Fig. 1. Schematic diagram of the SQUID RF amplifier with several SQUID parameters. Ls: SQUID inductance, Ic:junction critical current, RJ: junction shunt resistance, CJ:junction capacitance, Cc: coupling capacitance, L:linewidth of input coil line, S: space of input coil line, n:number of turns of input coil.
Fig. 2. Design of the DC-SQUID RF amplifier. (a) Overall chip design without cooling fins, (b) chip with cooling fins, and (c) details of the SQUID loop area with a coupling capacitor, input coil, Josephson junctions and shunt resistors.
Fig. 4. Typical current-voltage curves of the SQUID. (a) Current-voltage curve with an applied flux near Φ0/2, and (b) current-voltage with an applied flux near Φ0. X-axis is voltage (50 μV/div.) and Y-axis is current (10 μA/div).
Fig. 3. Structure of the SQUID package and test probe for I-V curve and gain curve measurements. (a) SQUID package with DC wiring and connector, and (b) structure of the test probe.
Fig. 5. SQUID gain versus RF power level at the SQUID input, where the output of the RF generator (network analyzer) was changed in a step of 5 dBm.
Fig. 6. Gain curves of the SQUID RF amplifiers versus numbers of the input coil turn. (a) 20, (b) 19, (c) 18, (d) 17 and (e) 16 turns. Input coil has 2 μm linewidth and 3 μm space.
Fig. 7. Gain curves versus shunt resistance of the junction. (a) Shunt resistance of 4, (b) 6 and (c) 8 Ω, respectively.
Fig. 8. Change of gain curve depending on the coupling capacitance in the input coil. (a) Coupling capacitance of 0.1, (b) 0.5 and (c) 1.9 pF, respectively. All the three SQUIDs have the same input coil turn number and shunt resistance.
참고문헌
- S. J. Asztalos et al., "Design and performance of the ADMX SQUID-based microwave receiver", Nucl. Instr. Meth. Phys. Res. A, 656, pp. 39-44, 2011. https://doi.org/10.1016/j.nima.2011.07.019
- S. Michotte, "Qubit dispersive readout scheme with a microstrip superconducting quantum interference device amplifier", Appl. Phys. Lett., 94, pp. 122512-1-3, 2009. https://doi.org/10.1063/1.3109793
- Y. H. Lee, K. K. Yu, J. M. Kim, S. K. Lee, Y. Chong, S. J. Oh, and Y. K. Semertzidis, "Correction of Resonance Frequency for RF amplifiers based on Superconducting Quantum Interference Device", Prog. Supercond. Cryog., 20, pp. 6-10, 2018.
- J. Clarke, A. T. Lee, M. Muck and P. L. Richards, "SQUID Voltmeters and Amplifiers", p. 22-115, Chap. 8, in The SQUID Handbook, Eds. J. Clarke and A. I. Braginski, 2006, Wiley-VCH.
- J. Clarke, M. Muck, M. Andre, J. Gain and C. Heiden, "The Microstrip DC SQUID Amplifier", p. 473-504, in Microwave Superconductivity, Eds. H. Weinstock and M. Nisenoff, 2001, Kluwer Academic Pub.
- M. Muck, and J. Clarke, "The superconducting quantum interference device microstrip amplifier: Computer models", J. Appl. Phys., 88, pp. 6910-6918. 2000. https://doi.org/10.1063/1.1321026
- Y. H. Lee, Y. Chong and Y. K. Semertzidis, "Review of low-noise radio-frequency amplifiers based on superconducting quantum interference device", Prog. Supercond. Cryog., 16, pp. 1-6, 2014.
- D. Kinion and J. Clarke, "Microstrip superconducting quantum interference device radio-frequency amplifier: Scattering parameters and input coupling", Appl. Phys. Lett., 92, 172503, 2008. https://doi.org/10.1063/1.2902173
- F. C. Wellstood, C. Urbina and J. Clarke, Hot-electron effects in metals", Phys. Rev. B, 49, pp. 5942-5956, 1994. https://doi.org/10.1103/PhysRevB.49.5942
- Y. H. Lee, J. M. Kim, K. Kim, H. Kwon, K. K. Yu, I. S. Kim and Y. K. Park, "64-channel magnetocardiogram system based on double relaxation oscillation SQUID planar gradiometers", Supercond. Sci. Technol., 19, pp. S284-S288, 2006. https://doi.org/10.1088/0953-2048/19/5/S25
- Y. H. Lee et al., "Development of SQUID-based high-frequency quantum amplifiers", Annual Report, IBS (IBS-R017-D1-2016-a01), 2016.
- J. Zeng et al., "High intrinsic noise and absence of hysteresis in superconducting quantum interference devices with large Stewart-McCumber parameter", Appl. Phys. Lett., 103, 042601, 2013. https://doi.org/10.1063/1.4816730