Showing papers on "Band-stop filter published in 2020"
••
TL;DR: A synchronous vibration control method with a two-stage notch filter for the magnetically suspended rotor system with strong gyroscopic effects and results demonstrate that the stability can be guaranteed by adjusting the phase shift angle of the notch filter over the entire speed range.
Abstract: The vibration suppression in the presence of gyroscopic effects is an important issue for safe operations in magnetic bearing levitated varying speed rotor system. This paper proposes a synchronous vibration control method with a two-stage notch filter for the magnetically suspended rotor system with strong gyroscopic effects. First, the dynamics of the magnetically suspended rotor system with synchronous vibrations in the rotational motion is modeled. Then the proposed two-stage notch filter is designed and the solution of the two-stage switching point is derived to distinguish low speed and high speed. Stability analysis is also presented in the low-speed region and the high-speed region, respectively. Finally, simulation results demonstrate that the stability can be guaranteed by adjusting the phase shift angle of the notch filter over the entire speed range. Further experimental results confirm the effectiveness of the proposed suppression method.
40 citations
••
TL;DR: In this brief, a class of microstrip bandpass filters (BPFs) with quasi-reflectionless behavior on both input and output ports is presented and two-cell and three-cell two-port reflectionless BPFs are fabricated and tested to verify the design concept.
Abstract: In this brief, a class of microstrip bandpass filters (BPFs) with quasi-reflectionless behavior on both input and output ports is presented. A single-port reflectionless BPF is proposed by shunt connecting one bandstop filter cell namely one-cell. This one-cell single-port reflectionless BPF is made up of a high impedance transmission line as a series band-pass filter section and a shunt-connected band-stop section with resistively terminated. In the operation passband, the bandpass filter section is used to transmit spectral energy, while the bandstop section is regarded as an open circuit. Besides, the out-of-band energy is absorbed by resistively component in the bandstop filter section. In order to achieve better out-of-band reflectionless characteristic, a two-cell two-port reflectionless BPF is constructed by shunt connecting two cells at input/output ports and one series bandpass filter section in the center. In addition, a three-cell reflectionless BPF is designed to further verify the improvement of out-of-band performance. Finally, two-cell and three-cell two-port reflectionless BPFs are fabricated and tested to verify the design concept. The measured results of these two reflectionless BPFs are in good agreement with the simulation ones.
33 citations
••
TL;DR: It is shown that the voltage control-loop bandwidth is limited to be below twice the line frequency to avoid instability and the modified notch filter and a modified resonant regulator are proposed, allowing to remove the constraint on the voltage loop bandwidth.
Abstract: Droop-controlled distributed energy resource converters in dc microgrids usually show low output impedances. When coupled with ac systems, second-order harmonics typically appear on the dc-bus voltage, causing significant harmonic currents at the converters resource side. In this paper, we show how to reduce such undesired currents by means of notch filters and resonant regulators included in the converters control loops. The main characteristics of these techniques in terms of harmonic attenuation and stability are systematically investigated. In particular, it is shown that the voltage control-loop bandwidth is limited to be below twice the line frequency to avoid instability. Then, a modified notch filter and a modified resonant regulator are proposed, allowing to remove the constraint on the voltage loop bandwidth. The resulting methods (i.e., the notch filter, the resonant regulator, and their corresponding modified versions) are evaluated in terms of output impedance and stability. Experimental results from a dc microgrid prototype composed of three dc–dc converters and one dc–ac converter, all with a rated power of $\text{5 kW}$ , are reported.
33 citations
••
TL;DR: In this paper, a novel graphene-on-insulator (GOI) band-stop filter in the mid-infrared region is presented, which is an excellent device to be used in an ultra-fast active graphene-based plasmonic systems for THz applications.
Abstract: This paper presents a novel graphene-on-insulator (GOI) band-stop filter in the mid-infrared region. The finite-difference time-domain method is used to model our GOI basic and advanced filters and calculate their transmission spectra for different graphene layers at every gate-source voltage. The numerical results reveal the resonance wavelength, modulation depth, and bandwidth of the advanced filter can be tuned in the range of 11.5 to 30 µm, − 57 to − 60 dB, and 2 to 4 µm, respectively. These results are obtained by variation of the physical parameters, such as the number of overlapped filters, the number of graphene layers, and the applied chemical potential. Our results indicate that the proposed advanced band-stop filter is an excellent device to be used in an ultra-fast active graphene-based plasmonic systems for THz applications.
