In this proposal the possibility for wide-band operation of a drop-in circulator has been discussed based on a recent patent disclosure. For this purpose two approaches have been attempted. Since the circulator is biased below resonance, frequency tracking conditions may be obtained via suitable use of the dielectric filling material and the subtension angle of the circulator pots. It is hoped that octave bandwidth operation of the device can be ultimately realized. The second approach is based upon the operational principles relating to a waveguide partial-height ferrite junction circulator. Since the field profile in the drop-in circulator junction is analogous to that associated with the partial-height ferrite in a waveguide junction, we believe that the bandwidth of a drop-in circulator can be extended to at least 30% of its center frequency by using metal transformer with a pinning stub. Finally, we propose that hexagonal ferrites shall be used in the fabrication of millimeter wave devices. This eliminates the need of external biasing field even at high frequency operation of the circulator.
