Dielectric constant reduction using porous substrates in finline millimetre and submillimetre detectors

摘要

Finlines are planar structures which allow broadband and low loss transition from waveguide to planar circuits.Their planar structure and large substrate makes them ideal for integration with other planar circuits andcomponents, allowing the development of an on chip polarimeter. We have developed a method of extending theemployment of finlines to thick substrates with high dielectric constants by drilling or etching small holes intothe substrate, lowering the effective dielectric constant. We present the results of scale model measurements at15 GHz and cryogenic measurements at 90 GHz which illustrate the excellent performance of finline transitionswith porous substrates and the suitability of this technique for extending the bandwidth of finline transitions.