Showing papers on "Band-stop filter published in 2016"

An Efficient and Robust Hybrid Damper for $LCL$ - or $LLCL$ -Based Grid-Tied Inverter With Strong Grid-Side Harmonic Voltage Effect Rejection

Abstract: A high-order ( $LCL$ or $LLCL$ ) power filter with a small grid-side inductor is becoming more preferred for a grid-tied inverter due to less total inductance and reduced costs. In a microgrid, the background harmonic voltage (BHV) may distort the injected currents of the grid-tied inverters. In order to resist the effect of the BHV, a feedforward voltage compensator and a proportional resonant regulator with harmonic compensation are often adopted. However, they still have their own limitations, particularly when there are higher order BHVs at the point of common coupling and when the equivalent grid impedance widely varies due to the different numbers of grid-tied inverters in parallel. Thus, an extra damper should be inserted to keep the system stable. In this paper, the control bandwidth limitation of a multiloop control active damping (AD) method is analyzed and illustrated by the capacitor-current-feedback AD. Based on this, a single-loop current control with a hybrid damper is proposed for a single-phase $LCL$ - or $LLCL$ -filter-based grid-tied inverter. A step-by-step design of the controller method is also introduced in detail. Experiments on a 2-kW prototype fully demonstrate the strong robustness of the stability and the high harmonic rejection ability of the inverter using the proposed control method.

Five Approaches to Deal With Problem of DC Offset in Phase-Locked Loop Algorithms: Design Considerations and Performance Evaluations

Abstract: The presence of the dc component in the phase-locked loop (PLL) input results in fundamental frequency oscillations in the phase and frequency estimated by the PLL. The removal of these oscillations is a challenging task because of their low frequency. The aim of this paper is to provide a detailed analysis of several approaches that little work has been conducted on their application for addressing the problem of dc offset in the PLL algorithms. These approaches include using the dq -frame delayed signal cancellation (DSC) operator and the notch filter (NF) as the PLL in-loop filtering stages, and using the $\alpha \beta$ -frame DSC operator, the complex coefficient filter, and a cross-feedback network for blocking the dc offset before the PLL input. Design aspects of these methods are presented, some methods to enhance their performances are proposed, and their advantages and disadvantages are evaluated.

Practical Realization of Tunable Fractional Order Parallel Resonator and Fractional Order Filters

Abstract: This paper introduces a tunable fractional order parallel resonator (FOPR) whose resonating frequency can be tuned by the coefficient of a fractional order (FO) element (fractor). At the same time, its $Q$ - factor can be set very high (theoretically infinite) by varying its resistor. Using this FOPR circuit, two simple FO filters (FO bandpass and FO notch) are also developed. The paper includes detail sensitivity analyses of these circuits for various circuit parameters and describes how different design parameters of proposed FOPR and FO filters are chosen accordingly. Proposed FOPR and FO filters are simulated in MATLAB and realized in hardware. The hardware circuits are tested practically, and detail experimental results are provided. It is found that the experimental data are in good agreement with the simulation data. In hardware, the realized FOPR has achieved a $Q$ -factor up to 360, and the realized FO notch filter has ${Q}>10$ when its attenuation is more than 30 dB. Different practical aspects of filter tuning are also described in detail.

Enhanced Frequency-Locked Loop With a Comb Filter Under Adverse Grid Conditions

Abstract: To improve the performance of frequency-locked loops (FLLs) under distorted grid conditions, the technique of harmonic decoupling with multiple notch filters was usually employed to remove the harmonic components, which, although offering good filtering abilities, suffers from complexity, high computational burden, and deteriorated dynamics. To alleviate these problems, this letter proposes an enhanced adaptive notch-filter-based FLL, which incorporates a comb filter and improves the filtering abilities by introducing purely imaginary zeros to achieve notch peaks and harmonic cancellation. In comparison with the typical existing solutions of multiple notch-filter-based FLLs for distorted grid systems, the proposed FLL features simple structure and low computational load, and it can completely block the dc component, odd and even harmonics of the input grid voltage without sacrificing the FLL dynamics. Experimental results and comparisons are presented to validate the effectiveness of the proposed FLL.

