New types of antennas are able to establish a connection to a satellite from an airplane and maintain it during the flight. Thanks to their extremely flat design, installation in the outer skin of the aircraft can save a significant amount of fuel compared to conventional solutions.

On closer inspection, airplanes have a hump at the top of the fuselage. The antennas for communication via the satellites in space are concealed under this bulge. This protective cover is called a radome. Using satellites from an airplane is no easy matter, as the plane moves and still has to maintain contact with the satellite. Until now, this has been done with antennas that are tracked mechanically. This is done in the same way as with movable satellite antennas, whose round dishes are installed on millions of houses to receive radio and television stations. The Institute of High-Frequency Technology (IHF) at Hamburg University of Technology is now breaking new ground and conducting research on the BANG (Broadband in Aviation - Next Generation) antenna project, which is being developed with the support of Lufthansa Technik. The supervising professor Arne Jacob explains how it works: "We are building the antennas from many very flat individual antennas. The modular design of the antenna makes it possible to replace individual modules and simplifies maintenance."

Fast internet while flying

In future, it should be possible to use them to make phone calls and be online during a flight. "This takes place on board via electromagnetic waves, at frequencies of several tens of gigahertz, at which the waves are not visible," says Prof. Jacob. "The task of antennas is to bundle these waves. You can think of it like the beam of a flashlight. And this beam - also known as the antenna lobe - is no longer directed mechanically, but electronically at the satellite." Such antennas (phased arrays) no longer have anything in common with conventional antennas. They consist of many small individual antennas, which in turn are assembled into modules about one centimeter thick. And they also work completely differently: each of these small antennas transmits or receives the same signal, but with a tiny time delay to its neighbors. This time delay is now set so that the waves constructively overlap in the desired direction. Because this is done electronically, the antenna lobe generated in this way can be tracked quickly and flexibly. Continuous transmission and reception is now possible without moving the antenna mechanically.

New technology saves fuel

"We want to carry out the first measurements on our demonstrator at our project partner Lufthansa Technik soon," says Prof. Jacob. The demonstrator is still much smaller than the real antenna that will one day be installed in the aircraft. It initially only consists of a single five by five centimeter module. Overall, however, the entire electronic antenna will be no larger than 0.25 square meters and particularly flat - so that the hump on top of the aircraft's outer skin will no longer be 35 centimeters high, but only a few centimeters. That doesn't sound like much, but it means considerably less air resistance for an aircraft. And therefore significantly lower fuel consumption. With the same aim, the transmitting and receiving antenna are to be integrated into an aperture in order to reduce the footprint and weight. For the demonstrator module, this means that eight of its antenna elements can transmit and receive and eight others only transmit. The modular design also makes the antennas safer to operate. With electronically controlled antennas in the aircraft, the frequent statement: "Unfortunately, I have no reception at the moment" should no longer occur.

More information

More information is avalaible on the website of the Institute of High-Frequency Technology