Speaker
Description
Yttrium-Iron-Garnet (YIG) ferrites have one-to-two orders of magnitude smaller magnetic permeability than Ni-Zn ferrites. In the frequency range above 10 MHz, Ni-Zn ferrites are too lossy to be useful. However in the frequency range roughly 30-120 MHz, YIG has high magnetic (and electrical) quality factor. Further, ferrites perpendicular-biased near saturation, have large incremental permeability due to the ferro-magnetic resonance (FMR). These properties presented an opportunity for effective wide-range RF cavity tuning, with low losses. Although high-Q narrow-range tuning was achieved, the promise of both wide tuning range and high Q was not achieved (despite more than a decade of development).This has never been explained, even prompting one author to suggest the magnetic Q (material property) varies quickly with frequency. Here we present a simple theory of cavity tuning with perpendicular biased ferrite (and FMR) that predicts tuning range and effective quality factor; and explains why the high Q cannot be maintained across a large range, and instead Q falls at low frequency.
| Paper status | Proceeding files received |
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