Microstrip Line Resonator Research Articles

Electrical properties of Y1Ba2Cu3Ox films grown by liquid phase epitaxy

Abstract Y 1 Ba 2 Cu 3 O x films were grown on MgO(100) substrates by liquid phase epitaxy and their structural and electrical properties were examined. From transmission electron microscopy (TEM) plan-view images, it was found that the films consisted of large grains whose misorientation angles were less than 1°. Although d.c. critical current density values decreased with increasing film thickness, even a 7 μ m-thick film showed the value of 9×10 5 A/cm 2 at 77 K. An rf first penetration field of the film is estimated to be 30 Oe at 10.8 GHz and 77 K, by using a microstrip line resonator with a resonant frequency of 10.8 GHz. The third-order intercept point of the resonator is at an input power of +43 dBm and output power of +30 dBm at 77 K. These results suggest that LPE grown Y 1 Ba 2 Cu 3 O x films have superior d.c. and rf electrical properties.

Empirical model of the microwave properties of high-temperature superconductors

This paper presents simple correct models of high-temperature superconductor (HTS) film parameters at microwave frequencies. The models are based on the enhanced two-fluid model of a superconductor. The quasi-particle scattering and peculiarities of the normal conductivity of the HTS at microwaves, including residual resistance of a material, are taken into account. The difference between the known Gorter and Casimir two-fluid model of low-temperature superconductor and the enhanced two-fluid model of HTS is proven. A simple quasi-static model of current distribution across the microstrip line and coplanar waveguide is used for a simulation of a contribution of the superconductor transport processes into impedance per unit length of the transmission lines considered. The models developed were applied to a simulation of microstrip line and coplanar waveguide resonators. Good agreement of simulated results and measurements in a wide temperature range has been demonstrated. The model presented can be considered as a starting point for the formation of the computer-aided design (CAD) package of HTS microwave components.

SiO 2 passivation film effects on microwave characteristics of YBa 2Cu 3O 7− x-based resonators

SiO 2 film coated as a passivation layer for YBa 2Cu 3O 7− x (YBCO)-based microwave devices is investigated by measuring the microwave characteristics of microstrip line resonators. The SiO 2 film is deposited with its 0.3 to 0.4 μm thickness by a sputtering method using Ar + 30%O 2 plasma. These deposition conditions do not degrade the microwave characteristics and the critical temperature ( T c). Next, the SiO 2 film coated resonators are compared with the uncoated ones for two kinds of degradation conditions: a 200°C annealing in air, and an exposure to air at 85°C and 85% RH (relative humidity). We find that the SiO 2 passivation film prevents the YBCO thin film from the surface degradation and reacting with water.

Field emission monotron for THz emission

Small-signal negative conductance of a field emission monotron was calculated, which was considerably higher than that of a thermionic monotron due to strong bunching of emitted electrons in a field emission. The amplification constant of 28dB/mm is achieved at THz wave region by applying the monotron to a distributed amplifier and is sufficient to overcome power loss in a transmission line. In addition, a wide band frequency tunable electromagnetic wave source may be developed at THz wave region by providing a low loss microstrip line resonator with field emission array due to the gate voltage dependent phase constant of the line.

Stacked niobium Josephson junction arrays under x-band irradiation

Stacked Josephson junction arrays located at the rf current antinodes of a superconducting microstripline resonator were investigated. The circuits were designed to obtain highly accurate voltages at cm-waveband microwave driving and low rf-power level. Nb-Al/AlO/sub x/-Nb Josephson junctions with tunneling area of 60 /spl mu/m/spl times/300 /spl mu/m and critical current density up to 7 A/cm/sup 2/ were used. We compared the average voltages of the rf induced maximal current steps in arrays with up to three junctions per stack. Quantized current steps up to 300 mV were observed under microwave irradiation at frequency of 19.20 GHz in circuits with 384 three-junction stacks. The dynamics of stacked tunnel junctions in the presence of rf-currents will be discussed with respect to application as voltage standards.

