IES85048Y1 - A dual polarized antenna - Google Patents

Abstract

ABSTRACT This invention relates to an antenna (1) of the type comprising a casing (3) having a reflector (5) defining a slot (7) and a PCB board (9) carrying a plurality of radiating elements (10) and a feed harness (11). The radiating elements and the feed harness form a dual polarized antenna pattern. The PCB is mounted in the casing and protrudes outwardly from the slot so that the radiating elements are on one side of the reflector and the feed harness is on the other side of the reflector. The PCB (9) is U- shaped in cross section. This provides a very compact construction that may be used in conjunction with existing antenna casings (3). The PCB may be formed into a U- shape by bending the PCB after heating the PCB above a predetermined temperature so that it becomes pliable. Alternatively, the PCB may be formed from a number of separate sections connected together.

Description

A dual polarized antenna introduction This invention relates to a dual polarized antenna comprising a casing having a reflector defining a slot, a plurality of radiating elements, a feed harness electrically connected to the radiating elements and a printed circuit board (PCB) carrying the radiating elements and the feed harness, the PCB being mounted in the casing and protruding outwardly therefrom through the slot so that the radiating elements are on one side of the reflector external the casing and the feed harness is substantially on the other side of the reflector internal the casing.

Dual polarized antennas are commonly used in the telecommunications field. These antennas emit signals in an orientation particularly suitable for reception by mobile telephones and the like. Generally speaking, dual polarized antennas comprise a plurality of radiating elements connected to a feed harness laid flat on a substrate which is in turn mounted in a protective casing. Although highly efficient in use, there are a number of problems with the known types of dual polarized antennas.

First of all, it is often desirable to replace an existing antenna with a dual polarized antenna when updating a communications network. However, due to the relatively large size of the substrate on which the radiating elements and feed harness are mounted, an entirely new antenna casing must be provided and it is not possible to use the existing antenna casing. As well as increasing the cost of implementing the new antenna, the provision of a new, larger antenna casing may require planning permission which may be difficult and time consuming to obtain. A second problem with the known types of dual polarized antennas is that their coverage area is often limited to approximately 60° and therefore at least six antennas are required to achieve 360° coverage.

One particularly efficient construction of antenna casing is that described in the applicants own PCT patent application numbers PCT/lB2004/004455 and PCT/EP2006/067163. This antenna casing is robust, lightweight, compact and relatively inexpensive to provide. The entire disclosures of the above identified PCT applications are incorporated herein by way of reference and in particular the disclosures relating to Sd5u48 the construction of antenna casing are incorporated herein. It is desirable to provide a dual polarized antenna that may be used with this type of antenna casing in particular. it is therefore an object of the present invention to provide a dual polarized antenna that may be used with the existing types of antenna casing. It is a further object of the present invention to provide a dual polarized antenna that is relatively simple and inexpensive to implement.

Statements of invention According to the invention there is provided an antenna comprising: a casing having a reflector defining a slot; a plurality of radiating elements; a feed harness electrically connected to the radiating elements; a printed circuit board (PCB) carrying the radiating elements and the feed harness, the PCB being mounted in the casing and protruding outwardly therefrom through the slot so that the radiating elements are on one side of the reflector and the feed harness is substantially on the other side of the reflector, characterised in that:- the radiating elements and the feed harness form a dual polarised antenna pattern; and the PCB is substantially U-shaped in cross-section and comprises a pair of legs bridged by a centre portion, the centre portion being located external the casing and the legs each extending inwardly from the centre portion to the interior of the casing.

By having such an antenna, it is possible to provide a dual polarized antenna in the existing antenna casing. This is deemed to be a particularly efficient configuration of antenna casing to use. Furthermore, a different antenna casing need not be provided which will obviate the need for planning permission to replace existing antennas and furthermore will reduce the cost of manufacturing. in addition to the above, the interference between the feed harness and the radiating elements will be reduced thereby providing a more effective antenna design.

In one embodiment of the invention there is provided an antenna in which the radiating elements are carried on the centre portion of the PCB. In another embodiment of the invention there is provided an antenna in which the feed harness is carried substantially on a leg of the PCB. In a further embodiment of the invention there is provided an antenna in which a portion of the feed harness is carried substantially on each leg of the PCB.

