwave power into a DC power for an array of smart actuators. To use microwave power effectively, the concept of a power allocation and distribution (PAD) circuit is adopted for networking a rectenna/actuator patch array. The PAD circuit is embedded into a single embodiment of rectenna and actuator array. The thin-film microcircuit embodiment of PAD circuit adds insignificant amount of rigidity to membrane flexibility. Preliminary design and fabrication of PAD circuitry that consists of a few nodal elements were made for laboratory testing. The networked actuators were tested to correlate the network coupling effect, power allocation and distribution, and response time. The features of preliminary design are 16- channel computer control of actuators by a PCI board and the compensator for a power failure or leakage of one or more rectennas.