a strip line circuit assembly consisting of a first and second strip line ch comprised of three dielectric layers having conductor strips on either side of the center layer and ground planes on the outsides of the outer layers which sandwich the center layer except for an open central portion which turns through a 180 ° curved bend . the three layer first and second layer strip lines are separated by the single layer central portion and are sandwiched between three holding plates . the center holding plate has a curved end extension containing axially spaced channels which receive the conductors of the center dielectric layer on the inside of the end . one of the outer two holding plates is placed upon each of the outer dielectric layers in contact with the ground planes on the outer surfaces of each layer . a ground plane cover having spaced conductor channels corresponding to those in the center holding plate end extension is secured to the ends of the two outer holding plates about the bend to enclose the conductors on the outer surface of the center dielectric layer .