New lumped element circulator by ceramic integrated circuit technology

A broadband and a compact lumped element circulator was developed by a co-firing method of a ferrite and inner conductor. A circulator fabricated by this method with the dimensions of 6/spl times/6/spl times/3 (mm) showed a 20 dB isolation bandwidth of 7% and an insertion loss of 0.7 dB at 800 MHz. The gyromagnetic inductance of this circulator was compared to that of a conventional circulator. The former always showed a higher inductance than the latter. This measurement and additional measurement of the inductance for non-magnetized ferrite disks with and without a gap have shown that a great portion of permeability increase came from the elimination of the demagnetizing field in the element. Although a broadbanding was obtained, the insertion loss of 0.7 dB could be improved by using a more conductive material. To optimize the isolation bandwidth, a refinement of the design method based on the gyromagnetic inductance measurement should also be established. In spite of these problems, the magnetically closed circuit circulator, mC/sup 3/, seems to be the ultimate lumped element circulator from its broadband characteristics, compact size and simplified structure, to reduce production costs. Furthermore, the broadband characteristics decrease the loaded Q-factor causing an increase in the handling power of the circulator which is a useful feature in broadcasting equipment.<
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