Compact 3D MMIC spiral baluns using multilayer CPW technology

This paper describes the design, fabrication and characterization of a novel broadband monolithic passive spiral Marchand balun using the great flexibility of three-dimensional multilayer technology by The Electromagnetics Centre, The University of Manchester. As a measured result, the insertion loss better than -5 dB including the 3 dB power splitting loss over the 15 to 27 GHz bandwidth and the return loss better than -30 dB have been achieved at the perfectly matched frequency of 20 GHz. Amplitude and phase imbalance of 1 dB and 10 degrees, respectively, were achieved over the frequency band from 15 to 27 GHz. The balun occupies a small area as 0.26 mm².