ANTENNA ARRAY

Abstract

An antenna array includes an array of antenna bodies (121, 122) arranged on a planar structure (110), which, in turn, contains a circuit board (210) with a ground-plane layer (420). The array of antenna bodies (121, 122) is arranged on a top side of the circuit board (210). Each of the antenna bodies (121, 122) is dome shaped and attached to the top side of the circuit board (210) along its base. Each of the antenna bodies (121, 122) is connected to a respective top transmission line (450) configured to convey microwave signals to and/or from said antenna bodies (121, 122). The top transmission lines (450) are further connected to bottom transmission lines (430) via coaxial probes (440) through the ground-plane layer (420). A resonance cavity (460) is arranged below the top side of the circuit board (210) between each of the antenna bodies (121, 122). This accomplishes a highly compact design that can be produced in a cost-efficient manner.

Claims

1. An antenna array comprising an array of antenna bodies (121, 122) arranged on a planar structure (110), the planar structure (110) comprising a circuit board (210) and a ground-plane layer (220, 320, 420, 520, 620, 720, 820), the array of antenna bodies (121, 122) being arranged on a top side of the circuit board (210), each of said antenna bodies (121, 122) comprising a dome shaped structure which is attached to said top side of the circuit board (210) along a base of the dome shaped structure, each of said antenna bodies (121, 122) being connected to a respective top transmission line (350, 450, 550, 650, 750, 850) configured to convey microwave signals to and/or from said antenna bodies (121, 122), the top transmission lines (350, 450, 550, 650, 750, 850) being further connected to bottom transmission lines (330, 430, 530, 630, 730) via coaxial probes (340, 440, 540, 640, 740, 840) through said ground-plane layer (220, 320, 420, 520, 620, 720, 820), and a resonance cavity (260, 360, 460, 560, 660, 760, 860) being arranged below a bottom side of the circuit board (210) between each of said antenna bodies (121, 122).

2. The antenna array according to claim 1, wherein: a first electrically conductive surface element (121H) of a first antenna body (121) of said antenna bodies (121, 122) is configured to constitute a first portion of an antenna horn, and a second electrically conductive surface element (122H) of a second antenna body (122) of said antenna bodies (121, 122) is configured to constitute a second portion of the antenna horn, the first and second antenna bodies (121, 122) adjoining one another in such a manner that the first and second electrically conductive surface elements (121H; 122H) are located closer to one another than any other surface elements of the first and second antenna bodies (121, 122).

3. The antenna array according to claim 2, wherein: each of said antenna bodies (121, 122) is mirror symmetric in exactly two planes being orthogonal to one another, said antenna bodies (121, 122) are arranged in said array according to a pattern in which said first and second electrically conductive surface elements of adjoining antenna bodies pairwise form a respective antenna horn in such a manner that said antenna array comprises antenna elements configured to transmit and/or receive signals of a first polarization direction via a first subset of said horns and transmit and/or receive signals of a second polarization direction via a second subset of said horns, the first and second polarization directions being orthogonal to one another and each of said antenna bodies (121, 122) forming part of at least one horn included in the first subset and at least one horn included in the second subset.

4. The antenna array according to claim 3, wherein: the base of the dome shaped structure of each of said antenna bodies (121, 122) is octagon shaped, and each of the horns formed by said first and second electrically conductive surface elements (121H; 122H) has a tapered profile towards the top side of the circuit board (210), and an aperture between said first and second electrically conductive surface elements (121H; 122H) is symmetric around a normal to the top side of the circuit board (210).

5. The antenna array according to any one of the preceding claims, wherein: the ground-plane layer (420) is electrically connected to a first circuit pattern (425) on the bottom side of the circuit board (210), which first circuit pattern (425) is further electrically connected to a second circuit pattern on the top side of the circuit board (210) by means of a plurality of vias (370, 470, 570, 670, 770, 870, 970) through the circuit board (210) so as to extend a ground plane represented by the ground-plane layer (420) to the top side of the circuit board (210).

6. The antenna array according to any one of the preceding claims, wherein: the top transmission line arrangement is implemented in suspended stripline design (350), and the bottom transmission line is implemented by means of one of a suspended stripline design (330), a coaxial cable (430, 630), stripline design (730) and microstrip design (830).

