| 摘要 |
A magnetically tuned resonant circuit for coupling r.f. energy between input and output coupling circuits thereof in a first mode of operation and isolating such energy between such coupling circuits in a second mode of operation includes a current path circuit provided to selectively change the resonant frequency of the magnetically tuned resonant circuit. In a first embodiment of the current path circuit, a microstrip transmission line used to form one of such coupling circuits, having a pair of planar spaced strip conductor portions adjacent a resonant body, is configured to provide the current path around such body. In the presence of an external magnetic field HDC, a pulse of current is fed around the current path and in response thereto provides a pulse magnetic field HDCp in the region of the resonant body. Such field HDCp either aids or opposes the external magnetic field HDC and in response thereto shifts a resonant frequency omega o of such circuit in accordance with the equation omega o= gamma (HDC+/-HDCp) where gamma is a quantity known as the gyromagnetic ratio. In an alternate embodiment of the circuit, the circuit includes a coil supported on a dielectric substrate to provide the current path, with such coil being disposed adjacent the resonant body. A pulse of current is fed to the coil providing a magnetic field HDCp, and in the presence of the external magnetic field HDC, the resonant frequency of such circuit is shifted in accordance with the equation omega o= gamma (HDC+/-HDCp).
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