Integrated solar array and X-band RF communications system. The device is approximately 9 cm2 (3 cm by 3 cm) and consists of six photovoltaic cells connected in series and four X-band patch antennas.
Several advancements were made in integrated photovoltaic and communications technology this year. In the first, NASA Glenn Research Center’s Photovoltaic Branch, in collaboration with Glenn’s Antenna, Microwave and Optical Systems Branch and personnel from the Naval Research Laboratory demonstrated photovoltaic (PV, or solar cell) technologies integrated with radiofrequency (RF) and optical communication technologies. The PV-RF-optical communications demonstration (see the preceding photograph) consists of a high-efficiency monolithic multijunction solar array (indium-galium-phosphide/gallium arsenide, InGaP/GaAs) integrated with X-band RF patch antennas. The electrically insulating semiconductor substrate used to fabricate the solar array structure also serves as the dielectric spacer between the coplanar RF waveguide feed network, which is deposited on the rear surface, and the patch antenna elements located on the front surface. By altering the geometry of the feed network on the rear surface, one can alter the radiating pattern to radiate in any direction needed. Thus, a large solar array could be composed of various patch antenna sections, each designed to radiate in a particular direction. A simple RF switching network would be all that was required to effectively steer the beam. Another application of this integrated technology is in miniaturized antennas for surface-to-surface or distributed systems technologies, whereby a miniature package could contain power generation and RF communications, as well as a variety of sensor or functional capabilities.
The second advancement, a partnership of researchers from Glenn and the Naval Research Laboratory, demonstrated a matchbook-sized system consisting of a solar array and a modulating retroreflector (MRR) optical communication system (see the next photograph). The MRR technology (developed at the Naval Research Laboratory) operates by modulating a reflected laser beam, thereby encoding data. Thus, to communicate via the MRR, an interrogator directs a laser beam (1550 nm in this example) onto the MRR. An optical corner cube reflects the incident beam back to the interrogator. A semiconductor modulator in front of the corner cube alternately transmits or absorbs the reflected beam. The demonstration device transmitted a digital identification code at a 100-kHz data rate while consuming 3.5 mW of power. With the addition of a supercapacitor for energy storage, the system was capable of extended operation in the absence of sunlight. The battery shown in this photograph is included only as a size reference.
Matchbook-sized solar-powered MRR demonstration. The battery was added for scale purposes only.
For the third advancement, Glenn developed a PV device capable of generating the required electrical power from the probe laser beam used to interrogate the MRR. The device (see the final photograph) consists of four PV arrays connected in parallel, with each array tuned to efficiently convert 1550-nm laser illumination into electrical energy. The MRR resides beneath a1-cm-diameter aperture in the center of the wafer.
1550-nm-laser-power converter.
Last updated: October 7, 2006
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