Microstrip antenna having a metal frame for control of an antenna lobe

• US 6,023,244 A
• Filed: 02/13/1998
• Issued: 02/08/2000
• Est. Priority Date: 02/14/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Torstensson, Lars, Lindqvist, Christer, Snygg, Goran
• Primary Examiner(s): LE, HOANGANH T
• Application Number:
  US09/023,874
• Time in Patent Office: 725 Days
• Field of Search: 343/700 MS, 343/846, 343/848, 343/789, 343/841, 343/797, 343/793
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001

Abstract

A device for and/or comprised in antennas, in particular microwave antennas such as microstrip antennas, for controlling the antenna lobe and completely or partially suppressing cross-coupling between the polarizations in dual-polarized antenna elements. A metal frame, the sides of which can be angled for a desired lobe width, is positioned around each antenna element on top of the ground plane of the antenna. The shape and positioning of the metal frame around the antenna element also control the antenna lobe. In this way, the antenna lobe can be controlled in the desired manner irrespective of the size of the ground plane of the antenna, which depends, for example, on a desired microstrip distribution network for the antenna.

Claims

1. A microstrip antenna for receiving and transmitting electromagnetic signals mainly within the microwave frequency range with an antenna lobe in a direction relative to the normal of the microstrip antenna, which microstrip antenna comprises a ground plane and at least one antenna element, the ground plane comprising a first side and a second side, the antenna element being mounted at a predefined distance from the first side of the ground plane, and the antenna element being fed be feed means from the second side of the ground plane, wherein a metal frame is arranged directly on the ground plane, on the first side of the ground plane around a projection of the antenna element on the first side of the ground plane in order thus to control the size and direction of the antenna lobe with the shape and positioning of the metal frame on the first side of the ground plane, and the metal frame comprises a first and a second side where the second side of the metal frame faces the projection of the antenna element and where the first and second sides of the metal frame are electrically interconnected at least along one edge which forms a line along the metal frame.

2. The microstrip antenna according to claim 1, wherein a first angle is formed at the edge between the first side of the metal frame and the normal of the first side of the ground plane through the edge, where the first angle is considered positive from the normal of the first side of the ground plane through the edge and away from the antenna element, and in that the first angle is greater than zero in order thus to control the antenna lobe.

3. The microstrip antenna according to claim 2, wherein at least one angle changes in value at least once around the metal frame in order thus to control the antenna lobe.

4. The microstrip antenna according to claim 1, wherein a second angle is formed at the edge between the second side of the metal frame and the normal of the first side of the ground plane through the edge, where the second angle is considered positive from the normal of the first side of the ground plane through the edge and towards the antenna element, and in that the second angle is greater than zero in order thus to control the antenna lobe.

5. The microstrip antenna according to claim 1, wherein a first angle is formed at the edge between the first side of the metal frame and the normal of the first side of the ground plane through the edge, where the first angle is considered positive from the normal of the first side of the ground plane through the edge and away from the antenna element, and in that a second angle is formed at the edge between the second side of the metal frame and the normal of the first side of the ground plane through the edge, where the second angle is considered positive from the normal of the first side of the ground plane through the edge and towards the antenna element, and in that the first angle is greater than zero and in that the second angle is negative with an absolute value which is smaller than the first angle, in order thus to control the antenna lobe.

6. The microstrip antenna according to claim 1, wherein a first angle is formed at the edge between the first side of the metal frame and the normal of the first side of the ground plane through the edge, where the first angle is considered positive from the normal of the first side of the ground plane through the edge and away from the antenna element, and in that a second angle is formed at the edge between the second side of the metal frame and the normal of the first side of the ground plane through the edge, where the second angle is considered positive from the normal of the first side of the ground plane through the edge and towards the antenna element, and in that the second angle is greater than zero and in that the first angle is negative with an absolute value which is smaller than the second angle, in order thus to control the antenna lobe.

7. The microstrip antenna according to claim 1, wherein the edge lies between the ground plane and a parallel plane in which the antenna element mainly lies.

8. The microstrip antenna according to claim 1, wherein the edge lies mainly in a plane in which the antenna element lies and which is parallel to the ground plane.

9. The microstrip antenna according to claim 1, wherein the edge lies beyond a plane in which the antenna element lies, in relation to the parallel ground plane.

10. The microstrip antenna according to claim 1, wherein the distance of the edge from the ground plane along the normal of the ground plane varies around the metal frame in order thus to control the antenna lobe.

11. The microstrip antenna according to claim 1, wherein the metal frame is electrically connected to the ground plane.

12. The microstrip antenna according to claim 1, wherein the metal frame is mainly centered around the projection of the antenna element on the first side of the ground plane.

13. The microstrip antenna according to claim 1, wherein the metal frame is arranged asymmetrically around the projection of the antenna element on the first side of the ground plane.

14. The microstrip antenna according to claim 1, wherein the antenna element is an aperture-coupled patch.

15. The microstrip antenna according to claim 1, wherein the antenna element is dual-polarized.

16. The microstrip antenna according to claim 1, wherein a edge line of the metal frame is parallel or at right angles to the polarization or polarizations of the antenna element.

17. The microstrip antenna according to claim 1, wherein a edge line of the metal frame forms a square.

18. The microstrip antenna according to claim 1, wherein the microstrip antenna is an array antenna with at least two antenna elements each having its own metal frame.

19. The microstrip antenna according to claim 1, wherein the antenna element is a ±

45°

dual-polarized aperture-coupled patch.

20. An array antenna for receiving and transmitting electromagnetic signals mainly within the microwave frequency range with an antenna lobe in a direction relative to the normal of the array antenna, which array antenna comprises a ground plane and at least two microstrip antenna elements, where the ground plane comprises a first side and a second side, the microstrip antenna elements are mounted at a predefined distance from the first side of the ground plane and are ±

45°

dual-polarized aperture-coupled patches which are fed by a microstrip distribution network from the second side of the ground plane, wherein a metal frame is arranged directly on the ground plane, on the first side of the ground plane around a projection of each microstrip antenna element on the first side of the ground plane, in order thus to control the size and direction of the antenna lobe by means of the shape and positioning of the metal frame on the first side of the ground plane, where the metal frame comprises a first and a second side with the second side of the metal frame facing the projection of the respective microstrip antenna element and where the first and second sides of the metal frame are electrically interconnected at least along one edge which forms a line along the metal frame, and where a first angle is formed at the edge between the first side of the metal frame and the normal of the first side of the ground plane through the edge and where a second angle is formed at the edge between the second side of the metal frame and the normal of the first side of the ground plane through the edge.

21. The array antenna according to claim 20, wherein at least one of the first and the second angles changes around the metal frame.

22. The array antenna according to either claim 20, wherein the edge of the metal frame which forms a line around the metal frame is equidistant from the microstrip antenna element along the whole line.

23. The array antenna according to any one of claim 20, wherein the metal frame of at least one microstrip antenna element is positioned asymmetrically around the projection of the microstrip antenna element in order thus to control the direction of the antenna lobe.

24. The array antenna according to any one of claim 23, wherein the respective metal frames of different microstrip antenna elements are not the same.