Showing papers on "Band-stop filter published in 2018"
Patent•
AT&T1
TL;DR: In this paper, an analog surface wave repeater pair includes a first launcher configured to transmit and receive first guided electromagnetic waves that propagate on an outer surface of a first segment of a transmission medium.
Abstract: In accordance with one or more embodiments, an analog surface wave repeater pair includes a first launcher configured to transmit and receive first guided electromagnetic waves that propagate on an outer surface of a first segment of a transmission medium. A second launcher is configured to transmit and receive second guided electromagnetic waves that propagate on an outer surface of a second segment of the transmission medium. A first transceiver includes a first notch filter is configured to attenuate signals in a fourth generation (4G) wireless frequency band from the first microwave signal generated by the first launcher in response to receiving the first guided electromagnetic waves. A second transceiver includes a second notch filter configured to attenuate signals in the fourth 4G wireless frequency band from a second microwave signal generated by the second launcher in response to receiving the second guided electromagnetic waves.
123 citations
TL;DR: Simulation as well as practical results prove the feasibility of FCS-MPC application in HAPF reactive power control and allow tracking fluctuations and abrupt changes in load reactive power.
Abstract: This paper applies finite control set model predictive control (FCS-MPC) for dynamic reactive power compensation using a hybrid active power filter (HAPF). The FCS-MPC uses a model based on LCL -filter equations to predict the system behavior and optimize the control action. In fact, the application of FCS-MPC in grid-connected converters with LCL -Filter is quite recent. This algorithm is a very promising control technique for power electronics converters and its use for reactive power control of hybrid filter has not been reported in the literature yet. This paper uses the FCS-MPC in a multivariable structure along with an adaptive notch filter to damp resonance. The main purpose is to improve the dynamic response of the HAPF. Simulation as well as practical results prove the feasibility of FCS-MPC application in HAPF reactive power control. The dynamic response of the equipment was significantly improved and represents the main contribution of this paper. As a result, the FCS-MPC allows tracking fluctuations and abrupt changes in load reactive power.
88 citations
TL;DR: In this paper, a detailed review on the topics involving the mathematical modeling and design of the main structures and strategies for damping in a grid-connected three-phase PV system based on LCL filter is presented.
Abstract: Distributed generation systems have been expanded considerably in recent years. These systems are generally based on power electronics converters, whose switching harmonics need to be reduced by means of passive filters. LCL filter is a solution that has been strongly employed. However, LCL filter presents a resonant frequency that needs to be damped. This work presents a detailed review on the topics involving the mathematical modeling and design of the main structures and strategies for damping in a grid-connected three-phase PV system based on LCL filter. Four techniques are analyzed: Series passive damping (SPD), capacitor current feedback based strategy (CCF), capacitor voltage feedback based strategy (CVF) and notch filter based method (NF). This study analyzes low frequency models, control design and operation in weak grid conditions. Finally, transfer functions of the harmonic rejection capability of each damping strategy are illustrated. This work finishes with a case study of a 10 kW inverter, which evaluates all issues previously approached.
85 citations
TL;DR: Experimental results reveal that the developed chip collects real-time ECG data efficiently, and the proposed ETPC algorithm achieves higher energy savings of 35.5% with a slightly larger packet loss ratio (PLR) as compared to conventional TPC (e.g., constant TPC, Gao's, and Xiao’s methods).
