关键词: 正交检波, 核磁共振, 相敏检波器, 数据拟合

Abstract: Quadrature detection is widely used in modern NMR spectrometers, as it provides such advantages as avoiding peak overlapping, reducing the power requirement for the excitation radiofrequency pulse, and increasing signal-to-noise ratio of detection. However, mirror peaks may arise if the gain of the two receiver channels used in quadrature detection are not matched, or the phase difference between two channels is not exactly 90 degree. To a certain degree, the problem can be overcome by applying phase cycling during acquisition. However, manual correction is necessary when the gain difference between the two channels become large or the phase difference is far from 90 degrees. This paper proposes a simple method to correct gain and phase mismatch in quadrature detection experimentally.

Key words: NMR, quadrature detection, phase-sensitive detector, data fitting