Aperture coupled patch antenna arrangement

It is provided an aperture coupled patch antenna comprising a substrate comprising a planar electrically conductive ground plane, an electrically conductive box arranged on and electrically connected to the ground plane to form an air filled cavity between the box and the ground plane, the box comprising an aperture in the form of at least one elongate slot. The antenna further comprises an electrically conductive patch arranged in parallel with the ground plane and at a distance from the box such that the aperture of the box is located between the patch and the ground plane and a distribution network comprising at least one elongate distribution element arranged in parallel with the ground plane between the ground plane and the patch, at a distance from the substrate and the ground plane and at a distance from the box such that a gap is formed between the distribution element and the box, wherein the extension of the distribution element intersects the extension of the aperture.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. § 371 National Stage of International Patent Application No. PCT/EP2016/067643, filed Jul. 25, 2016, designating the United States.

TECHNICAL FIELD

The present disclosure relates to microwave antenna systems capable of transmitting and receiving microwave radiation, and in particular to an aperture coupled patch antenna arrangement for use in a microwave antenna system.

BACKGROUND

Aperture coupled patch antennas are often used in the field of microwave radio communication. Aperture coupled patch Antennas are known for good performance on e.g. cross polarization.

From U.S. Pat. No. 4,903,033 it is known that a dual polarization aperture coupled antenna usable for microwave signals. Orthogonal linearly polarized signals can be transmitted, and received, via a number of microstrip patches and a ground plane aperture which is in the shape of two orthogonal slots intersecting at their midpoints. Two identical fork shaped signal feed networks feed signals to and from the slots.

Aperture coupled antennas are often cavity backed, as the antenna described in U.S. Pat. No. 5,896,107. For antenna integrated radio products and Advanced Antenna System (AAS) products the radio is often located in a layer behind the antenna. The cavity solution in U.S. Pat. No. 5,896,107 gives a problem to connect the antenna to the radio located in the layer behind the antenna. Cables and/or connectors are needed and hence cost and power loss added.

Accordingly, there is a need for an improved antenna arrangement for use in the field of microwave radio communication.

SUMMARY

In view of above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an improved aperture coupled patch antenna arrangement for use in a microwave radio communication system.

According to a first aspect, it is provided an aperture coupled patch antenna comprising a substrate comprising a planar electrically conductive ground plane, an electrically conductive box arranged on and electrically connected to the ground plane to form an air filled cavity between the box and the ground plane, the box comprising an aperture in the form of at least one elongate slot. The antenna further comprises an electrically conductive patch arranged in parallel with the ground plane and at a distance from the box such that the aperture of the box is located between the patch and the ground plane and a distribution network comprising at least one elongate distribution element arranged in parallel with the ground plane between the ground plane and the patch, at a distance from the substrate and the ground plane and at a distance from the box such that a gap is formed between the distribution element and the box, wherein the extension of the distribution element intersects the extension of the aperture.

Hereby, a patch antenna including a distribution element is provided which exhibits reduced dielectric losses as a result of the distribution element being arranged at a distance from the box, i.e. free hanging, without the need for a supporting circuit board. Moreover, the antenna can be fabricated separately using known manufacturing techniques after which it can be mounted on a substrate such as a circuit board. An advantage of arranging the antenna directly on a circuit board is that there is no need for connectors between the circuit board and the antenna since the antenna feed can be connected directly to a transmission line of the circuit board, e.g. by soldering.

According to some aspects, the distribution element is located between the box and the ground plane.

By arranging a distribution element arranged inside the box, efficient shielding of the distribution element from adjacent antennas is provided, thereby leading to lower distortion. This is particularly advantageous when the antenna is used in an array of antennas.

According to some aspects, the antenna arrangement further comprises at least one support element arranged between the box and the distribution element to suspend the distribution element at a distance from the box.

Hereby, the support element provides mechanical support for the distribution element to enable various configurations of antennas comprising one or more distribution elements.

According to some aspects, the distribution element is arranged to be in contact with the substrate at one point of the substrate.

According to some aspects, the distribution element is arranged to be in contact with the substrate at two points of the substrate, thereby providing additional mechanical support for the distribution element.

According to some aspects, the aperture comprises two intersecting orthogonal slots, and the distribution network comprises two distribution elements, each distribution element intersecting a corresponding slot.

Hereby, a dual polarized aperture coupled patch antenna is provided.

