Function generator for nmr system

Abstract

A modular function generator for generating a plurality of analog waveforms for use in an NMR imaging system. The function generator includes a plurality of waveform synthesizer modules which are interconnected by a main bus to a central controller CPU. Each synthesizer is adapted to produce one analog waveform for the NMR imaging system. A synthesizer module includes a memory and an address sequencer which produces a sequence of addresses which control the retrieval of data from the memory. Each data world of the memory contains several fields. An instruction field and a general data field control the address sequencer so that the sequence of addresses is, in turn, controlled by the memory data. Other fields from the memory define analog and digital outputs produced by the synthesizer module. The fields are generated by program control means which are organized to have data segments which define a set of elementary analog waveform segments and subroutines which are controlled by a main program. The execution of each subroutine produces a segment of an analog waveform. The subroutines generate a segment by accessing given data segments and concatenating a plurality of elementary segments into a single analog output. A plurality of synthesizer modules interconnected by an interchannel communications bus which allows each synthesizer to signal every other synthesizer whereby the operations of the synthesizers can be synchronized.