Backhaul radio with an aperture-fed antenna assembly
View Patent ↗Directive gain antenna elements implemented with an aperture-fed patch array antenna assembly are described. A feed network for the aperture-fed patch array may include offset apertures and may also include meandering feed lines. Scalable aperture shapes and orientations that can be used with antennas operating at any frequency and with dual orthogonal polarizations are also disclosed. Directive gain antenna elements implemented with arrays of orthogonal reflected dipoles are also described with optimal feed networks and parasitic elements to achieve desired directive gain characteristics. Such arrayed dipole antennas feature dual orthogonal polarizations with assembly tabs that lower cost and improve reliability. Backhaul radios that incorporate said antennas are also disclosed.
1. An antenna assembly comprising:
a first substrate comprising a plurality of conductive patch elements;
a second substrate comprising a first layer with at least a conductive ground plane and a plurality of pairs of apertures, wherein the number of pairs of apertures is equal to the number of conductive patch elements, and a second layer with at least a first transmission line feed network coupled to a first feed point and a second transmission line feed network coupled to a second feed point; and
a spacer interposed between the first substrate and the second substrate, the spacer comprising a dielectric material and at least one spacer opening in the dielectric material, wherein the dielectric material is absent within the at least one spacer opening;
wherein the first transmission line feed network overlaps a first aperture of each pair of the plurality of pairs of apertures and the second transmission line feed network overlaps a second aperture of each pair of the plurality of pairs of apertures;
wherein the first aperture of each pair of the plurality of pairs of apertures electromagnetically couples the first transmission line feed network and the second aperture of each pair of the plurality of pairs of apertures electromagnetically couples the second transmission line feed network to a respective one of the plurality of conductive patch elements; and
wherein the first aperture of each pair of the plurality of pairs of apertures is orthogonal to the second aperture of each pair of the plurality of pairs of apertures,
wherein each of the first aperture and the second aperture of each respective pair of the plurality of pairs of apertures comprises an aperture body,
wherein the first transmission line feed network is terminated by a first via to the conductive ground plane after a feedline portion of the first transmission line feed network crosses over the aperture body of the first aperture of each pair of the plurality of pairs of apertures, and
wherein the second transmission line feed network is terminated by a second via to the conductive ground plane after a feedline portion of the second transmission line feed network crosses over the aperture body of the second aperture of each pair of the plurality of pairs of apertures.
2. The antenna assembly of claim 1 , wherein the first substrate is a printed circuit board.
3. The antenna assembly of claim 1 , wherein the second substrate is a printed circuit board.
4. The antenna assembly of claim 3 , wherein the second substrate is a printed circuit board comprising more than two layers.
5. The antenna assembly of claim 4 , wherein the first transmission line feed network and the second transmission line feed network each comprise striplines.
6. The antenna assembly of claim 1 , wherein the first transmission line feed network and the second transmission line feed network each comprise microstrip lines.
7. The antenna assembly of claim 1 , wherein the first feed point and the second feed point are each coupled to respective components on an outside layer of the second substrate.
8. The antenna assembly of claim 7 , wherein the respective components are at least one of an RF bandpass filter or a low noise amplifier within a receiver.
9. The antenna assembly of claim 1 , wherein the at least one spacer opening extends beyond a projected area of one or more of the plurality of conductive patch elements by at least a distance equal to a thickness of the spacer.
10. The antenna assembly of claim 1 , wherein the first aperture of each pair of the plurality of pairs of apertures excites a respective resonant radiating cavity formed between each respective one of the plurality of conductive patch elements and the conductive ground plane in an electromagnetic mode corresponding to a vertical polarization far-field pattern, and wherein the second aperture of each pair of the plurality of pairs of apertures excites said respective resonant radiating cavity in an electromagnetic mode corresponding to a horizontal polarization far-field pattern.
11. The antenna assembly of claim 1 , further comprising a plurality of plastic fasteners to hold the first substrate, the second substrate and the spacer together.