7. The antenna array according to any one of the claims 1 to 5, wherein: the top transmission line arrangement is implemented in microstrip design (450), and the bottom transmission line is implemented by means of one of a suspended stripline design (330), a coaxial cable (430, 630), stripline design (730) and microstrip design (830).

8. The antenna array according to any one of the claims 1 to 5, wherein: the top transmission line arrangement is implemented in stripline design (550), and the bottom transmission line is implemented by means of one of a suspended stripline design (330), a coaxial cable (430, 630), stripline design (730) and microstrip design (830).

9. The antenna array according to any one of the preceding claims, wherein said antenna bodies (121, 122) are attached to the top side of the circuit board (210) by at least one of soldering and mechanical fasteners.

10. The antenna array according to any one of the claims 1 to 8, comprising shell member (1000) of a non-conductive material, which shell member (1000) is arranged on the planar structure (110) and comprises a plurality of cavities (Cn1, Cn2, Cn3, . . . , Cnm) each of which constitutes one of said antenna bodies (121, 122) by means of an electrically conductive layer (1015) covering a respective active surface of each cavity of said plurality of cavities (Cn1, Cn2, Cn3, . . . , Cnm), which active surface faces the top side of the circuit board (210).

11. The antenna array according to claim 10, wherein the shell member (1000) comprises a generally flat exterior surface (1010) facing away from the top side of the circuit board (210).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

[0022] FIG. 1 shows a planar structure with antenna bodies according to one embodiment of the invention;

[0023] FIG. 2 shows a top side of a ground-plane layer included in the planar structure according to one embodiment of the invention;

[0024] FIGS. 3-8 illustrate, by means of cross-section side views, the structure of the antenna array according embodiments of the invention;

[0025] FIG. 9 shows a bottom side of the circuit board included in the planar structure according to one embodiment of the invention; and

[0026] FIG. 10 shows a cross-section side view of a shell member implementing the antenna bodies according to one embodiment of the invention.

DETAILED DESCRIPTION

[0027] FIG. 1 shows a planar structure 110 with antenna bodies according to one embodiment of the invention. The antenna bodies are arranged in an array on a top side of a circuit board that is included in the planar structure 110. This means that the antenna bodies are organized in a pattern of straight rows and columns. The exact number of antenna bodies is not critical. However, of course, a larger number of antenna bodies is associated with higher efficiency than a ditto lower number. Preferably, although not necessarily, the pattern is equilateral, i.e. the number of rows equals the number of columns, say 2 by 2 to 40 by 40, preferably 6 by 6 to 25 by 25. In FIG. 1, first and second exemplifying antenna bodies are designated by reference numerals 121 and 122 respectively.

[0028] The planar structure 110 further contains a ground-plane layer that is arranged below a bottom side of the circuit board, i.e. opposite to antenna bodies 121 and 122. FIG. 2 shows an example of such a ground-plane layer 220 seen from a top side thereof. The ground-plane layer 220 is made of an electrically conductive material, such as a metal, e.g. aluminum.

[0029] Each of the antenna bodies 121 and 122 contains a dome shaped structure, which is attached to the top side of the circuit board 210, for example by means of soldering and/or mechanical fasteners. The antenna bodies 121 and 122 are attached along a respective base of the dome shaped structure. The mechanical fasteners may be represented by snap in fasteners or an arrangement of compressed springs configured to provide galvanic contact between the antenna bodies 121 and 122 and a circuit pattern on the top side of the circuit board.

[0030] Turning now to FIG. 3, we see a cross-section side view, illustrating the structure of the antenna array according to one embodiment of the invention.

[0031] Each antenna body 121 and 122 is connected to a respective top transmission line 350, which is configured to convey microwave signals to and/or from the antenna body 121 or 122 respectively, i.e. for transmitting and/or receiving electromagnetic energy. Here, the top transmission lines 350 are implemented in suspended stripline design. The top transmission lines 350 are further connected to bottom transmission lines 330 via a respective coaxial probe 340 through the circuit board 210 and the ground-plane layer 220. The ground-plane layer 220 may be a solid piece of metal in which a pattern of cavities and openings have been milled out. In this embodiment, also the bottom transmission line 330 is implemented in suspended stripline design. However, as will be discussed below, a number of alternative bottom transmission line designs are also conceivable according to the invention. In fact, the same is true for the top transmission line design. Furthermore, according to the invention, any combination of top and bottom transmission line design is possible. The choice of the designs used is merely a matter of what is most suitable for the specific implementation.

