received by the International Bureau on 19 October 2020 (19.10.2020)

1. A radio frequency (RF) aperture comprising:

an array of electrically conductive tapered projections arranged to define a curved aperture surface.

2. The RF aperture of claim 1 wherein the array of electrically conductive tapered projections are arranged to define a semi-cylinder aperture surface.

3. The RF aperture of claim 1 wherein the array of electrically conductive tapered projections are arranged to define a cylinder aperture surface.

4. The RF aperture of claim 3 wherein the array of electrically conductive tapered projections includes:

a first array of electrically conductive tapered projections arranged to define a first semi-cylinder aperture surface; and

a second array of electrically conductive tapered projections arranged to define a second semi-cylinder aperture surface;

wherein the first and second semi-cylinder aperture surfaces are mutually arranged to define the cylinder aperture surface.

5. The RF aperture of any one of claims 3-4 further comprising:

a top array of electrically conductive tapered projections arranged to define a top aperture surface.

6. The RF aperture of claim 5 wherein the top aperture surface is a planar top aperture surface.

7. The RF aperture of claim 6 wherein a cylinder axis of cylinder aperture surface is perpendicular to the plane of the planar top aperture surface.

8. The RF aperture of claim 1 wherein the array of electrically conductive tapered projections are arranged to define a curved aperture surface that is conformal with a curved surface of a fuselage of an aircraft or unmanned aerial vehicle (UAV) or with a curved surface of a hull of a ship or submarine or with a curved surface of a satellite.

9. The RF aperture of any one of claims 1-8 comprising:

at least one printed circuit board; and

RF circuitry disposed on the at least one printed circuit board and electrically connected with the electrically conductive tapered projections to receive or apply differential RF signals between neighboring pairs of electrically conductive tapered projections.

10. The RF aperture of claim 9 wherein the array of electrically conductive tapered projections are arranged to define a semi-cylinder aperture surface.

11. The RF aperture of claim 9 wherein the array of electrically conductive tapered projections are arranged to define a cylinder aperture surface.

12. The RF aperture of claim 11 wherein the array of electrically conductive tapered projections includes:

a first array of electrically conductive tapered projections arranged to define a first semi-cylinder aperture surface; and

a second array of electrically conductive tapered projections arranged to define a second semi-cylinder aperture surface;

wherein the first and second semi-cylinder aperture surfaces are mutually arranged to define the cylinder aperture surface.

13. The RF aperture of any one of claims 11-12 further comprising:

a cylindrical support supporting the array of electrically conductive tapered projections arranged to define the cylinder aperture surface;

wherein the at least one printed circuit board comprises a plurality of printed circuit boards disposed inside the cylindrical support.

14. The RF aperture of claim 13 wherein the plurality of printed circuit boards comprise perpendicular printed circuit boards each having an edge proximate to an inside surface of the cylindrical support and each being perpendicular to the cylindrical support at the edge proximate to the cylindrical support.

15. The RF aperture of claim 14 wherein the perpendicular printed circuit boards are radially oriented perpendicular printed circuit boards.

16. The RF aperture of claim 15 wherein the edge of each radially oriented perpendicular printed circuit board that is proximate to the inside surface of the cylindrical support is secured with the inside surface of the cylindrical support.

17. The RF aperture of any one of claims 15-16 wherein the edge of each radially oriented perpendicular printed circuit board that is proximate to the cylindrical support is positioned between two adjacent rows of adjacent electrically conductive tapered projections.

18. The RF aperture of claim 13 wherein the plurality of printed circuit boards comprise circular printed circuit boards disposed concentrically inside the cylindrical support and having circular perimeters that are proximate to an inside surface of the cylindrical support.

19. The RF aperture of claim 18 wherein a cylinder axis of the cylindrical support is perpendicular to the circular printed circuit boards.

20. The RF aperture of any one of claims 18-19 wherein the circular perimeters of the circular printed circuit boards are secured with the inside surface of the cylindrical support.

21. The RF aperture of any one of claims 18-20 wherein the circular printed circuit boards are positioned between adjacent rings of electrically conductive tapered projections.

22. The RF aperture of any one of claims 9-21 further comprising:

baluns mounted on the at least one printed circuit board wherein each balun has a balanced port electrically connected with two neighboring electrically conductive tapered projections of the array of electrically conductive tapered projections to receive or apply a differential RF signal between the two neighboring electrically conductive tapered projections, and further has an unbalanced port;

wherein the RF circuitry disposed on the at least one printed circuit board is electrically connected with the unbalanced ports of the baluns.

23. The RF aperture of claim 22 wherein the at least one printed circuit board includes:

a first at least one printed circuit board carrying a first subset of the baluns whose balanced ports are electrically connected with the first array of electrically conductive tapered projections; and

a second at least one printed circuit board carrying a second subset of the baluns whose balanced ports are electrically connected with the second array of electrically conductive tapered projections.

24. The RF aperture of claim 23 wherein:

the first at least one printed circuit board is planar, and the balanced ports of the first subset of the baluns are electrically connected with the first array of electrically conductive tapered projections by coaxial cables; and

the second at least one printed circuit board is planar, and the balanced ports of the second subset of the baluns are electrically connected with the second array of electrically conductive tapered projections by coaxial cables.

25. The RF aperture of any one of claims 1-24 wherein the array of electrically conductive tapered projections comprise:

dielectric tapered projections; and

an electrically conductive layer disposed on a surface of the dielectric tapered projections.

26. The RF aperture of any one of claims 1-24 wherein the electrically conductive tapered projections are hollow.

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27. The RF aperture of any one of claims 1-24 wherein the electrically conductive tapered projections are solid.

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