Analysis of Substrate Parameters’ Variations in a PCB-based 60 GHz GCPW Marchand Balun Design

This paper presents the design of a 60 GHz grounded coplanar waveguide (GCPW) based Marchand balun that is robust against variations of substrate height or dielectric constant. The via-free design and minimum trace width and trace-to-trace clearance of 0.1 mm makes this balun compatible for fabrication with economical printed circuit board (PCB) development technology. For optimal choice of height for a given substrate with known dielectric constant, simulation results show 33% bandwidth with maximum amplitude and phase imbalance of 0.2 dB and 13 degree, respectively. The substrate dependency analysis in terms of height and dielectric constant show the possibility of implementing this GCPW balun on substrates with deviations in height or dielectric constant with tolerable performance degradation. It provides a cost-effective rapid solution of measuring differential antennas and commercially available differential millimeter-wave components using single-ended laboratory equipment. Simulation results are verified through fabrication and laboratory measurements of two baluns backto-back connected through their differential ports. The measured results are in accordance with the simulated results.