12. The antenna assembly of claim 1 , wherein the first aperture of each respective pair of the plurality of pairs of apertures is oriented relative to the second aperture of each respective pair of the plurality of pairs of apertures in a T-shape.
13. The antenna assembly of claim 1 , wherein the aperture body is a rectangular aperture body with an aperture body width, and wherein each of the first aperture and the second aperture of each respective pair of the plurality of pairs of apertures further comprises a pair of aperture ends with an aperture end width.
14. The antenna assembly of claim 13 , wherein each aperture end comprises a rectangular end and a semi-circular end with a radius equal to one half of the aperture end width.
15. The antenna assembly of claim 14 , wherein the aperture end width is at least five times greater than the aperture body width.
16. The antenna assembly of claim 13 , wherein each aperture end is tapered or rounded.
17. The antenna assembly of claim 14 , wherein the rectangular end has a width equal to the aperture end width and a thickness equal to one sixth of the aperture end width.
18. The antenna assembly of claim 13 , wherein the aperture end width is equal to one third of an aperture length.
19. The antenna assembly of claim 1 , wherein the plurality of conductive patch elements is arranged in an array with a plurality of rows wherein each row comprises at least one conductive patch element.
20. The antenna assembly of claim 1 , wherein the plurality of conductive patch elements is arranged in an array with a plurality of rows and a plurality of columns wherein each row comprises a number of conductive patch elements equal to the number of columns.
21. The antenna assembly of claim 20 , wherein the number of columns is equal to two.
22. The antenna assembly of claim 21 , wherein a first feedline portion of the first transmission line feed network crosses over a rectangular aperture body of the first aperture of each pair of the plurality of pairs of apertures in a first direction for each first aperture that excites each respective resonant radiating cavity formed between each respective one of the plurality of conductive patch elements and the conductive ground plane for conductive patch elements arranged in a first column and a second feedline portion of the first transmission line feed network crosses over the rectangular aperture body of the first aperture of each pair of the plurality of pairs of apertures in a second direction for each first aperture that excites each respective resonant radiating cavity formed between each respective one of the plurality of conductive patch elements and the conductive ground plane for conductive patch elements arranged in a second column, and wherein the second direction is opposite to the first direction.
23. The antenna assembly of claim 22 , wherein the second feedline portion is electrically longer than the first feedline portion by a distance equivalent to 180 degrees in phase at a target operating frequency for the antenna assembly.
24. The antenna assembly of claim 23 , wherein a third feedline portion of the second transmission line feed network crosses over a rectangular aperture body of the second aperture of each pair of the plurality of pairs of apertures in a third direction for each second aperture that excites each respective resonant radiating cavity formed between each respective one of the plurality of conductive patch elements and the conductive ground plane for conductive patch elements arranged in the first column and a fourth feedline portion of the second transmission line feed network crosses over the rectangular aperture body of the second aperture of each pair of the plurality of pairs of apertures in a fourth direction for each second aperture that excites each respective resonant radiating cavity formed between each respective one of the plurality of conductive patch elements and the conductive ground plane for conductive patch elements arranged in the second column, and wherein the third direction is the same as the fourth direction.
25. The antenna assembly of claim 24 , wherein the third feedline portion is equivalent in electrical length to the fourth feedline portion.
26. The antenna assembly of claim 19 , wherein each of the first transmission line feed network and the second transmission line feed network comprises at least one meandering line portion.
27. The antenna assembly of claim 26 , wherein each meandering line portion comprises one or more bends, and wherein an electrical length of each meandering line portion matches a group delay from the respective first or second feed point to at least one of the respective first or second apertures with that of another group delay from the respective first or second feed point to at least one other of the respective first or second apertures.
28. The antenna assembly of claim 19 , wherein each of the first transmission line feed network and the second transmission line feed network comprises at least one tunable element.
29. The antenna assembly of claim 28 , wherein an input signal applied to at least one tunable element adjusts at least one characteristic of the antenna assembly, said characteristic being at least one selected from the group consisting of a far-field radiation pattern, a coupling between the first feed point and the second feed point, and a coupling to one or more nearby antennas.