Device and method for an antenna array with switchable wide-angle coverage
View Patent ↗In order in simple manner to switchably cover a wide angle in sectors using an antenna array with broad main lobe, an antenna elements are so arranged, that the elements can be individually selected, so that some elements of the array can be operated in-phase and other elements operated in phase-opposition relative to each other. In order to determine the entry direction of a received signal, it is possible to operate the antenna array with non-symmetric antenna diagram, or however also to additively influence the symmetry of antenna characteristic by the use of a supplemental receiver element.
1. A monopulse antenna array comprised of individual antennas for increasing the directional resolution and angular coverage, of which the radiation directional characteristic is characterized by a sum diagram and a differential diagram,
wherein the individual antennas are connected via one or more phase-shifters and one or more hybrid junctions,
wherein the antenna array includes a sum input for selecting the individual antennas, so that the radiation directional characteristic exhibits a sum diagram,
wherein the antenna array includes a differential input for selecting the individual antennas so that the radiation pattern exhibits a differential diagram,
wherein at least one of the phase shifters or hybrid junctions is switchable, so that the radiation directional characteristic exhibits further differential diagrams by the resulting change of the phase behavior due the selection of the individual antennas,
wherein the means by which the individual antennas are connected with each other comprises a 3 dB four-grid hybrid junction, two three-grid power dividers ( 5 ), a switch ( 6 ) for the alternating connection of inputs and outputs of a first set of said antennas ( 8 ) and ( 9 ), a second set of antennas ( 7 ) and ( 10 ), as well as the connecting lines between said antennas, junctions, dividers, and switch,
wherein the connecting line length between the second set of antennas ( 7 ) and ( 10 ) and the inputs of the three-grid power dividers ( 5 ) are equal in length, in order to take into consideration the switch ( 6 ), and
wherein the inputs of the four-grid 3 dB hybrid junction ( 4 ) are connected with the three-grid power divider ( 5 ) with and without a λ/4-detour line.
2. An antenna array according to claim 1 , wherein a double switch ( 6 ) is realized by first and second 3 dB hybrid junctions ( 13 ) and ( 14 ), two switches ( 15 ) driven in synchrony, and two circuit segments ( 16 ) and ( 17 ), wherein the two circuit segments ( 16 ) and ( 17 ) differ in their length so that the length difference corresponds to an uneven multiple of the half wave length of the waves passing through the array, and wherein the first and second 3 dB hybrid junctions ( 13 ) and ( 14 ) are switched in series, so that one output from the first hybrid junction ( 13 ) is directly coupled with the input from the second hybrid junction ( 14 ), while a coupling of the other output from the first hybrid junction ( 13 ) and one of the two circuit segments ( 16 ) or ( 17 ) occurs via the switch ( 15 ).
3. An antenna array according to claim 1 , wherein the switch ( 6 ) is a simple two way switch, with which it is possible to switch between a circuit of length L and a circuit of length L+λ/2.
4. An antenna array according to claim 3 , wherein the switch ( 6 ) is a 3 dB hybrid junction.
5. An antenna array according to claim 1 , wherein for increasing the directional resolution, the antenna array is supplemented with an additional separate antenna element, and wherein this antenna element is positioned with such a spacing from the antenna array that, wherein the combined radiation path of said array comprises a plurality of lobes, and in the combined radiation pattern of said array and, said additional antenna element one of said main lobes is at least partially suppressed.
6. A process for operating a monopulse antenna array consisting of individual antennas in order to enhance the directional resolution and angular coverage, of which the radiation directional characteristic is associated with a sum diagram and a differential diagram, the process comprising:
connecting the individual antennas with each other via at least one phase shifter and at least one hybrid junction, such that the radiation directional characteristic of the antenna array during selection via a sum input produces a sum diagram, and such that the radiation directional characteristic of the antenna array upon selection of a differential input produces a differential diagram, and such that at least one of the phase shifter or hybrid junctions is switchable such that the radiation directional characteristic exhibits further differential diagrams due to the resulting change of the phase behavior upon the selection of the individual antennas,
further comprising determining the entry direction of a received signal by:
driving the antenna elements non-symmetrically, so that the antenna diagram is deformed, and
comparing the change of the thus received signal at the differential channel with the signal received via the undeformed sum or differential channel.
7. A process according to claim 6 , further comprising measuring the phase angle of the output of the differential channel for determining the entry direction of a received signal.
8. A process according to claim 6 , comprising placing a supplemental antenna element with suitable spacing beside the antenna array, wherein the combined radiation path of said array comprises a plurality of lobes, and in the combined radiation pattern of said array and said additional antenna element one of said main lobes is at least partially suppressed, and
comparing the output signal of the device without taking into consideration the supplemental antenna element, with the additive output signal of the total device with the supplemental antenna element, to thereby determine the entry direction of the received signal.