Josephson voltage standard microwave circuits fabricated in a modified all-niobium technology for operation at low drive frequencies

A resonant type of cryoelectronic microwave circuit for the generation of frequency-scaled Josephson voltages is presented. The circuits consist of superconducting microstripline resonators with series arrays of Josephson tunnel junctions located on the microwave current antinodes. This microwave design was chosen to obtain highly accurate Josephson voltages at low microwave power levels and low drive frequencies. The resonator circuits have been fabricated in both niobium-lead and all-niobium technology. At present, we have observed long-term stable Josephson voltages up to 0.75 V for niobium-lead circuits with 1320 junctions and 0.66 V for all-niobium circuits with 1456 junctions, respectively.

Novel microstrip-line directional filters

This paper presents two new structures of four-port microwave directional filters incorporating microstrip-line resonators, uniplanar 180/spl deg/ phase-reversal units, and two or four identical p-i-n diodes. These filters provide substantially improved frequency characteristics compared to the conventional constructions. The unique feature of them is that they ensure high-level isolation independent of frequency between opposite ports. Due to this electrical property the proposed filters may be suitable for some pulse-radar applications.

Stability of NdBa 2Cu 3O 7− x based resonators in humid conditions

The surface stability of NdBa 2Cu 3O 7− x thin film is utudied using the conditions referred to as standard accelerated humidity testing. NdBa 2Cu 3O 7− x thin film is compared with well studied YBa 2Cu 3O 7− x thin film by evaluating the surface resistance ( R s) obtained from their film-based microstrip line resonators. The R s of the NdBa 2Cu 3O 7− x thin film indicates better stability than that of YBa 2Cu 3O 7− x in the low and relatively high microwave power range.

Effect of Ar+O2 Plasma Etching on Microwave Characteristics of YBa2Cu3O7-x Based Resonators

We present an improvement in the patterning process of microwave devices by suppressing the oxygen effusion from the patterning edge of YBa2Cu3O7-x (YBCO) thin film. The damage in the edge is estimated from unloaded Q factors of YBCO-based micro-stripline resonators, because the high frequency current is limited along the edge. The unloaded Q factors increase with the oxygen content during the plasma etching. This result suggests that oxygen radicals in the Ar+O2 plasma restore the oxygen in the edge and reduce the loss of microwave devices.

Effects of oxygen content on the penetration depth in YBCO thin films

By varying oxygen content of the microstrip line resonator of YBa2Cu3O7−x , the effective penetration depth was studied. Based on the two-fluid model, we fit the data of the resonant frequency by means of the inductance formula. It allows us to determine the zero-temperature penetration depth of the fully oxygenated, (O∼7) and oxygen deficient (O=6.8) states in the same strip to be 483.2nm and 789.8nm, respectively. The ratio of the superconducting carrier densities with different oxygen contents is then derived and found to be consistent with the result of Hall measurement. A correlation between oxygen contents and charge carriers of the samples will be obtained in our work as accurately as possible.

High temperature superconducting microstrip line resonators for measuring surface resistance

Microstrip line resonators with transmission-line structures have been investigated to characterize microwave properties of rf sputtered YBa 2 Cu 3 O 7 − δ thin film deposited on LaAlO 3 substrates. Microstrip line resonators were designed to have fundamental resonant frequencies at 0.45 GHz and 7 GHz for meander line and straight line type resonators, respectively. With these resonators, the surface resistance of high T c superconducting films was measured and discussed as a function of temperature, input power and frequency. The low surface resistances of about 300 μΩ and 700 μΩ were observed at 0.458 GHz and 7.015 GHz, respectively. Experimental results of high T c superconducting resonators show pronounced improvement in unloaded quality factors Q u , compared to those of gold resonators. The resonant frequency shift with temperature was also verified.

Josephson voltage standard microwave circuits operating at 10 GHz

A new type of microwave circuit for the generation of frequency-scaled voltages is investigated. The circuit is designed as a superconducting microstrip line resonator and series arrays of Josephson tunnel junctions located within the rf current antinodes. The circuits are designed to obtain highly accurate voltages at low rf power level and low frequencies of about 10 GHz. For a resonator circuit with 432 junctions driven at about 10 GHz we have observed steps up to 0.25 V, the lifetime of which is about 20 minutes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Edge-coupled microstrip loop resonators with capacitive loading

Novel edge-coupled microstrip loop resonators with capacitive loading have been developed. A preliminary investigation has shown that the novel coupled resonators have a smaller size and similar frequency responses as compared with the conventional coupled microstrip line resonators. This makes them attractive to the monolithic microwave integrated circuits (MMIC) and the microwave superconductive circuits where size reduction is of primary importance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

