Dual-band hybrid balun structure using transmission-lines and lumped component resonators

This paper presents a new dual-band rat-race balun structure for microwave circuit designs and applications. The methodology of designing the dual-band rat-race calls for conventionally designing it at the higher frequency (f1) using distributed components and augmenting the resulting design by adding resonators connected to open stubs to achieve as well as good performance at the lower frequency (f2). This leads to a size reduction as the main body of the balun is designed for the smaller wavelength. A dual-band rat-race balun has been designed and fabricated at 2.14 and 3.6 GHz. Measurement and momentum simulation results found to be in good agreement.