Design and study of enhanced wideband transition between coplanar waveguide and broadside coupled stripline

Abstract

Enhanced wideband transition between coplanar waveguide (CPW) and broadside coupled stripline (BCS) with arbitrary characteristic impedance ratio is developed on a basis of an improved tightly coupling, via-hole-free structure. The E-field of CPW gradually changes to that of BCS within a wide bandwidth with ratio up to 10.4:1. Parametric studies of the transition are carried out and four different back-to-back prototypes are simulated, fabricated and measured. It is shown that maximum operation bandwidth from 1.16 to 12.01 GHz for return loss higher than 10 dB and average insertion loss of 1.41 dB can be obtained.