Compact Planar Balanced Crossover With Bandpass Response

A planar balanced crossover with bandpass response is proposed. This crossover consists of a ring resonator and four half-wavelength resonators. It acts as a third-order filter between two diagonal ports under differential-mode (DM) excitation and exhibits isolation between two adjacent ports under DM excitation or two arbitrary ports under common-mode excitation. To demonstrate the design, a crossover working at 2.41 GHz is fabricated and measured. The measured results exhibit good agreement with the simulation results.