Abstract: Rapid progress and emerging trends in miniaturized medical devices have enabled the un-obtrusive monitoring of physiological signals and daily activities of everyone’s life in a prominent and pervasive manner. Due to the power-constrained nature of conventional wearable sensor devices during ubiquitous sensing (US), energy-efficiency has become one of the highly demanding and debatable issues in healthcare. This paper develops a single chip-based wearable wireless electrocardiogram (ECG) monitoring system by adopting analog front end (AFE) chip model ADS1292R from Texas Instruments. The developed chip collects real-time ECG data with two adopted channels for continuous monitoring of human heart activity. Then, these two channels and the AFE are built into a right leg drive right leg drive (RLD) driver circuit with lead-off detection and medical graded test signal. Human ECG data was collected at 60 beats per minute (BPM) to 120 BPM with 60 Hz noise and considered throughout the experimental set-up. Moreover, notch filter (cutoff frequency 60 Hz), high-pass filter (cutoff frequency 0.67 Hz), and low-pass filter (cutoff frequency 100 Hz) with cut-off frequencies of 60 Hz, 0.67 Hz, and 100 Hz, respectively, were designed with bilinear transformation for rectifying the power-line noise and artifacts while extracting real-time ECG signals. Finally, a transmission power control-based energy-efficient (ETPC) algorithm is proposed, implemented on the hardware and then compared with the several conventional TPC methods. Experimental results reveal that our developed chip collects real-time ECG data efficiently, and the proposed ETPC algorithm achieves higher energy savings of 35.5% with a slightly larger packet loss ratio (PLR) as compared to conventional TPC (e.g., constant TPC, Gao’s, and Xiao’s methods).
75 citations
TL;DR: A generalized design framework of FLLs based on the Popov adaptive theory is proposed and an enhanced FLL (referred to as EFLL) is recommended.
Abstract: Despite many intensive researches regarding frequency-locked loops (FLLs) in recent years, the basic problems of principles, models, and structures of FLL algorithms remained open. Conventional FLL comprises a notch filter and a frequency adaptive loop. The notch filter can be categorized into two types: real coefficient filter (RCF) and complex coefficient filter (CCF). However, the principles, models, and structures of RCF and CCF are generally explained by various theories, and thus, a unified understanding and further developments of FLLs are restricted. This paper proposes a generalized design framework of FLLs based on the Popov adaptive theory. Grounded on the proposed framework, three main contributions can be achieved: 1) the mathematical equivalence of RCF-based FLLs and CCF-based FLLs are revealed; 2) not only the wellknown FLLs (e.g., the DSOGI-FLL and the AVF-FLL) can be derived, but also the other FLLs with novel features can be generated, and thus, the existing case designs of FLLs are developed into a family of designs; 3) the performance differences in terms of stability and convergence speed of the FLLs are quantitatively analyzed, and thereby an enhanced FLL (referred to as EFLL) is recommended. The designs and analyzes have been verified by both simulations and experiments.
74 citations
TL;DR: In this paper, the authors proposed a balanced quasi-absorptive single/dual-band bandpass filter (BPF) with symmetrical quasi-reflectionless differential-mode behavior.
Abstract: Microwave planar balanced single-/dual-band bandpass filters (BPFs) with symmetrical quasi-reflectionless differential-mode behavior are presented in this letter. They are made up of a direct single-/dual-band BPF branch with virtually short-ended stubs in differential-mode operation, whose input and output accesses are loaded with stub-loaded-type single-/dual-band bandstop filter (BSF) branches that are terminated with a resistor. These BSF branches exhibit a quasi-complementary transfer function with regard to the one of the BPF branch and absorb the differential-mode input-signal energy not transmitted by the filter to achieve quasi-reflectionless capabilities. The theoretical foundations of the proposed balanced quasi-absorptive single-/dual-band BPFs and synthesis examples are given. Furthermore, for experimental-demonstration purposes, microstrip prototypes of 3-GHz second-order single-band and 2.85/3.15-GHz first-order dual-band BPFs are manufactured and characterized.
71 citations
TL;DR: This systematic study leads to an optimized link performance of a Si3 N4-photonic-chip-based microwave photonic notch filter, demonstrating an RF net gain, a sub-20-dB noise figure and an overall third-order spurious-free dynamic range of 115 dB.
