Resonator Filters Research Articles

A Low-Profile Dielectric Resonator Filter with Wide Stopband for High Integration on PCB.

A low-profile dielectric resonator (DR) filter is proposed to achieve the feature of high integration and wide stopband. The high integration is due to the structure of printed circuit board (PCB) substrate instead of metal cavity, which can be easily integrated with other planar circuits. Thus, the proposed design can improve the integration level and reduce installation errors. Moreover, the out-of-band harmonics can be well suppressed by the structure combined with introducing rectangular hollowing in the center of the dielectric block, coupling the feed and loading 1/4λ wavelength branch. For demonstration, it is fabricated and measured. The simulated and experimental results with good agreement are presented, the insertion loss is as low as 1.1 dB, the profile height is only 0.77λg, and the stopband reaches 2.61f0.

Low-Sidelobe Microstrip Patch Filtenna Array Fed by Higher Order Mode SIW Cavity

In this letter, a 1 × 3 microstrip patch (MP) filtenna array with low sidelobe level fed by TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</sub> -mode substrate integrated waveguide (SIW) cavity is investigated. Benefiting from the fact that the magnetic field amplitude at the adjacent region of the two central quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> modes of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</sub> -mode SIW cavity is twice that of the single quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode on either side of the edge, it enables the filtenna array to obtain a binomial power distribution and then achieve low sidelobe level. In the fusion design of filtering power divider (FPD), the SIW cavity and the patch radiators are regarded as first and second resonators of filter respectively, meanwhile, the power dividing function is fulfilled by the coupling process between them. For demonstration, a filtenna array prototype centered at 13.2 GHz is designed, fabricated and measured. The measured results show that a peak gain of 11.6 dBi and a maximum efficiency of 85%. The measured sidelobe levels in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -planes are both below than -19.1 dB at 13.06 GHz and 13.32 GHz. Good agreement between the simulation and measurement can be observed.

Unified Active Damping Strategy Based on Generalized Virtual Impedance in LCL-Type Grid-Connected Inverter

Extensive solutions have been proposed to damp <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter resonance. However, the time delay caused by computation and modulation process aggravates the complexity of current loop analysis. In this paper, a generalized virtual impedance model for six kinds of commonly used active damping methods is proposed, and the physical meaning is established by introducing the metric of “damping factor”. To ensure system robustness in a wide range of grid conditions, a hybrid active damping strategy that combines inverter current feedback and capacitor voltage feedforward is proposed. Importantly, this method only requires inverter current and capacitor voltage sensors, which are the basic variables for over-current protection, power control and synchronization. The superposition theorem is also utilized to analyze the damping capability provided by parasitic resistances, current feedback loop and voltage feedforward loop. Finally, experimental results verify the feasibility and robustness of the proposed damping method.

Speed Sensorless Control Method of Synchronous Reluctance Motor Based on Resonant Kalman Filter

When estimating the active back electromotive force (AEMF) of synchronous reluctance motor (SynRM) at medium and high speed, the traditional Kalman Filter (KF) will produce large phase delay due to the low-pass filter characteristics. A novel speed sensorless control scheme of SynRM based on resonant Kalman filter (RKF) is proposed in this paper. Firstly, the AEMF observer based on KF is designed and the bandwidth performance is analyzed. To solve the phase delay problem caused by KF, a generalized integral resonance perturbation estimator (GIRPE) is introduced to the framework of KF and the proposed RKF is formed. The estimation error of AEMF is compensated through GIRPE in the current error feedback loop of KF observer. In this way, the high-precision position estimation at high speed range is obtained. Finally, an improved dynamic position compensator (IDPC) is proposed to enhance the position estimation performance under dynamic case. The effectiveness of proposed scheme is validated at a 1.5kW SynRM drive, and the computational burden of the proposed method is assessed quantitatively.

