A Slotline DC Block for Microwave, Millimeter, and Submillimeter Circuits

DC blocks are used frequently in planar circuits to enable separate dc voltage/current biasing of active components inserted along the transmission lines. In this letter, we present a slotline dc block design where the conductors of the transmission line can be physically broken while allowing the propagation of the RF signal across the discontinuity with negligible insertion loss. The dc block comprises two breaklines with narrow gaps, patterned on the two ground planes of a slotline with each breakline connected to an RF choke. The RF chokes present open circuit nodes that prevent the RF power from leaking into the breaklines gaps. We have fabricated and tested the dc block and demonstrated that the measured performance agrees very well with simulated results. The insertion loss was close to -0.5 dB in the designated range of 12-16 GHz, demonstrating that the RF leakage through the dc block is indeed negligible.