Dual band MIMO antenna and wireless access point

1. An antenna array, comprising:

a first antenna formed on a first surface of a planar substrate,

a second antenna formed on the first surface of the planar substrate displaced from the first antenna in a first direction;

a third antenna formed on the first surface of the planar substrate displaced from the first antenna in a second direction perpendicular to the first direction; and

a fourth antenna formed on the first surface of the planar substrate displaced from the first antenna in both the first and second directions such that the first, second, third, and fourth antennas are disposed in a first 2×2 grid,

wherein each of the first, second, third, and fourth antennas is linearly polarized in the first direction and provides a roughly cardiod radiation pattern in a plane normal to the first direction, a null of the cardiod radiation pattern aligned in the second direction, and

wherein the nulls in the cardiod radiation patterns of the first and second antennas face the third and fourth antennas, respectively, and the nulls in the cardiod radiation patterns of the third and fourth antenna face the first and second antennas, respectively.

2. The antenna array of claim 1 , wherein

each of the first, second, third, and fourth antennas is a tapered slot antenna,

wherein open ends of the tapered slots of the first and second antennas face away from the third and fourth antennas, and opens ends of the tapered slots of the third and fourth antennas face away from the first and second antennas.

3. The antenna array of claim 2 , wherein

each of the tapered slot antennas is a dual-band tapered slot antenna including two folded stubs.

4. The antenna array of claim 1 , wherein

the first, second, third, and fourth antennas are first, second, third, and fourth sub-arrays, each sub-array comprising two tapered slot antenna elements displaced in the first direction and coupled to a common feed point,

wherein open ends of the tapered slots of the first and second sub-arrays face away from the third and fourth sub-arrays, and opens ends of the tapered slots of the third and fourth sub-arrays face away from the first and second sub-arrays.

5. The antenna array of claim 4 , wherein

each of the tapered slot antenna elements is a dual-band tapered slot antenna element including two folded stubs.

6. The antenna array of claim 1 , wherein

each of the first, second, third, and fourth antennas extend from a common ground plane.

7. The antenna array of claim 1 , wherein

each of the first, second, third, and fourth antennas includes a respective feed line formed on a second surface of the planar substrate.

8. The antenna array of claim 1 , further comprising:

a fifth antenna formed on the first surface of the planar substrate displaced from the third antenna in the second direction;

a sixth antenna formed on the first surface of the planar substrate displaced from the fifth antenna in the first direction;

a seventh antenna formed on the first surface of the planar substrate displaced from the fifth antenna in the second direction;

a eighth antenna formed on the first surface of the planar substrate displaced from the fifth antenna in both the first and second directions such that the fifth, sixth, seventh, and eighth antennas are disposed in a second 2×2 grid adjacent to the first 2×2 grid; and

a ground plane disposed parallel to and in close proximity to the planar substrate,

wherein each of the fifth, sixth, seventh, and eighth antennas are linearly polarized in the first direction and provide a roughly cardiod radiation pattern in a plane normal to the first direction, a null of the cardiod radiation pattern aligned in the second direction, and

wherein the nulls in the cardiod radiation patterns of the fifth and sixth antennas face the seventh and eighth antennas, respectively, and the nulls in the cardiod radiation patterns of the seventh and eighth antenna face the fifth and sixth antennas, respectively.

9. An access point, comprising:

an antenna array, comprising:

a first antenna formed on a first surface of a planar substrate,

a second antenna formed on the first surface of the planar substrate displaced from the first antenna along a first axis;

a third antenna formed on the first surface of the planar substrate displaced from the first antenna along a second axis normal to the first axis; and

a fourth antenna formed on the first surface of the planar substrate displaced from the first antenna along both the first and second axis such that the first, second, third, and fourth antennas are disposed in a 2×2 grid defined by the first axis and the second axis,

wherein each of the first, second, third, and fourth antennas are linearly polarized in a direction of the first axis and provide a roughly cardiod radiation pattern in a plane normal to the first axis, a null of the cardiod radiation pattern aligned along the second axis, and

wherein the nulls in the cardiod radiation patterns of the first and second antennas face the third and fourth antennas, respectively, and the nulls in the cardiod radiation patterns of the third and fourth antenna face the first and second antennas, respectively.

