“…In the millimetre and sub-millimetre frequency range coplanar waveguides are more commonly used in the design of circuits (Argarwal et al, 1998), (Haydl et al, 1999), (Hirose et al, 1998), (Papapolymerou et al, 1999). Many studies have, indeed, shown that coplanar waveguides can be considered as a good alternative to microstrip lines in this frequency range (Houdard, 1976), (Hirota & Ogawa, 1987), (Ogawa & Minagawa, 1987), (Brauchler et al, 1996), (Kulke & Wolff, 1996), (Herrick et al, 1998). Because all conductors are located on the same plane, the ground connections through via-holes are eliminated and no reverse side processing is needed, which significantly reduces cost.…”