Wideband antenna

Abstract

A wideband/broadband antenna is described, comprising a dielectric substrate with a first surface with an antenna feed with two conductors, comprising a first feed connection and a second feed connection, wherein the second feed connection is or acts as the ground. A first conductive layer extends from the antenna feed in a first direction and is electrically connected to the first feed connection, wherein the first conductive layer extends in a direction away from the antenna feed, and to a first end edge. A second conductive layer extends in a second direction, away from the first conductive layer, and is electrically connected to the second feed connection. A non-conductive zone separates the first and second conductive layers. On a second surface of the substrate there is a third conductive layer which extends from a second end edge in the direction towards the antenna feed, the extent of which at least in part coincides with that of the first conducting layer at the first surface. The first end edge of the first conducting layer and the second end edge of the third conducting layer substantially coincides, and the first and third electrical layers are electrically connected with each other at or near said end edges. Apart from said electrical interconnection at the edges, the layers are electrically separated from each other.

Claims

1. A wideband/broadband antenna comprising: a dielectric substrate with a first and second surface, wherein the first surface comprises: an antenna feed with two conductors, comprising a first feed connection and a second feed connection, wherein the second feed connection is or acts as the ground; a first conductive layer which extends from the antenna feed in a first direction and which is electrically connected to the first feed connection, wherein the first conductive layer extends in a direction away from the antenna feed, and to a first end edge; a second conductive layer that primarily extends in a second direction, away from the first conductive layer, and which is electrically connected to the second feed connection; and a non-conductive zone separating the first and second conductive layers; and wherein the second surface comprises: a third conductive layer which extends from a second end edge in the direction towards the antenna feed, the extent of which at least in part coincides with that of the first conductive layer at the first surface, the first end edge of the first conductive layer and the second end edge of the third conductive layer coinciding, and wherein the first and third conductive layers are electrically connected with each other at or near said end edges, and wherein the first and third conductive layers, apart from said electrical interconnection at the edges, are electrically separated from each other; wherein the second conductive layer has a fork-shaped configuration, with two fork arms extending along the sides of the first conductive layer, past said antenna feed and in a direction towards the first end edge, and wherein the first conductive layer forms a solid layer having a continuously or incrementally increasing width in a direction away from the antenna feed and towards the first end edge.

2. The antenna of claim 1, wherein the first conductive layer has a continuously increasing width in the direction away from the antenna feed.

3. The antenna of claim 1, wherein the two fork arms differ in width and area.

4. The antenna of claim 1, wherein at least one of the two fork arms are wedge-shaped and has a decreasing width in the direction of the end edge of the first conductive layer over at least part of its extension.

5. The antenna of claim 1, wherein the second conductive layer comprises a surface with a constant width, extending from the antenna feed and away from the first conductive layer.

6. The antenna of claim 1, wherein the antenna feed is arranged relatively centrally on the first surface.

7. The antenna of claim 1, wherein the third conductive layer has a different shape than the first conductive layer, whereby the third conductive layer only partially overlaps with the first conductive layer.

8. The antenna of claim 1, wherein the third conductive layer has fork-shape, with arms extending at the sides in a direction away from the second end edge.

9. The antenna of claim 1, further including a fourth conductive layer on the second surface, the extent of which at least in part coincides with the second conductive layer on the first surface.

10. The antenna of claim 9, wherein the second and fourth conductive layers are electrically connected by a plurality of interconnection points.

11. The antenna of claim 9, wherein the third and fourth conductive layers are separated from each other by a non-conductive zone.

12. The antenna of claim 9, wherein the fourth conductive layer has an area and geometry which largely coincides with that of the second conductive layer.

13. The antenna of claim 1, wherein the electrical interconnection between the first and third conductive layers is distributed over the length of the end edge.

14. The antenna of claim 1, wherein both of the two fork arms are wedge-shaped and have a decreasing width in the direction of the first end edge of the first conductive layer over at least part of its extension.

15. A wideband/broadband antenna comprising: a dielectric substrate with a first and second surface, wherein the first surface comprises: an antenna feed with two conductors, comprising a first feed connection and a second feed connection, wherein the second feed connection is or acts as the ground; a first conductive layer which extends from the antenna feed in a first direction and which is electrically connected to the first feed connection, wherein the first conductive layer extends in a direction away from the antenna feed, and to a first end edge; a second conductive layer that primarily extends in a second direction, away from the first conductive layer, and which is electrically connected to the second feed connection; and a non-conductive zone separating the first and second conductive layers; and wherein the second surface comprises: a third conductive layer which extends from a second end edge in the direction towards the antenna feed, the extent of which at least in part coincides with that of the first conductive layer at the first surface, the first end edge of the first conductive layer and the second end edge of the third conductive layer coinciding, and wherein the first and third conductive layers are electrically connected with each other at or near said end edges, and wherein the first and third conductive layers, apart from said electrical interconnection at the edges, are electrically separated from each other; wherein the second conductive layer has a fork-shaped configuration, with two fork arms extending along the sides of the first conductive layer, past said antenna feed and in a direction towards the first end edge, wherein the first conductive layer forms a solid layer having a continuously or incrementally increasing width in a direction away from the antenna feed and towards the first end edge, and wherein the first conductive layer has a triangular shape.

