Antenna system for georadar
An antenna system for ground penetrating radar, comprising at least two orthogonally mounted transmitter antenna elements ( 1, 2 ) and at least two orthogonally mounted receiver antenna elements ( 3, 4 ), in which the antenna elements consist of triangular monopoles formed by adding metal surfaces to a plate carrier ( 6 ), made of fiberglass substrate, that is mounted on the bottom side of a layer of radar absorbing material ( 7 ), wherein the upper side of the absorber is covered by a metallic ground plane ( 8 ).
1. Antenna system for a ground penetrating radar, comprising:
two plate-shaped antenna devices which are connected ( 14 ) with each other by adjacent edge structures ( 12 , 13 ) and which during operation are orientated to have a downwards slope from said edge structures ( 12 , 13 ),
wherein the two antenna devices respectively comprise at least two orthogonally mounted transmitter antenna elements ( 1 , 2 ) and at least two orthogonally mounted receiver antenna elements ( 3 , 4 ),
in which the antenna elements ( 1 – 4 ) in each antenna device consist of monopoles formed by metal surfaces being applied to an electrically insulating plate carrier ( 6 ) that is located on the bottom side of a layer of radar absorbing material ( 7 ),
in which the upper surface of the absorbing material ( 7 ) is covered by a metallic ground plane ( 8 ).
2. Antenna system in accordance with claim 1 , wherein the plate carrier ( 6 ) is a laminate, in particular a printed circuit board laminate, preferentially consisting of a fibreglass substrate.
3. Antenna system in accordance with claim 1 , wherein the antenna elements ( 1 – 4 ) have a triangular shape.
4. Antenna system in accordance with claim 1 , wherein the antenna elements ( 1 – 4 ) are mounted with a 45 degree angle to the symmetry axis ( 5 ) between the two antenna devices.
5. Antenna system in accordance with claim 1 – 4 , wherein the angle (α) in the vertical plane between the two antenna devices can be adjusted by a hinge ( 14 ) connecting said edge sections ( 12 , 13 ) to each other.
6. Antenna system in accordance with claim 1 , wherein the transmitter antenna elements ( 1 , 2 ) serve for transmission of electromagnetic waves with two orthogonal polarisations (A and B, respectively), and the receiving antenna elements ( 3 , 4 ) serve for reception of electromagnetic waves having the same two orthogonal polarisations (A and B, respectively).
7. Antenna system in accordance with claim 1 , wherein the feed points ( 9 ) of the antenna elements ( 1 – 4 ) are located in their respective metal boxes ( 12 , 13 ) at said edge structures of the two antenna devices, wherein each metal box ( 12 , 13 ) besides containing the electronics ( 20 , 30 ) of the radar also comprises a fixture for the plate carrier ( 6 ) and the ground plane ( 8 ).
8. Antenna system in accordance with claim 1 , wherein the outer edges of the antenna elements ( 1 – 4 ) are connected to the ground planes ( 8 ) through resistors ( 10 ) and spacers ( 11 ).
9. Antenna system in accordance with claim 1 , comprising several transmitter antenna elements and several receiver antenna elements forming an array of antenna subgroups distributed along the symmetry axis ( 5 ) between the two antenna devices, wherein each antenna subgroup consists of two transmitter antenna elements ( 1 , 2 ) and two receiver antenna elements ( 3 , 4 ).
10. Antenna system in accordance with claim 9 , wherein at least some of the antenna subgroups overlap each other, wherein the overlapping neighbour antenna elements ( 2 , 16 ) are separated in each intersection by an electrically insulating material ( 17 ).