Robust discrete sliding mode controller design for a single-phase onboard integrated electric vehicle charger with disturbance estimation

A new sliding mode controller (SMC) design is proposed for a single-phase current source rectifier (CSR) integrated into onboard electric vehicle (EV) chargers. The controller's design aims to reduce the impact of varying grid impedance on the CSR's performance by using a disturbance estimator. The proposed method utilizes the Lagrange extrapolation technique for disturbance estimation, which accurately estimates disturbances caused by changes in the grid impedance. The precise state-space equation provided by the disturbance estimator is essential for designing the SMC, which can effectively handle mismatched disturbances. To mitigate the impact of the capacitor inductance filter's resonance frequency, a virtual parallel resistance with the capacitor is used, reducing the resonance amplitude. The proposed controller also controls the power factor to ensure the capacitor voltage and grid current are in phase. Simulation and experimental results demonstrate that the proposed method achieves stability and meets the harmonic content limitations of the IEC61000–3–2 standard. The total harmonic distortion (THD) is also kept below 5% despite changes in the grid impedance, demonstrating the effectiveness of the proposed method in handling varying grid conditions.

Fabrication of Cu grating guided-mode resonance filter by electroplating

A polarization wavelength filter was fabricated using two-beam interference and electroplating methods. The device consists of a Cu grating with a pitch of 400 nm on an ITO film. For normal incidence, the transverse magnetic (TM) transmission spectrum had a sharp spectrum at a wavelength of 648 nm and a significant dip at 735 nm. Furthermore, a sharp reflection spectrum in TM-light was obtained at a 685 nm wavelength and incident angle of 40°, and the peak wavelength shifted to a longer wavelength as the incident angle increased. This fabrication method is less complex and inexpensive than conventional methods.

Offset free generalized model predictive control for 3-phase LCL-filter based grid-tied inverters

This paper presents a Generalized Model Predictive Control (GPC) in the natural reference frame for a 3-phase LCL-filter based grid-tied inverter. The proposed controller can track the sinusoidal reference without steady-state phase and amplitude offsets. This is achieved by parameterizing the control law matrices with considering the future reference trajectory.To cope with the LCL filter resonance, traditional controllers need a damping method. The proposed controller has inherent damping against the LCL filter resonance and extra sensors are avoided. The controller parameters are selected by a sensitivity analysis that guarantees the closed-loop stability.The proposed controller provides high accuracy in controlling active and reactive currents, robustness against grid inductance variations, low real-time computation, and a fixed switching frequency. The simulation and experimental results prove the performance of the controller in tracking the grid-side reference currents.

Design of Reflective Tunable Structural Color Metasurface Based on Guided-Mode Resonance Filter and Sb2S3

In recent years, dynamically tunable structural color has attracted great interest. Here, we introduce the guided-mode resonance (GMR) filter and the phase-change material Sb2S3 to design a reflective optical metasurface to produce tunable structural color, in which the combination of the GMR filter, with narrow resonant wavelength, and the Sb2S3, with a much larger bandgap and higher refractive index, helps to produce high-quality tunable structural color. The simulation results indicate that through the phase transition between the amorphous and crystalline states of Sb2S3, the proposed metasurface can generate tunable structural color that can be perceived by the naked eye. Furthermore, the metasurface can sensitively sense environmental changes through changes in structural color. This work provides a new method for realizing dynamically tunable structural color, and paves the way for the application of controllable structural color in dynamic displays, optical stealth, colorimetric sensing, and other fields.

Developing high performance, low temperature sintering and temperature stable K40 material in Co2O3/Nb2O5-modified Ba3Ti4Nb4O21 microwave dielectric ceramics for 5G-LTCC communication devices

The comprehensive properties and sintering temperature of microwave dielectric ceramics are the key factors limiting their practical application. In this work, a novel strategy of complex (Co1/3Nb2/3)4+ ions substituted and adding glass (Li2O-B2O3- SiO2-CaO-Al2O3: LBSCA) was proposed to greatly enhance the microwave dielectric properties of Ba3Ti4-x(Co1/3Nb2/3)xNb4O21 (0 ≤ x ≤ 12 mol%, xCN-BTN) ceramics. A new ceramic of (Co1/3Nb2/3)4+ substitution improved hexagonal phase BTN was successfully fabricated and systematically investigated. As the increased of (Co1/3Nb2/3)4+ ions concentration, the Q×f was greatly increased because of higher packing fraction, and the reduction in the [Nb1/Ti1O6] octahedral distortion caused great changes of τf. Besides, the P-V-L theory revealed that the Ti/Nb ratio greatly contributed in permittivity εr, and the Nb-O bonds mainly affected dielectric loss, especially in Nb(1)-O2(1) bond. As a result, the superior microwave dielectric properties were obtained in 6CN-BTN ceramic sintered at 950 °C: εr∼40.99 ± 0.48, Q×f∼17,310 ± 565 GHz, and τf∼8.62 ± 4.34 ppm/°C. More encouragingly, 6CN-BTN showed good compatibility with silver, making it a promising K40 LTCC material for filter and dielectric resonators. This study presented a new strategy to improve the properties of BTN-based materials by complex ions substitution, which was expected to provide a general approach for the design of advanced microwave dielectric ceramics for other material systems.

