Journal article

Application of Time-Variable Feedback to the Input Amplifier of Pulse Magnetic Resonance Spectrometers : Experimental Studies


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Publication Details

Subtitle: Experimental Studies

Author list: Koptioug, Andrei

Publisher: Springer-Verlag

Place: Austria

Publication year: 2002

Start page: 455

End page: 473

Number of pages: 19

ISSN: 0937-9347


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Experimental research on the improvement of the sensitivity and time resolution of pulsedmagnetic resonance spectrometers is discussed. It is shown that application of a time-variable feedbackof a signal to the input of the receiver amplifier can decouple the ""fixed"" relationship betweenthe quality factor Q and the ringdown time of the resonance system. Experiments were performedwith low-frequency, radio-frequency and microwave pulse-type magnetic resonance receivers. Modificationsof an S/C-band electron spin echo modulation spectrometer carried out to check the ?timevariablefeedback? performance is described. It is demonstrated that application of a time-variablefeedback can significantly reduce the ringdown time and improve the recovery properties of the magneticresonance receiver system. It is also demonstrated that the time-variable feedback can improvethe overall receiver sensitivity due to the fact that working bandwidth of the resonance system canbe optimized separately for the transmit and receive modes. Signal values could be increased at leastthree times and the signal-to-noise ratio about 1.5?2 times. The largest improvement is achieved withthe initially overcoupled resonator. Experimental spectra of test samples for different settings of thetime-variable feedback are shown.


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