Connection structure of high-frequency transmission line

A connection structure of a high-frequency transmission line that connects a coaxial line and a planar transmission line, comprising:

• a columnar central conductor having one end connected to an inner conductor of the coaxial line and the other end connected to the planar transmission line;
• a coaxial mode block electrically connected to the coaxial line;
• a coplanar mode block electrically connected to the planar transmission line;
• a buffer block arranged between the coaxial mode block and the coplanar mode block,
• the coaxial mode block including
• a first outer conductor including a first hole that is formed coaxially with the central conductor and is larger than an outer diameter of the central conductor, and arranged on a side of the one end of the central conductor, and
• a first dielectric body filled between the central conductor and the first outer conductor,
• the coplanar mode block including
• a second outer conductor including a second hole that is formed coaxially with the central conductor and is larger than the outer diameter of the central conductor, and arranged on a side of the other end of the central conductor, and
• a second dielectric body filled between the central conductor and the second outer conductor, and
• the buffer block including
• a third outer conductor including a third hole that is formed coaxially with the central conductor and is larger than the outer diameter of the central conductor, and arranged between the first outer conductor and the second outer conductor, and
• a third dielectric body filled between the central conductor and the third outer conductor,
• wherein in a direction perpendicular to each of an axial direction of the central conductor and a direction perpendicular to the planar transmission line, a shortest distance between the central conductor and the first outer conductor is longer than a shortest distance between the central conductor and the third outer conductor, and the shortest distance between the central conductor and the third outer conductor is longer than a shortest distance between the central conductor and the second outer conductor,
• in the direction perpendicular to the planar transmission line, a shortest distance between the central conductor and the first outer conductor is longer than a shortest distance between the central conductor and the third outer conductor, and a shortest distance between the central conductor and the second outer conductor is longer than the shortest distance between the central conductor and the first outer conductor, and
• the third dielectric body is arranged inside a region filled with the first dielectric body when viewed from the axial direction of the central conductor.