Notch Filter Research Articles

Laser Thomson scattering system for anisotropic electron temperature measurement in NUMBER

A laser Thomson scattering system is developed to obtain anisotropic electron temperature in a pulse operated electron cyclotron resonance plasma device. Injecting a laser with an oblique angle to the external magnetic field and detecting scattering photon from a line of sight along another oblique angle enable us to obtain parallel and perpendicular components of electron temperature. Backward (165°) scattering spectrum corresponds to quasi perpendicular velocity distribution, while that for forward (15°) scattering; quasi parallel. Collecting lenses are set in vacuum to maximize solid angle in a limited space of port, where the laser path and collecting optics share an ICF152 flange. Rayleigh scattering intensity is measured as a function of argon gas pressure. An initial result on residual stray light intensity is equivalent to the argon Rayleigh scattering intensity under ≤ 1 kPa of filled pressure. In order to obtain Thomson scattering spectra, a notch filter type stray light rejection optics, which utilize a reflective type volume holographic grating, is evaluated. Notch width (0.2 nm) and flat transmittance (≥ 90%) outside the notch measured for a prototype show that it is an effective optics.

Three inputs and one output voltage-mode universal biquadratic filter using one CCII and one CCIII

A voltage-mode universal biquadratic filter using one second-generation current conveyor (CCII), one third-generation current conveyor (CCIII), two capacitors and two resistors is presented. The proposed voltage-mode biquadratic circuit has three input terminals and one output terminal and can realize all the standard filter functions that are highpass, bandpass, lowpass, notch and allpass filters without changing the circuit topology. Both its active and passive sensitivities are small. The proposed circuit does not need one more active component for the unity-gain inverting of the input signal in each filter realization.

Research on an active control method of double crystal monochromator with disturbance observer

The double crystal monochromator (DCM) is the core equipment of high flux and high monochromatic light on the synchrotron beamline, which directly affects the performance of the synchrotron hard X-ray beamline in terms of stability. To meet the requirements for the stability of the nano-radian magnitude of the DCM for the 4th-generation synchrotron light source, this paper presents a method to suppress the primary resonance of the system using an integral lead compensation notch filter and eliminate the higher-order positive and negative resonance peaks with a dual second-order notch filter. The bandwidth of the DCM system is enhanced to meet the system speed requirements. Meanwhile, the mechanical coupling is considered equivalent to the system's internal disturbance. The disturbance observer is designed to ensure the stability and dynamic performance of the DCM system. The simulation results show that after correction by the integral lead compensation notch filter and the dual second-order notch filter, the system bandwidth can reach 308Hz while maintaining a phase margin of approximately 25°. Furthermore, the stability of DCM can reach an RMS of 0.139 nrad, 16.610 nrad, and 1.431 nm in the Pitch, Roll, and Gap direction, respectively, with the help of a disturbance observer. The paper proposes a method to develop stable DCMs in 4th-generation synchrotron radiation facilities while improving the X-ray beamline performance.

Multimaterial fiber as a physical simulator of a capillary instability

Capillary breakup of cores is an exclusive approach to fabricating fiber-integrated optoelectronics and photonics. A physical understanding of this fluid-dynamic process is necessary for yielding the desired solid-state fiber-embedded multimaterial architectures by design rather than by exploratory search. We discover that the nonlinearly complex and, at times, even chaotic capillary breakup of multimaterial fiber cores becomes predictable when the fiber is exposed to the spatiotemporal temperature profile, imposing a viscosity modulation comparable to the breakup wavelength. The profile acts as a notch filter, allowing only a single wavelength out of the continuous spectrum to develop predictably, following Euler-Lagrange dynamics. We argue that this understanding not only enables designing the outcomes of the breakup necessary for turning it into a technology for materializing fiber-embedded functional systems but also positions a multimaterial fiber as a universal physical simulator of capillary instability in viscous threads.

Design of auto‐tuning‐based adaptive controllers for voltage source converters with inductive loads

AbstractThis paper presents an auto‐tuning method for dc‐ac voltage source converters (VSCs) with an inductive load that is based on the modified relay feedback test (MRFT). Controllers tuned by the proposed method can produce near‐optimal dynamic performance for dc–ac VSCs without requiring knowledge of the plant's parameters. The controller consists of a PID cascaded with a digital notch filter. The tuning involves two steps. In the first step, the MRFT is used to tune the digital notch filter to compensate for the LCL resonance resulting from the LC filter's interaction with the inductive load. In the second step, one more MRFT is used to tune the PID controller using optimal tuning rules that are derived in advance (offline). The proposed optimal for the class of the dc–ac VSCs tuning rules can guarantee a specified phase margin and near optimal transient performance for any randomly picked VSC. The performance of the proposed tuning of the PID + notch filter is verified by simulations and experiments. The dynamic response of the auto‐tuned controller compares well to the response of a theoretically optimal but non‐auto‐tuned PID + notch filter designed using the full knowledge of the LC filter and the load.

