Series of narrow wall windows to feed partially-dielectric-filled oversized-rectangular waveguide with slot array

A series of narrow wall windows is presented for excitation of a quasi plane wave in a slotted partially dielectric filled oversized rectangular waveguide. Its 3-dimensional analysis model is simplified by solving separately two 2-dimensional structures which are orthogonally uniform. A 12 narrow wall window array suppress reflection below −15 dB at 61.25 GHz in measurements. A successful excitation of the quasi-TEM wave was confirmed by the measurements of the uniform aperture field with ripple less than 3 dB and 30 deg. A simulation shows a 0.5 dB and 6% in antenna gain and efficiency enhancement due to reduction of the dielectric. As the antenna size increases, the larger gain enhancement is expected.