Multi-input multi-output (mimo) antenna

A multi-input multi-output antenna, comprising:

• a substrate;
• a first multi-band antenna formed on the substrate, wherein the first multi-band antenna comprises a first radiator and a second radiator operated in a first band and a second band, respectively, the second radiator extends from a first terminal of the first radiator and surrounds the first radiator, and an operating frequency of the first band is higher than an operating frequency of the second band;
• a second multi-band antenna formed on the substrate, wherein the second multi-band antenna comprises a third radiator and a fourth radiator operated in the first band and the second band, respectively, and the fourth radiator extends from a second terminal of the third radiator and surrounds the third radiator;
• and
• a multi-band filter having a first filter part and a second filter part orthogonal to each other, wherein the first filter part is formed over the substrate and has two corresponding terminals respectively connecting to the first multi-band antenna and the second multi-band antenna, the second filter part is disposed on the substrate, the first filter part has a projection overlapping with the second filter part, the first filter part filters a first current flowing through the first radiator and/or the third radiator, and the second filter part filters a second current flowing through the second radiator and/or the fourth radiator.