THEORETICAL-ANALYSIS OF COUPLING AND CROSS-POLARIZATION OF PERPENDICULAR SLOT ANTENNAS ON A DIELECTRIC HALF-SPACE

In this paper, design curves are given for minimizing the coupling bet ween two perpedicular slot antennas on a dielectric half space. Such a ntennas may be utilized in polarimetric receivers in which coupling mu st be minimized to ensure polarization purity and in polarization dipl exed quasi-optical receivers in which the local oscillator (LO) is rec eived in a polarization perpendicular to that of the RF signal. For th is analysis, Galerkin's method in the spectral domain is applied along the length of the slots and point matching across their widths. At th e second resonance, for equal length slots and for constant width/leng th (w/L) of the slots, there is a decrease of about 2-dB coupling for a factor of three increase in dielectric constant (epsilon(1) = 1.0 -- > 3.8 and epsilon(1) = 3.8 --> 12.8). For fixed dielectric constant th ere is a 1-2-dB increase in coupling for a factor of two increase in w /L. For slots of unequal length (L-2 = L-1/2), the changes are even sm aller. Design curves are shown for various relative positions of the s lots in two dimensions, A strong correllation between coupling levels and peak cross-polarization levels is found.