Gogo Inc. recently completed a series of flight tests with its Ku-band satellite technology, part of its new wireless broadband system for commercial aircraft, which delivers high data rates to passengers traveling not only over the equator, but also in higher latitudes. The tests validated the coordinated pair of mechanically phased array antennas that serve as the foundation of the system.
The new technology is significant because it accounts for the disadvantages of electronically and mechanically steered antennas that have been traditionally used to provide broadband service to airlines. Gogo’s technology, 2Ku, is built around two beam-forming antennas: one designated for transmitting data, and another for receiving signals from more than 180 compatible Ku-band satellites. The company says that that the dual antennas are symmetrical in design and, because of their large aperture area, have significantly higher spectral efficiency than other in-flight broadband antennas.
The antennas were designed by ThinKom, an antenna design company based in Torrance, Calif. that provides technology for aerospace and other mobile communications. The antennas are unique in that they create beams by mechanically rotating a series of internal plates with precise resonance characteristics. Although the internal disks are moved mechanically, the antennas are not pointed directly at the satellites. Instead, slight changes in the plate position adjust the scan angle in elevation and azimuth direction, according to a patent filing from ThinKom.
The antennas themselves are based on Variable Inclination Continuous Transverse (VICTS) arrays. VICTS were first developed by Raytheon Corp. with research support from ThinKom, MIT, and the Air Force Electronic Systems Center in 2006. The ThinKom version “involves the simple rotation (common and differential) of two coplanar plates, one comprised of a one-dimensional lattice of continuously radiating stubs, and the second one comprised of one or more static line sources,” according to a white paper published by Gogo and ThinKom.
What separates the 2Ku system from more conventional aerospace antennas is that it combines technical benefits from both electronic phased arrays and mechanically steered antennas (including reflectors and flat panels). Like electronic phased arrays, the 2Ku antennas support the highest data rates over the equatorial region, where the maximum area of the antenna plate is facing the satellite. In contrast, flat panel and reflector antennas struggle with interference caused by high skew angles near the equator. They are forced to compensate for this interference by lowering their transmit power, which reduces data rates to the aircraft.
