AbstractTo realize the desired aperture distribution in a radial line slot antenna (RLSA), accurate evaluation of the coupling, guided wavelength and radiation phase of slot sets are required. Moreover, for the slot set similarly to the linearly polarized RLSA whose reflection is essentially large, reflection from one slot set should be reduced sufficiently to realize the desired traveling wave operation; therefore, the reflection coefficient should also be evaluated.In this paper, the scattering matrix equivalent circuit of the slot set is presented for the design of the radial line slot antenna. Using this equivalent circuit, the slot set configuration can be optimized for reflection characteristics, and it becomes possible to realize traveling wave operation with arbitrary polarization.Compared with the conventional analysis assuming uniform slot array, this method has greatly reduced the computation time, and the analysis and design of the antenna has become possible. This analysis has established first the designing of a RLSA with arbitrary polarization.