On-chip Integratable Self-biased Microstrip Circulator for Millimeter-wave Frequency Communication

This study focuses on the design and fabrication of a self-biased ferrite microstrip circulator intended for the millimeter-wave frequency band, with a target frequency range of 45-47 GHz. The design utilizes SrM-type ferrite material with high anisotropy fields and incorporates photoresist as a doping material. The self-biased ferrite microstrip circulator was simulated and measured using HFSS simulation software, and the physical device was fabricated using the spin-coating method. Measurements of the device were conducted in the 34-56 GHz frequency range, yielding an isolation greater than 25 dB and a return loss exceeding 22 dB despite the measured insertion loss was slightly higher than the desired result of 1.5 dB, the design met the required specifications mostly. The simulation and measurement results suggest that this design has significant potential for further practical applications.