Non-linear effect in the superconducting transmission line

Edward Tong, R. Blundell, B. Bumble +2 more

A non-linear superconducting transmission line has been successfully employed in heterodyne detection of sub-millimeter waves. In our experiments an Nb/Al/AlOx/Nb tunnel junction, measuring 0.15×40 μm, with a critical current density of about 2500 A/cm2 is used as a distributed mixer element. We have demonstrated that quantum limited sensitivity can be achieved with this type of device. At 460 GHz, a Y-factor of 2.5 has been recorded, corresponding to a double-side-band receiver noise temperature of 80 K. The double-side-band conversion loss is about 1 dB and the mixer noise temperature is estimated to be 18(±10) K.

D. Valenzuela

Marric Stephens

Kohki Nakagawa, Masanori Takeda, Atsushi SAITO +1 more

Abstract Fishbone-type superconducting transmission lines (FSTLs) is a periodic transmission line. Herein, we analyzed the characteristic impedance and effective wavelength of FSTLs using the equivalent circuit. Based on the obtained results, we designed and fabricated an FSTL half-wavelength resonator. The resonator measurement revealed that the effective wavelength of the FSTL is shorter than half of that of the coplanar waveguide. Furthermore, we obtained the kinetic inductance per unit length of the FSTL by comparing the analyzed and measured resonance frequencies.

James C. Booth, Christopher L. Holloway, Edward F. Kuester

Superconducting planar circuits possess properties that can be very different from their normal-metal counterparts, which makes modeling efforts more complicated for superconducting components. In this paper we present closed-form expressions for the resistance and internal inductance per unit length of superconducting planar transmission lines in terms of the relevant material parameters. We also include a simple calculation of the nonlinear response of superconducting devices based on a current-dependent superconducting penetration depth. Taken together, these two descriptions can be used to predict the linear and nonlinear response of superconducting planar devices in a manner that is conducive to use in circuit design. The results of these calculations compare well with 76 K measurements of coplanar waveguide transmission lines and resonators fabricated from thin films of the high T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//.

T. M. Klapwijk, D. R. Heslinga, Wim M. van Huffelen