Computationally-efficient statistical design and yield optimization of resonator-based notch filters using feature-based surrogates

Modern microwave devices are designed to fulfill stringent requirements pertaining to electrical performance, which requires, among others, a meticulous tuning of their geometry parameters. When moving up in frequency, physical dimensions of passive microwave circuits become smaller, making the system performance increasingly susceptible to manufacturing tolerances. In particular, inherent inaccuracy of fabrication processes affect the fundamental operating parameters, such as center frequency or bandwidth, which is especially troublesome for narrow-band structures, including notch filters. The ability to quantify the effects of tolerances, and—even more—to account for these in the design process, are instrumental in making the designs more reliable, and to increase the likelihood that adequate operation is ensured despite manufacturing errors. This paper proposes a simple yet computationally efficient and reliable procedure for statistical analysis and yield optimization of resonator-based notch filters. Our methodology involves feature-based surrogate models that can be established using a handful of training data points, and employed for rapid evaluation of the circuit fabrication yield. Furthermore, a yield optimization procedure is developed, which iteratively sets up a sequence of feature-based models, constructed within local domains relocated along the optimization path, and uses them as predictors to find a robust (maximum yield) design at a low computational cost. The presented approach has been demonstrated using two complementary split ring resonator (CSRR)-based notch filters. The cost of statistical design is about a hundred of EM simulations of the respective filter, with yield evaluation reliability corroborated through EM-based Monte Carlo analysis.

Electrically Tunable Topological Notch Filter for THz Integrated Photonics

AbstractElectromagnetic filtering is essential for emerging integrated photonic technologies and widely adaptable processing of high‐bandwidth signals. The conventional electro‐optic modulator‐based photonic approach for signal filtering at microwave frequencies cannot be implemented at terahertz (THz) frequencies due to the unavailability of the THz signal‐driven optical modulator. Here, an electrically tunable on‐chip THz photonic notch filter based on the topologically protected valley hall waveguide‐cavity platform is demonstrated. The device shows a significantly large notch suppression depth of more than 20 dB with a return loss of 13 dB in the entire tuning range of notch frequency. The feedback control circuit enables precise control of the notch frequency shift with a minimum step size of 7 MHz. This work extends the application of topological photonic crystals in developing THz‐integrated photonic devices for transformative technologies, including sixth‐generation (6G) communication and high‐resolution spectral sensing.

Stochastic cooling notch filter developments for the high-precision spectrometer ring in the high intensity heavy-ion accelerator facility project.

Stochastic cooling of the high-precision spectrometer ring (SRing) at the High Intensity Heavy-Ion Accelerator Facility (HIAF) project in China, which is used mainly for experiments with radioactive fragment beams, is applied to speed up the cooling process of a stored ion beam. In this article, a new coaxial-type notch filter with an amplitude equalizer in the long branch and an optical-type notch filter with phase-stabilized optical fiber are discussed and evaluated for the SRing stochastic cooling system. Both prototypes of coaxial and optical notch filters are fabricated and tested. The minimum notch depth of coaxial and optical notch filters reaches to 26 and 40 dB, respectively. The performance of both coaxial notch filter and optical fiber notch filter is presented in this work. These developments will be used not only for the longitudinal stochastic cooling system but also have potential for the beam feedback system.

Coordinated Control for Seamless Integration of Wind Energy Conversion System With Small Hydrogenerator Through Modified Notch Filters

This paper deals with the seamless integration of doubly fed induction generator (DFIG) based wind energy conversion system (WECS) with local grid constituted by a permanent magnet based small hydrogenerator (PMHG). The seamless integration is carried out using a solid state static transfer switch (SSSTS). The WECS-PMHG system is operated using a coordinated control strategy based on modified notch filters. The modified notch filters are adopted for the computation of (a) sensorless speed and position of the DFIG rotor, (b) fundamental constituents of unbalanced/nonlinear load current and (c) filtered DFIG stator voltages and phase angle. Moreover, the notch filters are also used for mitigating the effects of unbalance/nonlinearity in load currents on the stator and rotor currents of DFIG as well as PMHG currents. Additionally, the control methodology ensures no power interaction between the WECS and the PMHG during the synchronization process. This enables transient-free WECS and PMHG currents. Further, the coordinated control regulates the amplitude and frequency of system voltages even amidst wide variations in wind speed and load. The DFIG stator and wind currents are injected at unity power factor with the system voltages, while the excitation requirement of the DFIG is met by its machine side converter. The validness of the control is demonstrated experimentally through a developed laboratory-scale test bench.

