60 GHz Double Edge Coupled Marchand Balun for PCB Implementation

This paper presents a planar Marchand balun design for 60 GHz applications. This design provides a low cost and rapid solution of testing commercially available mmWave ICs working with differential signalling on the PCB with the available single-ended laboratory equipment. This microstrip-based balun is designed to be compatible for PCB implementation keeping the minimum line and gap width greater than 0.1 mm. Simulation results indicate 30% bandwidth with a maximum amplitude and phase mismatch of 1.7 dB and 11° respectively. For the practical demonstration, two back-to-back connected baluns are fabricated on Isola I-TERA MT40 substrate along with special CPW-to-microstrip conversion structures for probe-station measurements. Measured results are compared with the simulated response to evaluate the design. Furthermore, a re-simulation taking into account the manufacturing deviations is carried out showing results in good agreement with the measured data.