Improving the Patch-Based Crossovers by Parasitic Modes and a Sub-Element Technique

This brief introduces new methodologies to design microstrip line crossovers on a high-speed interconnection circuit. The crossover is based on a simple square patch, which employs TM
₁₀₀
and TM
₀₀₁
to achieve mode orthogonality so that two sets of intersecting signals can transmit along microstrip lines with a high isolation. Compared with rectangular waveguide crossovers that employ high modes, namely TE
₁₀₂
and TE
₂₀₁
, it shows advantages like a smaller size and easier manufacturing. Then, the relevant techniques for performance improvement, including radiation suppression and bandwidth widening, are studied for practical circuit designs. Finally, based on the sub-element technique, the study designs a controllable frequency response for two intersecting signals and miniaturization of patch based crossovers. Two examples are implemented, manufactured and measured to justify the validity of the sub-element technology. In addition, the design steps of this method are simplified compared with relying on full-wave simulations entirely.