The present invention relates to a half-mode substrate integrated antenna structure for radiating and/or receiving electromagnetic signals.
The half-mode substrate integrated antenna structure according to the present invention hereby bases on the known substrate integrated wave guide technology, in which wave guides for microwave and millimeter wave applications are created by placing metallic layers on a top and a bottom side of a dielectric substrate and by creating a channel for the electromagnetic signals by means of series or rows of conducting vias. Such wave guides usually have a length which is two or more times larger than the width and a very small height as compared to the width so that a high integration of these wave guides is possible. Further, these wave guides can be manufactured at low cost, for example by a printed circuit board fabrication process, while still providing a high performance. Normal (full-mode) wave guides comprise two at least partially parallel series or rows of conducting vias connecting the two conducting layers on the top and the bottom side of the substrate, whereby the electromagnetic signals are guided in between the two rows or series of conducting vias. More recent developments have found that it is possible to build half-mode substrate integrated wave guides which only comprise a single row or series of conducting vias and therefore have only half the size of a full-mode substrate integrated wave guide. Hereby, by basically cutting the full-mode substrate integrated wave guide in half in the length direction creates an open side along the middle between the formerly two rows of conducting vias, whereby the open side is almost equivalent to a perfect magnetic wall due to the high ratio of width to height. In other words, half-mode substrate integrated wave guides provide almost the same performance as full-mode substrate integrated wave guides, but with half the size. It has further been found that such half-mode substrate integrated wave guides can be used as antennas.
The object of the present invention is to propose a substrate integrated antenna structure enabling a high integration and more versatile applications as compared to the prior art.
The above-object is achieved by a half-mode substrate integrated antenna structure for radiating and/or receiving electromagnetic signals according to claim 1. The half-mode substrate integrated antenna structure according to the present invention comprises a substrate made of a dielectric material with a top and a bottom side, the substrate being at least partially of a flat shape having a main plane, a conductive layer arranged on said top and a conductive layer arranged on said bottom side of the substrate, a series of conductive vias extending between the conductive layers of the top and the bottom side of the substrate so that a wave guide having a feeding end and an antenna end is formed, whereby said antenna end is formed by end regions of said conductive layers and said substrate so that at a radiation pattern of said antenna structure essentially extends in the main plane.
The half-mode substrate integrated antenna structure according to the present invention is particularly adapted to operate in broad band applications, preferably in the microwave and/or millimeter wave range. The antenna structure of the present invention has a small size and can therefore be integrated easily, is simple to manufacture and can be used for various applications in a very flexible manner. Particularly, since the antenna structure of the present invention has a radiation pattern which is essentially extending in the main plane of the antenna structure, a plurality of antenna structures according to the present invention can be integrated very efficient by, i.e. in other words it is possible to arrange a plurality of antenna structures according to the present invention next to each other.
Advantageously, the conductive layers in the substrate at the antenna end form an open end structure.
Further advantageously, the series of vias extends along the length of said antenna structure from said feeding end towards said antenna end wherein end parts of said end regions of said conductive layers are free of conductive vias. Hereby, advantageously, the length of said end parts is between 3% and 15%, preferably between 5% and 10%, of the length of said conductive layers. Further advantageously, the series of vias in intermediate parts of said end regions adjacent to said end parts is arranged essentially along in middle line of said conductive layers in the length direction so that the radiation pattern of said antenna structure essentially extends in the length direction of the antenna structure. Alternatively, the series of vias in intermediate parts of said end regions adjacent to said end parts is arranged essentially at an angle to a middle line of said conductive layers in the length direction so that the radiation pattern of said antenna structure essentially extends in the direction of said angle. Advantageously, the length of said intermediate region is between 3% and 15%, preferably between 5% and 10%, of the length of said conductive layers.
