Quadrature detection circuit for nuclear magnetic resonance apparatus
AssigneeKabushiki Kaisha Toshiba
InventorsYoshio Machida, Masahiko Hatanaka
Life of this patent
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Abstract
A quadrature detection circuit compensates for phase and amplitude differences in an NMR quadrature detection apparatus. The quadrature detection circuit comprises a test signal generator, first and second modulators, amplitude detectors, phase error detectors and a corrector. The corrector compensates the NMR signal as to phase and amplitude factors determined during an initial calibration mode utilizing the test signals, thus eliminating ghost images of the object which would otherwise be formed during image reconstruction.
Claims12
A quadrature detection circuit for nuclear magnetic resonance apparatus, comprising:
- (a) means for generating first and second reference signals having a phase shift relative to one another, and having a common frequency f.sub.o ;
- (b) a test signal generator for generating a test signal having a frequency .DELTA.f.sub.o which is slightly different from that of said first and second reference signals;
- (c) first and second demodulating means for demodulating the test signal with said first and second reference signals respectively to respectively produce first and second demodulated signals;
- (d) amplitude detecting means for detecting first and second amplitudes of said first and second demodulated signals to obtain an amplitude difference therebetween;
- (e) phase error detecting means for detecting the period of at least one of said first and second demodulated signals and phase difference between said first and second demodulated signals to obtain a phase error;
- and,
- (f) compensating means for compensating an NMR signal demodulated by said demodulating means with said first and second reference signals for said phase error and amplitude difference.
A method of compensating an NMR signal for amplitude and phase errors comprising the steps of:
- (a) generating first and second reference signals having a phase shift relative to one another and having a common frequency f.sub.o,
- (b) generating a test signal having a frequency .DELTA.f.sub.o which is slightly different from that of said first and second reference signals;
- (c) demodulating said test signal with said first and second reference signals respectively to respectively produce first and second demodulated signals;
- (d) detecting first and second amplitudes of said first and second demodulated signals to obtain an amplitude difference therebetween;
- (e) detecting the period of at least one of said first and second demodulated signals and phase difference between said first and second demodulated signals to obtain a phase error;
- (f) demodulating said NMR signal with said first and second reference signals to respectively produce first and second demodulated NMR signals;
- and
- (g) compensating said first and second demodulated NMR signals for said phase error and amplitude difference.
Dependencies are inferred from the claim text.