Space observation missions demand stringent pointing requirements. This article thus investigated a dual-stage vibration isolation and precision pointing system consisting of a cubic Stewart platform and a Piezoelectric mirror. Due to the unloading control among these stages and the limited control bandwidth of Piezoelectric mirror caused by the low sampling rate of the charge-coupled device (CCD), the closed-loop performance is inevitably restricted. Therefore, a high- bandwidth disturbance feedforward method based on hybrid measurement of the inertial gyro and the CCD is proposed to compensate residual vibrations, which breaks the limitation of closed-loop bandwidth and thereby enhances the disturbance resistance performance. To avoid the dependence on the accurate inverse model of the control plant in high frequency, the proposed feedforward controller is designed based on partial compensation principle, further optimizing the feedforward controller utilizing a constructed low-pass filter instead of the typical integrator. Besides, a frequency splitting strategy is presented to eliminate motion coupling existing in gyro signals, so as to realize unloading control under disturbance loading. Simulations and experiments demonstrate the effectiveness of the proposed method.

This article presents a miniaturized C-band triplexer fabricated with high-temperature superconducting (HTS) microstrip lines and to be applied to quantum computers. The triplexer consists of three bandpass filters and branch lines. In the design of the bandpass filters, folded step impedance resonators (SIRs) are firstly used to achieve good stopband performances by harmonic suppression. Secondly, cross-coupling structures are also utilized to further improve the passband edge steepness of the bandpass filters. Finally, the parasitic transmission zeros originating from the assembling box sizes are employed to achieve a deeper out-of-band rejection. Three bandpass filters are designed and connected to the common input port of the triplexer. After that, the triplexer is coarsely optimized by advanced design system (ADS) for time-saving and is finely optimized by Sonnet for better accuracy. The optimized layout of the triplexer is fabricated on a 2-inch diameter and 0.5 mm thickness MgO wafer; here, the MgO wafer is double-sided coated with HTS YBa2Cu3O7 (YBCO) thin films. The measured passband bandwidths (return loss greater than 12 dB) of the triplexer are 6.420-6.680 GHz, 6.780-7.030 GHz, and 7.110-7.380 GHz, respectively, which satisfy the required design specifications.

This paper presents high quality YBa 2 Cu 3 O 7– δ (YBCO) thin films on LaAlO 3 substrate for microwave devices prepared by pulsed laser deposition (PLD). The double-sided YBCO films cover a large area and have been optimized for key parameters relevant to microwave device applications, such as surface morphology and surface resistance ( R s ). This was achieved by improving the target quality and increasing the oxygen pressure during deposition, respectively. To evaluate the suitability of the YBCO films for microwave devices, a pair of microwave filters based on microstrip fabricated on films from this work and a commercial company were compared. The results show that the YBCO films in this work could completely meet the requirements for microwave devices.

This paper presents high quality YBa2Cu3O7-δ (YBCO) thin films on LaAlO3 substrate for microwave devices prepared by Pulsed Laser Deposition (PLD). The YBCO films are double-sided and are with large area. The key parameters for microwave device applications such as surface morphology and surface resistance (Rs) were optimized by improving target quality and increasing oxygen pressure during deposition, separately. A pair of microwave filters based on microstrip fabricated on films of this work and commercial company were compared. The comparison results indicate the YBCO films in this work could completely meet the requirements of microwave devices.

High-temperature superconducting films can be used for fabricating the cutting-edge high-temperaturesuperconducting microwave devices because of their low microwave surface resistances. However, the microwavesurface resistances of high-temperature superconducting materials are particularly sensitive to microstructuredue to their special two-dimensional superconducting mechanisms and extremely short superconductingcoherence lengths. To investigate the correlations between microstructure and microwave surface resistance ofhigh-temperature superconducting materials, YBa2Cu3O7-d (YBCO) films with different thickness are grown on(00l)-oriented MgO single-crystal substrates by using the pulsed laser deposition (PLD) technique. Electricalmeasurements reveal that their superconducting transition temperatures and room temperature resistances donot show significant difference. However, their microwave surface resistances in superconducting state display asignificant difference. The characterizations of the microstructures of YBCO films by synchrotron radiationthree-dimensional reciprocal space mapping(3D-RSM) technique show that the number of the grains with CuO2face parallel to the surface (c crystals), and the consistency of grain orientation are the main causes for thedifference in microwave surface resistance

