Coupling piece between rectangular waveguide and dipole wave conductor - has dielectrically loaded transition stages in relatively small steps of similar length

摘要

To minimise reflection losses the transitions between a wave guide (1) of height (b) in the E-plane, and the slit conductor with a slit width (W4) between the metallised areas (3), step charges should be as gradual as possible without requiring too large a length. This is achieved by the substrate (2) being completely free from any metallisation over a length (L2), with a first step of the length (L2) reducing the metal-free portion to a smaller width (W2), and a further stage having a metal-free width still narrower (W3), until finally reducing to the dipole conduction strip width (W4), which may be only a fraction of a millimeter in the medium Ghz range. The effectiveness of these transitions is due to the di-electric loading by the substrate material within the otherwise empty wave guide. In a specific case, the impedance of the wave guide was 1700 Ohm reduced by the coupling piece to a strip conductor impedance of only 70 Ohm. This substantial transformation was attained at an attenuation of only 02 db.