29 citations
••
TL;DR: A new method for obtaining the total harmonic distortion (THD) using few math operations, a low-pass filter (LPF), and a grid monitoring system able to provide the fundamental and harmonics components of the grid voltage is proposed.
Abstract: This article proposes a new method for obtaining the total harmonic distortion (THD) using few math operations, a low-pass filter (LPF), and a grid monitoring system able to provide the fundamental and harmonics components of the grid voltage. The method is particularly developed by using the second-order generalized integrator (SOGI) error signal notch filter transfer function characteristics of a standard SOGI-FLL monitoring system. The method is accurate and has a small computational burden, so it is suitable for the online assessment of the grid voltage or current THD and can easily be implemented into a digital signal processor. The accuracy and transient response of the system have been analyzed, showing that they can easily be determined by the tuning of the SOGI filter and the LPF. The method also shows to be robust to grid perturbations, such us voltage sags, or swells, and frequency step changes. Simulations and experimental results are provided to validate the proposed THD method. Moreover, comparison with a fast Fourier transform (FFT)-based THD is also presented, which shows that the proposed THD method results to be faster, more accurate, and simpler than the FFT-based one.
22 citations
••
TL;DR: Three types of infinite impulse response filter i.e. Butterworth, Chebyshev type I and elliptic low pass, high pass, band pass and band stop filter have been designed in this paper using MATLAB Software.
Abstract: In the field of digital signal processing, the function of a filter is to remove unwanted parts of the signal such as random noise that is also undesirable. To remove noise from the speech signal transmission or to extract useful parts of the signal such as the components lying within a certain frequency range, filters are necessary. Filters are broadly used in signal processing and communication systems in applications such as channel equalization, noise reduction, radar, audio processing, speech signal processing, video processing, biomedical signal processing that is noisy ECG, EEG, EMG signal filtering, electrical circuit analysis and analysis of economic and financial data. In this paper, three types of infinite impulse response filter i.e. Butterworth, Chebyshev type I and Elliptical filter have been discussed theoretically and experimentally. Butterworth, Chebyshev type I and elliptic low pass, high pass, band pass and band stop filter have been designed in this paper using MATLAB Software. The impulse responses, magnitude responses, phase responses of Butterworth, Chebyshev type I and Elliptical filter for filtering the speech signal have been observed in this paper. Analyzing the Speech signal, its sampling rate and spectrum response have also been found.
22 citations
••
TL;DR: Simulation and experimental results show that the method can effectively eliminate the synchronous current in a widely operating speed range and improve the stability of the system.
Abstract: In order to suppress the influence of the synchronous vibration generated by the unbalance of magnetically suspended control moment gyro on the attitude control accuracy and stability of the satellite platform, this article first introduces the working principle of the magnetically suspended high-speed rotor system, and also establishes the dynamic model of the magnetically suspended rotor with unbalance mass. At the same time, the main sources of unbalance vibration are also analyzed. Finally, an improved adaptive notch filter based on double input is designed. The filter takes the rotor radial X, Y two-channel displacement sensor signals as inputs, and uses the characteristics orthogonal to each other to simultaneously enter the system. The rotor can be automatically balanced by adjusting the convergence factor and the compensation angle to adaptively suppress the synchronous current in a widely operating speed range. Simulation and experimental results show that the method can effectively eliminate the synchronous current in a widely operating speed range and improve the stability of the system. This research on the microvibration of the rotor is of great significance and application value.
21 citations
••
TL;DR: In this paper, a mushroom-type surface-based waveguide slot filtering antenna is proposed, which has nearly the same radiation characteristic while realizes an additional filter selectivity with almost no extra volume occupancy.
