Nuclear magnetic resonance spectroscopy employing difference frequency measurements

Claim 2

An impulse nuclear magnetic resonance spectrometer comprising means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference subtance having a single strong resonance line separated from the sample resonance lines, to produce simultaneous free induction decay signals from the sample and the reference at their respective radio frequency resonance frequencies to produce a plurality of successive composite decay signals therefrom, means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating includes means for weighting said sample free induction decay signal by its local signal-to-noise ratio for optimum signalto-noise ratio, means coupled to said demodulating means for extracting the composite signal comprising the difference frequencies between the sample and reference resonances, means for Fourier transforming said composite signal to obtain a difference frequency spectrum, and means for recording said difference frequency spectrum.

Claim 3

An impulse nuclear magnetic resonance spectrometer comprising means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the sample resonance lines, to produce simultaneous free induction decay signals from the different resonant bodies within the sample and the reference at their respective radio frequency resonance frequencies to produce a plurality of successive composite decay signals therefrom, means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating including means for weighting said sample free induction decay signal by its local signal-to-noise ratio for optimum signal-to-noise ratio, a low-pass filter means coupled to said demodulating means for passing all frequencies in the composite signal up to and including the diffErence frequencies between the sample and reference resonances, analog-to-digital converting means coupled to said low-pass filter for sampling said passed composite signal, means coupled to said converter for forming a time-averaged signal from the successive decay signals and for subtracting the reference substance response from said time-averaged signal to form a corrected difference frequency response, means for Fourier transforming said corrected difference frequency response, and means for recording said transformed response.

Claim 4

An impulse nuclear magnetic resonance spectrometer comprising means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the sample resonance lines, to produce simultaneous free induction decay signals from the different resonant bodies within the sample and the reference at their respective radio frequency resonance frequencies to produce a plurality of successive composite decay signals therefrom, means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating including means for weighting said sample free induction decay signal by its local signal-to-noise ratio for optimum signal-to-noise ratio, a low-pass filter means coupled to said demodulating means for passing all frequencies in the composite signal up to and including the diffErence frequencies between the sample and reference resonances, analog-to-digital converting means coupled to said low-pass filter for sampling said passed composite signal, means coupled to said converter for forming a time-averaged signal from the successive decay signals and for subtracting the reference substance response from said time-averaged signal to form a corrected difference frequency response, means for Fourier transforming said corrected difference frequency response, and means for recording said transformed response.

Claim 5

An impulse type nuclear magnetic resonance spectrometer comprising transmitter means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the resonance lines of the sample, to produce simultaneous free induction decay signals from the sample and the reference at their respective radio frequency resonance frequencies and thus produce a plurality of successive composite decay signals therefrom, receiver means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating including means for weighting said sample free induction decay by its local signal-to-noise ratio for optimum signal-to-noise ratio; a low-pass filter means coupled to said demodulating means for extracting from the composite signal all frequencies up to and including the difference frequencies between the sample and reference resonances to form a difference signal, means comprising an analog Fourier analyzer coupled to said extracting means for providing a difference frequency spectrum of said composite difference signal, said analog analyzer being synchronized in phase with said pulses of driving radio frequency magnetic field, a reference frequency, a sequence generator, said sequence generator being responsive to said reference frequency, said sequence generator providing first and second pulses, said first pulses for gating on said transmitter and gating said receiver off and for gating off said transmitter and said receiver on, and means for recording said spectrum.

Claim 6

An impulse type nuclear magnetic resonance spectrometer comprising transmitter means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the resonance lines of the sample, to produce simultaneous free induction decay signals from the sample and the reference at their respective radio frequency resonance frequencies and thus produce a plurality of successive composite decay signals therefrom, receiver means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating including means for weighting said sample free induction decay by its local signal-to-noise ratio for optimum signal-to-noise ratio; a low-pass filter means coupled to said demodulating means for extracting from the composite signal all frequencies up to and including the difference frequencies between the sample and reference resonances to form a difference signal, means comprising an analog Fourier analyzer coupled to said extracting means for providing a difference frequency spectrum of said composite difference signal, said analog analyzer being synchronized in phase with said pulses of driving radio frequency magnetic field, a reference frequency, a sequence generator, said sequence generator being responsive to said reference frequency, said sequence generator providing first and second pulses, said first pulses for gating on said transmitter and gating said receiver off and for gating off said transmitter and said receiver on, and means for recording said spectrum.

Claim 7

The spectrometer of claim 3 including a gated integrator and a hold circuit wherein said second pulse of said sequence generator is coupled to said gated integrator to cause the integrator to transfer the stored value of signal to a hold circuit.

Claim 14

An impulse nuclear magnetic resonance spectrometer comprising means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the sample resonance lines, to produce simultaneous free induction decay signals from the sample and the reference at their respective radio frequency resonance frequencies resulting in a plurality of successive composite decay signals therefrom, means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating includes means for weighting said free induction decay signal by its local signal-to-noise ratio for optimum signal-to-noise ratio, means coupled to said demodulating means for discarding from the composite signal substantially all frequencies lower than the difference frequencies between the sample and reference resonances to remove the reference response and to form a remaining composite signal, means for Fourier transforming said remaining composite signal to obtain a difference frequency spectrum, and means for recording said difference frequency spectrum.

Claim 15

An impulse nuclear magnetic resonance spectrometer comprising means for applying a plurality of pulses of driving radio frequency magnetic field simultaneously to the sample under analysis and to a reference substance in a polarizing magnetic field, said reference substance having a single strong resonance line separated from the sample resonance lines, to produce simultaneous free induction decay signals from the sample and the reference at their respective radio frequency resonance frequencies resulting in a plurality of successive composite decay signals therefrom, means for sensing the successive composite radio frequency decay signals from said sample and reference substance, means coupled to said sensing means for demodulating the separated sample and reference resonance lines of said sensed successive composite signals, said means for demodulating includes means for weighting said free induction decay signal by its local signal-to-noise ratio for optimum signal-to-noise ratio, means coupled to said demodulating means for discarding from the composite signal substantially all frequencies lower than the difference frequencies between the sample and reference resonances to remove the reference response and to form a remaining composite signal, means for Fourier transforming said remaining composite signal to obtain a difference frequency spectrum, and means for recording said difference frequency spectrum.