Active Balancing Control of AMB-Rotor Systems Using a Phase-Shift Notch Filter Connected in Parallel Mode

Abstract: The vibration controllability is an important feature in the applications of active magnetic bearings (AMBs). This paper addresses the two key challenges on the active balancing control of AMB-rotor systems: presenting a parallel-mode scheme to enhance the notch performance at high speeds, and proposing a phase-shift notch filter to ensure stable operations over the entire speed ranges. First, both the frequency characteristics of the simplified notch filter in series and in parallel mode are discussed. The analysis shows that the closed-loop system with a parallel-mode notch filter has a deeper notch depth and faster convergence. The capacities of the synchronous current elimination are also improved at high speeds. Then, an improved phase-shift notch filter connected in parallel with the controller is modeled and analyzed. In order to understand the sensibility of the proposed solution to phase-shift variations, the stability analysis of the closed-loop system in the entire operational speed range is performed using the frequency response method. Experimental results on a high-speed centrifugal air blower test rig show the effectiveness of the proposed solution.

A New Second-Order All-Pass Filter in 130-nm CMOS

Abstract: This brief presents a novel wide-bandwidth second-order voltage-mode all-pass filter derived from a canonical single transistor bandpass filter. The core of the circuit consists of only one transistor, two resistors, and two energy storage elements. The operation of the proposed filter is validated experimentally. A filter implemented in an IBM 0.13- $\mu\mbox{m}$ CMOS was measured to have a 55-ps group delay across a 6-GHz bandwidth while consuming 18.5 mW from a 1.5-V supply. This work experimentally demonstrates a CMOS all-pass filter that operates at multigigahertz frequencies and achieves the highest delay-bandwidth product compared to previously published CMOS all-pass filters known to the authors.

Lossless and high-resolution RF photonic notch filter.

Abstract: A novel technique to create a lossless and tunable RF photonic bandstop filter with an ultra-high suppression is demonstrated using the combination of an overcoupled optical ring resonator and tailored stimulated Brillouin scattering gain. The filter bandwidth narrowing is counterintuitively synthesized from two broad optical resonance responses. Through a precise amplitude and phase tailoring in the optical domain, the RF filter achieves a minimum insertion loss ( 50 dB), and a tunable 3 dB bandwidth (60–220 MHz) simultaneously with wide frequency tunability (1–11 GHz). This ultra-low loss RF filter paves the way toward broadband advanced spectrum management with low loss, high selectivity, and improved signal-to-noise ratio.

Dual-band single-layer quarter ring frequency selective surface for Wi-Fi applications

Abstract: This study proposes a frequency selective surface (FSS) design to be used in Wi-Fi shielding applications as either a band reject or band pass dual-band single-layer filter. The proposed design consists of a combination of basic elements, that is, ring loops/slots, and is tuned at both 2.4 and 5.2 GHz Wi-Fi frequency bands. It has a relatively stable frequency response in the aforementioned Wi-Fi bands for incidence angles ranging from 0° to 45°. Both band reject and band pass designs are presented, along with their unit cell dimensions. Simulation and model validation through measurements demonstrate the performance of the proposed FSS design. Active variants are also proposed and briefly evaluated, in simulation environment, which should allow for applications where an on-off switching is desired at 2.4 and 5.2 GHz Wi-Fi bands.

