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Low-Loss Silicon Micromachined Waveguides Above 100 GHz Utilising Multiple H-Plane Splits

For sub-millimeter and millimeter wave applications rectangular waveguides are an ideal transmission medium. Compared to conventional, metal-milled rectangular waveguides, silicon micromachined waveguides offer a number of advantages. In this paper we present a low-loss silicon micromachined waveguide technology based on a double H-plane split for the frequency bands of 110 – 170 GHz and 220 – 330 GHz. For the upper band a reduced height waveguide is presented, which achieves a loss per unit length of 0.02 – 0.10 dB/mm. This technology has been further adapted to implement a full height waveguide for the lower frequency band of 110 – 170 GHz. The full height waveguide takes advantage of the benefits of the double H-plane split technique to overcome the challenges of fabricating micromachined waveguides at lower frequencies. With measured insertion loss of 0.007 – 0.013 dB/mm, averaging 0.009 dB/mm over the whole band, this technology offers the lowest insertion loss of any D-band waveguide to date. The unloaded Q factor of the D-band waveguide technology is estimated to be in excess of 1600, while a value of 750 has been measured for the reduced height upper band waveguide.