Input Impedance of an Infinite Linear Scanned Array of Flat Rectangular Strips Inside a Dielectric Loaded Parallel Plate Waveguide

摘要

Impedance variation as a function of H-plane scan angles of an infinite linear array of flat rectangular monopoles (strips) inside a dielectric loaded parallel plate waveguide is studied both theoretically and experimentally in the S-band frequencies. In theoretical analysis simplified along the probes (monopole strips) and neglect of the effect of the gap at the junction of a probe and its coaxial feed line, were made. It is found that this simplified theory can predict qualitatively the experimental data of interest, such as input impedance. both theory and experiments show that a dielectric slab with a relatively low dielectric constant (1.3) inserted in an appropriate manner can improve the bandwidth and impedance performance of the array. Certain experimental results show a bandwidth of about 28% with respect to the center frequency 3.5 GHz, having a VSWR<2. Another interesting result is the relation between the width W of a flat rectangular probe and the radius rho of a circular probe situated similarly inside two identical rectangular waveguides. The probe impedances or VSWR's for these situations are found to be the same, respectively, for all practical purposes when W approx. 4.882 rho, which was obtained numerically representing a correction to the electrostatic result W = 4 rho found by Wheeler. (Author)