A circuit for a nuclear magnetic resonance probe uses three resonators to
create resonances intermediate to the resonator resonant frequencies. The
circuit is particularly useful for creating magnetic fields for two
closely spaced high frequencies, such as those used for the excitation of
.sup.1H and .sup.19F. The resonators are arranged in a parallel
combination, or the electrical equivalent thereof, with input ports
connected to it for inputting the desired high frequency resonances.
Admittance inverters may be used to provide isolation between the input
ports. Some of the resonators and the admittance inverters may be
transmission lines. The transmission lines may have additional ports for
additional input signals of lower frequencies located at null points for
the frequencies of the signals coupled to the primary input ports.
Adjustable dielectric components in the resonator transmission lines may
be used for tuning purposes.
