Application of time-variable feedback to the input amplifier of pulse magnetic resonance spectrometers: Experimental studies

Koptioug, Andrei; Reijerse, Edward J.; Klaassen, A. A. K.

doi:10.1007/bf03166126

Cited by 1 publication

(3 citation statements)

References 68 publications

(91 reference statements)

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“…A proper model should not be too complex and at the same time should enable one to perform the required generalized analysis. Equivalent diagrams with lumped elements have been established as a good choice [10,11,[17][18][19][20][21][22][23][24][25][26][27][28][29]. In the present approach the resonator ~ and coupling structure are modelled asa set of lumped elements: inductors, capacitors and resistors.…”

Section: Equivalent-diagram Analysismentioning

confidence: 99%

“…With the pulse spectrometer systems it could be of advantage to change the input receiver bandwidth with submicrosecond time resolution to provide a shorter receiver "dead time". Recently it was suggested to use "time-variable" feedback in the input amplifier to conduct such a fast bandwidth change [19][20][21]. The experiments performed have shown that receivers with time-variable feedback could be very promising for the pulse spectrometers, but some effects were hard to comprehend.…”

Section: Introductionmentioning

confidence: 99%

“…This probtem was studied both in conjunction with narrow-band MR receivers [10,11,[17][18][19][20][21][22][23][24] and with the general case of communication devices including wide-band receiver architectures [25][26][27][28][29]. As a rule, for the analysis, the ideal voltage amplification section with resistive or capacitive feedback represents an amplifier.…”

Section: Introductionmentioning

confidence: 99%

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Application of the time-variable feedback to the input amplifiers of pulse magnetic resonance spectrometers: Theoretical considerations

Koptioug

2002

Appl. Magn. Reson.

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An analytical model for the optimization of the signal-to-noise (S/N) performance for the receiver with input resonance circuit and variable feedback is developed. It is shown that by varying the feedback type and depth optimization of the receiver the best S/N performance could be achieved. This approach is based upon a resonator-receiver model with lumped elements. These assumptions are retatively general for the model to be applicable for the design of both continuous and pulse receivers in radio-frequency and microwave bands. The overall S/N performance of the receiver upon the noise properties of its elements and ~he feedback settings in the input amplifier is studied for different parameter settings. It is shown that the separate optimization of individual elements does not necessarily lead to the best S/N performance of the receiver, especially when bando width properties and noise cont¡ of the elements are substantially different. It is shown that critical coupling of the amplifier to the resonance structure could be lar from optimum. In some cases the optimum S/N performance could be achieved with coupling settings below the c¡ value. But under the assumptions made the coupling above the critical value does not correspond to the best reeeiver S/N performance. Suggestions on the optimum architecture of magnetic resonance spectrometer receivers with variable feedback are made.

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