Pulse modulated fourier transform magnetic resonance spectrometer utilizing quadrature phase detection and high pass filter to eliminate undesired strong resonance lines

Claim 3

The method as claimed in claim 1 wherein the transmitter frequency applied to the sample to produce resonance is set at the frequency of said particular to-be-deleted resonance line.

Claim 4

The method as claimed in claim 2 wherein said step of phase detecting includes the steps of mixing a signal at the transmitter frequency with a second radio frequency signal to obtain a reference intermediate radio frequency signal, mixing the multiline resonance signal output from the sample with said second radio frequency signal to obtain an intermediate frequency composite output signal, and mixing said intermediate frequency composite output signal with said reference intermediate frequency to obtain a first audio signal output to be sampled, and mixing said intermediate frequency composite output signal with a signal at the frequency of said reference intermediate frequency but in phase quadrature therewith to obtain a second audio signal output to be sampled, the transmitter frequency component of the resonance signal output lying at approximately the zero frequency position of the audio output spectrum with said first and second audio signal outputs lying on either side of the zero position, said first and second audio signal outputs being filtered to eliminate the components from said audio signal outputs corresponding to the frequency substantially at the transmitter frequency.

Claim 5

The method as claimed in claim 3 including the step of applying a second driving radio frequency magnetic field to said sample near the carrier frequency value for double resonance.

Claim 6

The method as claimed in claim 1 including the step of applying a second driving radio frequency magnetic field to said sample near said particular resonance line frequency for double resonance.

Claim 7

The method of claim 1 wherein the step of causing said reference signal to coincide with the frequency of a to-be-deleted signal includes deriving said reference signal from said transmitter frequency.

Claim 8

The method of claim 1 wherein the step of causing said reference signal to coincide with the frequency of a to-be-deleted signal includes deriving said reference signal from a master oscillator.

Claim 11

The method as claimed in claim 8 wherein the transmitter frequency applied to the sample to produce resonance is set at the frequency of said to-be-deleted resonance line.

Claim 12

The method as claimed in claim 8 wherein said step of phase detecting includes the steps of mixing a signal at the transmitter frequency with a second radio frequency signal to obtain a reference intermediate radio frequency signal, mixing the multiline resonance signal output from the sample with said second radio frequency signal to obtain an intermediate frequency composite output signal, and mixing said intermediate frequency composite output signal with said reference intermediate frequency to obtain a first audio signal output to be sampled, and mixing said intermediate frequency composite output signal with a signal at the frequency of said reference intermediate frequency but in phase quadrature therewith to obtain a second audio signal output to be sampled, the transmitter frequency component of the resonance signal output lying at approximately the zero frequency position of the audio output spectrum with said first and second audio signal outputs lying on either side of the zero position, said first and second audio signal outputs being filtered to eliminate the components from the audio signal outputs corresponding to the frequency substantially at the transmitter frequency.

Claim 13

The method as claimed in claim 10 including the step of applying a second driving radio frequency magnetic field to said sample at the carrier frequency value for double resonance.

Claim 14

The method as claimed in claim 8 including the step of applying a second driving radio frequency magnetic field to said sample at said carrier frequency for double resonance.

Claim 15

The method as claimed in claim 8 wherein said RF pulses applied to the sample are applied in a pseudorandom sequence.

Claim 16

Apparatus for obtaining a magnetic resonance spectrum from a sample under analysis comprising a driving radio frequency magnetic field transmitter for applying RF pulses to the sample in a probe to produce simultaneous resonance of the multiple magnetic resonance lines in the spectrum of the sample, means for detecting the composite resonance signal output and means for sampling and storing said detector output to obtain a multiplicity of time-displaced components, including means for sampling and storing time-displaced components a number of times and adding each new stored value to the previously stored respective time-displaced components, means to Fourier transform said stored signals to produce a magnetic resonance spectrum for recording and display, one of said multiple resonance lines being an unwanted line which is to be eliminated from the displayed output spectrum, certain resonance lines being positioned on either side of said particular resonance line, wherein said means for detecting includes a quadrature phase detector, said phase detector having an output terminal, means to generate a selectable reference signal, said phase detector being adapted to receive a signal from said reference signal generator and from said probe, high pass filter means having a pair of outputs, said high pass filter means being connected to said phase detector output terminal for removing the frequencies substantially near and including zero frequency, said outputs of said high pass filter means being coupled to said meaNs for sampling.

