Dielectric constant reduction using porous substrates in finline millimetre and submillimetre detectors - North, C; Audley, MD; Glowacka, D; Goldie, D; Grimes, P; Johnson, B; Maffei, B; Melhuish, S; Piccirillo, L; Pisano, G; Tsaneva, V; Withington, S; et al. (MILLIMETER AND SUBMILLIMETER DETECTORS AND INSTRUMENTATION FOR ASTONOMY IV, 2008)