This article presents the effective dielectric constant (ϵeff) and attenuation constant (α) of an unshielded slot line and a coplanar strip line on a high‐resistivity (5000–10,000 ω‐cm) silicon wafer. The ϵeff (dc to 40 GHz) and α (dc to 26.5 GHz) in each case are determined from the measured resonant frequencies and insertion loss of a ring resonator. The measurements are carried out at room temperature. No dc bias is applied to the transmission lines. The attenuation for slot line and coplanar stripline on silicon are compared with microstrip line and coplanar waveguide on other semiconductor substrate materials. Lastly, a microstrip‐to‐slot‐line transition and its use in a feed network for linearly tapered slot antennas is demonstrated. © 1994 John Wiley & Sons, Inc.