[0032] A plurality of vias 370 through the circuit board 210 connect the ground-plane layer 220 to circuitry on the top side of the circuit board 210 so that the ground plane effectively extends above the circuit board 210 and thus can be further connected to the antenna bodies 121 and 122.

[0033] A resonance cavity 360 is arranged below the bottom side of the circuit board 210 between each of said antenna bodies 121 and 122 respectively. The resonance cavity 360 constitutes a stub, i.e. a length of waveguide connected at one end only, which is configured to direct as much as possible of the electromagnetic energy from the top transmission line 350 “upwards” towards the antenna bodies 121 and 122. Analogously, when the antenna operates in a receiving mode, the resonance cavity 360 configured to direct as much as possible of the electromagnetic energy that reaches the antenna bodies 121 and 122 “downwards” towards the top transmission line 350.

[0034] In FIG. 2, the resonance cavity is represented by the reference numeral 260. As can be seen here, the resonance cavity 260 is, in fact, a continuous milled-out volume between all the antenna elements, which each is mounted on a respective “island” 221 and 222 respectively where no, or only relatively little, material has been milled out from the solid piece of metal.

[0035] According to one embodiment of the invention, each antenna body 121 and 122 contains electrically conductive surface elements. Specifically, here, a first electrically conductive surface element 121H of a first antenna body 121 is configured to constitute a first portion of an antenna horn. Analogously, a second electrically conductive surface element 122H of a second antenna body 122 is configured to constitute a second portion of the antenna horn. The first and second antenna bodies 121 and 122 adjoin one another in such a manner that the first and second electrically conductive surface elements 121H and 122H respectively are located closer to one another than any other surface elements of the first and second antenna bodies 121 and 122. Thus, together, the first and second electrically conductive surface elements 121H and 122H form a horn configured to convey electromagnetic waves towards or from the top transmission line 350 depending on whether the antenna receives or transmits signals.

[0036] Each of the horns formed by the first and second electrically conductive surface elements 121H and 122H has a tapered profile towards the top side of the circuit board 210, for example as illustrated in FIG. 3. An aperture towards the resonance cavity 360 between the first and second electrically conductive surface elements 121H and 122H is symmetric around a normal to the top side of the circuit board 210.

[0037] The distance between the first and second electrically conductive surface elements 121H and 122H along the circuit board 210, the center distance between the first and second antenna bodies 121 and 122, the height of the first and second antenna bodies 121 and 122 above the circuit board 210 and the profile of the first and second electrically conductive surface elements 121H and 122H are different design parameters, which are selected depending on the frequency spectrum, the efficiency required and various physical constraints placed on the implementation.

[0038] Preferably, each antenna body 121 and 122 is mirror symmetric in exactly two planes that are orthogonal to one another. For example, the base of the dome shaped structure of the antenna bodies 121 and 122 may be octagon shaped, as shown in FIG. 1.

[0039] The antenna bodies 121 and 122 are further preferably arranged in the array according to a pattern in which the first and second electrically conductive surface elements 121H and 122H of adjoining antenna bodies pairwise form a respective antenna horn in such a manner that the antenna array contains horns of first and second subsets. The horns of the first subset are configured to transmit and/or receive signals of a first polarization direction, and the horns of the second subset are configured to transmit and/or receive signals of a second polarization direction, which is orthogonal to the first polarization direction. Moreover, each of the antenna bodies 121 and 122 form part of at least one horn that is included in the first subset and at least one horn that is included in the second subset. In FIG. 1, the first subset horns may contain all the electrically conductive surface elements 121H and 122H extending along a vertical direction, and the second subset horns may contain all the electrically conductive surface elements extending along a horizontal direction in the array of antenna bodies.

[0040] An antenna array, wherein the base of the dome shaped structure of each antenna body 121 and 122 is octagon shaped is advantageous because such geometry provides high isolation between signals representing the two orthogonal polarization directions. At the same time, the octagon shape renders it straightforward to configure the antenna bodies so that their tapered profile and the distances between the antenna bodies is optimized to match a particular range of the electromagnetic spectrum in which the antenna array is to operate. For example, in contrast to a design where the antenna bodies are circularly symmetric, the octagon-shaped base makes it possible to vary a distance along which an opening between the first and second electrically conductive surface elements 121H and 122H are effectively parallel to one another towards the resonance cavity 360 without the need to alter a center-to-center distance between the antenna bodies. From a design point-of-view, this is very beneficial when optimizing the design to a match particular frequency range of operation.