Model reference adaptive controllers with improved performance for applications in LCL-filtered grid-connected converters

This work presents a control strategy combining a direct Model Reference Adaptive Control (MRAC) with a robust state feedback for current control of grid-connected converters with LCL filters operating under grid impedance variations. The MRAC is based on a gradient law, providing properly current reference tracking and voltage disturbance rejection. The inclusion of a state feedback inner loop provides robust active damping of the filter resonance for an entire range of grid impedances. A systematic control design procedure is proposed, and the combination of both control actions in a multi-loop approach does not add significant computational complexity. The proposal allows to increase the MRAC gains adaptation dynamics, providing suitable responses under grid current reference variations and under typical grid voltage disturbances, including grid faults. Performance indexes as the grid-currents total harmonic distortion and the mean squared error are also improved. In addition, robust stability analysis based on Lyapunov functions are carried out for the inner control loop and for the outer control loop, considering the grid impedance uncertain and with unmodeled dynamics. The strategy is implemented in a commercial digital signal processor, and the compliance of the grid currents with the IEEE 1547 Std. is verified with controller hardware-in-the-loop and experimental results in a 5.4 kW prototype.

Image denoising using adaptive bi-dimensional stochastic resonance system

Using stochastic resonance (SR) mechanism, the output signal can be enhanced by adding noise to the nonlinear system. Therefore, an image denoising algorithm based on adaptive bi-dimensional stochastic resonance (ABSR) is proposed in this paper. Firstly, the image is sampled as a bi-dimensional signal, and an adaptive bi-dimensional dynamic nonlinear system model is constructed. The peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) of the output image are used as the double evaluation model of the adaptive system, and the optimal parameters of the model are automatically obtained by adjusting the parameters of the dynamic nonlinear system using the reverse positioning method. Compared with the traditional mean filter, median filter and one-dimensional stochastic resonance, the image restoration effect of dynamic adaptive bi-dimensional stochastic resonance is more closer to the original image, and the histogram, PSNR and SSIM of the output image are also significantly better than the other three methods. The results show that dynamic adaptive bi-dimensional stochastic resonance has better denoising effect and better robustness to the change of noise intensity in image processing.

Synthesis of Wideband Cross-Coupled Resonator Filter for Direct Circuit Implementation Using Lumped Elements

A synthesis method of wideband cross-coupled resonator filter with inductive and capacitive coupling components is presented using similarity transformation. The synthesized admittance matrix can fully represent the frequency-dependent characteristics of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$J$</tex-math> </inline-formula> -inverters that are used to implement the coupling components. All negative inductive-coupling elements obtained from the conventional wideband filter synthesis method can be transformed to positive capacitive coupling elements by solving the equation derived from similarity transformation, so that the resulted admittance matrix can be directly implemented using lumped elements. All values of the lumped elements can be calculated without any optimization. A third-order triplet with fractional bandwidth (FBW) of 50% and one transmission zero (TZ) in the lower stopband and a fourth-order quadruplet with FBW of 50% and two symmetric TZs are synthesized to demonstrate the proposed method.

Model Predictive Control for a Voltage Sensorless Grid-Connected Inverter With LCL Filter Using Lumped Disturbance Observer

This paper introduces a disturbance observer-based model predictive control for a voltage sensorless grid-connected inverter (GCI), which minimizes the number of sensor measurements and eliminates the steady-state error by estimating the lumped disturbance in the presence of grid impedance variations. A full-state estimation and lumped disturbance observer are obtained based on the Luenberger observer and gradient steepest descent method, respectively. A cost function, which consists of state error, is used for controller gain design. An optimal full-state observer and controller gains are obtained by solving an optimization problem based on linear matrix inequality. The discrete-time frequency responses analysis of open-loop and closed-loop systems is presented to demonstrate the filter resonance suppression. The robustness of the proposed control against grid impedance variation is analyzed through the pole-zero map approach. Simulations and experiments are conducted for a GCI under the grid impedance variation to demonstrate the theoretical analysis and the efficacy of the proposed control schemes.

