Abstract

The receiver channel determines such important features of an NMR spectrometer as signal-to-noise (S/N) ratio, signal offset and signal phase precision. Digital techniques provide the possibility to solve in a radical way many traditional problems connected with these important parameters and guarantee the perfect time stability of the receiver.

We have examined several different architectures in order to optimize the quality, development time and final costs of the receiver. Accent was placed on direct digital sampling for frequencies up to 90 MHz (using the most modern ADCs), data demultiplexing for parallel processing, digital quadrature detection, filtering and multiplexing. For processing of signals with frequencies above 90 MHz, the undersampling technique was considered.

The adoption of an FPGA (Field Programmable Gate Array) integrated circuit for the implementation of the receiver leads to a system which can keep adapting to the ever increasing requirements of our Users.