Reduction of UWB Far-End Crosstalk in Microwave and Millimeter-Wave Band of Parallel Periodically Loaded Transmission Lines With Discontinuous Structured Guard Lines

Abstract

A novel method is proposed to reduce the ultra-wideband (UWB) far-end crosstalk (FEXT) of the parallel microstrips (MSs), in which subwavelength periodically loaded transmission lines (PLTLs) with discontinuous structured guard lines (DSGLs) are appropriately used. The motivation is to innovate a structure to eliminate the FEXT for devices in microwave and millimeter-wave band. In the scheme, the single PLTL has enhanced self-inductance, and the PLTL pairs with interline DSGLs can realize added mutual capacitance and slightly changed mutual inductance, comparing with the conventional MS pairs. Therefore, the equalization of capacitive coupling ratio and the inductive coupling ratio is realized, which dramatically reduce the FEXT in a wide bandwidth range. The lumped parameters are extracted for mechanism validation, then several MS circuits are designed on FR-4 PCB by full-wave simulation. The comparisons with the previous methods indicate that the best cancellation of the FEXT is achieved by the proposed method. To demonstrate the design strategies, MS circuits operating from DC to 40 GHz are designed using the above proposed method and further fabricated on Al2O3 ceramic board of 0.127-mm thickness. The measured results reveal that more than 35-dB FEXT suppression is obtained from DC to Ka-band, indicating the validity of the proposed method.