ANTENNA AND METHOD OF MANUFACTURE

Abstract: Method of making a slant antenna array by forming antenna elements (4, 6) on a planar substrate (1) and then bending the substrate (1) to orientate the antenna elements (4, 6) so that these are in parallel with each other and at an angle to the main antenna structure, and a slant antenna array. A dual polarised slant antenna array can be produced from two slant antenna arrays provided in back to back relationship with the respective antenna elements (4, 6) arranged at an angle with respect to each other.

Description: ANTENNA & METHOD OF MANUFACTURE BACKGROUND TO THE INVENTION A slant polarised antenna array comprises a plurality of antenna elements which are arranged generally in parallel to each other, but which are at an angle with respect to the overall antenna structure. Conventionally, such an antenna array is formed by forming a plurality of individual antenna elements on separate substrates, mounting the substrates in an assembly, each at the required angle, and connecting the elements to a feed network and to ground. This is an expensive and time consuming method of manufacture due to the number of separate parts which are made, and their assembly. SUMMARY OF THE INVENTION According to a first aspect of the present invention, a method of manufacturing a slant polarised antenna array comprises the steps of forming a plurality of antenna elements on a generally planar substrate and subsequently bending the substrate to orientate each of the antenna elements at a predetermined angle. With the method according to the present invention, all of the antenna elements are first formed on a single generally planar substrate. Typically the substrate includes a layer of copper or other metal, and this is etched or otherwise shaped to form the elements. Alternatively, the elements may be deposited on an insulating substrate. Thereafter, the substrate is bent so that the elements are all at the required angle. It is therefore not necessary to form the antenna elements when the substrate is bent, this being very difficult. Further, there is no need to individually form the plurality of antennas, and to mount these separately as is required in the prior art. It is therefore more simple and less expensive to manufacture the array according to the method of the present invention than using the known methods. According to a second aspect of the present invention, a slant polarised antenna array comprises a plurality of antenna elements formed on substrate, the substrate being bent so that each of the antenna elements are parallel to each other and are at a predetermined angle to the antenna structure. It is preferred that the substrate is bent into a generally serpentine shape. Whilst the individual antenna elements can be connected individually to a discrete feed network, it is advantageous that the feed network is deposited on the substrate before this is bent. The feed network will include a ground plane. The ground plane and the rest of the feed network may be provided on the same or on opposite sides of the substrate. The antenna elements may be formed on either side of the substrate depending on the type of radiating element, for example patch radiating elements may be formed on the same side of the substrate as the feed network, whilst dipole radiating elements will usually be formed on the same side as the ground plane. It is advantageous that the areas of the substrate on which the antenna elements are formed are generally planar after the substrate is bent to give planar antenna elements. It is therefore preferred that the substrate includes a main longitudinal portion, or side bar, with a plurality of element surfaces connected to the side bar by thin connecting portions, and in which the step of bending the substrate comprises the step of bending only the connecting portions or the side bar. In this way the element surfaces are not bent. Where the substrate includes the feed network, it is advantageous for this to be substantially surrounded by a conductive box. This gives shielding of the feed network. In this case, the conductive box is preferably connected to the ground plane. It is preferred that the antenna array is formed so that the angle of each antenna element with respect to the main antenna structure is 45°. Where a dual polarised slant antenna array is required, for which two arrays of antenna elements are required with each of the antenna elements in one of the arrays being parallel to each other, and the antenna elements in the different arrays not being parallel to each other, two antenna arrays manufactured in accordance with the method of the present invention can be formed and placed back to back. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a side view of an antenna element array, prior to bending of the substrate; Figure 2 shows a plan view of a substrate including antenna elements after bending; Figure 3 shows a sectional view of an antenna array; and, Figure 4 shows a plan view of a dual polarised antenna array. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Figure 1 shows a side view of a substrate for use in the present invention. The substrate is generally planar, and includes a side bar 1 and a plurality of element surfaces 2 connected to the side bar 1 by thin connecting portions 3. The substrate is an insulating substrate with a metal layer, typically of copper, formed on one or both surfaces. A conductive pattern for a feed network is formed on one face of the side bar 1 by photoetching. On the other face of the side bar 1, a conductive pattern for a ground plane is formed using a similar technique. Radiating elements are formed on each of the element surfaces 2 using similar techniques. The radiating elements can be formed on either side of the substrate depending on the type of element, for example the radiating elements may be formed on the same side of the substrate as the feed network for patch elements, and on the opposite side for dipole elements. After forming the radiating elements, feed network and ground plane on the substrate, the side bar 1 is bent into a serpentine shape, as shown in Figure 2. This orientates the element surfaces 2 of the substrate at a predetermined angle, with the antenna elements 4 on each of the element surfaces 2 being arranged at a predetermined angle with respect to each other. As only the side bar 1 is bent, and the element surfaces 2 are only connected to the side bar 1 by thin connecting portions 3 , the element surfaces 2 and hence the antenna elements 4 provided on the element surfaces 2 remain generally planar. As shown in Figure 3, the substrate is provided in a conducting box 5, with the side bar 1 including the feed network arranged within the conducting box 5. The box 5 is electrically connected to the ground plane, and the connecting portions 3 of the substrate, the element surfaces 2 and antenna elements 4 projecting outside the box 5. The grounded conductive box 5 shields the feed network to minimise interference. As shown in Figure 4, two antenna arrays can be arranged back to back to give two arrays of antenna elements, each of the elements 4 in one array being in parallel to each other, and being at a different angle from the antenna elements 6 in the other array, each of which are parallel to each other. This arrangement gives a dual polarised antenna array.

