Multiple-input multiple-output (MIMO) antennas with multi-band wave traps

1. An antenna comprising:

a first radiating element;

a second radiating element;

a common ground plane between the first radiating element and the second radiating element; and

a wavetrap structure coupled to the ground plane and configured to reduce correlation between the first and second radiating elements at first and second RF frequencies;

wherein the wavetrap structure comprises:

a first ground post connected to the ground plane;

a second ground post connected to the ground plane;

a first conductive strip coupled to the first ground post and having an electrical length that is one quarter of a wavelength of the first RF frequency; and

a second conductive strip coupled to the second ground post and having an electrical length that is one quarter of a wavelength of the second RF frequency;

wherein the ground plane has a first end and a second end opposite the first end;

the first radiating element is adjacent the first end of the ground plane and the second radiating element is adjacent the second end of the ground plane;

the first and second ground posts are proximate the first end of the ground plane;

the first conductive strip extends away from the first ground post toward the second end of the ground plane; and

the second conductive strip extends away from the second ground post toward the second end of the ground plane; and

the ground plane has a first side and a second side opposite the first side;

the antenna further comprising:

a first feed element coupled to the first radiating element at a first end of the first radiating element proximate the first side of the ground plane; and

a second feed element coupled to the second radiating element at a first end of the second radiating element proximate the first side of the ground plane;

the first ground post and the second ground post are proximate the second side of the ground plane;

the first conductive strip extends from the first ground post toward an open end of the second radiating element opposite the first end of the second radiating element; and

the second conductive strip extends from the second ground post toward the open end of the second radiating element.

2. The antenna of claim 1 , further comprising a capacitive element between an open end of the first conductive strip opposite the ground post and the ground plane.

3. The antenna of claim 1 , wherein the ground post comprises an inductive element.

4. The antenna of claim 3 , further comprising a capacitive element between an open end of the first conductive strip opposite the ground post and the ground plane.

5. The antenna of claim 1 , wherein the first and second radiating elements have an envelope correlation coefficient less than 0.5 for a first frequency in the first RF frequency range and for a second frequency in the second RF frequency range.

6. The antenna of claim 1 , wherein the wavetrap structure comprises: a ground post connected to the ground plane; and a patch structure coupled to the ground post and configured to resonate at the first RF frequency.

7. The antenna of claim 1 , wherein the wavetrap structure comprises: a ground post connected to the ground plane; and a spiral structure coupled to the ground post and configured to resonate at the first RF frequency.

8. A wireless terminal, comprising:

a transceiver; and

an antenna coupled to the transceiver, the antenna comprising:

a first radiating element;

a second radiating element;

a common ground plane between the first radiating element and the second radiating element; and

a wavetrap structure coupled to the ground plane and configured to reduce correlation between the first and second radiating elements at first and second RF frequencies;

wherein the wavetrap structure comprises:

a first ground post connected to the ground plane;

a second ground post connected to the ground plane;

a first conductive strip coupled to the first ground post and having an electrical length that is one quarter of a wavelength of the first RF frequency; and a second conductive strip coupled to the second ground post and having an electrical length that is one quarter of a wavelength of the second RF frequency;

wherein:

the ground plane has a first end and a second end opposite the first end;

the first radiating element is adjacent the first end of the ground plane and the second radiating element is adjacent the second end of the ground plane;

the first ground post is proximate the second end of the ground plane;

the second ground post is proximate the first end of the ground plane;

the first conductive strip extends away from the first ground post toward the first end of the ground plane; and

the second conductive strip extends away from the second ground post toward the second end of the ground plane;

wherein the ground plane has a first side and a second side opposite the first side; the antenna further comprising:

a first feed element coupled to the first radiating element at a first end of the first radiating element proximate the first side of the ground plane; and

a second feed element coupled to the second radiating element at a first end of the second radiating element proximate the second side of the ground plane;

the first ground post is proximate the second side of the ground plane;

the second ground post is proximate the first side of the ground plane;

the first conductive strip extends from the first ground post toward a second end of the first radiating element opposite the first end of the first radiating element; and

the second conductive strip extends from the second ground post toward a second end of the second radiating element opposite the first end of the second radiating element.

9. The wireless terminal of claim 8 , further comprising a housing, wherein the ground plane is disposed within the housing and wherein the wavetrap structure is provided on an outer surface of the housing.