NASA’s Glenn Research Center is implementing a unique type of antenna technology to improve space communication by decreasing cost and increasing power efficiency. At Glenn, the Antenna Microwave and Optical Systems (RCA) Branch is developing a Ferroelectric Scanning Reflectarray Antenna.

Thin film ferroelectric phase shifter.

Since the late 1990s, Glenn has pioneered microwave applications of ferroelectric films. (A ferroelectric material can be polarized by applying a direct current electric field to it). Under their current project, Glenn is performing the design, device lithography, array assembly, and device/array characterization of the reflectarray antenna. Neocera Inc. (Beltsville, MD) has provided them with the films for the antennas.

Ferroelectric reflectarray concept.

The reflectarray is a more preferred alternative to Gallium Arsenide-based Monolithic Microwave Integrated Circuit-based phased array antennas. As a compound semiconductor, gallium arsenide is rare and expensive. Its high power consumption also makes it a less than ideal candidate for antenna applications.

615 element, 19 GHz reflectarray prototype (array diameter = 28 cm).

Conventional phased array antennas that are large enough to support high data rate communication at high frequencies are difficult to build and transport to space. Electronic beam steering directs the signal in a specific direction without physical motion, therefore causing no vibrations. The reflectarray surface is illuminated by a feed antenna, just like a parabolic reflector, thereby eliminating the need to distribute the energy to the individual antenna elements via transmission lines.

Since the instruments onboard the spacecraft are highly sensitive, eliminating potentially resolution-compromising vibrations is very beneficial. Even rapid electronic beam steering can be performed without affecting the sensitive equipment.

The use of the reflectarray for fine beam pointing is vital for future exploration missions to Mars and beyond where precise, efficient communication is necessary. This antenna technology offers a reduction in cost and an increase in efficiency – each estimated by a factor of 10.

Glenn’s RCA Branch has already tested a prototype reflectarray and hopes to perform a space experiment by 2012. Other space applications for reflectarray antenna technology include using it to improve radar detection of orbital debris and improve rendezvous and docking maneuvers of the spacecraft. Reflectarrays may also be used to develop collision avoidance radar systems for cars.