Good Frequency Response Characteristics Research Articles

Partial Discharge Detection Technology for Switchgear Based on Near-Field Detection

In view of the fact that the partial discharge (PD) signal energy is mainly concentrated below hundreds of megahertz, the ultra-high frequency part of the energy is weak, and the interior space of the switchgear is narrow, this paper proposes a new method for PD detection of the switchgear based on near-field detection. Firstly, based on the principle of PD, the field characteristics of the signal in the switchgear are analyzed. After that, the probe is designed with an electric small loop structure. Based on its equivalent circuit, its measurement principle and amplitude frequency characteristics are analyzed. The influence of probe size and material on amplitude frequency characteristics is obtained by using simulation software High Frequency Structure Simulator (HFSS), and the probe parameters suitable for PD detection in the switchgear are determined. Finally, the performance of the probe is measured by network analyzer, and the PD signal is tested on the simulated PD test platform. The results show that the probe works in the frequency band of 10–200 MHz and can receive PD signals containing more energy information. In the operating frequency band, the reflection coefficient of the probe port is very large, and its interference to the signal near field is particularly small. The probe also has good frequency response characteristics, and the fluctuation in the frequency band is less than 5 dB, which can obtain more accurate PD signal characteristics in subsequent processing. In addition, the probe is passive, with dimensions of 166 mm in length, 104 mm in width, and 2 mm in thickness, which is suitable for placing in the switchgear with small internal space. The results of PD receiving test show that the probe can reflect the occurrence of PD remarkably and accurately.

Numerical Evaluation and Experimental Test on a New Giant Magnetostrictive Transducer with Low Heat Loss Design.

Giant magnetostrictive transducer with micro and nano precision has a wide application prospect in the field of remote sensing. However, excessive heat loss of components could generate during the energy conversion and transfer from electric energy to magnetic energy, and magnetic energy to mechanical energy, thereby affecting its long-term service and also reducing energy utilization. In this paper, a new magnetostrictive transducer is proposed and its excitation coil, internal and external magnetic circuit are optimized from the perspective of reducing heat loss. With the help of theoretical and finite element analysis, the response law between key parameters and heat loss of key components are summarized, which provides a basis for reducing heat loss. Finally, according to the optimization scheme, the prototype is processed, and the temperature rise and dynamic output performance of the transducer are tested by constructing an experimental setup. The results show that the transducer has a low temperature rise and good frequency response characteristics, which can provide support for long-time precise actuation on-orbit.

Identification and Filtering of Random Error in Fiber Optic Current Transducer

With the advantages of excellent insulation performance, wide dynamic measurement range, good frequency response characteristics and high sensitivity, fiber optic current transducer (FOCT) has become the mainstream of current measurement technology. The structure of fiber-optic current transformer is complex, and random error becomes one of the major problems that affect the application of fiber-optic current transformers in power engineering. It is urgent to study the random error characteristics of fiber current transformers and propose effective measures to suppress random errors. The characteristics of random error in FOCT are analyzed, and time series model is established by preprocessing and statistical inspection of FOCT output data. Based on the random error characteristics of the FOCT output signal, it makes prerequisite preparation for the signal filtering optimization modelling and the construction of the state function equation. With the derived random error state function of FOCT, the Wavelet filtering algorithm combining with Kalman filtering algorithm is proposed, then, the time domain and frequency domain local area transforms are used to detect the random error characteristics and identify various types of random error information accurately. Real-time multi-scale decomposition and optimal estimation of random error in FOCT are realized. Experimental results demonstrate that the time series modelling and Wavelet filtering algorithm can accurately identify the random error characteristics of the FOCT and automatically match the parameter filtering to improve current measurement accuracy.

Research on planar frequency selective fabrics with Jerusalem-shaped units

Planar frequency selective fabrics (FSFs) with Jerusalem-shaped units were proposed in this paper. In accordance with the previous work, the design process was specifically for 10 GHz. Through simulation and optimization procedures, the ideal structure parameters were obtained, and the proposed FSFs with optimized parameters showed good stability to differential and integral algorithms, transmission modes and incidence angles of electromagnetic (EM) waves. To further explore the internal EM transmission mechanism of FSFs, the surface currents at 4, 10 and 14 GHz were analyzed comparatively. Based on the simulated results, 10 samples with the polyester fabric substrate were fabricated through the computer-based carving method and the transmission characteristics were tested using the Shielding Room Method. The fabricated FSFs indeed showed good frequency response characteristics, as expected, and the comparison of measured and simulated results verified the validity of the design procedures. The influence rules of structure parameters ( p, a, b, c) were further studied in detail by changing their values properly, and the simplified equivalent circuit model was proposed to explore the corresponding physical mechanism, which could provide physical insight into the performance of the FSFs.