Abstract: A mushroom-type surface-based waveguide slot filtering antenna is proposed herein. First, using a mushroom-type surface replacing the conventional metal plane in the bottom of a rectangular waveguide, a novel filtering waveguide is achieved. This filtering waveguide functions as a bandstop filter when the surface performs as a perfect magnetic conductor. Then, a filtering waveguide slot antenna is obtained by cutting radiating slots on the top of the filtering waveguide. Compared with a traditional waveguide slot antenna, the proposed antenna has nearly the same radiation characteristic while realizes an additional filter selectivity with almost no extra volume occupancy. A prototype is demonstrated in Ku -band with operating in 12.25–12.75 GHz and rejecting over 14.0–14.5 GHz, which can be a candidate for receiving antenna of satellite communication. The measured results agree well with the designed ones, showing a suppression level stronger than 40 dB in the rejecting band.
19 citations
••
TL;DR: An improved non dominated sorting genetic algorithm II (NSGA-II) based on objective importance vector based on LaTeX notation based on an individual selection strategy is developed to obtain the optimized solution for a task which has multiple objectives with different importance.
Abstract: This paper develops an improved non dominated sorting genetic algorithm II (NSGA-II) based on objective importance vector γ, abbreviated as γ-NSGA-II. Different importance levels for the multiple objectives are incorporated in the objective importance vector, which is applied to determine the individual selection of sorting individuals in the critical layer. And such an individual selection strategy is developed to the NSGA-II algorithm in order to obtain the optimized solution for a task which has multiple objectives with different importance. The differences between the γ-NSGA-II algorithm and the traditional NSGA-II algorithm are discussed in detail. A notch filter is designed for the conducted emission suppression of a transformer rectifier unit (TRU) used in C919 flight testing, and then the parameters optimization design of a notch filter is discussed and conducted based on the γ-NSGA-II algorithm. The non-linear relationship between the filter's parameters and the suppression effect of the conducted emission is also discussed with the help of an electromagnetic compatibility (EMC) evaluation model based on a back propagation (BP) neural network. The experimental results show that the optimized design of the notch filter is effective and the improved γ-NSGA-II algorithm be more specific.
19 citations
••
TL;DR: In this article, high-order quasi-reflectionless bandpass filters with improved passband flatness and good impedance matching both in-band and out-of-band are proposed.
Abstract: High-order quasi-reflectionless bandpass filters with improved passband flatness and good impedance matching both in-band and out-of-band are proposed in this work. The proposed design consists of conventional coupled-lines bandpass sections loaded with the presented absorptive stubs at the input and output. Analysis shows that the absorptive stub is equivalent to a 2-pole bandstop filter. Compared to the prior art, the higher-order nature of the presented absorptive stub enables a flatter passband and better out-of-band rejection. The overall filter stopband attenuation can be readily improved by increasing the number of coupled-lines sections without altering the passband responses. Furthermore, cross-coupling between the two absorptive stubs can be used to improve the out-of-band rejection by introducing two transmission zeros without affecting the absorption characteristics. The proposed design concepts are experimentally validated by the design and fabrication of a set of 2.4-GHz 1-, 2-, and 3-pole microstrip quasi-reflectionless bandpass filters. Measured frequency responses of these filters closely match those of the simulation.
17 citations
••
TL;DR: In this paper, a microwave photonic system for determining the angle of arrival (AOA) of a continuous wave (CW) or pulsed microwave signal is presented based on a dual-polarisation dual-drive Mach-Zehnder modulator followed by an optical notch filter for carrier suppression.
Abstract: A new microwave photonic system for determining the angle of arrival (AOA) of a continuous wave (CW) or pulsed microwave signal is presented. It is based on a dual-polarisation dual-drive Mach–Zehnder modulator followed by an optical notch filter for carrier suppression. Two orthogonal-polarised carrier- suppressed optical signals are detected by low-frequency photodetectors that generate two DC voltages. An incoming microwave signal AOA can be obtained from the ratio of the two DC voltages, without the need of a calibration procedure or measuring the incoming microwave signal power level, which are required in previously reported structures. The proposal system can be incorporated with a conventional radar receiver front end consists of mixers and filters, for measuring the AOA of a pulsed microwave signal. Experimental results demonstrate 0°–63° AOA measurement with less than 2° errors for an input microwave signal having different frequencies and different power levels.
