II. Applications of the Josephson Effect
II. Applications of the Josephson Effect
II. Applications of the Josephson Effect
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R. Gross, A. Marx, and F. Deppe © Wal<strong>the</strong>r-Meißner-Institut (2001 - 2013)<br />
AS-Chap. 4 - 31<br />
4.1.5 Read-Out Schemes<br />
• bias current reversal:<br />
- bias current is modulated (to suppress low-frequency noise <strong>of</strong> <strong>Josephson</strong> junctions)<br />
- asymmetric part <strong>of</strong> critical current fluctuations can be eliminated<br />
double modulation technique<br />
• additional positive feedback:<br />
- asymmetric hVi(F ext ) (part <strong>of</strong> <strong>the</strong> bias current is used)<br />
- steeper slope larger V/F<br />
direct read-out with RT electronics<br />
• digital read-out schemes:<br />
- cryogenic digital feedback schemes compact, wide bandwidth<br />
digitized output signals for transmission to RT<br />
• relaxation oscillation schemes:<br />
- hysteretic junctions<br />
- SQUID shunted by series LR<br />
- frequency <strong>of</strong> relaxation oscillations depends on flux<br />
large SQUID output voltage
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