Claim 17

Apparatus for obtaining a magnetic resonance spectrum from a sample under analysis comprising a driving radio frequency magnetic field transmitter for applying RF pulses to the sample in a probe to produce simultaneous resonance of the multiple magnetic resonance lines in the spectrum of the sample, means for detecting the composite resonance signal output and means for sampling and storing said detector output to obtain a multiplicity of time-displaced components, including means for sampling and storing time-displaced components a number of times and adding each new stored value to the previously stored respective time-displaced components, means to Fourier transform said stored signals to produce a magnetic resonance spectrum for recording and display, one of said multiple resonance lines being an unwanted line which is to be eliminated from the displayed output spectrum, certain resonance lines being positioned on either side of said particular resonance line, wherein said means for detecting includes a quadrature phase detector, said phase detector having an output terminal, means to generate a selectable reference signal, said phase detector being adapted to receive a signal from said reference signal generator and from said probe, high pass filter means having a pair of outputs, said high pass filter means being connected to said phase detector output terminal for removing the frequencies substantially near and including zero frequency, said outputs of said high pass filter means being coupled to said meaNs for sampling.

Claim 18

Apparatus of claim 14 wherein said high pass filter means includes a pair of similar filters, each said similar filter having a low frequency cutoff greater than the frequency components representative of the unwanted line.

Claim 19

Apparatus for obtaining a magnetic resonance spectrum from a sample under analysis comprising a driving radio frequency magnetic field transmitter for applying RF pulses to the sample in a probe to produce simultaneous resonance of the multiple magnetic resonance lines in the spectrum of the sample, means for detecting the composite resonance signal output and means for sampling and storing time-displaced components a number of times and adding to the previously stored respective time-displaced components, means to perform a Fourier transformation on the stored signals to produce a magnetic resonance spectrum for recording and display, said transmitter being adapted to provide the driving radio frequency of the RF pulses at a frequency value fo corresponding to the frequency of any particular magnetic resonance line of the sample which is to be eliminated from the output spectrum, means for mixing a signal at frequency fo with a second radio frequency signal at a frequency value of fo - fIF to obtain a reference intermediate signal at fIF, means for mixing the resonance signal output from the sample with said second radio frequency signal to obtain an intermediate frequency resonance signal, means for mixing said intermediate frequency resonance signal with a first reference intermediate signal at fIF to obtain a first audio signal output to be sampled and means for mixing said intermediate frequency resonance signal with a second reference signal at fIF but in phase quadrature with said first reference intermediate signal to obtain a second audio signal output to be sampled, the fo component of the resonance signal output lying at approximately the zero frequency position of the audio output spectrum with said first and second audio signal outputs lying on either side of the zero position, and high pass filtering means connected to said first and second audio signal outputs to eliminate the component of the audio signal output corresponding to the driving radio frequency value fo.

Claim 20

Apparatus for obtaining a magnetic resonance spectrum from a sample under analysis comprising a driving radio frequency magnetic field transmitter for applying RF pulses to the sample in a probe to produce simultaneous resonance of the multiple magnetic resonance lines in the spectrum of the sample, means for detecting the composite resonance signal output and means for sampling and storing time-displaced components a number of times and adding to the previously stored respective time-displaced components, means to perform a Fourier transformation on the stored signals to produce a magnetic resonance spectrum for recording and display, said transmitter being adapted to provide the driving radio frequency of the RF pulses at a frequency value fo corresponding to the frequency of any particular magnetic resonance line of the sample which is to be eliminated from the output spectrum, means for mixing a signal at frequency fo with a second radio frequency signal at a frequency value of fo - fIF to obtain a reference intermediate signal at fIF, means for mixing the resonance signal output from the sample with said second radio frequency signal to obtain an intermediate frequency resonance signal, means for mixing said intermediate frequency resonance signal with a first reference intermediate signal at fIF to obtain a first audio signal output to be sampled and means for mixing said intermediate frequency resonance signal with a second reference signal at fIF but in phase quadrature with said first reference intermediate signal to obtain a second audio signal output to be sampled, the fo component of the resonance signal output lying at approximately the zero frequency position of the audio output spectrum with said first and second audio signal outputs lying on either side of the zero position, and high pass filtering means connected to said first and second audio signal outputs to eliminate the component of the audio signal output corresponding to the driving radio frequency value fo.

Claim 21

Apparatus as claimed in claim 16 wherein said means for mixing said intermediate frequency output signal with siad first and second reference signals comprises a first mixer circuit and a second mixer circuit, and wherein said high pass filtering means comprises a first high pass filter coupled to the output of said first mixer and a second high pass filter coupled to the output of said second mixer.