Performance Improvement of Quasi-Type-1 PLL by using a Complex Notch Filter

Abstract: The synchronous reference frame phase-locked loop (SRF-PLL) is widely used for synchronization applications. However, it suffers from a poor performance under unbalanced and distorted grid conditions. To improve the filtering capability of SRF-PLL, moving average filter (MAF) is incorporated into its control loop at the cost of a slow transient response of PLL in recently published literature. To further improve their dynamic performance without compromising the disturbance rejection capability and stability, a novel PLL based on quasi-type-1 PLL structure is proposed in this paper. A complex notch filter is incorporated into the QT1-PLL to eliminate the fundamental frequency negative sequence voltage component. The window length of MAF in QT1-PLL is reduced. And MAF is responsible for rejecting the rest of harmonics. Parameter design guidelines are suggested to obtain the minimum settling time for both phase jump and frequency jump. The proposed PLL provides a faster transient response with higher stability margins. The effectiveness of the proposed PLL is confirmed through simulation and experimental results and comparison with advanced PLLs.

Narrowband interference suppression for GPS navigation using neural networks

Abstract: Since the Global Positioning System (GPS) satellites broadcast signals travel a long distance, the received signals are attenuated below the thermal noise level. Such weak signals are seriously subject to intentional or unintentional interferences from hostile or friendly noise sources. We propose an NN-based predictor for GPS anti-jamming applications. This new method exploits the adaptive notch filter as a cascade filter and the simple structure of Sigma-Pi neural network (Σ-ź NN). The Σ-ź NN can be trained quickly while avoiding the huge exponential computation for updating weights and thresholds in each layer, which allows easy hardware implementation. Simulation results show that its signal-to-noise ratio (SNR) improvement factor exceeds the factors of conventional multilayer perceptron, recurrent neural network, and other compound methods in single-tone and multi-tone continuous wave interference environments. Besides improving SNR, the anti-jamming performances are evaluated by computing root mean squared (RMS) prediction error and space vehicle (SV) observation number. The proposed algorithm provides the desired SV observation number, even for more than four vehicles, increases SNR improvement by about 46 % on average, and reduces RMS by about 27 % in average in both jamming mitigation processes.

An Intelligent Adaptive Filter for Elimination of Power Line Interference From High Resolution Electrocardiogram

Abstract: Electrocardiogram (ECG) is a non-invasive method to monitor electric activities inside the heart. The signals observed on the surface of human body have very low amplitude, and thus, ECG is highly vulnerable to noise. One of the most devastating noise is power line interference (PLI) and its harmonics, which are interlaced with ECG signal even if the ECG equipment is operated on battery. The problem is further complicated when the frequency of PLI is not static, making the conventional notch filter completely ineffective. High-resolution electrocardiogram (HRECG) is a specialized technique in which higher frequency components present in the ECG signal are observed; here, we need to eliminate the harmonics of PLI as well. In this paper, we propose an intelligent adaptive noise rejection filter, which tracks and eliminates PLI as well as its harmonics. The proposed system can estimate the frequency of PLI and tune the adaptive filter for precise elimination of PLI as well as its harmonics without the requirement of an auxiliary reference input. The proposed system is based on recursive state space model, inherited with less computational complexity and performs well in a non-stationary environment. The proposed system responds well to the ongoing variations in amplitude and frequency of PLI present in the HRECG signal as well as intracardiac signal. The proposed system does not require any reference signal for tracking the PLI and its harmonics, and it is capable to self-adjust its tracking frequency for highly precise filtration of first, third, and fifth harmonics of PLI.

Varactor-Tuned Compact Dual-Mode Tunable Filter With Constant Passband Characteristics

Abstract: This paper presents a second-order Chebyshev constant fractional bandwidth (CFBW) tunable bandpass filter with compact size and frequency invariant-passband characteristics using tunable external quality factors. The filter is designed using a stub loaded dual-mode resonator and two sets of varactors for tuning the center frequency and the return loss level. The design is featured with the net-type filter of a short grounded-stub so that the CFBW property can be assured. In addition to the conventional design, a pair of varactors is included at the ends of feeding transmission lines to keep the external quality factors constant while tuning. Within the tunable range of the varactors, the proposed filter is tunable from 1.7 to 2.1 GHz with a 5% CFBW. The measurement results show a 20-dB return loss and insertion loss below 2.9 dB over the entire tuning range.