High-Precision Suppression of Harmonic Vibration Force by Repetitive Controller With Triple-Loop Structure

The harmonic vibration force generated by multi-source disturbances through the magnetic bearing closed-loop control system seriously affects the improvement of the performance of the magnetically suspended control moment gyroscope (MSCMG). The harmonic noise introduced by the displacement sensor generates harmonic components through a closed-loop control system, and the compensation accuracy of synchronous displacement stiffness force is reduced by the low-pass characteristics of the power amplifier. In this paper, the rotor displacement signal and current signal are used as inputs to the repetitive controller and notch filter, and the power amplifier and repetitive controller are constructed into three closed-loop systems to achieve high-precision suppression of harmonic vibration forces. Finally, the effectiveness of the method is demonstrated by using a 200Nms MSCMG and a micro-vibration test system.

Current-Fed Phase-Shifted Full-Bridge Converter With Secondary Harmonic Current Reduction for Two-Stage Inverter in Energy Storage System

For the low voltage, high current, isolated DC-DC converter applications, current-fed type converter has the chance to achieve higher efficiency due to the lower transformer root mean square current compared with other well-known converters such as dual active bridge or LLC. A current-fed phase-shifted full-bridge, CFPSFB converter has the advantages of nearly full range zero-voltage-switching and soft-commutating without large size of passive or active snubber circuit because the phase-shift of secondary full-bridge is controlled to be proportional to the input current. However, as a front-end stage of a single phase inverter, the input secondary harmonic current (SHC) propagating from the output AC load may cause large voltage spike to damage the primary MOSFETs due to losing the soft-commutating property. SHC may also reduce the conversion efficiency and the lifespan of battery intensely. This paper proposes a simple control scheme based on virtual series impedance method with a notch filter in control loop to reduce the SHC and maintain good dynamic performance. A small-signal model of CFPSFB for a reliable controller design is derived and verified by simulation. A 48 V/3 kW maximum output power inverter prototype is built to verify the theoretical analysis. The maximum efficiency of the DC-DC stage is 97.4% and the peak to peak SHC is less than 10% of the average input current.

A Ku-Band CMOS Balanced Driver Amplifier With Transformer-Based Notch Filter for SATCOM Phased Arrays

This brief presents a Ku-band balanced driver amplifier (BDA) for SATCOM phased arrays. To facilitate a flexible and low-loss coupler design, the non-correlation between the coupling coefficient and the output power of BDA is illustrated. The passive transformer-based notch filter is co-optimized with the inter-stage matching network. The sideband rejection is improved while maintaining high gain and linearity. The second harmonic trap technique is also applied to alleviate the amplitude-to-phase (AM-PM) distortion. Fabricated in 65-nm CMOS technology, the proposed BDA provides the maximal gain of 26 dB at 14 GHz with the highest sideband rejection of 26 dB. The input and output return losses are both better than -15 dB. It achieves a measured 1-dB compressed power (P1dB) of 19.5 dBm with the maximal power-added efficiency (PAEmax) of 27.8%. The small-signal gain and P1dB vary only 2 dB and 0.8 dBm from -55∘C to 85∘C, respectively.

Instantaneous multi-frequency tracker for nonstationary vibration signal in mechanical system

A novel instantaneous frequency (IF) tracking method for non-stationary measured signals with single-frequency, multi-frequency, and harmonic-frequency is presented in this paper. Firstly, the deficiency of the mainstream time-domain IF tracking methods, such as adaptive notch filter (ANF) and Extended Kalman Filter (EKF), etc., are analyzed. Then the relationship of the amplitude, frequency, and signal value of a periodic signal in adjacent time intervals is derived, the influence of amplitude change on IF tracking results is verified, and a new state-space model for the IF tracking of a non-stationary measured signal is constructed by using the adjacent non-stationary measured signal, signal amplitude, and frequency, and the EKF is used to update the state of the model. After that, a series of non-stationary signals whose amplitude, frequency, and phase change linearly, nonlinearly, and mutation over time are designed to verify the IF tracking performance of the proposed algorithm. From the simulation results and 1000 times Monte Carlo simulation results, the proposed algorithm has faster convergence speed, higher convergence accuracy, and better robustness, compared with mainstream time-domain frequency tracking algorithms, such as ANF and EKF. Based on the proposed single-frequency IF tracking model, a multi-frequency signal IF tracking model is constructed to track the IF of non-stationary measured signals containing multiple frequency components. The effectiveness of the proposed multi-frequency IF tracking algorithm for multi-frequency signal and harmonic signal IF tracking is verified by simulation cases. After that, some experimental cases are given to further verify the feasibility of the proposed IF tracking algorithm. From the experimental results, the effectiveness of the proposed algorithm is compared with other time-domain algorithms. In addition, the initial value of frequency is set to zero in all the processes of simulation and experiment, which effectively avoids the influence of the initial condition of frequency on the IF tracking result.

