Wave Analysis Method of Probe-Fed Radial Line Planar Antennas for Uniform Aperture Field Distribution

We propose a wave analysis method of a probe-fed Radial Line Planar Antennas (RLPA’s) for uniform aperture field distribution. The probe-fed RLPA’s [1]-[4] have an advantage of high efficiency, because the excitation probes of the radiating elements can be fed by a standing wave in the radial line with a short-circuited termination of its end. The authors proposed an analysis method [4] of aperture field distribution by calculating mutual coupling of probes using the Electromotive Force (EMF) method. Recently, other analysis methods of RLPA’s were reported [5][6], that use probes as a feeding structure of the radiating elements. However, the method [5] is not realistic because all probes inside radial line were imitated monopole antennas and their diameters are not considered. The analysis model [6] inevitably assumes rotational symmetry to the system. Therefore, its application to the scattering that breaks the symmetry is impossible. Also, even the application advisability to the 4 point fed RLPA’s is not obvious. In this paper, we describe a wave analysis method of uniform aperture field distribution for a probe-fed RLPA. This method can accommodate the effect of all the conductors including the termination wall by introducing the concept of equivalent posts [7]. It is possible to apply it to the cavity of various geometries including the circular one. Good correspondence has been confirmed between measured and calculated values on the aperture field distribution.