Synthesis and property of spinel porous ZnMn2O4 microspheres

Mesoporous ternary zinc manganese oxides on the Ti sheet substrate are prepared by easy and fast hydrothermal method for the first time. The obtained ZnMn2O4 materials with homogenously distributed pores have been characterized by XRD, SEM and Raman spectra, which show the good crystal phase and particles for improving supercapacitive performance. XRD and SEM images show that the as-prepared samples have good crystallinity, and ZnMn2O4 microsphere has an average diameter of 10μm. In addition, ZnMn2O4 are also characterized in 2M KOH solution using three-electrode system. In the work, we study that different substrates (Ti, carbon and nickel foam) have an important effect on the electrochemical performance of the samples. The research of cyclic voltammogram (CV) indicates that the obtained specific capacitance (155Fg−1) values on nickel foam substrate for the ZnMn2O4 microspheres are higher than the values reported for some inexpensive oxides. However, the specific capacitance of all ZnMn2O4 samples has almost no change at two different scan rates which shows good long-term cycling stability. The electrochemical impedance spectroscopy with a small resistance reveals that the as-synthesized samples have good frequency response characteristics. These results indicate that the unique ZnMn2O4 electrode would be a promising electrode for high-performance supercapacitor applications.

Research on 3D periodic structure velvet fabric and its frequency response characteristics

Frequency selective surfaces (FSSs) based on textile or textile composite materials are increasingly becoming popular due to their textile nature of high flexibility, softness, low-cost, easy fabrication, and other textile characteristics compared to the traditional metal FSS, especially the two-dimensional FSS fabrics. In this study, a three-dimensional (3D) fabric periodic structure with conductive textile fabricated vertically on the common textile substrate, forming a U-shaped array, is proposed. An experimental validation has been conducted to verify whether the 3D frequency selective structure fabric has good frequency response characteristics and great design ability. The model samples of 3D periodic structure based on velvet fabric with different structure or material parameters were fabricated by hand. Through testing and analysis of transmission and reflection coefficients at 2–18 GHz using the shielding chamber method, the results show that the velvet height of the fabric model periodic structure has an obvious effect on the resonant frequency. With an increase in velvet height, the resonant peak will move towards lower frequency. With an increase of vertical velvet spacing, the resonant frequency will also move towards lower frequency. Velvet material has a slight influence on the frequency response characteristics. The frequency response characteristics of this structure are stable under different incident angles. The 3D periodic structure offers more design freedom and possibilities. Significant effects of wave absorption or selective filtering by the periodic structure can be achieved by regulating the structural parameters and material parameters together.

New Microstrip Bandpass Filter Designs Based on Stepped Impedance Hilbert Fractal Resonators

ABSTRACTThe proposed microstrip bandpass filters in this paper have compact sizes and narrow band responses which are the requirements of modern wireless communication circuits. These filters are constructed from dual-edge coupled resonators; each resonator is based on applying step impedance resonator generator on first and second iteration of Hilbert fractal resonators on each segment of each iteration level. They have been designed for the industrial, scientific, and medical band (ISM) band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 9.6 and thickness of 0.508 mm. The performance of bandpass filters has been analysed using a method of moments (MoM) based on software package, Microwave Office 2009, from Advanced Wave Research Inc., which is widely adopted in microwave research and industry. Simulation responses show that these filters possess good frequency response characteristics with second harmonics suppression. Moreover, these filters showed noticeable miniaturization which is an important feature for many communication applications. The simulated and measured results are in good agreement.

A Bionic Fish Cilia Median-Low Frequency Three-Dimensional Piezoresistive MEMS Vector Hydrophone

AbstractA bionic fish cilia median-low frequency three-dimensional MEMS vector hydrophone is reported in this paper. The piezoresistive reasonable position was obtained through finite element analysis by ANSYS and the structure was formed by MEMS processes including lithography, ion implantation, PECVD and etching, etc. The standing wave barrel results show that the lowest sensitivity of the hydrophone is −200 dB and reach up to −160 dB (in which the voltage amplification factor is 300). It has a good frequency response characteristics in 25 Hz ∼ 1500 Hz band. Directivity tests displayed that the hydrophone has a good “8”-shaped directivity, in which the resolution is not less than 30 dB, and asymmetry of the maximum axial sensitivity value is less than 1.2 dB.

다중대역 6단자 직접변환 방식을 위한 전력 검파기 설계 및 제작

본 논문에서는 다중대역 6단자 직접변환 방식을 위한 메타물질 구조 전력 검파기를 설계하고 제작하였다. 다중대역 주파수를 수용하는 RF 단락회로를 메타물질 구조로 구성하여 다중대역 전력 검파기 구조를 해석하고, 집중소자와 분포정수 소자를 갖는 메타물질 구조 전력 검파기를 제작하였다. 제작 측정된 메타물질 구조 RF 단락회로는 시뮬레이션 결과와 일치하였으며, 집중소자 메타물질 구조 RF 단락회로는 1 dB 이내의 삽입손실과 설계 중심주파수와 일치하는 대역폭 특성을 나타내었다. 분포정수형 구조 RF 단락회로는 다소 적은 삽입손실과 양호한 대역폭 특성을 나타내었으며, 메타물질 구조 RF 단락회로를 갖는 전력 검파기는 다중대역 주파수 영역에서 양호하게 RF 입력 신호를 검파하여 기저대역 신호를 발생하였다. In this paper, the power detectors using metamaterials were designed and fabricated for multi-band six-port direct conversion method. The RF short-stubs for power detector were designed by using metamaterials which provide multi-band characteristics. The power detectors with metamaterial RF short-stub were analyzed and fabricated by using lumped and distributed element. The measured results of metamaterial power detectors show the good agreement with the simulation results. The performance of lumped-metamaterial RF short-stub shows the insertion loss below 1 dB and the good frequency response characteristics. Also, the distributed-metamaterial RF short-stub shows the good frequency response characteristics and the insertion loss under that of lumped-metamaterial RF short-stub. The multi-band power detectors with metamaterial RF short-stub detect the input RF signal in the designed dual frequency bands very well.

