Periodic mode-selective structure for surface wave scattering mitigation in millimeter wave antenna arrays
According to one embodiment, an RF front end includes an antenna array that is attached to a PCB. A structure is attached to the PCB. The structure has a plurality of concentric rings to enclose an antenna array on the PCB. Each of the plurality of concentric rings has a vertical portion attached to a ground plane of the PCB through a substrate of the PCB, and a planar strip attached to the vertical portion at an end that is opposite of the ground plane.
1. A structure which reduces surface wave propagation on a printed circuit board (PCB), the structure comprising:
a plurality of concentric rings to enclose an antenna array that is associated with an operating frequency and is fixed on the PCB, each of the plurality of concentric rings including
a vertical portion that runs continuously along each of the plurality of concentric rings and that is attached to a ground plane of the PCB through a substrate of the PCB, and
a planar strip attached to the vertical portion at an end that is opposite of the ground plane, wherein a height of the vertical portion and half a width of the planar strip have a combined length that is a quarter of a wavelength of the operating frequency that is associated with the antenna array, and wherein a first of the plurality of concentric rings comprises a first planar strip that is centered on a first vertical portion of the first of the plurality of concentric rings and a second of the plurality of concentric rings comprises a second planar strip that is off-centered on a second vertical portion of the second of the plurality of concentric rings, and wherein the plurality of concentric rings alternate between being centered and being off-centered as the plurality of concentric rings progress away from the antenna array.
2. The structure of claim 1 , wherein the planar strip is arranged in a layer of the PCB above the ground plane.
3. The structure of claim 1 , wherein the structure comprises at least one of: copper, silver, gold, or a combination thereof.
4. The structure of claim 1 , wherein the planar strip is continuous throughout each respective concentric ring.
5. The structure of claim 1 , wherein a gap is present between each pair of planar strips of the plurality of concentric rings that are adjacent to each other.
6. The structure of claim 5 , wherein each of said gap is less than or equal to 0.5 millimeters.
7. The structure of claim 1 , wherein at least one planar strip of the plurality of concentric rings is attached to the vertical portion at an edge of the planar strip.
8. The structure of claim 1 , wherein a first planar strip is centered on a first vertical portion of a first of the plurality of concentric rings and a second planar strip is off-centered on a second vertical portion of a second of the plurality of concentric rings.
9. The structure of claim 1 , wherein a first planar strip of a first of the plurality of concentric rings has a first width, and a second planar strip of a second of the plurality of concentric rings has a second width that is different from the first width.
10. The structure of claim 1 , wherein the planar strip of each of the plurality of concentric rings is parallel with the ground plane.
11. The structure of claim 1 , wherein the structure includes at least three concentric rings.
12. The structure of claim 1 , wherein each of the plurality of concentric rings has a rectangular shape.
13. The structure of claim 1 , wherein each of the plurality of concentric rings is unbroken and arranged around the antenna array to fully enclose the antenna array on the PCB.
14. The structure of claim 1 , wherein the antenna array includes an array of TX antenna elements.
15. The structure of claim 1 , wherein the antenna array includes an array of RX antenna elements.
16. The structure of claim 1 , wherein variation of one or more of: a gap width between the planar strips of the plurality of concentric rings that are adjacent to each other; a height of the vertical portion of each of the plurality of concentric rings; and a width of the planar strip of one or more of the plurality of concentric rings results in a change to a frequency or strength at which the structure reduces the surface wave propagation on the PCB.
17. A front end radio frequency (RF) circuit, comprising:
a printed circuit board (PCB);
an antenna array attached to the PCB; and
a structure attached to the PCB, the structure including a plurality of concentric rings to enclose an antenna array that is associated with an operating frequency and is fixed on the PCB, each of the plurality of concentric rings including
a vertical portion that runs continuously along each of the plurality of concentric rings and that is attached to a ground plane of the PCB through a substrate of the PCB, and
a planar strip attached to the vertical portion at an end that is opposite of the ground plane, wherein a height of the vertical portion and half a width of the planar strip have a combined length that is a quarter of a wavelength of the operating frequency that is associated with the antenna array, and wherein a first of the plurality of concentric rings comprises a first planar strip that is centered on a first vertical portion of the first of the plurality of concentric rings and a second of the plurality of concentric rings comprises a second planar strip that is off-centered on a second vertical portion of the second of the plurality of concentric rings, and wherein the plurality of concentric rings alternate between being centered and being off-centered as the plurality of concentric rings progress away from the antenna array.
18. An electronic device comprising a printed circuit board (PCB);
an antenna array attached to the PCB; and
a structure attached to the PCB, the structure including a plurality of concentric rings to enclose an antenna array that is associated with an operating frequency and is fixed on the PCB, each of the plurality of concentric rings including
a vertical portion that runs continuously along each of the plurality of concentric rings and that is attached to a ground plane of the PCB through a substrate of the PCB, and
a planar strip attached to the vertical portion at an end that is opposite of the ground plane, wherein a height of the vertical portion and half a width of the planar strip have a combined length that is a quarter of a wavelength of the operating frequency that is associated with the antenna array, and wherein a first of the plurality of concentric rings comprises a first planar strip that is centered on a first vertical portion of the first of the plurality of concentric rings and a second of the plurality of concentric rings comprises a second planar strip that is off-centered on a second vertical portion of the second of the plurality of concentric rings, and wherein the plurality of concentric rings alternate between being centered and being off-centered as the plurality of concentric rings progress away from the antenna array.