Ultra-broad bandwidth and low-loss GCPW-MS transitions on low-k substrates

A study of back-to-back grounded coplanar waveguide-microstrip (GCPW-MS) transitions is presented. By using low-permittivity substrates, both the attenuation and the bandwidth can be improved. An ultra-broad bandwidth up to 77 GHz could be obtained with the BCB polymer as substrate in thin film on low-resistivity silicon wafers.