Abstract: In a doppler VOR, a plurality of antennas (1) are arranged equidistantly on a circle (20). Two opposite antenna pairs on the circle are simultaneously activated by a commutator (13) in a manner to simulate as uniform a rotation of two opposite antennas as possible. Reciprocal power dividers (12) are disposed in the lines (15) between the commutator and the antennas. They couple out a given portion of the transmitter signal and transfer it to the two next antennas but one (I, V) in relation to an active antenna (III). These two antennas (I, V), the active antenna (III), and the two intermediate antennas (II, IV), which act as parasitic elements, form an antenna group. Since two adjacent antennas are active simultaneously, two antenna groups are active simultaneously. Their radiation patterns are approximately elliptical.

Abstract: In a Doppler VOR, the phase of the carrier wave of the carrier signal must lie symmetrically between the phases of the carrier waves of the sideband signals. To monitor these phase relationships, the carrier signal received by the sideband antennas (1) is applied to two mixers (14, 15) which are also fed with fractional signals of the upper and lower sidebands, respectively. The mixer output signals are applied to a phase comparator (16) whose output signal has a predetermined value corresponding to the prescribed phase relationships. The output signal of the phase comparator (16) is compared with a reference value in a monitoring facility (19).

Abstract: To isolate adjacent elements of an antenna array from each other, each feeder contains a power divider with four terminals, two of which are connected to the power dividers associated with the adjacent elements. The power dividers feed r.f. energy to the inactive elements in such a way that the latter no longer act as parasitic elements. The r.f. power dividers are so designed that three is a mismatch when looking from the antenna toward the power divider. This gives a further improvement in the isolation between adjacent antennas.