YBCO shielded LaAlO/sub 3/ dielectric resonators for stable oscillators

Abstract

We have investigated dielectric resonators (SDROs) fabricated from single crystalline LaA103 shielded by two epitaxial films of Y Ba2Cu307 (YBCO).At the resonant frequency of the TEoll-mode of 5.6GHz unloaded quality factors QO of 8 x lo5 at 20K and 4 x lo5 at 60K were obtained. These values were limited by dielectric losses in LaA103. At 50K we obtained a QO of 2 x lo5 at a level of dissipated rf power of 2 W corresponding to an average rf magnetic surface field of 1500e. Moreover, we used one SDRO as a feedback for a HP8349 amplifier to measure oscillator phase noise. At BOK and helium gas cooling the phase noise was beyond the sensitivity limit of our HP8565 spectrum analyzer of about -9OdBc/Hz at an offset frequency of 1kHz. For operation with Stirling cooler microphonics dominates the noise properties.

Thin‐Film‐Based Integrated High‐Transition‐Temperature Superconductor Devices

“…Furthermore, the same group presented an HTS monolithic microwave integrated circuit Josephson downconverter by combining a Josephson junction mixer, a band‐pass filter, a low‐pass filter, and a resonator on a single 10 × 20 mm 2 YBCO chip, showing high gain and stability . In addition to research in above devices, efforts have also been directed toward delay lines and other resonator applications, such as phase shifters, oscillators, and clocks …”

Thermal mechanism of microwave breakdown in HTSC films: theoretical arguments and experimental evidence

“…It follows from expressions (2) and ( 3) that B br obeys the same temperature dependence as B p . The comparison of expressions ( 2) and (3) with experimental data [12][13][14][15][16][17][18] demonstrates that the concept of film overheating by the microwave radiation in the vicinity of defects of size r d , d d ∼ = 1-10 µm allows one to describe qualitatively the results of measurements (see figure 1). In real HTSC films there are a number of defects of different geometry and size.…”

“…•, [13]; , [14]; , [15]; , ♦, [16]; , [17]; , [18]; curve 1, expression (1); curves 2, 3 and 4 correspond to the approximation of experiments [13], [14] and [15], respectively, by means of expressions The breakdown field B br is determined from experimental data as the field value at which the measured surface film resistance R starts to increase steeply (dR/dB → ∞). In fact, such a procedure has a limited accuracy, but it agrees with both theoretical arguments [19] and direct numerical simulation of the breakdown development [5].…”

“…Hence, long before the film overheating in the vicinity of the defects, the microwave breakdown may occur due to the superconductivity destruction by thermal disturbances in the defectless film regions. Thus, the analysis of experimental data [12][13][14][15][16][17][18] shows that the measured values of the breakdown field B br obey the temperature dependence B br ∝ (T c − T 0 ) 1/2 corresponding to the thermal mechanism of the microwave breakdown. The concept of the film overheating in the vicinity of defects of size 1-10 µm allows one to describe the experimental results.…”

“…The comparison of experimental data on breakdown field [12-18] with theoretical expressions (1)-(3). •, [12];•,[13]; ,[14]; ,[15]; , ♦,[16]; ,[17]; ,[18]; curve 1,…”