Ka-band diplexer design based on half-mode groove gap waveguide

This paper shows the practical design of a Ka-band tuning-less diplexer in half-mode groove gap waveguide (HM-GGW) technology for multi-beam satellite applications. This new technology can be easily manufactured, since it lets the design of two separate metallic pieces: one for the cover with periodic pins, and another one for the half-groove gap waveguide structure. The proposed diplexer is composed of two bandpass HM-GGW filters, an H-plane T-junction and the corresponding transitions to the input/output WR28 rectangular ports. To illustrate how this technology can be applied, a prototype has been successfully fabricated, showing in-band measured return and insertion losses of 21 dB and 0.87 dB in the lower band, 16 dB and 0.86 dB in the upper band, and a good isolation level (better than 32.5 dB) in the whole operational frequency range.