Low Loss Ferrite Y-Junction Circulator Based on Empty Substrate Integrated Coaxial Line at Ku-Band

A Y-junction circulator based on empty substrate integrated coaxial line (ESICL) technology is proposed in this paper. As ESICL is a novel transmission line, many of the common waveguide devices have not yet been developed in this technology, i.e., only filters, a power divider, a 90 degrees hybrid directional coupler or transition structures have been presented but no nonreciprocal devices. In this paper, a ferrite-based circulator has been designed and fabricated to operate at a central frequency of 12 GHz. Measurements performed with the help of an electromagnet confirms the stability of the circulator response under different DC biasing fields. Also, measurements with magnets have been done to integrate the circulator in communication systems. In addition, different temperature tests from 20 degrees C to 90 degrees C have been carried out with the aim of checking the scattering parameters variations. The experimental results confirm the results obtained by the full wave simulations: insertion loss better than 1 dB isolation and return loss below 10 dB from 10 to 14 GHz.