••
TL;DR: In this paper, a second-order Butterworth reflectionless bandstop filter centered at 2 GHz with fractional bandwidth of 8% has been designed, fabricated, and measured, and the measurement shows that the return losses ( $S 11}$ and $S 22}$ ) are overall larger than 10 dB from DC to $3f 0}$.
Abstract: In this letter, we present a systematic design method for a reflectionless bandstop filter using distributed-element resonators. One unique feature of the presented filter structure is that it is capable of producing a broadband impedance matching at both ports with a flat passband. For verifying the design approach, a second-order Butterworth reflectionless bandstop filter centered at 2 GHz with fractional bandwidth of 8% has been designed, fabricated, and measured. The measurement shows that the return losses ( $S_{11}$ and $S_{22}$ ) are overall larger than 10 dB from DC to $3f_{0}$ .
••
TL;DR: In this article, a varactor-based tunable bandstop filter (BSF) using distributed coupling microstrip resonators with the capacitive terminal is presented, which is a floating pad connected to the cathode of the varactor, serving not only as a bias pad for the control voltage but also as an intrinsic capacitive path to ground.
Abstract: This letter presents a varactor-based tunable bandstop filter (BSF) using distributed coupling microstrip resonators with the capacitive terminal. Each distributed coupling microstrip resonator consists of a coupling microstrip line, a varactor, and a capacitive terminal which is a floating pad connected to the cathode of the varactor. The capacitive terminal serves not only as a bias pad for the control voltage but also as an intrinsic capacitive path to ground. Compared to the conventional inductive terminal with the metallized via, the capacitive terminal can be beneficial to realize much higher frequency responses by taking advantage of the capacitance to ground from the floating pad. High stopband suppression level is achieved by cascading multiple distributed coupling microstrip resonators. For demonstration, a tunable BSF prototype with the frequency tuning range of 11.3–16.5 GHz (37%) is designed and fabricated. Measured and simulated results agree well and validate the design principle.
••
TL;DR: In this paper, a wideband reflectionless filtering 90° coupler with a wide stopband is proposed, which consists of two parallel connected channels, the main channel is implemented by the stacked cross coupled-lines, and the stepped-impedance microstrip line, loaded cross-stub, and resistor are used to construct the absorptive bandstop filter in the auxiliary channel, which absorbs the reflected signal from the filtering coupler.
Abstract: In this letter, a wideband reflectionless filtering 90° coupler with a wide stopband is proposed, which consists of two parallel connected channels. The main channel is implemented by the stacked cross coupled-lines, which can not only introduce a filtering 90° coupler with a compact size but also achieve a wide-stopband response. Meanwhile, the stepped-impedance microstrip line, loaded cross-stub, and resistor are used to construct the absorptive bandstop filter in the auxiliary channel, which absorbs the reflected signal from the filtering coupler to obtain the wideband reflectionless operation. To verify the aforementioned mechanism, a wideband reflectionless filtering 90° coupler operating at 1.47–2.53 GHz is implemented and fabricated. The measured results demonstrate that the proposed coupler has the merits of low passband insertion loss, low amplitude and phase imbalances, wide stopband, and wide reflectionless range.
••
TL;DR: With the proposed NF-CDFS plus FLVDFS control strategy, low input harmonic current and low output voltage ripple are achieved and more than about 85% of dc-link capacitance is reduced compared to conventional methods.
Abstract: A single-phase isolated ac–dc–dc converter with low total harmonic distortion and high power factor usually suffers from a significant ripple power at double line frequency. The inherent ripple power brings a significant low-frequency voltage ripple on the dc-link capacitor. To reduce the voltage ripple, bulky electrolytic capacitors and hardware low-pass filter are widely adopted. However, the converter becomes bulky because of large capacitor. In order to reduce the dc-link capacitance, optimal control strategies are proposed for ac–dc and dc–dc converter, respectively, in this article. First, the notch filter with current disturbance feedforward strategy (NF-CDFS) are proposed to minimize input harmonic current of ac–dc converter. Second, the feedback linearization with voltage disturbance feedforward strategy (FLVDFS) is designed to suppress the output voltage ripple of dc–dc converter based on generalized state space averaging model. With the proposed NF-CDFS plus FLVDFS control strategy, low input harmonic current and low output voltage ripple are achieved. In addition, more than about 85% of dc-link capacitance is reduced compared to conventional methods.
