EXCITATION OF AN UNTILTED NARROW-WALL SLOT IN A RECTANGULAR WAVE-GUIDE BY USING ETCHED STRIPS ON A DIELECTRIC PLATE

We propose a novel excitation technique of an untilted slot in the nar row wall of a rectangular waveguide. The excitation is realized by ins erting into the slot a dielectric plate on which there are etched cond ucting strips, The strip excitation can control the coupling more easi ly and accurately than a conventional excitation using tilted wires. W e analyze the coupling to the slot by using the dyadic Green's functio n for the waveguide with the dielectric plate, derived by Seki's virtu al cavity method, A double resonance due to the strip and the slot res ults in large coupling as well as small variation of the phase of the transmitted wave, both over a wide frequency band, Some results are ve rified by measurements. The coupling can be tuned by varying the dista nce between the slot and the strip.