The 7-inch-high-by-14-inch-wide antenna performed so well that only one flight test was needed to determine its effectiveness, said Capt. Jeff Zhu, the Air Force program manager. This first iteration of the Advanced Multiband Communications Antenna System was designed to enable crewmembers aboard various Air Force platforms to receive satellite transmissions from the Military Strategic and Tactical Relay satellite, known as MILSTAR, in the extremely high frequency mode, or EHF. The ability to receive and ultimately send messages in the EHF domain is important for several reasons, Captain Zhu said. As it uses a much narrower beam than ultra high frequency, or UHF, EHF provides significantly lower probability of detection and interception. It also provides much higher data transmission rates — about 1.5 megabits per second in this case — than UHF.
“The higher data rate is especially important to intelligence, surveillance and reconnaissance platform operators who have a lot of detailed information that they need to send and receive quickly,” Captain Zhu said. The antenna’s small size makes it a “low profile” and exhibits very low aerodynamic drag, Captain Zhu said. That increases an aircraft’s ability to spend time on station. While not small enough to enable fighters to receive EHF satellite transmissions — a future effort may accomplish that — this antenna will fit multiple Air Force platforms, including the E-3 AWACS, E-8 Joint STARS, and RC-135 Rivet Joint. In addition to its compactness and EHF capabilities, the antenna can be “skin mounted” onto an aircraft, meaning it attaches easily with no need to modify the aircraft structure or remove the platform’s top metal layer. This is far less intrusive, and less expensive, than large radome mounting, and it reduces the amount of time the platform spends offline.
The team conducted the flight testing aboard a special 707, known as the Paul Revere, on a prescribed route between here and the southern New Jersey shore. The flight route included both straight, level flying and “highly-banked racetrack loops” that demonstrated the antenna system’s ability to function over a wide range of satellite look-angles, the captain said. AMCAS has been under way for four years. During that time the team held a competition among industries that resulted in four concept studies. After some additional evaluation, two were brought along to the testing phase. The product successfully tested this summer is Raytheon Corps‘ entry. Another by Thinkom Inc. is still being refined and will also be evaluated within a year. With the technology available, platform managers will have to decide how and when to incorporate it. That process needs to start now though, as managers consider their program objectives memorandum submissions, Captain Zhu said. “We want to make sure they know the capability is going to be available, so they can start planning to take advantage of it,” he said. The program team will now turn much of its attention to a compatible antenna, with the same size dimensions, that will allow operators to transmit within a frequency range covered by the Ka band. That effort will be followed by another designed to produce a transmit unit in the higher EHF band. (Source: Chuck Paone, 66th Air Base Wing)
