Tetsuji Inui

Effect of microstructure of YBa2Cu3Ox films on power handling capability studied with microstrip resonators

Microwave properties of two types of YBa2Cu3 Ox (YBCO) films with different microstructure have been studied at 4.2 K and 6 GHz. One type of film was grown at a constant substrate temperature of 705 °C during the film growth (constant‐growth films). The other type of film ws prepared with two‐stage process: initial growth at a lower temperature of 630 °C and subsequent higher‐temperature deposition at 705 °C (two‐stage‐growth films). Although both types of film have very similar intrinsic YBCO material properties such as c‐axis lattice constant, Tc, and unloaded quality factor Qu at low power levels, quite different microwave properties are observed at high power levels. The two‐stage‐growth films with small grains less than 100 nm show fairly small power dependence of Qu and resonance frequency on input power up to +10 dBm. On the other hand, the constant‐growth films with large grains (∼200 nm) show significant changes in these properties, accompanied by an appearance of asymmetric resonance curves. The...

Fabrication of Low-Loss Microstrip Band-Pass Filter Made from Double-Sided YBa2Cu3Ox Films

A three-pole microstrip band-pass filter, with a center frequency of 9.5 GHz and bandwidth of 2%, has been fabricated using YBa2Cu3Ox (YBCO) films deposited on both sides of (100)MgO substrates by pulsed laser ablation. A double-sided YBCO filter has a much lower passband insertion loss, 0.08 dB at 77 K and less than 0.04 dB below 60 K, compared with the 0.20 dB of a YBCO filter with a Au ground plane, and with the 1.1 dB of a conventional double-sided Au filter at 77 K. The extremely low insertion loss characteristics correspond to the element resonator unloaded quality factor (Q u) of 6000 at 77 K and greater than 10000 below 60 K. These results demonstrate that very compact high-Q u superconducting filters with waveguide-like performance can be achieved in planar microstrip configurations.

Properties of shielded microstrip line resonators made from double‐sided Y1Ba2Cu3Ox films

Double‐sided Y1Ba2Cu3Ox films are prepared on MgO(100) substrates for KrF excimer laser deposition and their electrical properties, both direct current and microwave frequencies, are examined. Double‐sided Y1Ba2Cu3Ox films show zero resistivity at temperatures higher than 88 K and ρ(300K)/ρ(100 K) higher than 2.7. Using a niobium shield, a double‐sided Y1Ba2Cu3Ox films microstrip line resonator at 5.7 GHz shows an unloaded Q value of 2.6×104 at 77 K and 1.1×105 at 4.2 K. These are the highest class of unloaded Q known to be reported for planar‐type resonators.

Microwave losses of Sn‐substituted polycrystalline Ca‐V‐garnets with large grains

Sn‐substituted calcium vanadium garnets with narrow resonance linewidth (ΔH?3 Oe at X‐band) composed of homogeneous large grains have been newly developed. Measurements of resonance linewidth as a function of frequency showed that the peak at the spinwave manifold (ω=2‖γ‖4πMs/3) vanished for materials of 460 μm average grain size. A ΔH of 0.8 Oe, the smallest figure ever reported in this garnet series, was obtained at a frequency a little less than 2‖γ‖4πMs/3. As the grain size was varied from 8 to 30 μm, ΔH was found to be inversely proportional to the average grain size for ω<2‖γ‖4πMs/3 and nearly independent of grain size for ω≳2‖γ‖4πMs/3.Values of μ″± were measured by using a cylindrical Te111 mode resonator filled with a sample measuring 10 mm diameter and 10 mm in length. A material with grain size of 460 μm has been found to exhibit values of μ″+=2×10−4 off the resonance region implying that this material is highly promising as a potential candidate for low‐noise circulators.Sn‐substituted calcium vanadium garnets with narrow resonance linewidth (ΔH?3 Oe at X‐band) composed of homogeneous large grains have been newly developed. Measurements of resonance linewidth as a function of frequency showed that the peak at the spinwave manifold (ω=2‖γ‖4πMs/3) vanished for materials of 460 μm average grain size. A ΔH of 0.8 Oe, the smallest figure ever reported in this garnet series, was obtained at a frequency a little less than 2‖γ‖4πMs/3. As the grain size was varied from 8 to 30 μm, ΔH was found to be inversely proportional to the average grain size for ω<2‖γ‖4πMs/3 and nearly independent of grain size for ω≳2‖γ‖4πMs/3.Values of μ″± were measured by using a cylindrical Te111 mode resonator filled with a sample measuring 10 mm diameter and 10 mm in length. A material with grain size of 460 μm has been found to exhibit values of μ″+=2×10−4 off the resonance region implying that this material is highly promising as a potential candidate for low‐noise circulators.