KAERNMAGNETISKT DELSYSTEM AV RESONANSAVBILDNINGSANTENN MED FLERA OORTOGONALA YTSPOLAR

An NMR antenna subsystem has a plurality of co-planar surface coils, each comprised of a plurality of segments and elements for tuning the coil to resonance at the Larmor frequency of a nuclei specie to be investigated. Each coil has circuitry for selectively detuning that surface coil when at least one other one of the plurality of surface coils is in use. One of a pair of co-planar surface coils can be utilized for signal reception and includes a parallel-resonant detuning circuit which operates only when a relatively large magnitude RF signal is induced by an excitation signal in a second surface coil. The second surface coil includes a circuit for detuning that coil except when an externally-provided signal is present; this signal may be the RF excitation signal itself or another signal provided simultaneously with the RF excitation signal.