Claims: CLAIMS 1. A method of manufacturing a slant antenna array, the method comprising the steps of: forming a plurality of antenna elements (4,6) on a generally planar substrate (1) ; and, subsequently bending the substrate (1) to orientate each of the antenna elements (4,6) at a predetermined angle. 2. A method according to claim 1, in which the substrate (1) is bent into a generally serpentine configuration. 3. A method according to claim 1 or 2 , in which the substrate is bent so that each of the antenna elements (4,6) is at an angle of about 45° to the main antenna structure. 4. A method according to any one of the preceding claims, in which a feed network including a ground plane is formed on the generally planar substrate (1). 5. A method according to claim 4, in which the substrate (1) has a first and a second surface, and in which the ground plane is formed on the first surface of the substrate (1), and the rest of the feed network is formed on the second surface of the substrate (1). 6. A method according to claim 4 or 5 , in which a conductive box (5) is provided around the feed network. 7. A method according to claim 6, in which the conductive box (5) is electrically connected to the ground plane of the feed network. 8. A method according to any one of the preceding claims, in which the substrate (1) includes a main longitudinal portion (1) and a plurality of antenna element receiving surfaces (2) connected to the longitudinal portion (1) by connecting pieces (3) , and in which the step of bending the substrate (1) comprises bending only the main longitudinal portion (1) and the connecting pieces (3). 9. A method of forming a dual polarised slant antenna array, comprising the steps of forming a first antenna array in accordance with any one of the preceding claims, and a second antenna array according to any one of the preceding claims, and further comprising the step of placing the first antenna array and the second antenna array in a back to back relationship such that the antenna elements (4) of the first antenna array are not parallel to the antenna elements (6) of the second antenna array. 10. A slant polarised antenna array comprising a plurality of antenna elements (4,6) formed on a substrate (1), the substrate (1) being bent so that each of the antenna elements (4,6) are parallel to each other and are at a predetermined angle to the antenna structure. 11. A slant polarised antenna according to claim 10, in which the substrate (1) has a generally serpentine configuration. 12. A slant polarised antenna according to claim 10 or 11, in which the substrate is bent so that each of the antenna elements (4,6) is at an angle of about 45° to the main antenna structure. 13. A slant antenna array according to any one of claims 10 to 12, further comprising a feed network including a ground plane provided on the substrate (1). 14. A slant antenna array according to claim 13, in which the substrate (1) has a first and a second surface, and in which the ground plane is provided on the first surface of the substrate (1) , and the rest of the feed network is provided on the second surface of the substrate (1) . 15. A slant antenna array according to claim 13 or 14, further comprising a conductive box (5) provided around the feed network. 16. A slant antenna array according to claim 15, in which the conductive box (5) is electrically connected to the ground plane of the feed network. 17. A slant antenna array according to any one of claims 10 to 16, in which the substrate (1) includes a main longitudinal portion (1) and a plurality of antenna element receiving surfaces (2) connected to the longitudinal portion (1) by connecting pieces (3). 18. A dual polarised slant antenna array, comprising a first antenna array according to any one of claims 10 to 17, and a second antenna array according to any one of the claims 10 to 17 provided in a back to back relationship such that the antenna elements (4) of the first antenna array are not parallel to the antenna elements (6) of the second antenna array.

Inventors: ADAMSON DAVID BARRIE, SHELLEY MARTIN, ADAMSON, DAVID, BARRIE, SHELLEY, MARTIN
Applicants: ERA PATENTS LTD, ERA PATENTS LIMITED
Application year: 1997
Main classification: H01Q21
IPC codes: H01Q1, H01Q13, H01Q21