Application of software defined radio in 500MHz NMR spectrometers

Digital signal processing is one of the most important techniques in 500 MHz NMR spectrometers. Free Induction Decay (FID) signal should be quadrature-demodulated from 20 MHz intermediate frequency (IF) signal, decimated to a user-defined sample rate and spectrum width. In the design of digital processor of NMR spectrometer console, the techniques of Software Defined Radio (SDR) are applied to achieve digital quadrature demodulation, digital filtering and data decimation. The CIC filter, half-band filter and linear phase FIR filter are designed to process the cascaded filtering and decimation of the demodulated signals. This following simulation shows that this method will achieve a satisfying processing and filtering effect.