Rat-race coupler

A rat-race coupler, comprising:

• an annular-shaped conductor, comprising:
• a first strip-shaped conductor, has a first terminal and a second terminal;
• a second strip-shaped conductor, has a third terminal and a fourth terminal;
• a third strip-shaped conductor;
• and
• a fourth strip-shaped conductor;
• wherein the first terminal is connected to the third terminal through the third strip-shaped conductor, the second terminal is connected to the fourth terminal through the fourth strip-shaped conductor;
• a first bandwidth adjustment part, comprising:
• a fifth strip-shaped conductor;
• a sixth strip-shaped conductor;
• and
• a seventh strip-shaped conductor, has a fifth terminal and a sixth terminal;
• wherein the fifth terminal is connected to the third terminal through the fifth strip-shaped conductor, the sixth terminal is connected to the fourth terminal through the sixth strip-shaped conductor;
• a first port, is connected to the fifth terminal;
• a second port, is connected to the first terminal;
• and
• a third port, is connected to the second terminal;
• wherein an electrical length from the first terminal through the first strip-shaped conductor to the second terminal, an electrical length from the third terminal through the second strip-shaped conductor to the fourth terminal, and an electrical length from the fifth terminal through the seventh strip-shaped conductor to the sixth terminal are both ½;
• wherein an electrical length from the first terminal through the third strip-shaped conductor to the third terminal, and an electrical length from the second terminal through the fourth strip-shaped conductor to the fourth terminal are both ¼;
• wherein an electrical length from the third terminal through the fifth strip-shaped conductor to the fifth terminal, and an electrical length from the fourth terminal through the sixth strip-shaped conductor to the sixth terminal are both n/4, wherein n is a positive integer.