The object stated above is further obtained by a method for manufacturing an aperture coupled patch antenna comprising: providing an electrically conductive box comprising an aperture in the form of at least one elongate slot, the box being open on the side opposing the side of the aperture; arranging an electrically conductive patch suspended on an outside of the box in parallel with the side of the box comprising the aperture and at a distance from the box; providing a distribution network comprising at least one elongate distribution element arranged in parallel with and at a distance from the side of the box comprising the aperture such that the aperture is located between the distribution element and the patch, wherein the extension of the distribution element intersects the extension of the aperture; providing a substrate comprising a planar electrically conductive ground plane; and arranging the conductive box on the ground plane to form an air filled cavity between the box and the ground plane.

Hereby, as discussed above in connection to the antenna as such, an improved aperture coupled patch antenna can be manufactured in an efficient manner at low cost and at high volumes. Further aspects discussed in relation to the antenna are equally applicable for the method for manufacturing an aperture coupled patch antenna.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the element, apparatus, component, means, step, etc.” are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

DETAILED DESCRIPTION

In the following detailed description, various aspects of the aperture coupled patch antenna according to the present technique are mainly described with reference to an antenna for use in a communications system.

FIG. 1schematically illustrates an aperture coupled patch antenna100comprising a substrate102in turn comprising a planar electrically conductive ground plane104, an electrically conductive box106arranged on and electrically connected to the ground plane104to form an air filled cavity between the box106and the ground plane104. The box106comprises an aperture108in the form of at least one elongate slot. An electrically conductive patch110is arranged in parallel with the ground plane104and at a distance from the box106such that the aperture108of the box106is located between the patch110and the ground plane104. The antenna100further comprises a distribution network comprising at least one elongate distribution element112arranged in parallel with the ground plane104between the ground plane104and the patch110, at a distance from the substrate102and the ground plane104and at a distance from the box106such that a gap is formed between the distribution element112and the box106, wherein the extension of the distribution element112intersects the extension of the aperture108.

Hereby, a low-loss aperture coupled patch antenna100is provided where the losses in the distribution element112are reduced as a result of the distribution element112being arranged at a distance from the box106such that a gap is formed. The gap is here illustrated as an air gap. Accordingly, there is no need for any additional element between the distribution element112and the box106, or between the distribution element112and the ground plane104. In particular, the distribution element112can be seen as free hanging or suspended since the distribution element112is not arranged on a circuit board or the like, thereby leading to reduced losses. Moreover, there is no need for a specific RF-connector to the antenna since the antenna is mounted directly on a substrate such as a circuit board, e.g. a radio board. The substrate may also be a metallic plate.

The ground plane104is typically provided in the form of a metallic layer on the substrate102, the metallic layer being connected to a ground potential. Herein, the extension of distribution element112refers to the length direction of the elongate distribution element112. Similarly, the extension of the aperture108refers to the length direction of the elongate aperture108as will be illustrated in further detail in the following.

The box106illustrated inFIG. 1is open on the side facing the substrate102such that the box106and the substrate102form a substantially enclosed cavity, with the exception of the aperture108forming an opening in the box106in the direction of the patch110. Moreover, the box106is typically a metal box, similar to a shielded box.

It should further be noticed that the described antenna operates according to well established principles for conventional aperture coupled patch antennas known by the skilled person. Therefore, dimensions and further properties of the antenna will not be discussed in detail in the present description.

As illustrated inFIG. 1, the distribution element112is located between the box106and the ground plane104. Thereby, the distribution element112is shielded from distortions, e.g. from adjacent antennas or other components. Moreover, the distribution element112is arranged to be in contact with the substrate102at one point of the substrate102.

FIG. 1further illustrates at least one support element114arranged between the box106and the distribution element112to suspend the distribution element112at a distance from the box106. Support elements114are also arranged between the patch110and the box106to arrange the patch110in the appropriate position in relation to the box106. The support elements114are electrically insulating, i.e. non-conductive, and provide mechanical support for the patch110and the distribution element112. In particular, as illustrated inFIG. 1, the distribution element112is suspended from the box106by means of support elements114. Moreover, the support elements114determine the distances between e.g. the distribution element112and the ground plane104which in turn influence the properties of the antenna100. In embodiments comprising support elements114between the box106and the distribution element112, the air gap is thus formed along at least part of the length of the distribution element112and the box106.

In the embodiments described herein, the distribution element112is a microstrip transmission line.

FIG. 2schematically illustrates an antenna200where the distribution element202is arranged to be in contact with the substrate102at two points of the substrate202, thereby providing additional mechanical stability of the distribution element202. Thereby, the support elements between the box106and the distribution element202may be reduced or eliminated.

