Miniaturized synthetic rectangular waveguide

An artificially engineered, dielectric-filled rectangular waveguide is presented. Such a synthetic waveguide, made by a conventional printed-circuit board (PCB) process, consists of two-dimensional periodical arrays at the top and bottom surfaces and two metallic sidewalls. A synthetic waveguide of cross-section 8.0 mm by 0.609 mm, relative permittivity (/spl epsiv//sub r/) 3.38, shows a cutoff frequency at 4 GHz with normalized propagation constant asymptotically approaching 4.5 at frequencies much greater than the cutoff frequency. Rigorous measurements show that the extracted dispersion curves agree well with theoretical data, demonstrating the feasibility of size reduction of the synthetic rectangular waveguide, breaking the well-known limit of 1//spl radic/(/spl epsiv//sub r/) imposed on conventional rectangular waveguides. Measured data show that the slow-wave factor is 185% higher and cutoff frequency 61.9% lower when comparing the synthetic waveguide with a conventional waveguide of identical dimensions and material constant.