••
TL;DR: A magnitude-reshaping strategy to increase the output impedance in all harmonic-frequency-bands, thereby suppressing the harmonics is proposed and the effectiveness of proposed control strategy is validated by experiment results.
Abstract: Driven by inertial demand from the grid, the virtual synchronous generators (VSGs) are widely utilized in distributed generation systems. However, harmonic sources in the distributed generation systems with high grid impedance will cause grid voltage distortion. Distorted voltage greatly affects the power quality of VSG. Moreover, it is difficult to suppress different types of harmonics (such as sub-synchronous harmonics and non-integer high-frequency harmonics) by one conventional solution in VSG-based grid-connected system. To solve the problem, this paper proposes a magnitude-reshaping strategy to increase the output impedance in all harmonic-frequency-bands, thereby suppressing the harmonics. The magnitude-reshaping strategy consists of a notch filter and harmonic regulator. The notch filter extracts harmonic components of grid current, whereas the harmonic regulator increases the equivalent harmonic impedance. The equivalent harmonic circuit of reshaped VSG-based system is equivalent to open circuit. Therefore, the power quality of grid-connected current can be guaranteed. To analyze the performance of the magnitude-reshaping method, frequency-coupling impedance model of VSG is established. Furthermore, Comparing with the conventional harmonic suppression methods, the frequency response characteristics of the equivalent harmonic impedance are analyzed. Finally, the effectiveness of proposed control strategy is validated by experiment results.
••
TL;DR: It is demonstrated that the optimal AOTF design for single-frequency operation as a narrow-band spatial frequency filter is obtained at acoustic propagation angle of 5.6° relative to the [110] axis.
Abstract: Optimization of a wide-angle paratellurite acousto-optic tunable filter (AOTF) is performed for applications in laser beam shaping systems. The AOTF configuration with annular transfer function is analyzed. It is demonstrated that the optimal AOTF design for single-frequency operation as a narrow-band spatial frequency filter is obtained at acoustic propagation angle of 5.6° relative to the [110] axis. The optimal design for maximization of AOTF resolution in multifrequency laser beam shaping operation mode is obtained at acoustic propagation angle of 13.8°.
••
TL;DR: In this article, the authors present a rigorous design method for a symmetric reflectionless bandstop filter with coupled lines, and verify the design equations and the filter structure using a third-order Butterworth filter example.
Abstract: In this article, we present a rigorous design method for a symmetric reflectionless bandstop filter with coupled lines. Analytic design equations and the detailed procedure for formulating narrowband reflectionless bandstop filter structures are given in this article. The presented design theory allows us to design a symmetric reflectionless bandstop filter with a predefined transmission response and an excellent impedance matching performance over a wide frequency range. Using the circuit formulation process with the closed-form design equations presented in this article, all circuit element values and the detailed physical dimensions of a filter can be obtained in a straightforward manner. In order to verify the design equations and the filter structure, a third-order Butterworth filter example has been designed, fabricated, and measured. Overall, the return loss was measured to be larger than 10 dB over a wide frequency range from dc to $4f_{0}$ ( $f_{0}$ : center frequency).
••
TL;DR: In this paper, a low profile and miniaturized ultra wideband frequency selective surface (UWB FSS) structure is proposed for shielding applications, which provides wide bandwidth for shielding.
Abstract: This article proposes a low profile and miniaturized ultra-wideband frequency selective surface (UWB FSS) structure which provides wide bandwidth for shielding applications. A single layer FSS constructed with a simple square loop and cross dipole structure provides bandstop filter response covering high frequencies from 4.85 GHz to 17.23 GHz at 10 dB insertion loss, with a bandwidth of 12.38 GHz and a fractional bandwidth exceeding 112%. The proposed FSS structure also provides excellent polarization independent behavior for angles of incidence up to 30°. A prototype of the proposed FSS is fabricated and the measurement result is compared with the simulation results, and both are in good agreement.
