Mobile communication base station antenna

1. A mobile communication base station antenna, comprising:

a plurality of polarization diversity antenna blocks which carries out Multiple Input Multiple Output (MIMO) communication, each of the polarization diversity antenna blocks comprising a plurality of polarization diversity antenna elements, each of the polarization diversity antenna elements comprising antenna elements that are disposed to be orthogonal to each other,

wherein the plurality of the polarization diversity antenna blocks comprise at least one first polarization diversity antenna block including polarization diversity antenna block elements and at least one second polarization diversity antenna block including polarization diversity antenna elements, and the polarization diversity antenna elements of the first polarization diversity antenna block are located outside the second polarization antenna block,

wherein tilt angles in a vertical plane of respective polarization diversity antenna blocks are different from each other,

wherein, in a plan view, centers of the polarization diversity antenna elements of said at least one first polarization diversity antenna block are located between centers of the polarization diversity antenna elements of said at least one second polarization diversity antenna block in an overlapped area of the antenna, and

wherein, in the plan view, a part of the polarization diversity antenna elements of said at least one first polarization diversity antenna block and a part of the polarization diversity antenna elements of said at least one second polarization diversity antenna block are located outside the overlapped area of the antenna.

2. The mobile communication base station antenna according to claim 1 , wherein the plurality of the polarization diversity antenna blocks are vertically arranged, and

wherein the tilt angles in the vertical plane of the respective polarization diversity antenna blocks are determined such that a correlation coefficient between the respective polarization diversity antenna blocks is 0.7 or less.

3. The mobile communication base station antenna according to claim 1 , wherein the tilt angles in the vertical plane of the respective polarization diversity antenna blocks are arbitrarily set by mechanically changing a direction of each of the polarization diversity antenna blocks.

4. The mobile communication base station antenna according to claim 1 , wherein the tilt angles in the vertical plane of the respective polarization diversity antenna blocks are arbitrarily set by shifting a signal phase by a phase shifter.

5. The mobile communication base station antenna according to claim 4 , wherein the phase shifter comprises a fixed phase shifter in which a shift amount of the signal phase is fixed.

6. The mobile communication base station antenna according to claim 4 , wherein the phase shifter comprises a variable phase shifter in which a shift amount of the signal phase is freely determined.

7. The mobile communication base station antenna according to claim 1 , wherein the plurality of polarization diversity antenna blocks is arranged linearly.

8. The mobile communication base station antenna according to claim 1 , wherein the plurality of polarization diversity antenna blocks is arranged in a line such that the centers of the polarization diversity antenna elements of said at least one first polarization diversity antenna block and the centers of the polarization diversity antenna elements of said at least one second polarization diversity antenna block are located on the line.

9. The mobile communication base station antenna according to claim 1 , wherein central parts of two sets of the antenna including two ports are partially overlapped.

10. The mobile communication base station antenna according to claim 9 , wherein the antenna elements are disposed vertically to ground to form an antenna that includes four ports in one radome.

11. The mobile communication base station antenna according to claim 1 , wherein, in the plan view, outside the overlapped area of the antenna, the polarization diversity antenna elements of said at least one first polarization diversity antenna block are located adjacent to each other.

12. The mobile communication base station antenna according to claim 1 , wherein the plurality of the polarization diversity antenna blocks have a same polarization characteristic.

13. The mobile communication base station antenna according to claim 1 , wherein the plurality of polarization diversity antenna blocks consists of said at least one first polarization diversity antenna block and said at least one second polarization diversity antenna block.

14. The mobile communication base station antenna according to claim 13 , wherein the polarization diversity antenna elements of said at least one second polarization diversity antenna blocks are interposed only between said at least one first polarization diversity antenna block.

15. The mobile communication base station antenna according to claim 1 , wherein the polarization diversity antenna blocks are limited to two of the polarization diversity antenna blocks.

16. The mobile communication base station antenna according to claim 1 , wherein antenna element pairs included in said at least one first polarization diversity antenna block and antenna element pairs included in said at least one second polarization diversity antenna block are arranged alternately in a vertical direction of the vertical plane, only partially, rather than over an entire length of the vertical plane in the vertical direction.

17. The mobile communication base station antenna according to claim 1 , wherein antenna element pairs included in said at least one first polarization diversity antenna block and antenna element pairs included in said at least one second polarization diversity antenna block are arranged in a vertical direction of the vertical plane in a linear column that extends from a lower part of the vertical plane to an upper part of the vertical plane.

18. The mobile communication base station antenna according to claim 17 , wherein, in the lower part and the upper part of the vertical plane, the antenna element pairs included in said at least one first polarization diversity antenna block and the antenna element pairs included in said at least one second polarization diversity antenna block are not arranged alternately in the vertical direction of the vertical plane.