Balanced Microstrip Line with Defected Ground Structure on Thin Flexible Substrate Film

Abstract

In this study, a low-loss balanced microstrip line (MSL) with a defected ground structure (DGS) on a thin, flexible substrate is proposed. This structure consists of a balanced MSL on a $25{-}\mu \mathrm{m}$-thick substrate and a defected structure formed on the ground plane. The measurements revealed that the balanced MSL with a DGS exhibited a transmission loss reduction of 1.5 dB/100mm at 40 GHz and maintained the same far-end crosstalk compared to a conventional balanced MSL fabricated on a $50{-}\mu \mathrm{m}$-thick substrate up to 40 GHz. For the same thickness substrate, the differential insertion loss of the balanced MSL with a DGS achieved an improvement of up to 4.9 dB/100mm relative to the conventional balanced MSL. The findings derived from the measurements confirm the effectiveness of the DGS. The proposed balanced line can use high-speed transmission standards in miniaturized electric devices to increase routing densities.