Effects of the microstructure on the performance of microstrip line resonator made of MOCVD YBa 2Cu 3O x film

Microstrip transmission lines in the form of an open-ended half wavelength resonator were fabricated on YBa 2Cu 3O x thin films deposited on MgO and LaAlO 3 substrates using MOCVD. The effects of the microstructure on the performance of the resonator were investigated. C-axis normal YBa 2Cu 3O x thin films deposited on LaAlO 3 substrate showed a higher quality factor and a lower surface resistance than that on MgO. The c-axis normal film showed a lower surface resistance than a, b-axis normal films. The lowest surface resistance of 22 mΩ was obtained for the c-axis normal film on LaAlO 3 substrate in this study.

Compact 900‐MHz hairpin‐line filters using high dielectric constant microstrip line

AbstractSeveral miniature bandpass filters have been developed by accurate modeling of experimental and computer‐generated coupling data of hairpin‐line microstrip line resonators on high dielectric constant (εr = 80 and 90) substrate. The materials are temperature stable and of high quality factor. The experimental results show excellent filter shapes and some novelty of the design approach. Besides the experimental results, this article also presents the curves and semiempirical models for the coupling coefficients between hairpin‐line resonators for two different dielectric materials and thicknesses. The method and the results will be useful in realizing compact planar filters for cellular radio, global positioning systems and superconducting microstrip filters.

Shielded YBa/sub 2/Cu/sub 3/O/sub 7/ microstripline characteristics

YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) microstripline resonator Q-values are discussed for both Au and Nb grounds at 6 GHz and at liquid He temperature. Unloaded Q-values (Q/sub u/) larger than 10/sup 5/ were obtained for good-quality YBCO microstrips with Nb grounds. Q/sub u/ power dependences and resonance curve asymmetries (due to nonlinear phenomena) were studied for YBCO films of different qualities with both Au and Nb grounds.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High T/sub c/ superconductor and III-V solid state microwave hybrid circuits

Several high-temperature superconductor (HTS)/III-V solid-state hybrid microwave circuits were designed, fabricated, and tested. The I-V curves, S-parameters, and noise behavior for several solid-state devices at cryogenic temperatures were measured. Several high-electron-mobility transistor (HEMT) and heterojunction bipolar transistor (HBT) C-band low-noise amplifiers were fabricated and tested at cryogenic temperatures with an additional gain of 3 dB when compared to their room-temperature gain. These amplifiers were also used in low-phase-noise oscillators stabilized by a HTS lambda /2 microstrip line resonator with a loaded Q-value of 3*10/sup 3/ or a sapphire-HTS resonator with a loaded Q-value of 1.2*10/sup 6/, both measured at 80 K. Preliminary measurement at 70 K indicates that the phase noise of an oscillator stabilized with a sapphire-HTS resonator was below -125 dBc/Hz at 10-kHz offset and limited by the test setup. >

Design concepts of a novel microwave active filter

A novel microwave active bandpass filter structure, using a combination of microstrip line resonators and FETs, is described. The resulting filter not only produces positive gain but also has good performance regarding sharpness of skirts, rejection, and input and output return losses. Capability of constructing wider bandwidth and its superior performance at harmonic band frequencies over an end-coupled filter structure are among advantages of this design.

Superconducting stripline resonator performance

Reliable techniques for evaluating the microwave properties of superconductors are essential in providing calibrated data for exchange between laboratories and for developing practical device designs. The authors are examining the techniques which utilize microwave stripline resonators. These resonators provide for the rapid measurement of microwave parameters in a repeatable fashion with minimal constraints on processing. Sandwiched microstrip line resonators are used to compare the performance at 4.2 K of OFHC copper and superconducting films of Pb, Nb, and YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) at C-band and X-band. Typical results for the Nb resonators show a loaded Q/sub L/ of about 8*10/sup 4/ with a transmission insertion loss of 5 dB at 3 GHz. Initial results on a YBCO a-axis film used as a ground plane in the Nb resonator yield a surface resistance value of about 10/sup -3/ Omega at 2.8 GHz. Preliminary results on the phase noise performance of a Nb resonator at 2.9 GHz are presented. >