Balun and Method for Manufacturing the Same

A balun, comprising:

• a substrate;
• first and second coplanar waveguide (CPW) couplers disposed on the substrate and cascaded with each other;
• each CPW coupler comprising:
• two first ground planes disposed on a first side of the substrate;
• a first microstrip line and at least two second microstrip lines which are disposed on the first side of the substrate between the two first ground planes, and can be coupled with each other by electromagnetic coupling;
• and
• at least one third microstrip line that is disposed on an opposite side of the substrate and electrically connects the at least two second microstrip lines with each other by via-holes.

A radio frequency (RF) device, comprising:

• a balun, the balun comprising:
• a substrate;
• a first coplanar waveguide (CPW) coupler and a second CPW coupler, the CPW couplers disposed on the substrate and cascaded with each other, each CPW coupler comprising:
• two first ground planes disposed on a first side of the substrate;
• a first microstrip line and at least two second microstrip lines which are disposed on the first side of the substrate between the two first ground planes, and can be coupled with each other by electromagnetic coupling;
• and
• at least one third microstrip line that is disposed on an opposite side of the substrate and electrically connects the at least two second microstrip lines with each other by via-holes.

A method for manufacturing a balun, the method comprising:

• providing a substrate;
• and
• forming first and second cascaded coplanar waveguide (CPW) couplers on the substrate;
• wherein the forming each CPW coupler comprises:
• forming two first ground planes on a first side of the substrate;
• forming, on the first side of the substrate between the two first ground planes, a first microstrip line and at least two second microstrip lines which can be coupled with each other by electromagnetic coupling;
• and
• forming, on an opposite side of the substrate, at least one third microstrip line that electrically connects the at least two second microstrip lines with each other by via-holes.