Directional coupler

Abstract

A small directional coupler includes a main line and a subline having a sufficient self-inductance value and achieving a very small insertion loss. A main-line conductor pattern and a subline conductor pattern are formed on the top surface of an insulating substrate by a method using photolithographic technologies. The main-line conductor pattern and the subline conductor pattern are formed in a spiral shape and so as to extend substantially parallel to each other. In order for the self-inductance value of the main line to be lower than the self-inductance value of the subline, the line width of the subline conductor pattern is narrower than the line width of the main-line conductor pattern. More specifically, it is preferable that the line width of the conductor pattern for a subline be about 50% to about 90% of the line width of the main-line conductor pattern.

Dependencies are inferred from the claim text.