10. The access point of claim 8 , further comprising:

first and second 2×2 multiple input multiple output (MIMO) radios, each of the first and second MIMO radios coupled to two antennas of the first, second, third, and fourth antennas.

11. The access point of claim 9 , further comprising:

a radio frequency switch coupled between the first and second MIMO radios and at least two of the first, second, third, and fourth antennas, the switch is configured to selectively couple the first and second MIMO radios to the first, second, third, and fourth antennas in either an omnidirectional mode or a sectored mode.

12. The access point of claim 8 , further comprising:

a 4×4 multiple input multiple output (MIMO) radio coupled to the first, second, third, and fourth antennas.

13. The access point of claim 8 , the antenna array further comprising:

a fifth antenna formed on the first surface of the planar substrate displaced from the third antenna in the second direction;

a sixth antenna formed on the first surface of the planar substrate displaced from the fifth antenna in the first direction;

a seventh antenna formed on the first surface of the planar substrate displaced from the fifth antenna in the second direction;

a eighth antenna formed on the first surface of the planar substrate displaced from the fifth antenna in both the first and second directions such that the fifth, sixth, seventh, and eighth antennas are disposed in a second 2×2 grid adjacent to the first 2×2 grid; and

a ground plane disposed parallel to and in close proximity to the planar substrate,

wherein each of the fifth, sixth, seventh, and eighth antennas are linearly polarized in the first direction and provide a roughly cardiod radiation pattern in a plane normal to the first direction, a null of the cardiod radiation pattern aligned in the second direction, and

wherein the nulls in the cardiod radiation patterns of the fifth and sixth antennas face the seventh and eighth antennas, respectively, and the nulls in the cardiod radiation patterns of the seventh and eighth antenna face the fifth and sixth antennas, respectively.

14. The access point of claim 13 , further comprising:

four 2×2 multiple input multiple output (MIMO) radios, each of the four 2×2 MIMO radios coupled to two antennas of the first, second, third, fourth, fifth, sixth, seventh, and eighth antennas.

15. The access point of claim 13 , further comprising:

two 4×4 multiple input multiple output (MIMO) radios, each of the two 4×4 MIMO radios coupled to four antennas of the first, second, third, fourth, fifth, sixth, seventh, and eighth antennas.

16. An antenna array, comprising:

a first group of N antennas, where N is an integer equal to, or greater than, two, formed on a first surface of a planar substrate, the antennas in the first group displaced from each other in a first direction;

a second group of N antennas formed on the first surface of the planar substrate, each of the antennas in the second group displaced from a respective antenna of the first group in a second direction perpendicular to the first direction, such that the antennas of the first and second groups are disposed in a 2×N grid,

wherein each of the antennas in the first and second groups are linearly polarized in the first direction and provide a roughly cardiod radiation pattern in a plane normal to the first direction, a null of the cardiod radiation pattern aligned in the second direction, and

wherein the nulls in the cardiod radiation patterns of the antennas in the first group face the respective antennas of the second group, and the nulls in the cardiod radiation patterns of the antennas in the second group face the respective antennas of the first group.

17. The antenna array of claim 16 , wherein

each of the antennas in the first and second groups is a tapered slot antenna,

wherein open ends of the tapered slots of the antennas in the first group face away from the respective antenna of the second group, and opens ends of the tapered slots of the antennas in the second group face away from the respective antennas of the first group.

18. The antenna array of claim 17 , wherein

each of the tapered slot antennas is a dual-band tapered slot antenna including two folded stubs.

19. The antenna array of claim 16 , wherein

each of the antennas in the first and second groups are sub-arrays, each sub-array comprising two tapered slot antenna elements displaced in the first direction and coupled to a common feed point,

wherein open ends of the tapered slots of the sub-arrays in the first group face away from the respective sub-arrays of the second group, and opens ends of the tapered slots of the sub-arrays in the second group face away from the respective sub-arrays of the first group.

20. The antenna array of claim 19 , wherein

each of the tapered slot antenna elements is a dual-band tapered slot antenna element including two folded stubs.