Rf pick-up coil circuit for a wide tuning range nuclear magnetic resonance probe

Claim 1

In a resonance pick-up circuit of a nuclear magnetic resonance spectrometer: magnetic pick-up coil means disposed in radio frequency magnetic field exchanging relation to a nuclear magnetic resonance sample region for sensing nuclear magnetic resonance of a sample in the sample region; tuning capacitor means series connected for RF current flow with said pick-up coil means for series resonating the inductance of said magnetic pick-up coil means at a nuclear magnetic resonant frequency of the resonance sample material; transmission line transformer means series connected for the series resonant radio frequency current flow with said pick-up coil means and said tuning capacitor means at said series resonance frequency for transforming the relatively low series resonance impedance of said series resonated pick-up coil means to a substantially higher impedance of the input to a radio frequency amplifier; said transformer means including first and second elongated conductors having an axially coextensive elongated portion, said transmission line comprising the distributed inductance and capacitance of said first and second coextensive conductors, said first conductor being series connected with said series resonated pick-up coil for flow of series resonant radio frequency current therethrough of one phase and for inducing a radio frequency current flow of opposite phase in said second conductor; and means for coupling the induced current in said second conductor onto the end of said first conductor, which faces toward said pick-up coil means, in phase with the current flow in said first conductor so that at the end of said first conductor facing said pick-up means there is the sum of the current flow in said first and second conductors and at the opposite end of said first conductor, which faces toward the amplifier, there is only the series resonant current flow on said first conductor.