In one embodiment of the invention there is provided an antenna in which the PCB comprises an elongate unitary piece of material, bent along two separate fold lines substantially parallel to a longitudinal axis of the PCB, thereby forming the centre portion and the pair of legs. This is seen as a particularly simple construction of PCB that will reduce the cost of and significantly simplify the manufacture of the antennae.

Furthermore, by having a single piece of PCB with the radiating elements and the feed harness thereon, less soldering will have to be done thereby simplifying construction and furthermore providing a more uniform construction of antenna that will operate in a more predictable manner.

In another embodiment of the invention there is provided an antenna in which the radius of curvature of the fold lines is of the order of between 1mm and 3mm. Preferably, the radius of curvature of the fold lines is of the order of 2mm. By having a radius of curvature of this order, the possibility of the ground plane on the reverse of the PCB cracking will be reduced and the effects of rippling on the tracks of the PCB will be minimised.

In a further embodiment of the invention there is provided an antenna in which the U- shaped PCB further comprises three separate PCBs connected together, a centre portion PCB and two leg PCBs, the leg PCBs being mounted on the centre portion PCB, one on either side of the centre portion PCB thereby forming the U-shaped PCB.

In one embodiment of the invention there is provided an antenna in which the legs each form an angle of the order of between 70° and 110° with the centre portion. In another embodiment of the invention there is provided an antenna in which the legs each fonn an angle of the order of 90° with the centre portion. This is seen as providing a compact configuration of antenna.

In a further embodiment of the invention there is provided an antenna in which there is provided a plurality of mounting holes in the PCB to permit selection of the distance by which the PCB protrudes from the casing. By being able to select the amount by which the antenna protrudes from the casing, it is possible to determine the azimuth bandwidth of the antenna thereby allowing the coverage area of the antenna and accordingly the coverage area of the network to be altered in a relatively simple manner. This will allow for other antenna to be incorporated into the network if need be in a relatively simple manner.

In one embodiment of the invention there is provided an antenna in which there is provided a signal reflective sheet mounted on the side of the centre portion proximal to the casing. In another embodiment of the invention there is provided an antenna in which the signal reflective sheet is mounted a distance equal to ‘/4 radiated signal wavelength from the antenna radiating elements. This will enhance the signal emitted from the antenna. in a further embodiment of the invention there is provided an antenna in which there is provided a signal directive patch mounted on the side of the centre portion of the PCB distal from the casing.

In one embodiment of the invention there is provided an antenna in which the casing is substantially box-shaped in cross section. This is seen as a particularly simple configuration of antenna to construct and handle. it is envisaged that additional equipment such as radomes and fins or corrugations may be provided on the antenna to enhance the signal emanating from the antenna.

In another embodiment of the invention there is provided an antenna as claimed in any preceding claim in which the PCB is constructed from polytetrafluoroethylene (PTFE).

In a further embodiment of the invention there is provided a process for manufacturing a dual polarised antenna comprising the steps of: printing a dual polarised antenna paltem comprising a plurality of radiating elements and a feed harness on a printed circuit board (PCB); constructing a U-shaped PCB from the printed PCB, the U-shaped PCB having a pair of legs bridged by a centre portion; and mounting the U-shaped PCB in a casing having a reflector defining a slot, the U-shaped PCB extending through the slot so that the centre portion is on one side of the reflector remote from the casing and the legs extend inwardly from the centre portion through the slot and are housed substantially within the casing. in one embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the step of constructing a U-shaped PCB from the printed PCB further comprises the steps of: heating the printed PCB to a predetermined temperature at which the PCB is pliable; and bending the heated PCB along a pair of fold lines into a substantially U-shape comprising the centre portion and the pair of legs.

This is seen as a particularly simple way of manufacturing the antenna and will significantly simplify the manufacturing process while at the same time reducing the cost of the manufacturing process. in another embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the step of heating the PCB to a predetermined temperature comprises heating the PCB to a temperature of at least 120° Celsius.

In a further embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the heated PCB is bent along each of the fold lines so that the legs each form an angle with respect to the centre portion of between 70°and 110°. In one embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the heated PCB is bent along each of the fold lines so that the legs each fon'n an angle with respect to the centre portion of the order of 90''.

