Propagation Characteristics for Periodic Waveguide Based on Generalized Conservation of Complex Power Technique

The propagation characteristics of surface waves with periodic waveguides is examined based on the characterization of a unit cell through the generalized conservation of complex power technique (GCCPT). The bounded approach, in which the periodic structure is enclosed by perfectly conducting walls, is applied to facilitate discussion. Comparison among different matching techniques, including the mode-matching technique (MMT), conservation of complex power technique (CCPT), improper MMT with power decrement or increment (PD/PI-MMT), is taken to derive some properties for the generalized scattering matrix (GSM) in conjunction with these techniques. It is shown that the improper PD/PI-MMT, in contrast to the equivalence between the MMT and CCPT in the context of a closed waveguide, is in contradiction to the principle of conservation of complex power, and cannot be employed to express GSM for discontinuity. Further analysis, however, suggests that PI-MMT and PD-MMT are in duality symmetry, and can, in combination, restore the continuity of complex power in a periodic environment, which gives rise to the GCCPT. The propagation constants are determined from the eigenvalues of a transmission matrix for a unit cell with the aid of a solution selection rule. A number of numerical results are shown to demonstrate the efficiency and accuracy of our approach