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Abstract

A multiply-tuned probe for magnetic resonance imaging or spectroscopy in which a driving inductor is separately coupled to two or more trap inductors. The impedance match at each frequency is adjusted independently of the impedance match at the other frequencies and independent of the tuning by using a novel coil geometry with no overcoupling. In a preferred embodiment, a triple-tuned probe has a first inductor L.sub.1 disposed in a first plane and tuned to a first resonant frequency and a second inductor L.sub.2 disposed in a second plane parallel to the first plane and tuned to a second resonant frequency. A driving and receiving primary inductor L.sub.p is disposed in a third plane parallel to the first and second planes and placed with respect to the first and second inductors L.sub.1 and L.sub.2 such that mutual inductance between L.sub.1 and L.sub.p in between L.sub.2 and L.sub.p is adjustable in accordance with the positions of the inductors L.sub.1, L.sub.2 and L.sub.p. A sample surface inductor L.sub.s tuned to a third resonant frequency provides the third frequency. Mutual inductance between L.sub.1 and L.sub.p in between L.sub.2 and L.sub.p is changed by repositioning the inductors L.sub.1, L.sub.2 and L.sub.p to vary the amount of overlap between the cross-sections of the primary inductor L.sub.p and the circular coils L.sub.1, L.sub.2 and the distances between inductors L.sub.1 and L.sub.p and between inductors L.sub.2 and L.sub.p. Since each inductive coupling adds another variable to the probe circuit, more and easier ways are provided for adjusting the tuning and impedance matching.

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