DETERMINATION OF ABNORMAL HARMONICS AND HARMONIC COMPOSITION COEFFICIENTS OF NON-SINUSOIDITY IN A 10 kV NETWORK WITH A VALVE ELECTRIC DRIVE OF DIRECT CURRENT

The operation process of the electric valve drive is accompanied by the generation of higher harmonics — canonical and non-canonical. Limitation of the level of canonical harmonics is carried out by power resonance filters, however, in the case of asymmetry of the control pulses of the thyristors of the converters, non-canonical harmonics are generated — both even and odd harmonics. The composition of non-canonical harmonics can be determined in the case of harmonic analysis of non-sinusoidal current and voltage coefficients. The conducted harmonic analysis makes it possible to determine the composition of the filter-compensating device in the case of its design.&#x0D; The article examines the operation of a power supply unit with a powerful valve electric drive powered by controlled six-phase converters. Experimental measurement of higher harmonics showed the following: canonical harmonics ν £ 13 do not exceed 1—1.5 %, while the non-sinusoidal voltage coefficient exceeds the standard by 5 % (equal to 5.5—8.2 %). Such a situation is possible in the presence of high-order abnormal harmonics, which can be explained by the asymmetry of thyristor opening pulses e ³ 3 el. deg. &#x0D; This study is devoted to the analysis of the operation of the power supply unit with a powerful DC valve electric drive powered by controlled six-phase converters. Measurements showed an insignificant level of canonical harmonics (up to 1.5 %), while harmonics ν = 21—39 exceeded 2.5—3.5 %. Such a situation can be explained by the presence of abnormal harmonics of a high order, when the asymmetry of the opening pulses of the thyristors of the converters exceeds 3 el. deg. The analysis of the non-sinusoidal coefficients as a random process and its decomposition into a Fourier series made it possible to determine the harmonic composition of the current and voltage non-sinusoidal coefficients. Thus, the task of the research is defined in the calculation of the harmonic composition of non-sinusoidal coefficients and the analysis of abnormal harmonics

Balanced single/dual band trisection filters

ABSTRACT This work presents balanced microstrip filters with asymmetrical frequency response based on a balanced trisection topology. The proposed balanced trisection topology has the feature of being used in single and multiband microwave filters. In this work, in order to test the topology flexibility, we address two applications, one for a single-band filter and the other for a dual-band filter. This topology introduces TZs on either side of the passband edges, improving the selectivity on one side of the passband. The non-adjacent resonators of the single-band trisection balanced filter are based on a Pi-network balanced resonator which is composed by six transmission lines (TLs) and two inductors (Ls). The differential-mode (DM) and common-mode (CM) resonances can be chosen independently with a proper selection of the impedances and the electrical lengths of TLs in order to have high DM stopband and intrinsic high common mode rejection (CMR). The Pi-network was modified and analyzed under the even and odd mode technique to have a dual-band behavior. Good agreement between simulation and measurement was achieved.

THz transmissive all-dielectric guided-mode resonance filter with high Q and tunability using suspended gratings.

Most currently available THz narrowband filters employ metal that introduces loss, or work in reflection mode, which limits their scope of application. Here, a transmissive all-dielectric guided-mode resonance filter in the THz region is presented. It contains a suspended grating layer and a waveguide layer, separated by an air layer. A fabrication process of the filter is proposed. Simulation results show that the designed filter exhibits excellent transmittance of ∼97.5% with a high Q value of ∼1500 at 1.64THz. Furthermore, this transmission peak is surrounded by a wide and flat sideband with width of ∼0.75T H z and transmission below 10%. Moreover, tunability of the filter is realized by geometric scaling and by varying the thickness of the air layer. Using geometric scaling, the filtering frequency can be widely tuned from 0.54 to 1.64THz, covering the 625-725 and 780-910GHz wireless communication windows. Additionally, fine tuning achieved by varying the air layer thickness could be used to compensate for a tiny shift of the designed filtering frequency caused by errors introduced in the fabrication process. The Q value can be further boosted to ∼11,500 by adding another layer of waveguide. Due to its transmissive nature and high-Q resonant mode with a wide sideband and tunability, the presented filter exhibits great potential in THz applications such as spectroscopy, imaging, and communication.