Abstract: Simultaneously achieving high link performance and advanced microwave photonic processing functionalities in compact integrated circuits is crucial but challenging for the deployment in future and existing practical applications. In this paper, we present the first comprehensive experimental study to optimize the link performance of a Si3 N4-photonic-chip-based microwave photonic notch filter. This systematic study leads to an optimized link performance of the chip-based filter, demonstrating an RF net gain, a sub-20-dB noise figure and an overall third-order spurious-free dynamic range of 115 dB.Hz2/3 over a frequency range of 0–12 GHz, in conjunction with advanced filtering functionalities with a notch rejection >50 dB. The achieved performance is based on a unique and low-loss chip-based filter scheme which offers the compatibility with existing link performance optimization techniques, while maintaining the advanced notch filter functionality. Numerical calculations are also performed to explore the future feasibility of implementing a fully integrated microwave photonic filter that approaches the same level of link performance demonstrated in this work. This study is expected to provide a feasible design route to approach fully integrated microwave photonic filters with high link performance.
58 citations
TL;DR: Two digital differentiators are proposed, which are directly developed in the discrete domain and exhibit the same derivative performance as the nonideal-GI differentiator, and they are more attractive for digital implementations due to their direct discrete natures, compact expressions, and easy algebraic manipulations.
Abstract: To damp the LCL -filter resonance in a grid-connected inverter, the feedback of capacitor current is usually adopted, and it can be replaced by the feedback of capacitor voltage as a low-cost solution, if an accurate digital differentiator can be made. The best way for realizing such a differentiator has so far proved to be an indirect nonideal generalized integrator (GI). As a simple alternative, this paper proposes two digital differentiators, which are directly developed in the discrete domain. They are a first-order differentiator based on backward Euler plus digital lead compensator and a second-order differentiator based on Tustin plus digital notch filter. The basic idea of the proposed methods is to correct their frequency responses to match the ideal differentiator with embedded digital filters. It is shown that the proposed differentiators exhibit the same derivative performance as the nonideal-GI differentiator, and they are more attractive for digital implementations due to their direct discrete natures, compact expressions, and easy algebraic manipulations. In particular, the proposed first-order differentiator is most competitive for its general representation and simplest implementation. Finally, a 12-kW prototype is built, and experiments are performed to verify the theoretical analysis.
47 citations
TL;DR: In this article, a varactor-based tunable bandstop filter is proposed, which is based on a dual-mode circuit developed by introducing inductive and capacitive couplings into a notch filter.
Abstract: A varactor-based tunable bandstop filter has been proposed in this letter. The proposed filter is based on a dual-mode circuit developed by introducing inductive and capacitive couplings into a notch filter. The frequency tunability is achieved by using varactor diodes instead of the lumped capacitors in the circuit. Next, the equivalent circuit model has been implemented in planar microstrip technology using thin inductive traces and varactor diodes. The fabricated filter prototype shows a continuous center frequency tuning range of 0.66–0.99 GHz with a compact size of $0.12\lambda _{g} \times 0.16\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at the middle frequency of the tuning range.
40 citations
TL;DR: An Adaptive Notch Filter (ANF) is proposed to suppress the digital-to-analog converter (DAC) clock leakage induced narrowband interference for the first time, and the bandwidth of the ANF is optimized to achieve the best BER performance.
Abstract: In this paper, we experimentally demonstrate the transmission of 56 Gbaud four-level pulse amplitude modulation (PAM4) signal over 2-km single mode fiber (SMF) with intensity modulation and direct detection (IM/DD) scheme, while the bit-error-ratio (BER) of the PAM4 signal is under hard-decision forward error correction (HD-FEC) threshold of 38 × 10−3 Linear pre-equalization is implemented in the transmitter side with a 3-tap finite-impulse-response (FIR) filter to compensate for the intersymbol interference (ISI) induced by system bandwidth limitation Receiver side equalization is realized with training sequence (TS) based feed-forward equalizer (FFE) with decision-feedback equalizer (DFE) Furthermore, an Adaptive Notch Filter (ANF) is proposed to suppress the digital-to-analog converter (DAC) clock leakage induced narrowband interference for the first time, and the bandwidth of the ANF is optimized to achieve the best BER performance
38 citations
TL;DR: In this article, the authors numerically simulate planar plasmonic waveguides and notch filters with excellent guiding and rejection of terahertz (THz) waves with super subwavelength confinement.