16. The antenna of claim 9, wherein the second and fourth conductive layers are electrically connected by a plurality of interconnection points distributed over said second and fourth conductive layers.

17. A wideband/broadband antenna comprising: a dielectric substrate with a first and second surface, wherein the first surface comprises: an antenna feed with two conductors, comprising a first feed connection and a second feed connection, wherein the second feed connection is or acts as the ground; a first conductive layer which extends from the antenna feed in a first direction and which is electrically connected to the first feed connection, wherein the first conductive layer extends in a direction away from the antenna feed, and to a first end edge; a second conductive layer that primarily extends in a second direction, away from the first conductive layer, and which is electrically connected to the second feed connection; and a non-conductive zone separating the first and second conductive layers; and wherein the second surface comprises: a third conductive layer which extends from a second end edge in the direction towards the antenna feed, the extent of which at least in part coincides with that of the first conductive layer at the first surface, the first end edge of the first conductive layer and the second end edge of the third conductive layer coinciding, and wherein the first and third conductive layers are electrically connected with each other at or near said end edges, and wherein the first and third conductive layers, apart from said electrical interconnection at the edges, are electrically separated from each other; and a fourth conductive layer on the second surface, the extent of which at least in part coincides with the second conductive layer on the first surface, wherein the fourth conductive layer has an area and geometry which largely coincides with that of the second conductive layer.

18. The antenna of claim 1, wherein the electrical connection between the first and third conductive layers at or near the end edges is distributed along the end edges.

19. The antenna of claim 1, wherein the first end edge of the first conductive layer and the second end edge of the third conductive layer wholly coincide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described in more detail with reference to exemplary embodiments, and with reference to the attached drawings. The figures of the drawings show:

(2) FIGS. 1a and 1b is a circuit board with an antenna in accordance with an embodiment of the invention, where FIG. 1a shows the top side of the circuit board, and FIG. 1b shows the bottom side of the circuit board;

(3) FIG. 2a-d are diagrams showing different antenna parameters measured with the antenna in accordance with FIG. 1; and

(4) FIG. 3a-h are radiation patterns at different frequencies measured with the antenna in accordance with FIG. 1.

DETAILED DESCRIPTION

(5) With reference to FIG. 1, a dielectric substrate 1, such as a printed circuit board (“Printed Circuit Board, PCB), is shown, conductive layers are provided to form an omnidirectional, wideband/broadband antenna in accordance with an embodiment thickness of e.g. a few tenths of a millimeter. The substrate can, advantageously, be rectangular, as shown in the illustrated embodiment. However, the circuit board may also adopt other shapes.

(6) The circuit board includes a first and second surface, which can also be denominated upper side and bottom side. However, it is to be appreciated by the skilled artisan that upper side and bottom side do not necessarily relate to the physical positioning of the sides, but depending on the mounting and application, the upper side may very well be below the bottom side. The first side, the upper side, is shown in FIG. 1a, while the other side, the bottom side, is shown in FIG. 1b.

(7) The first side is connected to an antenna feed with two conductors, connected to an external transmitter/receiver via e.g. a coax cable or another cable with two conductors. The antenna feed includes a first feed connection 2a and a second feed connection 2b. The second feed connector is, or acts as, ground.

(8) The antenna feed is preferably arranged relatively centrally on top of the substrate, at a distance, and preferably at about the same distance, from the two long sides and the two short sides. However, it is also possible to provide the antenna feed in a non-centralized position. For example, the antenna feed may be provided displaced towards one of the long sides, or even at one of the long sides.

(9) Further, the first side comprises a first conductive layer 3 which extends from the antenna feed in a first direction and which is electrically connected to the first feed connection 2a. The first conductive layer has an increasing width in a direction away from the antenna feed 2a and towards a first end edge 31. In the illustrative embodiment, the first conducting layer has a continuously increasing width, and has a triangular shape, with one of the ends connected to the antenna feed 2a, and the opposite triangle side forming the end edge 31. The first conductive layer can also be shaped in other ways. For example, the width may instead increase stepwise, and with areas of constant width in between. The increase in width can also be non-linear, so that the area instead, for example, has the shape of a funnel or a horn.