FIGS. 3A-Bschematically illustrate an antenna300,306where the distribution element302,304is located between the box106and the patch110. By arranging the distribution element outside of the box, it is possible to visually inspect the distribution element e.g. to identify any damage to the element, which for example may occur during assembly of the antenna.

InFIG. 3Bthe distribution element304is in contact with the substrate102at two points of the substrate102, thereby forming a bridge outside of the box106. The distribution element304in the form of a bridge is more mechanically stable in comparison to a distribution element having only one point of contact with the substrate.

Even though the box106inFIGS. 3A-Bis illustrated as a box being open in the direction of the circuit board, the102, the box may equally well be fully closed with the only opening being the aperture108of the box. Thereby, the air filled cavity is formed within the box.

FIGS. 4A-Cillustrate the antenna100ofFIG. 1in further detail whereFIG. 4Bis a schematic top view of the antenna andFIG. 4Cis an exploded view showing selected components of the antenna100.FIG. 4Ais a top view of the antenna100illustrating the alignment of the distribution element112in relation to the aperture108. Here, the aperture108comprises one elongate slot and the distribution element112comprises one elongate strip being arranged orthogonally to the aperture108and intersecting the aperture108. It should be noted that many different configurations of one or more distribution elements are possible, in a similar manner as for previously known aperture coupled patch antennas.

FIG. 4Cis an exploded view illustrating components of the antenna100and the order in which they are arranged to form the described antenna100. The distribution element112is thus located between the box106and the ground plane104. Even though the box106is illustrated herein as a rectangular box, the box may also have a circular outline as seen from above, i.e. as seen from the direction of the patch. Moreover, the patch may also have other shapes, such as circular.

FIGS. 5A-Cillustrate an antenna500where the aperture comprises two intersecting orthogonal slots502,504, and wherein the distribution network comprises two distribution elements506,508, each distribution element506,508intersecting a corresponding slot502,504.FIG. 5Ais a top view of the antenna500,FIG. 5Bis a perspective view of the antenna500andFIG. 5Cis an exploded view illustrating the orientation of selected components of the antenna500.

As can be seen inFIG. 5A, the two distribution elements506,508are elongated and arranged orthogonally to each other. Each distribution element506,508is orthogonally aligned with respect to a corresponding opening, i.e. slot502,504, of the aperture108. Hereby, a dual polarized antenna is provided.

The described antenna may advantageously be used in an antenna array comprising a plurality of antennas according to any one of the above described embodiments.

FIG. 6outlines the general steps of a method for manufacturing an aperture coupled patch antenna100,200,300,500. The method comprises providing602an electrically conductive box106comprising an aperture108in the form of at least one elongate slot, the box106being open on the side opposing the side of the aperture108, arranging604an electrically conductive patch110suspended on an outside of the box106in parallel with the side of the box106comprising the aperture108and at a distance from the box106; providing606a distribution network comprising at least one elongate distribution element112,202,302,304arranged in parallel with the ground plane104between the ground plane104and the patch110, at a distance from the substrate102and the ground plane104and at a distance from the box106such that a gap is formed between the distribution element112and the box106, such that the extension of the distribution element112intersects the extension of the aperture108. The method further comprises providing608a substrate102comprising a planar electrically conductive ground plane104; and arranging610the conductive box106on the ground plane104to form an air filled cavity between the box106and the ground plane104.

The described manufacturing method provides a straightforward and easily scalable manufacturing process suited for low cost high volume production of surface mounted aperture coupled antennas. The box106is similar to the type of box which is used for shielding box technologies, and well known shielding box manufacturing methods can easily be modified to provide a manufacturing process for the various embodiments of the antenna described herein.

In particular, by soldering the distribution network and the box to the circuit board, known production method can be used. The distribution network and the box can be individually mounted on the substrate as separate components. However, it may be even more preferable to assemble the distribution network and the box prior to mounting on the substrate such that only one step is required when soldering the antenna to the substrate.

This may for example be achieved by suspending the distribution element from the box by means of a suspension element.

Moreover, the distribution element can be made in many different ways. For example, the distribution element may be pre-mounted on the substrate with a box being subsequently arranged over the distribution element, the distribution element may be suspended from the inside or outside of the box by means of plastic support elements, and the distribution element may be made in metal or as metallized plastic.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art from a study of the drawings, the disclosure, and the appended claims. Also, it should be noted that parts of the connector arrangement may be omitted, interchanged or arranged in various ways, the connector arrangement yet being able to perform the functionality of the present invention. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.