Linear Variable Filter Based on a Gradient Grating Period Guided-Mode Resonance Filter

Abstract: In this letter, we fabricated and characterized a linear variable filter based on a guided-mode resonance filter (GMRF) with gradient grating periods. The GMRF was first fabricated through nanoreplica molding on a plastic substrate, which was followed by the deposition of a thin TiO2 film. The grating periods of the GMRF vary from 250 to 550 nm with a 2-nm increment in each period consisting of 100 cycles. The results show that a 6-mm-long GMRF has a filtering range of 506–915 nm.

Tunable megahertz bandwidth microwave photonic notch filter based on a silica microsphere cavity.

Abstract: We propose and experimentally demonstrate a tunable microwave photonic notch filter with a megahertz order bandwidth based on a silica microsphere cavity coupled by an optical microfiber The silica microsphere with a quality factor of hundreds of millions offers a full width at half-maximum bandwidth down to the order of megahertz in the transmission spectrum Due to the coupling flexibility between the microcavity and the optical microfiber, the bandwidth and suppression ratio can be tuned and optimized to get a rejection ratio beyond 30 dB The tunability of over 15 GHz is also achieved To the best of our knowledge, this single-stopband microwave photonic filter has the narrowest bandwidth filter that has ever been experimentally demonstrated This microwave photonic notch filter shows distinct advantages of high selectivity, compactness, flexibility, and low insertion loss

Tunable Single Bandpass Microwave Photonic Filter With an Improved Dynamic Range

Abstract: A tunable single bandpass microwave photonic filter (MPF) with an improved spurious free dynamic range (SFDR) using a dual-parallel Mach–Zehnder modulator (DP-MZM) and a phase-shifted fiber Bragg grating (PS-FBG) is proposed and experimentally demonstrated. The DP-MZM is employed to generate an equivalent phase-modulated (EPM) signal with an adjustable optical carrier to sideband ratio. The PS-FBG is used as an optical notch filter to remove one sideband of the EPM signal to convert the EPM signal to a single-sideband intensity-modulated signal. At the output of a photodetector, a microwave signal is detected. The entire operation is equivalent to a single passband MPF. The tunability is achieved by tuning the wavelength the optical carrier. The SFDR of the MPF is improved due to the gain enhancement by a partial suppression of the optical carrier. An experiment is performed. A single bandpass MPF with a passband width of 150 MHz and a frequency-tunable range of $\sim 5.5$ GHz with an improved SFDR by 11 dB is demonstrated.

Silicon-on-Insulator Dual-Ring Notch Filter for Optical Sideband Suppression and Spectral Characterization

Abstract: A new optical single-sideband (OSSB) modulation technique for wideband microwave photonic applications is presented. It is based on an integrated silicon-on-insulator dual-ring structure that exhibits weak electromagnetically induced transparency-like notch filter characteristics. Experimental results demonstrate optical sideband suppression of more than 29 dB for signals over 17–35 GHz with an achievable suppression as high as 40 dB. The OSSB structure is highly effective in suppressing dispersion penalties in microwave fiber transmission, with results showing a reduction in the electrical power ripple to less than ±1.5 dB for RF frequencies up to 30 GHz. The OSSB structure also enables new applications in optical vector network analyzers for optical component characterization, demonstrating the ability to measure both the amplitude and phase responses of a high-resolution ultranarrow filter based on stimulated Brillouin scattering, and also to perform wideband measurements over 10–30 GHz, offering an integrated approach for OSSB modulation that is compatible with silicon-based on-chip microwave photonic signal processing systems.