(10) The first side further includes a second conductive layer 4, which essentially extends in a second direction, away from the first conductive layer 3. The second conductive layer 4 is electrically connected to the second feed connection 2b, thus forming antenna grounding.

(11) A non-conductive zone 5 is provided between the first conductive layer 3 and the second conductive layer 4, thus forming an electrical separation between the layers.

(12) According to an embodiment, the second conductive layer 4 may have a substantially constant width, extending from the antenna feed and away from the first conductive layer. This area may be substantially rectangular. The width of this area can be substantially the same width as the widest part of the first conductive layer, i.e. in the case of the now showed embodiment, the width of the end edge 31.

(13) The second conducting layer can also have a fork shaped design, with two arms 41 and 42 extending along the sides of the first conductive layer 3, past the antenna feed 2a, 2b and towards the end edge 31. The two fork arms can have different widths and areas. In the illustrated example, the fork arm 41 has a broader base and a larger area than the fork arm 42. At least one, and preferably both, the fork arms is/are further preferably wedge-shaped, and has/have a decreasing width in the direction towards the end edge of the first conductive layer over at least part of its/their extension. Specifically, the wedge shape may be in the form of a truncated wedge, with a blunt end facing the end edge 31 of the first conductive layer 3. Expressed differently, the second conductive layer comprises a non-conductive indentation 43, into which the first conductive layer extends, and in the bottom of which the antenna feeds 2a and 2b are located.

(14) The second surface, the bottom side, includes a third conductive layer 6 which extends from a second end edge 61 in the direction towards the antenna feed 2a, 2b, and with an extension that at least in part coincides with the extension of the first conductive layer 3 on the first surface.

(15) The first end edge 31 at the first conductive layer 3 and the second end edge 61 of the third conductive layer 6 substantially coincide with each other, i.e. are above each other, but on either side of the substrate. Furthermore, the first and third conductive, electrical layers are electrically interconnected with each other at or near said end edges 31, 61. This electrical interconnection can be achieved by means of electrical through connections, called via holes, at or near the end edges, as is shown by means of dots in FIGS. 1a and 1b. Preferably several such electrical through connections are provided, and distributed along the end edges. The electrical connection can, however, also be accomplished in other ways, such as through a continuous connection that extends along the short edge of the substrate, by means of a number of wires that stretch along the short edge of the substrate, or the like. In addition to this electric interconnection at the edges, the first and the third layers are electrically separated from each other, i.e. there is no additional electrical interconnection between these layers.

(16) By this electric interconnection at the end edges, the third conductive layer forms a fold-over extension of the first conductive layer.

(17) The third conductive layer preferably has a different design and shape than the first conductive layer, whereby the third conductive layer only partially overlaps with the first conductive layer. Hereby, the first and third conductive layers both have surface areas that overlap, i.e. are above each other, and surface areas that do not coincide. Preferably, both the first and third conductive layer comprise surface areas which do not coincide with corresponding surface areas in the other layer.

(18) In the illustrated embodiment, the third conductive layer has a fork shape, with fork arms 62, 63 extending along the sides in a direction away from the end edge 61. These fork arms preferably extend along the long sides of the substrate, and outside the tip of the triangularly shaped first conductive layer, in the direction towards the antenna feed 2a, 2b.

(19) In the illustrated embodiment the third conductive layer initially, seen from the end edge 61, has a rectangular form, followed by the fork arms. The fork arms are preferably shaped with a first section, seen from the rectangular area, with a gradually decreasing width, and thereafter an end section with essentially uniform width. Differently expressed, the third conductive layer comprises a non-conductive indentation 64, wherein the indentation is relatively centrally arranged, and facing the antenna feed 2a, 2b.

(20) The length of the third conductive layer is preferably shorter than the length of the first conductive layer.

(21) The second surface may also comprise a fourth conductive layer 7. This layer is preferably electrically interconnected with the second conductive layer 4 at the first surface. The fourth conductive layer 7 and the second conductive layer 4 are preferably interconnected by numerous electrical through connections/via holes, as illustrated by means of dots in the figures, and which are distributed over the entire surfaces of the second and fourth conductive layers.

(22) The fourth conductive layer preferably has an extension which at least in part coincides with that of the second conductive layer at the first surface. In the illustrated embodiment, the fourth conductive layer has an area and geometry which largely coincides with that of the second conductive layer. Similar to the second conductive layer, the fourth conductive layer 7 may advantageously comprise a larger, rectangular portion, as well as fork arms 71, 72, which extend towards the third conductive layer. Hereby, also the fourth conductive layer preferably forms a non-conductive indentation 73 facing the third conductive layer. Unlike the second conductive layer 4, which has a wedge-shaped indentation in the illustrated embodiment, the fourth conductive layer 7 preferably has a substantially rectangular indentation, i.e. with fork arms that have the same or substantially the same width throughout their extensions.

