Patent ID: 7471165

Claim:
A balun for mutually converting an unbalanced line for unbalanced input/output and a balanced line for balanced input/output, wherein said unbalanced line and said balanced line are microstrip lines including a signal line arranged on one main surface of a substrate and a ground conductor arranged on the other surface of the substrate; comprising: a slot line formed by an aperture line arranged in said ground conductor in the other main surface of said substrate; wherein a microstrip line as said unbalanced line includes a first end portion used as an input/output end and a second end portion that traverses said slot line, electromagnetically couples to said slot line, and functions as an electric short-circuited end; and wherein a center portion of a microstrip line as said balanced line traverses said slot line and electromagnetically couples to said slot line and both end portions of said microstrip line as said balanced line are used as input/output ends.