In another embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the heated PCB is bent with the fold lines each having a radius of curvature of the order of between 1mm and 3mm. Preferably, the heated PCB is bent with the fold lines each having a radius of curvature of the order of 2mm. in one embodiment of the invention there is provided a process for manufacturing a dual , ularised antenna in which the step of constructing a U-shaped PCB from the printed PCB further comprises the steps of: cutting the printed PCB into three separate PCB sections, one section providing the centre portion and the other two sections providing the legs; mounting the legs on the centre portion, one on either side of the centre portion; and connecting the plurality of radiating elements electrically to the feed harness.

In this way, the antenna PCB may be printed in one piece before being cut into three sections that are then rejoined in the desired configuration. This may help to reduce the printing costs and times for creating the PCB.

In another embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the step of printing a dual polarised antenna pattern comprising a plurality of radiating elements and a feed harness on a PCB further comprises: printing three separate PCBs, one of the PCBs having the radiating elements printed thereon thereby fonning the centre portion and the other two PCBs having a portion of the feed harness printed thereon thereby forming the legs, and in which the step of constructing a U-shaped PCB from the printed PCB further comprises the steps of: mounting the legs on the centre portion, one on either side of the centre portion; and connecting the plurality of radiating elements electrically to the feed harness.

This is seen as a useful alternative as the cutting operation does not have to be performed and therefore it is possible to create three PCBs of very precise dimensions and specifications.

In a further embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the process further comprises the step of mounting a signal directive patch on the side of the centre portion of the PCB distal from the casing.

In one embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which process further comprises mounting the signal reflective sheet a distance equal of the order of to ‘/4 radiated signal wavelength from the antenna radiating elements.

In another embodiment of the invention there is provided a process for manufacturing a dual polarised antenna in which the process further comprises the steps of mounting a signal reflective sheet on the U-shaped PCB on the side of the centre portion proximal to the casing.

Detailed descrigtlon of the Invention The invention will now be more clearly understood from the following description of some embodiment thereof given by way of example only with reference to the accompanying drawings, in which :- Figure 1 is an end perspective view of an antenna according to the present invention; Figure 2 is an end perspective view of the antenna with part of the casing detached; Figure 3 is a top plan view of the antenna shown in figure 1; Figure 4 is an end perspective view taken from above of part of the antenna; Figure 5 is an end perspective view taken from below of part of the antenna; Figure 6 is a top plan view of the part of the antenna shown in figures 4 and 5; Figure 7 is a plan view of the printed PCB priorto bending; Figure 8 is an end perspective view of the printed PCB after bending; Figure 9 is a plan view of the reverse side of the printed PCB shown in figure 7 prior to bending; and Figure 10 is an alternative construction of PCB for use with the antenna according to the present invention.

Referring to the drawings and initially to figures 1 to 3 thereof, there is shown an antenna, indicated generally by the reference 1, comprising a casing 3 having a reflector defining a slot 7. The antenna 1 further comprises a U-shaped printed circuit board (PCB) 9 having a plurality of radiating elements (not shown) and a feed harness 11 printed thereon, the radiating elements and the feed harness forming a dual polarized antenna pattern. The U-shaped PCB 9 comprises a pair of legs 13, 15 bridged by a centre portion 17. The centre portion 17 is located external the casing and the legs 13, each extend inwardly from the centre portion 17 to the interior of the casing.

Therefore, the PCB 9 is mounted in the casing and protrudes outwardly therefrom through the slot 7. The dual polarized antenna 1 additionally comprises a signal reflective sheet 19 mounted on the side of the centre portion 17 proximal to the casing 3 and a signal directive patch mount 21 mounted on the side of the centre portion 17 distal from the casing. The signal directive patch mount 21 has a plurality of signal directive patches (not shown) mounted thereon.

Referring to figure 4 and 5 of the drawings, where like parts have been given the same reference numeral as before, there are shown some end perspective views of the antenna with the majority of the casing removed. The reflector 5 is mounted on the PCB 9, in this case by rivets (not shown) and the signal reflective sheet 19 is mounted on the PCB 9 using rivets 23. A plurality of plastic spacers 25 are used to mount the signal directive patch 21 on the side of the centre portion 17 distal from the casing (not shown).