••
TL;DR: The nonlinear time-varying (NTV) model of the SRF-PLL system is proposed and is used for the large-signal stability assessment and an adaptive tuning method is designed to improve its transient performance during and after the variation.
Abstract: Synchronous reference frame phase-locked loops (SRF-PLLs) are widely used in different technologies, such as wind turbines, electric vehicles, more electric aircraft, and motor drives, to estimate system’s variables. The SRF-PLL is an adaptive notch filter that is used to estimate a sinusoidal signal’s amplitude, phase angle, and frequency. However, when the input signal is subjected to a considerable variation or includes a significant noise, its stability and performance become challenging. In this paper, the stability of the SRF-PLL for substantial changes in the input signal’s variables are investigated. To do so, the nonlinear time-varying (NTV) model of the system is proposed and is used for the large-signal stability assessment. Then, an adaptive tuning method, based on the proposed NTV model, is designed to improve its transient performance during and after the variation. Simulation and experimental results are used to validate the proposed method.
••
01 Aug 2020TL;DR: In this article, a compact quad-band notch filter (QBNF) based on the extended composite right and left-handed transmission line (E-CRLH TL) has been presented.
Abstract: A new compact quad-band notch filter (QBNF) based on the extended composite right and left-handed transmission line (E-CRLH TL) has been presented. As known, E-CRLH TL behaves like a quad-band structure. A microstrip TL which is loaded with an open-ended ECRLH TL is presented as a QBNF. Four unwanted frequencies were used in a dual-band LTE receiver as four notch frequencies which must be eliminated (0.9 GHz, 1.3 GHz, 2.55 GHz, and 3.35 GHz). Also, this QBNF can be applied to simultaneous wireless power and data transfer (SWPDT) system to isolate the wireless power circuit from the data communication circuit. A design technique for the proposed QBNF is presented and its performance is validated using full-wave simulation results and theoretical analysis. The main advantage of this design is an overall rejection greater than 20dB at selected unwanted frequencies. Good agreements between the fullwave simulation and equivalent circuit model results have been achieved which verified the effectiveness of the proposed circuit model. The proposed QBNF is designed on an FR-4 substrate and the dimension of the proposed QBNF is 20 × 22 mm.
••
TL;DR: The proposed inertia enhancement method for inverter interfaced SPV sources is proposed, which adjusts only the PLL parameters with a notch filter (NF) in the SRF controller, and has been compared with two state-of-art methods to prove the superiority of the proposed approach.
Abstract: Synchronous reference frame (SRF) control strategy for solar photovoltaic (SPV) sources is widely used to deliver maximum power to the grid. However, poor inertia support just after a disturbance and improper phase angle tracking in presence of the harmonics and system unbalance are noticed when the conventional phase-locked loop (PLL) based SRF control structure is used. In this study, an inertia enhancement method for inverter interfaced SPV sources is proposed, which adjusts only the PLL parameters with a notch filter (NF) in the SRF controller. NF in PLL is used due to its disturbance rejection potential and accurate phase angle tracking, even during system unbalance. The dynamic equation of pseudo induced voltage (PIV) vector with respect to the point of common coupling is derived. The kinematic equation of the PIV angle vector correlates inertia contribution and inverter terminal voltage. The impact of the change in PLL parameters on inertia enhancement is analyzed by validating the proposed technique on a test system in the real-time digital simulator. The frequency response by the proposed method has been compared with two state-of-art methods to prove the superiority of the proposed approach in enhancing the inertia of the SPV source in a microgrid.
••
TL;DR: Finite-difference time-domain simulations show that the underlying mechanisms responsible for the resonance blueshift and linewidth broadening can be attributed to the photoinduced change in dielectric properties of the substrate.
