On the nuclear magnetic resonance detection characteristics of marginal and Robinson oscillators

Abstract

General expressions are obtained for the response of a steady-state oscillator to nuclear magnetic resonance. In particular, it is shown that the amplitude modulation and frequency modulation both give a mixture of chi ' and chi ". In the fm case, the chi " contribution depends on the 'dephasing' of the feedback current and may be quite large in practice, especially at high frequencies. In the am case, the chi ' contribution is normally small (<or approximately=1%) but may be much larger for low Q oscillators. Excellent agreement between experiment and theory is obtained using a specially constructed Robinson oscillator.