High-directivity directional coupler

A high-directivity directional coupler, applicable to a high-power radio frequency (RF) environment, comprising:

• a mainline metal segment;
• and
• at least one coupling metal segment including a continuous coupling line, the continuous coupling line comprising two first metal segments having a coupling effect with the mainline metal segment, and a second metal segment having no coupling effect with the mainline metal segment, each of the two first metal segments having a gradually changing width showing an asymptotic change trend;
• wherein the mainline metal segment is a mainline, the at least one coupling metal segment is a power coupling segment/side, the mainline metal segment couples energy to the at least one coupling metal segment through electromagnetic coupling, and each of the two first metal segments comprises a plurality of alternatingly arranged coupling lines and delay lines with an overall gradually changing width.