[0041] FIG. 4 shows a cross-section a side view illustrating the structure of the antenna array according to another embodiment of the invention. Here, the top transmission line arrangement is implemented in a microstrip design 450, and the bottom transmission line is implemented by means of a coaxial cable 430.

[0042] Analogous to the above, the planar structure 110 contains a circuit board 210 and a ground-plane layer 420, and the array of antenna bodies 121 and 122 being arranged on a top side of the circuit board 210, and each antenna body 121 and 122 contains a dome shaped structure being attached to the top side of the circuit board 210 along its base. Each antenna body 121 and 122 is connected to a respective top transmission line 450 configured to convey microwave signals to and/or from the antenna bodies 121 and 122. The top transmission lines 450 are connected to the bottom transmission lines 430 via coaxial probes 440 through the ground-plane layer 420. In addition, here a resonance cavity 460 is arranged below a bottom side of the circuit board 210 between each of the antenna bodies 121 and 122. The top transmission line 450 together with a slotline in between the antenna bodies 121 and 122 and the resonance cavity 460 constitutes a so-called balun, i.e. a balanced transmission line to an unbalanced transmission line conversion. The balun is configured to convert the signal from being a balanced signal along the top transmission line 450 to an unbalanced signal between the antenna bodies 121 and 122 and the resonance cavity 460.

[0043] A first circuit pattern 425 on the bottom side of the circuit board is electrically connected to the ground-plane layer 420. The first circuit pattern 425, in turn, is electrically connected to a second circuit pattern on the top side of the circuit board 210 by means of a plurality of vias 370 through the circuit board 210. Consequently, the ground plane also extends above the circuit board 210.

[0044] FIG. 9 shows the bottom side of the circuit board 910 and the first circuit pattern 425 according to this embodiment of the invention. Here, the reference numeral 970 designates the positions of said plurality of vias through the circuit board 910. The reference numeral 940 designates a portion of the first circuit pattern being connected to the coaxial probe 440 through the ground-plane layer 420.

[0045] FIG. 5 illustrates, by means of cross-section a side view, the structure of the antenna array according to another embodiment of the invention. Here, the top transmission line arrangement is implemented in a stripline design 550, and the bottom transmission line is implemented by means of a suspended stripline 530.

[0046] Analogous to the above, the planar structure 110 contains a circuit board 210 and a ground-plane layer 520, and the array of antenna bodies 121 and 122 being arranged on a top side of the circuit board 210, and each antenna body 121 and 122 contains a dome shaped structure being attached to the top side of the circuit board 210 along its base. Each antenna body 121 and 122 is connected to a respective top transmission line 550 configured to convey microwave signals to and/or from the antenna bodies 121 and 122, and the top transmission lines 550 are further connected to the bottom transmission lines 530 via coaxial probes 540 through the ground-plane layer 520. In addition, here a resonance cavity 560 is arranged below a bottom side of the circuit board 210 between each of the antenna bodies 121 and 122.

[0047] The ground-plane layer 520 is electrically connected to a first circuit pattern on the bottom side of the circuit board 210, which first circuit pattern is further electrically connected to a second circuit pattern on the top side of the circuit board 210 by means of a plurality of vias 570 through the circuit board 210 so as to extend a ground plane represented by the ground-plane layer 520 to the top side of the circuit board 210.

[0048] FIG. 6 illustrates, by means of cross-section a side view, the structure of the antenna array according to another embodiment of the invention. Here, the top transmission line arrangement is implemented in a suspended stripline design 650, and the bottom transmission line is implemented by means of a coaxial cable 630.

[0049] Analogous to the above, the planar structure 110 contains a circuit board 210 and a ground-plane layer 620, and the array of antenna bodies 121 and 122 being arranged on a top side of the circuit board 210, and each antenna body 121 and 122 contains a dome shaped structure being attached to the top side of the circuit board 210 along its base. Each antenna body 121 and 122 is connected to a respective top transmission line 650 configured to convey microwave signals to and/or from the antenna bodies 121 and 122, and the top transmission lines 650 are further connected to the bottom transmission lines 630 via coaxial probes 640 through the ground-plane layer 620. In addition, here a resonance cavity 660 is arranged below a bottom side of the circuit board 210 between each of the antenna bodies 121 and 122.

