In modern aircraft, a wide variety of antennas are needed for essential functions like navigation, communication systems, instrument landing, and radar altimeter.
These antennas, often numbering between 20 and 70 on military aircraft, significantly increase aerodynamic drag and fuel consumption [[2]].
At each antenna the current from the transmitter passes through a phase shifter device which are all controlled by a microprocessor (computer).
By controlling the phase of the feed current, the nondirectional radio waves emitted by the individual antennas can be made to combine in front of the antenna by the process of interference, forming a strong beam (or beams) of radio waves pointed in any desired direction.
In a conformal antenna, they are mounted on a curved surface, and the phase shifters also compensate for the different phase shifts caused by the varying path lengths of the radio waves due to the location of the individual antennas on the curved surface.