Abstract: We numerically simulate novel planar plasmonic waveguides and notch filters with excellent guiding and rejection of terahertz (THz) waves with super subwavelength confinement Our design is based on spoof surface plasmon polaritons—surface plasmon polaritons with a frequency that has been tuned using patterned conductive surfaces We find that by using patterns of periodically arranged spiral-shaped units, the dispersion characteristics can be engineered at will by tuning the parameters of the spirals We find that the resulting plasmonic waveguides have much lower asymptotic frequencies and much tighter terahertz field confinement when compared with conventional rectangular-grooved plasmonic waveguides We show it is possible to design a structure with lateral dimensions that are only 25% the size of the conventional spoof surface plasmon polariton waveguides but with the same asymptotic frequency Finally, we combined this architecture with broadband couplers to design an ultrawideband low-pass filter with sharp roll-off (cut-off frequency at 129 THz) and low insertion loss (<3 dB) Furthermore, by introducing double ring resonators based on spiral-shaped units, a planar plasmonic notch filter with rejection of more than 17 dB between 097 and 099 THz is demonstrated The proposed waveguides and notch filters may have great potential applications in the promising terahertz integrated plasmonic circuits and systems
TL;DR: To the best of the knowledge, this MPF demonstrates ultrahigh peak rejection and narrow bandwidth simultaneously in SOI for the first time with MRR of such propagation loss and avoids using external electrical devices to improve the rejection.
Abstract: We propose and demonstrate a silicon-on-insulator (SOI)-based widely tunable microwave photonic filter (MPF), which is implemented by using an under-coupled microring resonator (MRR) assisted by two cascaded tunable Mach-Zehnder interferometers. In the experiment, the MPF achieves an ultrahigh peak rejection exceeding 60 dB, a full width at half-maximum bandwidth of 780 MHz, and a frequency tuning range of 0-40 GHz, even when the propagation loss of the MRR is 1.65 dB/cm. To the best of our knowledge, this MPF demonstrates ultrahigh peak rejection and narrow bandwidth simultaneously in SOI for the first time with MRR of such propagation loss and avoids using external electrical devices to improve the rejection.
TL;DR: In this article, an integrated optical double notch filter using a cascaded pair of non-identical microring resonators, in conjunction with optical phase modulation, is presented, which results in minimal net phase being introduced by the overall filter at radio frequencies falling outside the region of the notch stopband.
Abstract: A novel-integration-based technique employing a cascaded pair of microring resonators on silicon-on-insulator platform that can achieve a tunable single-passband microwave photonic filter with improved shape factor and extinction ratio is presented. It is based on an integrated optical double notch filter using a cascaded pair of nonidentical microring resonators, in conjunction with optical phase modulation. This results in minimal net phase being introduced by the overall filter at radio frequencies falling outside the region of the notch stopband, thus enabling nearly full antiphase cancellation of the modulation sidebands, which results in the achievement of an improved filter shape factor and extinction ratio. Additionally, it features a bandwidth that is directly determined by the difference between the bandwidths of the two optical notch filters, rather than by their absolute individual bandwidths. Experimental results have verified the concept, and have demonstrated a single-passband filter having tuning range of 6–17 GHz, a shape factor of 1.78, shape-invariant tuning, and a good out-of-band suppression ratio of approximately 20 dB throughout the entire tuning range.
TL;DR: This paper investigates a hybrid fractional repetitive control (HFRC) scheme for magnetically suspended rotor systems to suppress harmonic current caused by mass imbalance and sensor runout and demonstrates the advantages of the proposed method.
