Recently, there has been a growing interest in radial line slot antennas (RLSA). Several configurations have been proposed for automotive collision avoidance radar in 60-80 GHz bands, wireless LANs, local multiport distribution system (LMDS), and satellite TV (DBS) reception. In RLSA, aperture slots are excited by rotationally symmetric travelling wave, and their arrangement determines the antenna radiation pattern and polarization. When compared with microstrip planar arrays, or most recent planar arrays using suspended line and triplate line, RLSA show a higher efficiency since they are basically free of loss. Despite these high-performances RLSA allows a mass production with low costs. For the design of a high-performance RLSA an accurate but efficient numerical method is desirable in terms of both dynamic memory and computation time. This is especially true for an optimization process of the antenna where many slightly different structures have to be analysed. Most of the works dealing with RLSA use a simplified model of the antenna that usually employs a single-mode lossy radial transmission line model whose radiation attenuation factor is estimated by the scattering parameters of a slotted rectangular waveguide with periodic walls excited by a TEM wave. This simplified model is useful for a first design of the antenna but it is not enough accurate for its fine optimization. In this paper an efficient method of moments (MoM) based formulation that allows the analysis of the full antenna, included the effect of the metallic or absorbing ring that truncates the parallel plate waveguide, is proposed. Specifically, for the interior region, the required (electrically large) circular cavity space-domain Green’s function is calculated by applying a Watson transformation to convert the slowly converging mode series representation into a rapidly convergent hybrid ray-mode series [W. Wasylkiwskyj IEEE AP-23, 4, 1975]. Furthermore, the slots coupling in the external region is convenient evaluated by the formulation proposed by T.S. Bird [IEEE AP-42, 7, 1994, pp. 1000-6]. This technique allows the reduction of the four-folded space integrals to double integrals, with an evident reduction of calculation time. The method is validated for simple slot configurations and the relevant convergence is investigated.
Full Wave Analysis of Radial Line Slot Antennas Using an Efficient Ray-Mode Expansion of the Green's Function for a Large Circular Cavity / M. Albani; G. La Cono; A. Freni. - STAMPA. - (2003), pp. 1-1. (Intervento presentato al convegno Piers 2003 tenutosi a Hawaii nel Oct. 13-16, 2003).