[0050] The ground-plane layer 620 is electrically connected to a first circuit pattern on the bottom side of the circuit board 210, which first circuit pattern is further electrically connected to a second circuit pattern on the top side of the circuit board 210 by means of a plurality of vias 670 through the circuit board 210 so as to extend a ground plane represented by the ground-plane layer 620 to the top side of the circuit board 210.

[0051] FIG. 7 illustrates, by means of cross-section a side view, the structure of the antenna array according to another embodiment of the invention. Here, the top transmission line arrangement is implemented in a stripline design 750, and the bottom transmission line 730 is likewise implemented by means of a stripline design.

[0052] Analogous to the above, the planar structure 110 contains a circuit board 210 and a ground-plane layer 720, and the array of antenna bodies 121 and 122 being arranged on a top side of the circuit board 210, and each antenna body 121 and 122 contains a dome shaped structure being attached to the top side of the circuit board 210 along its base. Each antenna body 121 and 122 is connected to a respective top transmission line 750 configured to convey microwave signals to and/or from the antenna bodies 121 and 122, and the top transmission lines 750 are further connected to the bottom transmission lines 730 via coaxial probes 740 through the ground-plane layer 720. In addition, here a resonance cavity 760 is arranged below a bottom side of the circuit board 210 between each of the antenna bodies 121 and 122.

[0053] The ground-plane layer 720 is electrically connected to a first circuit pattern on the bottom side of the circuit board 210, which first circuit pattern is further electrically connected to a second circuit pattern on the top side of the circuit board 210 by means of a plurality of vias 770 through the circuit board 210 so as to extend a ground plane represented by the ground-plane layer 720 to the top side of the circuit board 210.

[0054] FIG. 8 illustrates, by means of cross-section a side view, the structure of the antenna array according to one embodiment of the invention. Here, the top transmission line arrangement is implemented in a stripline design 850, and the bottom transmission line 830 is implemented by means of a microstrip design.

[0055] Analogous to the above, the planar structure 110 contains a circuit board 210 and a ground-plane layer 820, and the array of antenna bodies 121 and 122 being arranged on a top side of the circuit board 210, and each antenna body 121 and 122 contains a dome shaped structure being attached to the top side of the circuit board 210 along its base. Each antenna body 121 and 122 is connected to a respective top transmission line 850 configured to convey microwave signals to and/or from the antenna bodies 121 and 122, and the top transmission lines 850 are further connected to the bottom transmission lines 830 via coaxial probes 840 through the ground-plane layer 820. In addition, here a resonance cavity 860 is arranged below a bottom side of the circuit board 210 between each of the antenna bodies 121 and 122.

[0056] The ground-plane layer 820 is electrically connected to a first circuit pattern on the bottom side of the circuit board 210, which first circuit pattern is further electrically connected to a second circuit pattern on the top side of the circuit board 210 by means of a plurality of vias 870 through the circuit board 210 so as to extend a ground plane represented by the ground-plane layer 820 to the top side of the circuit board 210.

[0057] FIG. 10 shows a cross-section side view of a shell member 1000 implementing the antenna bodies according to an embodiment of the invention that is combinable with any of the above-described embodiments.

[0058] The shell member 1000 is made of a non-conductive material, and the shell member 1000 is arranged on the planar structure 110 instead of the antenna bodies 121 and 122.

[0059] The shell member 1000 contains a plurality of cavities Cn1, Cn2, Cn3, . . . , Cnm each of replaces one of the antenna bodies 121 and 122 by means of an electrically conductive layer 1015 that covers a respective active surface of each cavity of said plurality of cavities Cn1, Cn2, Cn3, . . . , Cnm. The active surface faces the top side of the circuit board 210, thus representing a circuit element equivalent to the outer surface an antenna body 121 or 122. Preferably, the shell member 1000 has a generally flat exterior surface 1010 facing away from the top side of the circuit board 210, since thereby the antenna obtains a nice-looking and easy to clean exterior surface.

[0060] The term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. However, the term does not preclude the presence or addition of one or more additional features, integers, steps or components or groups thereof.

[0061] The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.