Abstract: This paper investigates a hybrid fractional repetitive control (HFRC) scheme for magnetically suspended rotor systems to suppress harmonic current caused by mass imbalance and sensor runout. With parallel structure, HFRC consists of a frequency-adaptive dual-mode repetitive controller (DMRC) and a phase-shift notch filter. By introducing fractional delay filters, the proposed DMRC provides frequency adaptability to eliminate odd and even harmonics independently at fixed sampling rate. Its delay time is halved compared with the conventional repetitive control scheme, and the control gains can be weighted to ameliorate system dynamic response according to harmonics distribution. Moreover, as the domination of control current, fundamental frequency current is additionally rejected by the notch filter; thus, achieving smaller overshoot and faster suppression performance. An improved phase compensator is designed in HFRC to expedite current convergence rate while stabilizing the overall system. Experimental results on a magnetically suspended flywheel demonstrate the advantages of the proposed method.
TL;DR: An active damping current controller based on the internal model principle for a grid-connected VSC equipped with an LCL filter is proposed, showing significantly improved robustness with no degradation of transient behavior, has the ability to operate at low switching frequencies, and does not need additional sensors.
Abstract: Three-phase passive harmonic filters (e.g., LCL filters) are often utilized to attenuate harmonic currents caused by pulsewidth modulation of voltage-sourced converters (VSC) to achieve high power quality. However, LCL filters may jeopardize the system stability due to their inherent susceptibility to resonance. This paper proposes an active damping current controller based on the internal model principle for a grid-connected VSC equipped with an LCL filter. This controller can be considered a high-order multi-input multi-output transfer function, implemented in the $dq$ reference frame, including decoupling terms for improved transient behavior. Simulation case studies are performed in the PSCAD/EMTDC environment to evaluate the transient behavior of the controller and test its robustness against parameter variations and unbalanced and distorted grid conditions. Experimental results verify the performance of the proposed controller and confirm its ability to operate at low switching frequencies. The results are compared with two existing active damping strategies (virtual RC and notch filter methods), confirming that the proposed controller shows significantly improved robustness with no degradation of transient behavior, has the ability to operate at low switching frequencies, and does not need additional sensors.
TL;DR: An in-depth theoretical and practical analysis ofAbsorptive bandstop filters is performed, presenting design principles for reducing the sensitivity to process variation, increasing the tuning range over which the filters can operate with good performance, and addressing the practical non-ideal effects of implementation.
Abstract: Absorptive bandstop filters are a relatively new class of bandstop filter, which are able to achieve very high levels of stopband rejection with relatively low-quality-factor resonators, in contrast to typical reflective bandstop filters, whose stopband rejections are limited by the quality factors of their resonators. This paper performs an in-depth theoretical and practical analysis of this class of filter, presenting design principles for reducing the sensitivity to process variation, increasing the tuning range over which the filters can operate with good performance, and addressing the practical non-ideal effects of implementation, such as frequency variation of couplings and quality factor. Four varactor-tuned microstrip bandstop filters are presented to verify the presented theory. They illustrate the design tradeoffs between selectivity and tuning range, choice of coupling topology and tuning range, and show the benefits and drawbacks of cascading stages to create higher-order filters.
TL;DR: A more compact filter concept based on the Peano space filling curve is introduced to increase the tuning range while minimizing the DGS area and the measured results show a tuning range of more than 19 %.
Abstract: This paper proposes and validates a new principle in coplanar waveguide (CPW) bandstop filter tuning by shortcutting defected ground plane (DGS) inductor shaped spirals to modify the resonant frequency The tunable filter is fabricated on a high-resistivity silicon substrate based on a CMOS compatible technology using a $1\,\,\mu \text {m}\times 10\,\,\mu \text {m}$ long and 300 nm thick vanadium oxide (VO2) switch by exploiting its insulator to metal transition The filter is designed to work in Ka band with tunable central frequencies ranging from 282 GHz to 35 GHz The measured results show a tuning range of more than 19 %, a low insertion loss in the neighboring frequency bands (below 2 dB at 20 GHz and 40 GHz in on/off-states) while a maximum rejection level close to 18 dB in off-state, limited by the no RF-ideal CMOS compatible substrate The filter has a footprint of only $0084\cdot \lambda _{0} \times 0037\cdot \lambda _{0}$ (where $\lambda _{0}$ represents the free space wavelength at the highest resonance frequency) thus making it the most compact configuration using CPW DGS structures for the Ka frequency band In addition, a more compact filter concept based on the Peano space filling curve is introduced to increase the tuning range while minimizing the DGS area
TL;DR: A tunable dual-band bandpass-to-bandstop filter and its analysis are proposed, which could be obtained by changing the state of the p-i-n diode by using two sets of half-wavelength resonators loaded with varactors.
