National Research Development Corporation

Reginald A Willard

William S Percival

Nuclear magnetic resonance is excited in surrounding fluids by pulsing a first winding which with a capacitor forms a resonant circuit. In order to observe signals induced by NMR in the first winding between pulses, the pulses are given an envelope which rises linearly to a peak and then immediately decays linearly to zero. A waveform generator generates bursts of constant amplitude oscillations having a 180.degree. phase change at the centre of each burst. When such bursts are applied to the resonant circuit by way of a drive amplifier and a second winding wound over the first winding, the required envelope is generated in the first winding.

Waveform generator for nuclear magnetic resonance apparatus

Nuclear magnetic resonance is excited in surrounding fluids by pulsing a first winding which with a capacitor forms a resonant circuit. In order to observe signals induced by NMR in the first winding between pulses, the pulses are attenuated by connecting resistors across a second winding inductively coupled to the first winding. Connection of the resistors is made when required by forward biasing two MOSFETs connected 'back to back' to reduce transients when the MOSFETs cease conduction. A switching pulse for the MOSFETs which has a steep rising edge and an exponential trailing edge has been found advantageous.

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Middlesex, United Kingdom

Reginald A Willard