Balanced multi-tuned high-power broadband coil for nmr

Claim 1

A balanced, multi-tuned, broad and circuit for high-field solids NMR probes requiring high-frequency port carrying a signal of a high frequency and a low-frequency port carrying a low frequency, said multi-tuned circuit comprising: a multi-turn sample excitation coil with a first lead at a first end and a second lead at a second end; a first balancing inductor connected with low first-lead inductance between said first end of said excitation coil and ground, said first end of said excitation coil also coupled to said high-frequency port via a fist high frequency high voltage variable capacitor network; a low-frequency high-voltage tuning and matching capacitor network coupled to said low-frequency port; a second balancing inductor and second high frequency high voltage variable capacitor network connected with low second-lead inductance between said second end of said excitation coil and said low-frequency high-voltage tuning and matching capacitor network; said first and second balancing inductors each having inductance less than 50% but greater than 10% of that of said excitation coil; said second balancing inductor further comprising a solenoid with fewer than five turns and having inductance less than 60 nH; each of said balancing coils tuned to substantially equal values of capacitive reactance at the desired high frequency by said first and second high frequency high voltage variable capacitor networks; said excitation coil further characterized in having its self-resonant frequency greater than 110% of said high frequency.