Abstract: We demonstrate ultrafast tuning of a plasmonic spectral filter at terahertz (THz) frequencies. The device is made of periodically spaced gold crosses deposited on the surface of an undoped silicon wafer in which transient free carriers can be optically injected with a femtosecond resonant pulse. We demonstrate the concept by measuring the transmission spectrum of a notch filter using time-domain THz spectroscopy. Proper synchronization of the THz probe and visible excitation pulses leads to an enhanced transmission at the resonance by more than two orders of magnitude. Finite-difference time-domain simulations, which are in agreement with the experimental results, show that the underlying mechanisms responsible for the resonance blueshift and linewidth broadening can be attributed to the photoinduced change in dielectric properties of the substrate. This is supported by the numerically simulated field distribution and reflection/transmission coefficients. The device can be used in future pulse shaping and ultrafast switching experiments.
••
17 Jul 2020TL;DR: In this paper, a mutual coupling suppression technique using an open stub meandered (OSM) bandstop filter (BSF) design for MIMO applications was introduced, which is optimized and implemented on the ground plane side of a two-element patch array.
Abstract: Multiple-input and multiple-output (MIMO) systems utilize multiple antenna elements to improve channel capacity and achieve higher data rates. The successful implementation of MIMO systems requires low mutual coupling between antenna elements to reduce the envelope correlation coefficient (ECC) at the operating frequency. In this paper, we introduce a mutual coupling suppression technique using an open stub meandered (OSM) bandstop filter (BSF) design for MIMO applications. The OSM-BSF is optimized and implemented on the ground plane side of a two-element patch array. The designed filter provides high isolation of 60 dB at 2.4 GHz across a 30% bandwidth. A parametric study of antenna element spacing was carried out, showing at least 40 dB of mutual coupling suppression in the antenna array, irrespective of the antenna element spacing. A two-element antenna array prototype with OSM-BSF was fabricated and tested. Measurements showed that ≥ 57 dB isolation was achieved using OSM-BSF. Besides, the fabricated array provides a low ECC of 0.0093 at 2.42 GHz, while maintaining edge-to-edge spacing as little as $0.19\lambda _{0}$ .
••
01 Feb 2020TL;DR: A passive negative-transresistance (NTR) property of LPTV switched-capacitor circuits is reported to realize an N-path notch filter enhanced with reciprocal negative transresistance with ideally infinite depth regardless of the number of paths and a non-magnetic non-reciprocal widely tunable N- path inductorless isolator with low loss and infinite isolation in the reverse direction.
Abstract: Negative-resistance circuits are used for a variety of functions, including the realization of oscillators and loss compensation. Active negative-resistance circuits, such as cross-coupled gm cells, can provide power gain but, when used for loss compensation, must be carefully designed to avoid oscillation. In addition, they present noise, linearity, and power-consumption challenges. In the recent past, linear periodically-time-varying (LPTV) circuits, typically implemented using switched capacitors, have shown unexpected yet highly desirable properties, including tunable high-Q bandpass/bandstop filtering [1] and non-magnetic nonreciprocity [2]. Here, we report a passive negative-transresistance (NTR) property of LPTV switched-capacitor circuits. This property is utilized in this work to realize (1) an N-path notch filter enhanced with reciprocal negative transresistance with ideally infinite depth regardless of the number of paths and (2) a non-magnetic non-reciprocal widely tunable N-path inductorless isolator with low loss and infinite isolation in the reverse direction.
••
TL;DR: In this article, the capability of the coupling matrix-based band stop filter in mutual coupling reduction between the MIMO arrays is presented, and a microstrip band-stop filter with 3 GHz center frequency is designed using coupling matrix method.
Abstract: The capability of the coupling matrix-based band stop filter in mutual coupling reduction between the MIMO arrays is presented. Initially, a microstrip band-stop filter with 3 GHz center frequency is designed using coupling matrix method. This filter structure is then placed between 2×1 radiating patches separated by 0.22 λ in a reference MIMO antenna designed for 3 GHz WiMAX applications. Both array antennas with/without band stop filters are fabricated and the scattering parameters are obtained separately and plotted comparatively. A good agreement is achieved between measurement and simulation results, and about 28 dB isolation is observed at operating frequency after the proposed filter application. Besides, the Envelope Correlation Coefficient (ECC) is computed and surface current distributions are simulated for both cases. It is observed that ECC has dropped to almost zero and the surface currents induced in the second patch due to the first patch excitation are extinguished with the implementation of the proposed isolation wall. Finally, to clarify the advantages of our approach, a few related studies are summarized in a comparative table.