The signal reflective sheet 19 is mounted on the PCB 9 a distance equal to of the order of one quarter radiated signal wavelength from the antenna radiating elements (not shown). Figure 6 shows a plan view of the part of the antenna shown in Figures 4 and 5.

Referring to figure 7 there is shown a plan view of the printed PCB prior to bending. The PCB 9 comprises a plurality of radiating elements 10 and a feed harness 11. The radiating elements 10 are electrically connected to the feed harness 11 by way of the tracks 71 of the feed hamess. It can be seen that there are a number of breaks 73 in the tracks 71 of the feed harness. Typically. a phase shifting device will be electrically connected in the breaks 73 of the tracks 71 thereby providing the electrical connection between the radiating elements 10 and the feed harness 11. It will be understood that other pattems that provide a dual polarized signal could be implemented instead of that shown and the invention is in no way limited to the specific embodiment of dual polarized signal pattern shown.

Referring to figure 8 of the drawings, there are shown a PCB 9 having a plurality of radiating elements 10 and a feed harness 11, in a bent state. The PCB 9 comprises an elongated unitary piece of material, bent along two separate fold lines 81. 83 substantially parallel to a longitudinal axis of the PCB, thereby forming the centre portion 17 and the legs 13, 15. The centre portion 17 carries the radiating elements 10 whereas the legs carry the feed harness 11. In the embodiment shown, the legs each form an angle of the order of 70° with the centre portion. However, it is envisaged that the legs could each form an angle of the order of between 70° and 110° with the centre portion.

Preferably, the legs form an angle of the order of 90° with the centre portion. Indeed, the PCB shown in figure 8 is shown without a signal reflective sheet 19 connected thereto.

Once the signal reflective sheet is connected to the PCB of figure 8, the legs will each fonn angle of approximately 90° with the centre portion. The radius of curvature of the fold lines 81, 83 is of the order of between 1 mm and 3 mm, preferably 2 mm. In this way, the ground plane on the opposite side of the PCB will have less tendency to crack and furthermore the rippling effect of the fold lines on the feed harness will be less severe. This provides for a more predictable, unifonn antenna to be produced. When mounted in the casing, the radiating elements are substantially on one side of the reflector external the casing and the feed harness is substantially on the other side of the reflector internal the casing.

Referring to figure 9 of the drawings, there is shown the opposite side of the PCB 92 that shown in figures 7 and 8. This side is commonly referred to as the ground plane and is coated with a layer of conductive material. A number of holes are provided in the PCB 9 for reception of mounting rivets as well as providing vias for phase shifting or other equipment (not shown). The PCB 9 is provided with a number of holes to allow the PCB to be connected to the reflector 5. The amount by which the PCB protrudes from the casing detennines the coverage angle of the antenna. The coverage angle of the antenna can be altered from of the order of 60° upwards to 120°. Therefore, by choosing the amount by which the antenna protrudes from the casing, it is possible to increase or decrease the coverage area of the antenna and therefore more or less antennas may be utilized in a particular area in order to achieve the desired coverage in that area.

Referring to figure 10 of the drawings, there is shown an alternative construction of the PCB, indicated generally by the reference 101, for use with the antenna according to the -. .sent invention, where like parts have been given the same reference numeral as before. The PCB 101 comprises a pair of legs 13, 15 and a centre portion 17. Each of the legs 13, 15 and centre portion 17 comprise a separate PCB board. The legs 13, 15 are mounted on to the centre portion 17 and the radiating elements 10 and feed harness 11 are electrically connected together by way of soldering or coaxial connections.

The present invention further incorporates a process for manufacture of a dual polarized antenna. In order to manufacture the dual polarized antenna, a dual polarized antenna pattern is printed on a printed circuit board. The dual polarized antenna pattern comprises a plurality of radiating elements and a feed harness. The process further comprises the step of constructing a U-shaped PCB from the printed PCB, the U-shaped PCB having a pair of legs bridged by a centre portion, and thereafter mounting the U- shaped PCB in a casing having a reflector defining a slot. The U-shaped PCB is mounted in the casing in such a way so that the PCB extends through the slot with the centre portion on one side of the reflector remote from the casing and the legs extending inwardly from the centre portion through the slot and housed substantially within the casing.

