Confirmation of slow waves in a crosstie overlay coplanar waveguide and its applications to band-reject gratings and reflectors

A theoretical and experimental investigation of slow-wave propagation along a crosstie overlay slow-wave coplanar waveguide is discussed. The slow-wave factor observed agrees reasonably well with the theoretical prediction. This structure is used for construction of frequency-selective distributed Bragg reflectors (DBRs) of compact size. The effect of conductor loss is considered. A doubly periodic band-reject grating has been created from the DBRs, and the band-reject phenomenon was observed as predicted. To improve passband characteristics of the grating, a monolithic slow-wave Chebyshev reflector was designed and fabricated. Agreement between theory and preliminary experiment has been found. Based on this theory, a slow-wave reflector was improved characteristics is proposed and examined. Simplicity of the design procedure, lower loss, and better control of the passband ripple size have been achieved.>