••
TL;DR: In this paper, a dual-layer dual-band rejection filter based on Spoof Surface Plasmon Polaritons (SSPPs) is proposed. But the proposed filter is not suitable for low frequency bands.
Abstract: This paper presents a novel single-layer dual band-rejection-filter based on Spoof Surface Plasmon Polaritons (SSPPs). The filter consists of an SSPP-based transmission line, as well as six coupled circular ring resonators (CCRRs) etched among ground planes of the center corrugated strip. These resonators are excited by electric-field of the SSPP structure. The added ground on both sides of the strip yields tighter electromagnetic fields and improves the filter performance at lower frequencies. By removing flaring ground in comparison to prevalent SSPP-based constructions, the total size of the filter is significantly decreased, and mode conversion efficiency at the transition from co-planar waveguide (CPW) to the SSPP line is increased. The proposed filter possesses tunable rejection bandwidth, wide stop bands, and a variety of different parameters to adjust the forbidden bands and the filter's cut-off frequency. To demonstrate the filter tunability, the effect of different elements like number (n), width (WR), radius (RR) of CCRRs, and their distance to the SSPP line (yR) are surveyed. Two forbidden bands, located in the X and K bands, are 8.6-11.2 GHz and 20-21.8 GHz. As the proof-of-concept, the proposed filter was fabricated, and a good agreement between the simulation and experiment results was achieved.
••
TL;DR: A chip-scale plasmonic band-stop filter based on periodic staggered double-side trapezoidal resonators (PSDSTR) is proposed and investigated theoretically and numerically in this article.
••
TL;DR: The value of the proposed frequency correction algorithm in synthetic inertia (SI) control is shown and it shows that for a test power system the corrector algorithm is critical in preventing the SI controller from erroneously injecting power that can exacerbate system faults.
Abstract: This paper presents three frequency estimation algorithms, one based on extended Kalman filtering, another on quadrature phase-locked loop and an adaptive notch filter. The paper proposes using some internal signals of these algorithms as an inverse reliability metric to determine the quality of the frequency estimate. The paper presents an algorithm to correct frequency estimates using these inverse reliability metrics. The algorithm is tested with signals with phase jumps and severe distortions. Accurate frequency estimates are of particular importance in real-time control applications. This paper shows the value of the proposed frequency correction algorithm in synthetic inertia (SI) control. It shows that for a test power system the corrector algorithm is critical in preventing the SI controller from erroneously injecting power that can exacerbate system faults.
••
TL;DR: The methodology for the reconstitution of a given transfer function by means of Signal Flow Graphs (SFG) manipulation in canonical form is proposed leading to a fully differential g m -C biquad filter, whose value is comparable to that of a 7th order elliptic approach and some other 3rd order filters.
Abstract: A design strategy for the synthesis of high-selectivity/low-order analog filters in Complementary Metal-Oxide-Semiconductor (CMOS) technology for very high frequency (VHF) applications is presented. The methodology for the reconstitution of a given transfer function by means of Signal Flow Graphs (SFG) manipulation in canonical form is proposed leading to a fully differential g m -C biquad filter. As a practical example, the design of a notch filter intended to suppress interferers in the lower sideband (400 MHz) of the Medical Implant Communication Service (MICS), in single-poly, 6-metal layers; Mixed-Signal/RF 0.18 µm CMOS technology is realized. To compare the performance of the proposal with some other solution, the design of a 7th order elliptic notch filter based on Frequency Dependent Negative Resistors (FDNRs) was also accomplished. The attained simulation results prove that the proposal is competitive compared to the FDNR solution and some other state-of-the-art filters reported in the literature. The most salient features of the proposed notch biquad include: the selectivity, whose value is comparable to that of a 7th order elliptic approach and some other 3rd order filters; a high-frequency operation without resonators; linearity, with a +15 dBm I I P 3 ; a reduced form factor with a total occupied area of 0.004282 mm2 and mostly a low design complexity.