Air-gap technique for matching the aperture of miniature waveguide antennas

The authors present an air-gap technique that is used to match the extremely high aperture reflection of an open-ended dielectric-filled waveguide. Applications of this technique are shown together with the design of a new type of antenna, the microstrip-like antenna (MLA). The air-gap is considered as a matching nework. The scattering-transmission matrix approach allows the analysis of this network. The analysis demonstrates that the aperture reflection can be matched by tuning the air-gap length. Because of the selected size of the MLA, calibration and feed problems are confronted. Therefore, a calibration set of waveguides has been made for one of the possible configurations (MLA1). The waveguide measuring techniques for MLA aperture matching are described. Experimental results prove the merit of the air-gap technique, especially for the MLA structures