Coupler for communication system

A coupler, comprising:

• a first conductive trace comprising a first coupling section;
• a second conductive trace comprising a second coupling section that is galvanically isolated from and coupled to the first coupling section;
• and
• an intermediate conductor provided between the first coupling section and the second coupling section, the intermediate conductor galvanically isolated from and coupled to both the first coupling section and the second coupling section,
• wherein the first coupling section has a first perturbation structure configured to slow down a phase speed of a first radiofrequency signal transmitted in the first conductive trace, and configured to slow down a phase speed of odd-mode excitation signals on the first conductive trace and the second conductive trace than even-mode excitation signals on the first conductive trace and the second conductive trace;
• and
• wherein the intermediate conductor is between the first perturbation structure and the second coupling section.