Filter

A filter disposed on a base board, comprising:

• a first portion disposed on a first layer in the base board, the first portion configured to input signals;
• a second portion disposed on the first layer, the second portion configured to output signals;
• a ground portion disposed on a second layer in the base board;
• a first coupling portion comprising a first branch and a second branch, disposed on the first layer, wherein the first branch is electrically coupled to the first portion and the second portion, and second branch is electrically coupled to the ground portion through via holes;
• a second coupling portion comprising a third branch and a fourth branch, disposed on the first layer, wherein the third branch is electrically coupled to the first portion and the second portion, and the fourth branch is electrically coupled to the ground portion through other via holes;
• wherein
• the first branch and the second branch are rectangles;
• the first branch and the second branch are parallel to each other, the third branch and the fourth branch are rectangles;
• the third branch and the fourth branch and the first branch are parallel to each other;
• and the via holes comprises:
• a first via hole, wherein a wall of the first via hole is electrically coupled between a first end of the second branch and the ground portion;
• a second via hole, wherein a wall of the second via hole is electrically coupled between a second end of the second branch and the ground portion;
• a third via hole, wherein a wall of the third via hole is electrically coupled between a first end of the fourth branch and the ground portion;
• and
• a fourth via hole, wherein a wall of the fourth via hole is electrically coupled between a second end of the fourth branch and the ground portion.

A filter disposed on a base board, comprising:

• a first portion disposed on a first layer in the base board, the first portion configured to input signals;
• a second portion disposed on the first layer, the second portion configured to output signals;
• a ground portion disposed on a second layer in the base board;
• a first coupling portion comprising a first branch and a second branch, disposed on the first layer, wherein the first branch and the second branch are rectangles, and the first branch and the second branch are parallel to each other;
• and one end of the first branch is electrically coupled to the first portion, the other end of the first branch is electrically coupled to the second portion, one end of the second branch and the other end of the second branch are electrically coupled to the ground portion through via holes;
• and
• a second coupling portion disposed on the first layer wherein the second coupling portion is electrically coupled to the first portion and the second portion, the second coupling portion is electrically coupled to the ground portion through other via holes.