In this work, a wideband DC isolated substrate integrated coaxial line (SICL) transition for thick substrates is presented. The planar transition is devised utilizing a substrate truncated microstrip line as a transition to SICL section. Tapered slots etched on the top ground plane aid in improving the transition characteristics over a wide bandwidth. The DC isolation in the proposed transition is achieved by embedding a compact interdigital capacitor in a microstrip line connected to the SICL section. Performance of the transition with an embedded interdigital capacitor is analyzed. The proposed transition exhibits a fractional bandwidth of 22.37% with a measured mean insertion loss less than 1.2 dB in 9.09 GHz to 11.38 GHz band. The loss group delay characteristics of the wideband transition are studied in this work. Development of DC isolated transition for the self-packaged electromagnetically shielded SICL simplifies integration of active components for superior performance of the communication system. © 2021 EuMA.