There are number of ways of constructing a U-shaped PCB from the printed PCB. First of all, the printed PCB may be heated to a temperature of at least 120°C so that the PCB becomes pliable. At this temperature, the PCB is bent along a pair of fold lines into a substantially U-shaped configuration comprising the centre portion 17 and the pair of legs 13, 15. it is envisaged that a polytetrafluoroethylene (PTFE) PCB may be used as a suitable material for the PCB. The PTFE PCB is seen as useful due to its low loss characteristics, low-cost, and its degree of resilience. Furthermore, the PTFE is useful as it has similar thermal expansion characteristics to copper or steel. The PCB is bent along the pair of fold lines so that the legs form an angle of approximately 90° with respect to the centre portion. The radius of curvature is of the order of between 1 mm and 3 mm, preferably 2 mm so that the rippling of the feed harness 11 will not be too severe and the potential to damage the ground plane is practically obviated.

-][- The second way of constructing the U-shaped PCB is to cut the printed PCB into three separate sections, one of which providing the centre portion and the other to providing the legs. Once cut, the legs may be mounted, one on either side of the centre portion at an angle of the order of 90° to the centre portion and the feed harness may be electrically connected to the radiating elements by soldering or coaxial connections. A third way of constructing the U-shaped PCB is to print three separate PCB boards, one comprising the centre portion having the radiating elements thereon and the other two comprising the legs with feed harness. The two PCBs with the feed harness printed thereon may be mounted, one on either side of the centre portion at an angle of the order of 90° to the centre portion and the feed harness may be electrically connected to the radiating elements by soldering or coaxial connections. A signal reflective sheet and a signal directive patch may in turn be mounted on the PCB.

The order in which the signal reflective sheet, the signal directive patch and the reflector are mounted on the PCB is chosen to use the minimum number of rivets. After the PCB has been bent into a U-shape, the signal directive patch is connected to the PCB. The PCB, reflector and signal reflective sheet are then aligned and rivets are used to connect the PCB, reflector and signal reflective sheet together. Again, although the foregoing is seen as a logical and simple process for manufacturing the antenna, the order of the steps could be changed to suit individual needs.

In the specification and the terms ' comprise, comprises, comprised and comprising ' and the tem1s' include, includes, included and including ’ are deemed totally interchangeable and should be afforded the widest possible interpretation.

The invention is in no way limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the claims.

Claims (4)

1) An antenna comprising: a casing having a reflector defining a slot; a plurality of radiating elements; a feed harness electrically connected to the radiating elements; a printed circuit board (PCB) carrying the radiating elements and the feed harness, the PCB being mounted in the casing and protruding outwardly therefrom through the slot so that the radiating elements are on one side of the reflector and the feed harness is substantially on the other side of the reflector; characterised in that:- the radiating elements and the feed harness form a dual polarised antenna pattern; and the PCB is substantially U-shaped in cross-section and comprises a pair of legs bridged by a centre portion, the centre portion being located external the casing and the legs each extending inwardly from the centre portion to the interior of the casing.

2) An antenna as claimed in claim 1 in which the radiating elements are carried on the centre portion of the PCB and a portion of the feed harness is carried substantially on each leg of the PCB.

3) An antenna as claimed in any preceding claim in which the PCB comprises an elongate unitary piece of material, bent along two separate fold lines substantially parallel to a longitudinal axis of the PCB, thereby forming the centre portion and the pair of legs.

4) A process for manufacturing a dual polarised antenna comprising the steps of: printing a dual polarised antenna pattern comprising a plurality of radiating elements and a feed harness on a printed circuit board (PCB); constructing a U-shaped PCB from the printed PCB, the U-shaped PCB having a pair of legs bridged by a centre portion: mounting the U-shaped PCB in a casing having a reflector defining a slot, the U-shaped PCB extending through the slot so that the centre portion is on one side of the reflector remote from the casing and the legs extend inwardly from the centre portion through the slot and are housed substantially within the casing; and in which the step of constructing a U-shaped PCB from the printed PCB further comprises the steps of: heating the printed PCB to a predetermined temperature at which the PCB is pliable; and bending the heated PCB along a pair of fold lines into a substantially U- shape comprising the centre portion and the pair of legs. An antenna substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.