Modeling and experimental analysis of high-efficiency fluid temperature fluctuation attenuator based on phase regulator

Temperature fluctuation attenuators are important passive components for disturbance rejection in precise temperature control system, but previous attenuator researches mainly focused on increasing effective heat capacity to achieve better attenuation. In this paper, the temperature phase regulator (TPR) model is proposed as a superior method to reduce fluid temperature disturbances with less capacity. It achieves output temperature fluctuation attenuation by shifting the phase of the delay side temperature signal and mixing it with the normal side. Similar to the principle that notch filters can highly attenuate signals in specific frequency bands, we constructed TPR theoretical models under equal flow ratios and non-equal flow ratios. Different bandwidths, attenuation depths and target center frequencies can be achieved by changing the two parameters of equivalent heat capacity and flow ratio, and the mechanism of parameters affecting the TPR amplitude-frequency characteristics was analyzed. In terms of effect evaluation, we verified the correlation between the frequency domain and the time domain data, and compared the TPR with the thermal capacity attenuator and other popular attenuators in terms of MSE, MAE and Max-min of temperature data. In a typical temperature attenuation test, TPR can achieve 40% and 35% of MAE and Max-min value attenuation rates, which are exceeding the ideal upper limit of other attenuators and far superior to typical attenuators. The experimental data confirmed the feasibility of the heat capacity of the pipe to support the TPR delay side as a pure delay. The experimental results of non-equal flow ratios verified the model reference-ability of changing flow ratio. In the equal flow ratio test, the fit of the actual data curve and the theoretical curve showed the accuracy of the theoretical model, and the MAE attenuation ratio better than 70% reflected the excellent attenuation performance.

The Impact of Phase-Locked Loop (PLL) Architecture on Sub-Synchronous Control Interactions (SSCI) for Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-Based Type 4 Wind Farms

Electric vehicles (EVs) are a promising solution to reduce carbon dioxide (CO2) emissions, but this reduction depends on the fraction of renewable sources used to generate electricity. Wind energy is thus a vital candidate and has experienced a remarkable surge recently, establishing itself as a leading renewable power source worldwide. The research on Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-based type 4 wind farms has indicated that the Phase-locked Loop (PLL) bandwidth significantly impacts Sub-Synchronous Resonance (SSR). However, the influence of PLL architecture on SSR remains unexplored and warrants investigation. Therefore, this paper investigates PLL architectural variations in PLL Loop Filter (LF) to understand their impact on SSR in type 4 wind farms. Specifically, an in-depth analysis of the Notch Filter (NF)-based enhanced PLL is conducted using eigenvalue analysis of the admittance model of a PMSG-based type 4 wind farm. The findings demonstrate that the NF-based enhanced PLL exhibits superior performance and improved passivity in the sub-synchronous frequency range, limiting the risk of SSR below 20 Hz. Additionally, Nyquist plots are employed to assess the impact on system stability resulting in increased stability margins. In the future, it is recommended to further investigate and optimize the PLL to mitigate SSR in wind farms.

Stability control of high-speed magnetic levitation turbomolecular pumps with shock-excited disturbance

The disturbance suppression of magnetic levitation turbomolecular pumps is a critical problem in industrial applications. This work addresses the stability control of high-speed magnetic levitation turbomolecular pumps with shock-excited disturbance. A disturbance suppression method based on improved linear extended state observer is proposed to attenuate the impact of external low-frequency disturbing force on a magnetic levitation turbomolecular pump. Firstly, a linear extended state observer of an active magnetic bearing is obtained by analyzing the rotor dynamics model. Then, the detailed descriptions of external disturbance suppression method using linear extended state observers and adaptive notch filters are discussed for the system. The boundary condition of the parameters of the improved linear extended state observer is determined. The root loci of the closed-loop system with improved linear extended state observers is also investigated. Finally, simulation and experimental results on a magnetic levitation turbomolecular pump show the applicability of the proposed method. The results show that the proposed method can attenuate the rotor vibration displacement caused by impact by 46.9%.

