Comparison of hollow waveguide and dielectric fibre based SPDT switches for W-band

This work presents as a first approach, the comparison of two non-tuneable/switchable W-band single pole double throws (SPDTs), one realised in hollow waveguide and one in subwavelength dielectric fibre technology. For pre-investigations, both SPDTs are equipped with non-tuneable phase shifters, providing a fixed differential phase shift of 90° between the two paths. The waveguide SPDT shows a reflection better than -10 dB and an isolation between the two output ports of around 16 dB. The fibre SPDT shows reflections better than -10 dB over a wide frequency range and down to -25 dB at 100 GHz, but an isolation between 4 dB to 10 dB only. This deviation compared to simulations is due to the sensitivity of the system in terms of fabrication tolerances whereby the needed differential phase shift of 90° has been exceeded. Next, these phase shifters will be replaced by continuously tuneable phase shifters based on liquid crystal technology. At this point, dielectric fibres are a very promising alternative to hollow waveguides.