The electromagnetic characteristics of a circular metal waveguide with a coaxial cylindrical dielectric insert and a layer of absorbing liquid that fills the space between the insert and the waveguide wall have been studied. The transverse waveguide dimensions are comparable with the wavelength. Dependences of the attenuation and phase coefficients of waveguide modes on the structure size and material properties of the layers are found by solving the boundary value problem. It is shown that based on the proposed layered waveguide with the HE 11 type of wave, a measuring cell can be designed to work at either fixed frequency with high differential sensitivity or in the frequency range of the single-mode waveguide operation. The cell is of class of cells with calculable geometry. In this case, a reference liquid with known dielectric properties is not required for absolute measurements of the complex permittivity (CP) of the absorbing liquid. The method of finding the CP of absorbing liquids are verified using electromagnetic modeling with CST Microwave Studio.

High quality epitaxial thin films of FeSe 1―x Te x (x = 0―1) have been successfully fabricated. Their superconducting transition temperatures are around 8―13 K. Microwave properties of a film (x = 0.7) was studied by a sapphire dielectric cavity at 9.315 GHz. The cavity, which has a quality factor of 45000 in room temperature with TE 011 -mode, is specially designed for the measurement of small samples with the sapphire cylinder having a small hole in the center. Thin film samples with dimension of 1―2 mm can be put in the middle of the hole, supported by a very thin sapphire rod. The cavity is sealed in a vacuum chamber soaked in the liquid 4 He and the temperature of the thin sapphire rod (hence the sample) can be controlled from 1.6 K to 60 K with a stability about ±1 mK. Temperature dependence of transmission response and Q-factors were measured by a network analyser (Agilent N5230C). The results showed a clear signature of multi-gap superconductivity. No evidences of existence of node in the energy gap were found as the normalized change in the surface reactance and the corresponding normalized change in the in-plane penetration depth have flat dependence at low temperatures.

High quality epitaxial thin films of FeSe 1-x Te x (x=0-1) have been successfully fabricated. Their superconducting transition temperatures are around 8-13 K. Microwave properties of a film (x=0.7) was studied by a sapphire dielectric cavity at 9.315 GHz. The cavity, which has a quality factor of 45000 in room temperature with TE 011 -mode, is specially designed for the measurement of small samples with the sapphire cylinder having a small hole in the center. Thin film samples with dimension of 1-2 mm can be put in the middle of the hole, supported by a very thin sapphire rod. The cavity is sealed in a vacuum chamber soaked in the liquid 4 He and the temperature of the thin sapphire rod (hence the sample) can be controlled from 1.6 K to 60 K with a stability about ±1 mK. Temperature dependence of transmission response and Q-factors were measured by a network analyser (Agilent N5230C). The results showed a clear signature of multi-gap superconductivity. No evidences of existence of node in the energy gap were found as the normalized change in the surface reactance and the corresponding normalized change in the in-plane penetration depth have flat dependence at low temperatures.

In this paper, we will report microwave study of FeSe1-XTex (x=0.7) film by a sapphire dielectric cavity at 9.375 GHz. The resonator is a close analogy. The film was deposited on LaAlO3 substrate and has Tc =11.8 K. The cavity, which has a Q-factor of 45000 in room temperature with TE011-mode, is specially designed for the measurement of small samples with the sapphire cylinder having a small hole in the centre. The 100 nm thickness sample with dimension of 1-1.5 mm is put in the middle of the hole, supported by a very thin sapphire rod but isolated from the cylinder. The cavity is sealed in a vacuum chamber soaked in the liquid He and the temperature of the sapphire rod (hence the sample) can be controlled from 1.6 K to 60 K with a stability about ±1 mK while keeping the cavity remains in 4.2 K. Temperature dependence of resonance frequency and Q-factor of the resonator were measured by a vector network analyzer (Agilent N5230C) for both thin film and also the same substrate with no film on it.