Advantageously, the wave guide comprises a middle region in which the series of vias is arranged essentially along a straight line. The series of vias acts as a wave or field guide for the electromagnetic signals in cooperation with the magnetic wall. Hereby, the straight line is advantageously the middle line of said conductive layers in their length direction. Further advantageously, the length of the middle region is between 30% and 70%, preferably between 40% and 60%, of the length of said conductive layers.
Advantageously, the antenna structure of the present invention further comprises a feeding structure coupled to said feeding end of said wave guide at or adjacent to a side wall thereof, wherein said wave guide comprises a feeding region adjacent to said feeding end, wherein the series of vias arranged in said feeding region is arranged closer to an opposite side wall of the wave guide and to the side wall at or adjacent to which the feeding structure is coupled. Hereby, the length of said feeding region is advantageously between 20% and 50%, preferably between 30% and 40%, of the length of said conductive layers.
The present invention is further explained in the following detailed description of preferred embodiments in relation to the enclosed drawings, in which
a shows a schematic side view of an antenna structure of the present invention with its radiation pattern,
b shows a schematic side view of an alternative antenna structure of the present invention,
A conductive layer 3a is arranged on the top side 2a of the substrate and a conductive layer 3b is arranged on the bottom side 2b of the substrate 2, cf.
The antenna structure 1 further comprises a series or a row of conductive vias 4 extending between the conducive layers 3a, 3b so that a wave guide feeding end 5 and an antenna end 6 is formed. The conductive vias 4 are conductive posts or rods connecting the two conductive layers 3a, 3b, as shown in
On the feeding end of the wave guide, the feeding structure 12 for supplying electromagnetic signals to or from the wave guide is connected at the corner of the longitudinal side 14a which forms the magnetic wall forming the electromagnetic signals. In different applications, the feeding structure 12 may not be located directly at the corner but may just be connected closer to the longitudinal side 14a forming the magnetic wall than to the opposite longitudinal side 14b of the wave guide. The opposite end of the feeding end 5 in the longitudinal direction of the wave guide is an antenna end 6, which is formed by end regions 7 of the conductive layers 3a, 3b and the substrate 2. The schematic side view of the antenna structure 1 shown in
The series or row of conductive vias 4 extends along the length of the antenna structure 1 from the feeding end 5 towards the antenna end 6 in a consecutive manner, except that the end parts 7a of the end region 7 of the conductive layers 3a, 3b are free of conductive vias 4. In other words, the end parts 7a of the end region 7 bordering the edge or the side of the open end 8 do not have conductive vias. The length l6 of the end parts 7a is between 3% and 15%, preferably between 5% and 10% and in the shown example about 7.5% of the length l2 of the conductive layers 3a, 3b. The end regions 7 further comprise an intermediate part 7b arranged adjacent to the end parts 7a and a middle region 9 of the conductive layers 3a, 3b. The intermediate parts 7b have conductive vias 4, whereby the arrangement of the vias 4 in the intermediate parts 7b influences the direction of the radiation pattern in the main plane M. In the antenna structure 1 of the first embodiment shown in
The antenna structure 1 of the present invention further comprises a middle region 9 which is adjacent to the intermediate region 7b of the end region 7. In the middle region 9, the series of conductive vias 4 is arranged essentially along a straight line. In the shown embodiment, the straight line is the middle line C of the conductive layers 3a, 3b in the length direction, which is separating the conductive layers 3a, 3b in the middle, i.e. at a distance of W2/2 to each longitudinal side 14a and 14b. The length l4 of the middle region 9 is advantageously between 30% and 70%, preferably between 40% and 60%, in the shown example about 50% of the length l2 of the conductive layers 3a, 3b.
As discussed above, the antenna structure 1 of the present invention may further comprise the feeding structure 12 coupled to that feeding end 5. In the first embodiment shown in
The antenna structure 10 of the second embodiment shown in
The series of vias 4 in the intermediate part 7b of the end region 7 of the antenna structure 11 of the third embodiment shown in
It has to be noted that
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