Leaky-wave phenomena and their unfavorable effect in millimeter-wave circuit devices

It is now known that printed-circuit transmission lines used in millimeter-wave devices can exhibit power-leakage effect. This leakage effect occurs in two different types of the wavenumber behavior even on uniform length of printed-circuit transmission lines. Such wavenumber behaviors yield the unexpected limit of the usable frequency only for the bound-dominant-mode operation and also this limit frequency changes significantly depending on the structural dimensions of a line cross section. Therefore, this paper gives a good grasp of the behavior of the limit frequency which is extremely important for high-performance millimeter-wave device design.