EQUIPMENT FOR SELECTIVE EXCITATION IN NMR-SPECTROSCOPY - ENHANCED TECHNIQUES FOR RADIOFREQUENCY MODULATION AND DIGITAL PULSE-SHAPE GENERATION

This paper describes readily constructed electronic equipment for generating shaped pulses for use in nuclear magnetic resonance spectroscopy. A radio-frequency modulator is controlled by the analogue waveshape supplied by a digital waveform generator. The modulator makes use of a double-balanced mixer in a circuit, which extends its linear range. Both the modulator and the digital section embody enhancements over conventional techniques. The equipment was designed to be integrated into Bruker spectrometers controlled by ASPECT computers; modification to accept data from other machines should not involve major changes. The analogue output of the waveform generator could also be used to control field gradient pulse shapes