2017/10/31 by George Che, Samuel Gordon, Che, George +17 · 1 citation
Engineering · Physics and Astronomy · #FOS: Physical sciences #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Microwave Engineering and Waveguides #Radio Frequency Integrated Circuit Design #Superconducting and THz Device Technology
paper · pdf · doi:10.48550/arxiv.1710.11335
openalex publication_date 2017/10/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The W-Band (75-110 GHz) sky contains a plethora of information about star formation, galaxy evolution and the cosmic microwave background. We have designed and fabricated a dual-purpose superconducting circuit to facilitate the next generation of astronomical observations in this regime by providing proof-of-concept for both a millimeter-wave low-loss phase shifter, which can operate as an on-chip Fourier transform spectrometer (FTS) and a traveling wave kinetic inductance parametric amplifier (TKIP). Superconducting transmission lines have a propagation speed that depends on the inductance in the line which is a combination of geometric inductance and kinetic inductance in the superconductor. The kinetic inductance has a non-linear component with a characteristic current, I_*, and can be modulated by applying a DC current, changing the propagation speed and effective path length. Our test circuit is designed to measure the path length difference or phase shift, Δϕ, between two symmetric transmission lines when one line is biased with a DC current. To provide a measurement of Δϕ, a key parameter for optimizing a high gain W-Band TKIP, and modulate signal path length in FTS operation, our 3.6 × 2.5 cm chip employs a pair of 503 mm long NbTiN inverted microstrip lines coupled to circular waveguide ports through radial probes. For a line of width 3 μm and film thickness 20 nm, we predict Δϕ≈1767 rad at 90 GHz when biased at close to I_*. We have fabricated a prototype with 200 nm thick Nb film and the same line length and width. The predicted phase shift for our prototype is Δϕ≈30 rad at 90 GHz when biased at close to I_* for Nb.