  The design and characterization of a novel toroidal split-ring resonator
(SRR) is described in detail. In conventional cylindrical SRRs, there is a
large magnetic flux within the bore of the resonator. However, there also
exists a non-negligible magnetic flux in the free space surrounding the
resonator. The energy losses associated with this radiated power diminish the
resonator's quality factor. In the toroidal SRR, on the other hand, the
magnetic field lines are strongly confined within the bore of the resonator
resulting in high intrinsic quality factors and stable resonance frequencies
without requiring additional electromagnetic shielding. This paper describes
the design and construction of a toroidal SRR as well as an experimental
investigation of its cw response in the frequency-domain and its time-domain
response to an rf pulse. Additionally, the dependence of the toroidal SRR's
resonant frequency and quality factor on the strength of inductive coupling to
external circuits is investigated both theoretically and experimentally.