(23) The third conductive layer 6 and the fourth conductive layer 7 are preferentially separated from each other by a non-conductive zone 8.

(24) The fourth conductive layer 7 preferably has a larger area than the third conductive layer 6.

(25) The antenna can be scaled in dependence of which frequency ranges it is to be optimized for. With a scale factor X, which may for example be 1, the antenna can advantageously have the following dimensions: The total length can be in the range of 10×-20×cm, and preferably 12×-18×cm, and most preferably 13×-17×cm, such as 15×cm. The total width can be in the range of 2×-7×cm, and preferably 3×-6×cm, and most preferably 3×-5×cm, such as 3.8×cm. The length of the first conductive layer can be in the range of 5×-10×cm, and preferably 6×-9×cm, and most preferably 7×-8×cm, such as 7.8×cm. The length of the second conductive layer can be in the range of 7×-15×cm, and preferably 8×-12×cm, and most preferably 9×-11×cm, such as 10.2×cm. The length of the third conductive layer can be in the range of 2×-6×cm, and preferably 3×-5×cm, and most preferably 4×-5×cm, such as 4.3×cm. The length of the fourth conductive layer can be in the range of 7×-15×cm, and preferably 8×-12×cm, and most preferably 9×-11×cm, such as 9.7×cm.

(26) The antenna according to the above discussed embodiment has been tested experimentally. In these measurements it has been demonstrated that the antenna has very good performance over a very wide frequency range.

(27) In FIG. 2a the measured efficiency (%) for different frequencies are shown. In general, an efficiency of at least 30% is considered good, and over 70-80% as extremely good. It can be seen that the new antenna has extremely high efficiency over a wide frequency range, and especially for the frequencies used for GSM, CDMA, LTE, ISM, GPS, UMTS, HSPA, WiFi, Bluetooth, etc., which are marked as grey in the diagram.

(28) FIG. 2b shows the measured return loss in dB for different frequencies. Here, too, it turns out that the measured antenna has very satisfactory performance over the whole measured frequency range.

(29) FIG. 2 c shows the measured VSWR (Voltage Standing Wave Ratio) at different frequencies. Generally speaking, VSWR values at 1-3 are fully acceptable, and it was found that the measured antenna has sufficiently low VSWR values over the entire frequency range measured.

(30) FIG. 2d shows the measured Peak Gain (dB) over different frequencies. Peak Gain is a measure of the directivity of the antenna, and for an omnidirectional antenna, it is generally preferred to have relatively low Peak Gain values. It was found that the measured antenna has relatively low values for Peak Gain at all frequencies, and in particular at all frequency ranges that are of interest with respect to available telecommunication standards.

(31) FIGS. 3a-h show radiation patterns for various frequencies in dBi, and in X (landscape), Y (portrait) and Z (page position). More specifically, the following is shown: FIG. 3a shows the radiation pattern for 800 MHz; FIG. 3b shows the radiation pattern for 1200 MHz; FIG. 3c shows the radiation pattern for 1500 MHz; FIG. 3d shows the radiation pattern for 1900 MHz; FIG. 3e shows the radiation pattern for 2100 MHz; FIG. 3f shows the radiation pattern for 2400 MHz; FIG. 3g shows the radiation pattern for 2600 MHz; and FIG. 3h shows the radiation pattern for 3000 MHz.

(32) All radiation patterns clearly show that satisfactory omnidirectional radiation is achieved at all the measured frequencies.

(33) The invention has now been described by use of exemplary embodiments. It should, however, be appreciated by the skilled reader that many alternatives and modifications of these embodiments are possible. For example, the geometries of the different conductive layers may be varied in different ways, as is also discussed above. Moreover, it suffices for many applications with a ground plane arranged only at one of the sides/surfaces, instead of using dual ground planes, as in the above discussed embodiment. In multilayer substrates, more than two ground planes may also be used. In the above discussed embodiment the substrate is further dimensioned so that the substrate's extension substantially coincides with the extension of the antenna. This is an advantage if the antenna is to be manufactured as a stand-alone device. However, it is also possible to arrange the antenna as part of a larger substrate. Such a larger substrate may then also contain additional conductive/wire structure and/or components, such as a transmitter/receiver for the antenna, a battery, a display, signal processing circuits, a processor, etc. These and other related alternatives of the invention shall be regarded as falling within the scope of protection defined in the appended claims.