Integration of a Microstrip Circulator With Planar Yagi Antennas of Several Directors

An integration methodology is presented to design antenna systems incorporating a ferrite circulator. Two integrated systems comprised of a microstrip circulator and Yagi planar-type antennas are presented as validation of the proposed methodology. Excellent pass band characteristics are observed in the experimental and numerical data for both systems. Furthermore, one system is magnetically tuned to realize 30 dB isolation over a bandwidth of 850 MHz. Both systems maintain excellent return loss and show improved insertion loss specifications even though the ferrite is biased into partial saturation. Extensive measurement data of the ferrite material and system network parameters are provided to corroborate the claims made herein.