Comments on the "Criterion of leakage from printed circuit transmission lines"

For original articles see ibid., vol. MTT-38, p. 1719-30 (1990) and vol. MTT-39, p. 54-63 (1991). Leakage of power in printed transmission lines can be due to the excitation of both volume and surface waves. Depending on the frequency of operation several surface waves can be excited in the background waveguide, contributing to the transversal leakage of power. A crucial point in the analysis is to determine how many of these surface modes contribute to the leakage. In this letter, we try to discuss the possibility of excitation of surface-wave modes exponentially growing transversally, but with a wave number less than the phase constant of the transmission line.<>