Abstract: In conventional NMR, quadrature detection of free induction decay signal employs two channels of phase sensitive detector. With this technique, phase cycling for canceling the spectral distortion due to unbalance between two channels is indispensable. This makes the experiment time longer than necessary when the signal-to-noise ratio is good enough to ensure one scan sampling. In order to overcome this problem, a digital quadrature detection technique is proposed and carried out on an MSL-300 spectrometer in the present article. The method utilizes only one channel of analog-to-digit conversion. Therefore, distortion caused by the unbalance between two channels can be fully avoided. As a result, no phase cycling for canceling the distortion mentioned above is necessary.

Key words: NMR, Digital quadrature detection