Design optimization of condenser microphone: A design of experiment perspective

A well-designed condenser microphone backplate is very important in the attainment of good frequency response characteristics--high sensitivity and wide bandwidth with flat response--and low mechanical-thermal noise. To study the design optimization of the backplate, a 2(6) factorial design with a single replicate, which consists of six backplate parameters and four responses, has been undertaken on a comprehensive condenser microphone model developed by Zuckerwar. Through the elimination of insignificant parameters via normal probability plots of the effect estimates, the projection of an unreplicated factorial design into a replicated one can be performed to carry out an analysis of variance on the factorial design. The air gap and slot have significant effects on the sensitivity, mechanical-thermal noise, and bandwidth while the slot/hole location interaction has major influence over the latter two responses. An organized and systematic approach of designing the backplate is summarized.

微弯光纤振动传感频率响应实验研究

We make an experimental study on vibration frequency response of micro-bend optic-fiber sensor, and single-mode fibers and multi-mode fibers are used as the sensitive optic-fibers. Contrast between the two sensitive fibers is presented. Result shows that the micro-bend optic-fiber sensor has good frequency response characteristics and strong ability to restore the waveform. With the frequency varying in the range of 500-4762 Hz, the vibration sensors using multi-mode optic-fiber as the sensitive fiber is more sensitive than that using single-mode optic-fiber. And the former has better frequency response characteristics and stronger capacity of waveform revivification. But with the frequency in the range of 287-500 Hz, the latter is better.

Continuously tunable incoherent microwave photonic filter using a tunable Mach‒Zehnder interferometer as the slicing filter

AbstractA continuously tunable incoherent microwave photonic filter employing a tunable Mach‐Zehnder interferometer (MZI) as the slicing filter is studied. By incorporating the optical variable delay line (OVDL), the frequency spacing of the MZI can be tuned continuously, which in turn makes the whole microwave photonic filter continuously tunable in a wide frequency range. The frequency response characteristics are studied and some simulation results are also given to optimize the present microwave photonic filter. Experimental results show the present filter has good frequency response characteristics and tuning linearity. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2382–2386, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22732

Low-pass filter for the DFT process and its application to impulse response of sound-field and ultrasonic B-mode echo simulator

Convolution and correlation are closely related operations that are basic to many areas of signal processing. To obtain the frequency component of the signals using discrete Fourier transform (DFT), the continuous signals must first be sampled. A low-pass antialiasing filter which is simple to implement is proposed. The low-pass filter has equally good frequency response characteristics and can be used to eliminate possible aliasing effects by ensuring that the signal to be sampled is limited in the spectral content. The impulse response of the sound field was calculated by using the proposed low-pass antialiasing filter and compared with the rigorous solution to verify the realizability of the filter. The filter was also applied to construct the ultrasonic B-mode image of a 3-D phantom model.

Micromachined silicon microphones and hearing aids: Performance and potential

Small size, good frequency response characteristics, wide dynamic range, low cost, low sensitivity to external influences such as vibration, and low power requirements (extended battery life) of associated electronics have long been recognized as desirable properties of microphones used in hearing aids. New technologies of micromachined silicon capacitive microphones show promise not only for present hearing aid applications, but also for evolving array-based ones that may become practical for improving speech reception in the presence of noise and reverberation. Stability of microphone sensitivity can be particularly important in maintaining the designed directionality of arrays during their service lifetime. Designers of new microphones need reliably measured performance data to develop these new technologies and to optimize designs for specific applications. NIST measurement services long available to the public have been extended to obtain these data. Examples, including free-field sensitivity level versus frequency characteristics, are discussed for some experimental prototype omnidirectional microphones recently designed by J. Bernstein of Draper Laboratory, a customer of these services. Some possible lines of research and development of micromachined silicon transducers for hearing aid applications are suggested and discussed.

Implementing Fourier algorithm by linear modulation method for distance relaying application

Abstract The Fourier algorithm, due to its good frequency response characteristics, is frequently used in calculating the peak value of a distorted wave for real time measuring applications. A new method, using the linear modulation method, is proposed to implement the algorithm. It improves the defect of a large number of arithmatic operations during implementation of the algorithm. This paper describes the structure and theory of the proposed linear modulated Fourier algorithm. Test results, including the required arithmatic operations and the numerical accuracy, are reported. Moreover, application to the digital impedance relay was simulated, and the simulation results show that the proposed algorithm is suitable for relaying applications.