A novel control strategy for Matrix Converters based on Transient Power Balance

The Matrix Converter is a power electronics topology that allows direct conversion of an alternating-current (AC) source to an AC load operating at a different frequency. The associated control problem is inherently difficult since it is both nonlinear and underactuated. This paper describes a novel control strategy for Matrix Converters based on Transient Power Balance. The scheme achieves the following design objectives: tracking of a desired load current, tracking of a desired supply (leading or lagging) power factor, rapid active damping of supply-current oscillations, arising from a supply-side resonant filter, without needing any additional resistance on the supply side, and mitigation of supply-current distortion arising from supply-voltage distortion. Achieving these goals simultaneously has hitherto been an open problem in this area. All of these goals are achieved in the face of significant errors in circuit component values. A proof of local asymptotic stability of the proposed algorithm is given and associated design constraints are addressed. The claims are illustrated by simulation studies.

Optimal control method of induction motor torque ripple based on harmonic component

AbstractThe torque ripple of an induction motor has strong harmonic interference, which causes stator current distortion. Stability control is always a difficult problem in this field. An optimal control method for the torque ripple of induction motors based on harmonic components is proposed. To address the instability and significant energy loss caused by torque ripple in induction motors, an optimization control method for torque ripple in induction motors based on harmonic components is studied and designed. On the basis of the induction motor model, according to the characteristics and generation principle of torque ripple, combined with controllable and uncontrollable parts of harmonic torque, the stator current harmonics are used to suppress torque harmonics and minimize torque ripple. For the purpose of to cancel the harmonic component of the output voltage, achieve digital output voltage filtering, reduce the harmonic component of the stator current, and achieve optimal control of the torque ripple of the induction motor, the resonant digital filter is simultaneously deployed at the controller's output. The test results showed that the maximum torque ripple value was 2 Nm and the minimum torque ripple value was 0.1 Nm, which can restrain the distortion of stator current to the greatest extent and reduce the harmonic content of torque. In summary, the optimization control method proposed in the study can effectively suppress harmonic interference, which has important practical implications for future harmonic research.

Two-Layered Cross-Coupled Post-Loaded SIW Filter With Microstrip Ports

In this brief, we propose a new structure for reducing the number of substrates of a post-loaded substrate-integrated waveguide (SIW) resonator filters with microstrip ports. For using fewer substrates, the proposed structure has microstrip ports and each capacitive gap (the dielectric gap between one side of each post and the ground) on one side of the filter structure, which has not been reported to date. Hence, it does not necessitate another substrate designated for the implementation of the dielectric-filled gaps for the capacitive posts of post-loaded resonators. In addition, a new cross coupling structure for SIW resonators is also presented in this brief. Negative couplings can be easily implemented by using the proposed slot structure.

Improving transmittance of long-wave infrared guided-mode resonant filters

The long-wave infrared (LWIR) spectral region spanning from 8 to 12 μm is useful for many scientific and industrial applications. Many of these applications require use of either a bandpass or a bandstop filter that can be realized by the guided-mode resonance (GMR) effect with subwavelength periodic features in layered dielectric materials transparent in the LWIR. The GMR filters operating in the LWIR region are fabricated by depositing an amorphous germanium (Ge) film to form a zero-contrast (ZC) waveguide-grating (WGG) on a polished zinc selenide (ZnSe) substrate. In general, the backside of a ZnSe substrate with refractive index 2.41 is uncoated causing a 17% Fresnel-reflection loss in the light transmitted through the filter due to a large impedance mismatch at the ZnSe/air interface. Because we use such filters in the LWIR laser experiments for notch filtering, to improve the filter transmittance we used ZnSe substrates coated on one-side with broadband antireflection coating (ARC) covering the 7 to 12 μm spectral range to fabricate GMRFs with one-dimensional (1D) Ge ZC WGG. We employed high-spatial resolution e-beam lithography and reactive-ion etching nanofabrication techniques to achieve high-performance large-area (12 × 12 mm2) 1D notch filters with subwavelength periods. We characterized polarization dependent spectral performance of the prototype filters with both coherent and incoherent incident light using a tunable quantum cascade laser system that spans the 7 to 12 μm region, and a Fourier transform infrared spectrometer with collimated incident beam to achieve close to 15% improvement in the peak transmittance as well as significant reduction in coherent noise compared to our earlier results with GMRFs without ARC. Here, we present the filter design simulation and measurement results.