Design and development of leaky least mean fourth control algorithm for single‐phase grid‐connected multilevel inverter

SummaryThis paper proposes leaky least mean fourth (LLMF) algorithm for the control of five‐level series connected H‐bridge multilevel inverter (5L SCHB‐MLI). The SCHB multilevel inverter is a popular configuration due to its wide application for high‐power and medium‐voltage applications. The complete system comprising the grid, load, and compensator is modeled in MATLAB/SIMULINK. Prototype hardware is also developed in the laboratory for experimental validation. The 5L SCHB inverter is connected in a single‐phase power distribution system and controlled as a compensator. The voltage across both DC links of the H‐bridges is regulated to almost equal value by the proposed control algorithm. The closed loop system is designed to mitigate total harmonic distortion (THD) in the source current and improve the power quality of the proposed system. The system is analyzed under the steady state and dynamic state, and the results are also verified on the hardware prototype developed in the laboratory. The proposed algorithm is also compared with conventional least means square (LMS) algorithm and notch filter algorithm on several parameters. The paper discusses a detailed simulation and hardware analysis on the control of five‐level MLI topology.

Radio Frequency Interference Mitigation via Nonnegative Matrix Factorization for GNSS

A radio frequency interference (RFI) mitigation approach based on nonnegative matrix factorization (NMF) for global navigation satellite systems (GNSS) signals is proposed. The proposed approach employs NMF to separate the interference from the GNSS signals, and it can be deployed in a supervised or semi-blind manner. The supervised NMF framework assumes prior knowledge about the RFI whereas its semi-blind counterpart does not require any <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> information about the RFI. Results indicate that both schemes are able to mitigate narrow and wideband RFI signals, outperforming Kalman, notch filter and wavelet-based techniques, enabling GNSS signal acquisition even in scenarios where the interference is 50 dB stronger than the GNSS signals. In addition, the proposed approach is able to mitigate multiple, different types of RFI corrupting the received GNSS signal.

Analysis and Elimination of Speed Measurement Ripple in Sinusoidal Coded Gearwheel Encoder for Spindle Motor Drive

The gearwheel encoder with a magnetoresistive (MR) sensor is robust, simple, and widely used in high-speed industrial motor drives. Moreover, a high-precision rotor position detection is possible with the gearwheel encoder due to its large number of output pulses per revolution. The MR sensor outputs two sinusoidal signals that are 90 degrees apart, the period of which matches with one tooth of the gearwheel. However, these output signals are not perfectly sinusoidal because the MR sensor is manually mounted, and the magnitudes of these signals depend on the distance between the MR material and gearwheel. This slight imperfection in the output signals provokes large speed ripples in the speed measurement. This study analyzed the speed measurement ripples, and an effective ripple-elimination method was devised based on the results of the analysis. Ripple components caused by each signal error were calculated from the error signal models, and exact ripple frequencies were extracted. From the calculation results, a frequency adaptive series notch filter algorithm was designed. The simulation and experimental results demonstrated the effectiveness of the analysis and proposed approach. It is obviously shown through the experimental results that the speed measurement ripple is almost eliminated with the proposed method, and, thus, the analysis is valid.

Off-Board Bidirectional Electric Vehicle Charger Featuring Reactive Power Compensation and Reduced Total Harmonic Distortion for Enhanced Efficiency and Power Quality

The purpose of this study is to explain a recently developed off-board battery charger system for electric vehicles (EVs) that is capable of supporting grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operations, in addition to adjusting for reactive power. A utility-connected AC-DC cascaded H-bridge (CHB) converter is included into the system design. This converter is responsible for controlling the power exchange that occurs between the grid and the battery while a bidirectional DC-DC converter is located at the rear end of the system. There is galvanic separation between the grid and the user end of the charger, which is included for the purpose of increasing safety. In order to manage electric vehicle power and battery current, the suggested system makes use of an ANFIS controller. This controller adheres to active power orders for both G2V and V2G modes, and it also provides reactive power adjustment when it is necessary. Furthermore, a control algorithm that is based on an adaptive notch filter has been developed in order to estimate network phases and achieve accurate current synchronization without the need for phase-locked loops (PLLs). This has resulted in the simplification of controller design and an improvement in both the steady-state and dynamic performance of the system. The efficiency of the suggested system in regulating reactive power in V2G and G2V scenarios is shown by the experimental results that were achieved in a MATLAB environment.