E-Band Plate-Laminated Waveguide Filters and Their Integration Into a Corporate-Feed Slot Array Antenna With Diffusion Bonding Technology

Abstract: This paper demonstrates plate-laminated waveguide filters in diffusion bonding technology for the first time and shows their uses in the integration with a corporate-feed slot array antenna for E-band ultrahigh capacity point-to-point communications. First, a single-cavity resonator model is studied and the measured high unloaded quality of 2121 at 79.07 GHz indicates its potential in the design of low-loss filters. Consequently, a sixth-order T-shaped cavity bandpass filter that comprises of ten cavity resonators is developed. It exhibits insertion losses of 3.4 and 3.3 dB at 78.5 GHz at two output ports, a 3-dB fractional bandwidth of 20.5%, as well as a small in-band amplitude/phase difference. Then, a fourth-order bandstop filter based on a band-rejection element is presented. It provides a high rejection level of 55 dB at 78.5 GHz and insertion losses of 0.44 and 0.28 dB at 73.5 and 83.5 GHz. The architectures of the proposed filters show attractive compatibility properties for integration. Finally, the proposed filters are fully integrated into a corporate-feed circuit of a $16 \times 16$ -element slot array antenna without an interconnection circuit. With the seamless integration, the proposed building blocks demonstrate well-preserved high efficiency (only a low loss is introduced by the filters) and unchanged radiation characteristic (low sidelobe level, low cross polarization, and high directivity) in the designed passband, as well as specified bandstop performance.

Multielement Resonant Converters With a Notch Filter on Secondary Side

Abstract: This letter proposes novel multielement resonant converters, which are improved topologies of the conventional LLC resonant converter, for voltage step-up applications. A notch filter is introduced into the secondary side of the LLC resonant converter. The voltage gain of the proposed resonant converters can be as low as zero with limited switching frequency range. Therefore, the start-up and short output circuit protection issues of the conventional LLC resonant converter can be solved with the proposed solutions. Furthermore, the circulating energy of the resonant tank can be reduced as well. In comparison with the multielement resonant converters with a notch filter on primary side, the proposed converter can help to reduce the conduction losses associated with the notch filter and provide higher voltage gain at the resonant frequency. The topologies and characteristics of the proposed resonant converters are analyzed. Experimental results are given to verify the effectiveness and the advantages of the proposed solutions.

Mobile terminal antenna system and mobile terminal

Abstract: The invention discloses a mobile terminal antenna system and a mobile terminal. The mobile terminal antenna system comprises a metal conductor, a (near field communication) NFC feed source, a diversity antenna feed source, a band stop filter circuit, a loading circuit and a reference ground that are in non-electrical connection with a mobile terminal metal shell; the NFC feed source is connected with the metal conductor through a first match circuit; the diversity antenna feed source is connected with the metal conductor through a second match circuit; one end of the band stop filter circuit is connected with the metal conductor while the other end of the band stop filter circuit is connected with the reference ground; one end of the loading circuit is connected with the metal conductor while the other end of the loading circuit is connected with the reference ground; an NFC antenna system is formed by the NFC feed source, the first match circuit, the metal conductor, the band stop filter circuit, the loading circuit and the reference ground; a diversity antenna system is formed by the diversity antenna feed source, the second matching circuit, the metal conductor, the band stop filter circuit and the reference ground; and the NFC antenna system and the diversity antenna system share the metal conductor to be used as the antenna radiator. According to the mobile terminal antenna system, the problem of relatively high cost in designing the NFC antenna independently is solved.

Compact Second-Order Bandstop Filter Based on Dual-Mode Complementary Split-Ring Resonator

Abstract: A compact dual-mode bandstop filter is presented in this letter. From an equivalent circuit viewpoint, a second-order response is obtained by designing a two-pole notch filter with inductive coupling. This equivalent circuit is then implemented by using a dual-mode complementary split-ring resonator. The proposed bandstop filter prototype has dimensions of $0.1\lambda_{g}\times 0.18\lambda_{g}$ , where $\lambda_{g}$ defines the guided-wave wavelength. An experimental validation at the center frequency $f_{0}$ of 2 GHz shows that the proposed filter can extend the harmonic-free upper passband up to $4.2f_{0}$ .

Low-noise tunable filter design by means of active components

Abstract: A low-noise tunable filter with high dynamic range and minimum power consumption is presented and addressed with circuit details. It is based on an active solution simulating an inductive behaviour that allows improving the filter quality factor without affecting the noise performance. The low-order bandpass filter is realised with minimum number of components and it is suitable to be integrated in integrated circuit or used in hybrid transceiver and modern reconfigurable radio systems. A prototype board with discrete components has been fabricated and tested with good results.

