A Compact Ultra-Wideband Conductor-Backed CPW Crossover with Improved Isolation

An ultra-wideband conductor-backed coplanar waveguide (CB-CPW) crossover is presented here. Utilizing the orthogonal properties of electric fields of two perpendicular CB-CPW s, isolation characteristic of the crossover is greatly improved. At the same time, the crossover is compact and provides low insertion loss. A prototype crossover fabricated in a 20 mil thick RO4003C substrate of dielectric constant 3.55 occupies a rectangular area of 14.5×4 mm². Measured insertion loss for both of the ports is less than 0.5 dB, return loss is less than 12.5 dB, and isolation is more than 26.5 dB over 0-14.5 GHz.