Measured performance parameters of gradiometers with digital output

Drung, D.; Crocoll, E.; Herwig, R.; Neuhaus, M.; Jutzi, W.

doi:10.1109/20.92465

Cited by 35 publications

(8 citation statements)

References 15 publications

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“…Fig. 30 proper electronics (Simmonds, 1980;Koch et al , 1983;Foglietti et al , 1986;Drung et al , 1989). In addition, the critica1 current fluctuations have been found to scale inversely proportionally to the junction area .…”

Section: Sensitivity Of the DC Squidmentioning

confidence: 99%

“…The 1/f noise in SQUIDs can be reduced by reversing the bias-current synchronously with Aux modulation (Simmonds, 1980;Koch et al , 1983). Many schemes, with effective reduction of low-frequency noise, have been described (Foglietti et al , 1986;Kuriki et al , 1988;Drung et al , 1989). Bias-current modulation, however, complicates the electronics and therefore is not a very tempting solution in devices where the simultaneous operation of a large number of SQUIDs is required.…”

Section: E DC Squid Electronicsmentioning

confidence: 99%

“…An interesting alternative to conventional readout techniques is to employ an integrated A/D converter on the same cryogenic chip as the SQUID. The output voltage can then be changed into digital form at low temperatures, for example, with a hysteretic dc SQUID of nonunique Aux-to-voltage characteristics, used as a comparator (Drung, 1986;Drung et al , 1989). This is illustrated in Fig.…”

Section: Oigital Readoutmentioning

confidence: 99%

“…The distribution of positive and negative pulses V" then depends on the external Aux. These pulses can be used to add or subtract flux e' Flux-noise values of 7 X 10 4O/+Hz above 1 kHz and 5 X 10 No/&Hz at 0.1 Hz, when an additional low-frequency noisecompensating modulation scheme was used, have been reported (Drung et a/. , 1989).…”

Section: Oigital Readoutmentioning

confidence: 99%

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Magnetoencephalography—theory, instrumentation, and applications to noninvasive studies of the working human brain

et al. 1993

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Magnetoencephalography(MEG) is a noninvasive technique for investigating neuronal activity in the living human brairi. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2 -3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT -1 pT magnetic fields produced by electric currents fiowing in neurons are measured with multichannel SQUID {superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begiri with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefiy as well.

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Section: Sensitivity Of the DC Squidmentioning

confidence: 99%

Section: E DC Squid Electronicsmentioning

confidence: 99%

Section: Oigital Readoutmentioning

confidence: 99%

Section: Oigital Readoutmentioning

confidence: 99%

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Magnetoencephalography—theory, instrumentation, and applications to noninvasive studies of the working human brain

et al. 1993

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“…V.A. Fujimaki and co-workers 41 and Drung and co-workers 42 have devised schemes in which the output from the SQUID is sensed digitally and fed back as an analog signal to the SQUID to flux-lock the loop. Fujimaki et al 41 used…”

Section: G Alternate Read-out Schemesmentioning

confidence: 99%