Frequency-Tunable Low- $Q$ Lumped-Element Resonator Bandstop Filter With High Attenuation

Abstract: This paper presents a new lumped-element absorptive bandstop filter topology. It exhibits infinite attenuation at the center frequency and no reflection regardless of the quality factor ( $Q$ -factor) of the resonators. The new topology exhibits the absorptive characteristic with extremely low- $Q$ resonators, whereas an absorptive bandstop filter topology in the literature cannot be used for such resonators. This superiority of the new filter topology is verified by comparing it with the topology in the literature. The filter designed using the new topology can change its center frequency by tuning only the capacitor values of the resonators. A 1.6:1 frequency tuning range maintaining the absorptive characteristic has been obtained by measurement.

Tunable reflecting terahertz filter based on chirped metamaterial structure

Abstract: Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping.

Signal interference RF photonic bandstop filter

Abstract: In the microwave domain, signal interference bandstop filters with high extinction and wide stopbands are achieved through destructive interference of two signals. Implementation of this filtering concept using RF photonics will lead to unique filters with high performance, enhanced tuning range and reconfigurability. Here we demonstrate an RF photonic signal interference filter, achieved through the combination of precise synthesis of stimulated Brillouin scattering (SBS) loss with advanced phase and amplitude tailoring of RF modulation sidebands. We achieve a square-shaped, 20-dB extinction RF photonic filter over a tunable bandwidth of up to 1 GHz with a central frequency tuning range of 16 GHz using a low SBS loss of ~3 dB. Wideband destructive interference in this novel filter leads to the decoupling of the filter suppression from its bandwidth and shape factor. This allows the creation of a filter with all-optimized qualities.

Investigation of New Microstrip Bandpass Filter Based on Patch Resonator with Geometrical Fractal Slot

Abstract: A compact dual-mode microstrip bandpass filter using geometrical slot is presented in this paper. The adopted geometrical slot is based on first iteration of Cantor square fractal curve. This filter has the benefits of possessing narrower and sharper frequency responses as compared to microstrip filters that use single mode resonators and traditional dual-mode square patch resonators. The filter has been modeled and demonstrated by Microwave Office EM simulator designed at a resonant frequency of 2 GHz using a substrate of er = 10.8 and thickness of h = 1.27 mm. The output simulated results of the proposed filter exhibit 22 dB return loss, 0.1678 dB insertion loss and 12 MHz bandwidth in the passband region. In addition to the narrow band gained, miniaturization properties as well as weakened spurious frequency responses and blocked second harmonic frequency in out of band regions have been acquired. Filter parameters including insertion loss, return loss, bandwidth, coupling coefficient and external quality factor have been compared with different values of perturbation dimension (d). Also, a full comparative study of this filter as compared with traditional square patch filter has been considered.

Analog filters design in VLC analog front-end receiver for reducing indoor ambient light noise

Abstract: Visible Light Communication (VLC) technology in indoor implementation is challenged by ambient light and other lighting noise, such as fluorescent lamp and bulb. The ambient light could create a DC offset or signal with specific frequency range. Thus, we propose analog filters design in the VLC Analog Front-End (AFE) receiver that can eliminate the ambient light noise. The proposed design uses DC offset removal, incorporated with automatic and manual adjustment mode. In automatic mode, we design the analog filter using High Pass Filter (HPF) which have fc = 10Hz; meanwhile, in manual mode we design a reference circuit using potentiometer and differential amplifier for direct current blocking. For reducing signal interference from lamp flickering, the proposed design uses Band Stop Filter (BSF) which has fc = 100Hz. The experimental results, both simulation and realtime, show that our proposed design can reduce signal interference and ambient light. We also test the design using PWM and BPSK modulation to evaluate Bit Error Rate (BER) performance.