In-plane hollow waveguide crossover based on dielectric insets for millimeter-wave applications

This paper presents an in-plane hollow waveguide crossover for W-band frequencies. This kind of crossover can be implemented e.g. into a Butler matrix, to simplify the fabrication process significantly. It is based on a partially dielectric filling of the waveguide, focussing the field in the center. The dielectric is placed in the center of a hollow waveguide crossing and has a star-shape. Inside the dielectric filled region, a higher order mode propagation is possible, which has no significant influence on the overall performance of the crossover. It shows an insertion loss between 0.8 dB to 1.0 dB in the frequency range of 101.5 GHz to 108.0 GHz, while the matching is better than -10 dB and even down to -20 dB between 105 GHz to 108 GHz. The isolated ports show transmission coefficients better than -20 dB over the whole frequency range and even down to -50 dB in the best performing frequency range.