Abstract: In this paper, a tunable dual-band bandpass-to-bandstop filter and its analysis are proposed. The bandpass-to-bandstop transformation could be obtained by changing the state of the p-i-n diode. Using two sets of half-wavelength resonators loaded with varactors, the center frequency of each band can be tuned independently by adjusting the varactors. In order to achieve the controlling of the external quality factors ( ${Q} _{e}$ ) for the bandpass mode, the feeding lines are loaded with two varactors and wide tuning range of ${Q} _{e}$ can be obtained. In the bandpass mode, the lower passband tuning range is from 1.7 to 2.2 GHz (25.6% tuning range) with return loss better than 10.5 dB, and the tuning range of higher passband is from 2.2 to 2.7 GHz (20.4% tuning range) with return loss better than 12.9 dB. For the bandstop mode, the lower stopband tuning range is from 1.7 to 2.3 GHz (30% tuning range) and the higher stopband tuning range is from 2.3 to 2.9 GHz (23.1% tuning range), while the rejection level is higher than 16.4 dB in the stopband.
TL;DR: The proposed CFAR method based on the notch filter provides a promising technique for the detection of ships using HP SAR data using the same benchmark for the comparison of the detectability of HP and conventional linear DP SAR data.
Abstract: Compact polarimetric data exploitation, especially in hybrid-polarimetric (HP) mode, is currently attracting increasing interest due to the new generation of synthetic aperture radar (SAR) systems. Recently, it has been demonstrated that the notch filter is useful for ship detection in either full- or dual-polarization (DP)-mode SAR images. In this paper, the notch filter investigation is further extended to HP SAR architecture for ship detection on the ocean surface. First, a version of the notch filter that is suitable for HP SAR is proposed based on the definition of the corresponding feature partial scattering vector from the covariance matrix of the HP SAR. Subsequently, a novel model characterizing the statistics of the notch distance of sea clutter in the HP mode is developed. Based on the statistical model, the threshold of constant false-alarm rate (CFAR) ship detection is theoretically and analytically derived, which allows the automatic and adaptive implementation for ship detection in varying sea backgrounds in practical applications. Experiments on the HP SAR data emulated from full-polarization L-band Aerospace Exploration Agency Advanced Land Observation Satellite Phased-Array type L-band SAR and C-band RADARSAT-2 SAR measurements validate not only the soundness of the proposed CFAR detection but also the high accuracy of the presented model in fitting HP SAR data. Furthermore, the notch filter and its CFAR realization provide the same benchmark for the comparison of the detectability of HP and conventional linear DP SAR data. Preliminary findings suggest that the detection performance of HP SAR is superior to that of DP SAR in ship observation. Therefore, the proposed CFAR method based on the notch filter provides a promising technique for the detection of ships using HP SAR data.
TL;DR: The proposed control strategy does not need an accurate MSR model, and the methods of adaption to parameter variations in the amplifier model are suitable for various applications according to the elimination precision and computational effort.
Abstract: For a magnetically suspended control moment gyro (MSCMG), the mass imbalance of the high-speed magnetically suspended rotor (MSR) will induce a synchronous force, which is the main disturbance for the attitude control of satellites. In this work, an elimination method with an adaption to parameter variations in an amplifier model is presented. First, the MSR system with a hybrid magnetic bearing is modeled. Next, a generalized notch filter is utilized to identify the synchronous displacement, according to which a feedforward controller is designed to generate synchronous current so that the electromagnetic force can counteract the permanent magnetic force precisely. To keep the feedforward controller unaffected by the power amplifiers whose parameters vary with the temperature, another notch filter is adopted to obtain the synchronous coil current, and then two types of adaptive controllers, which can tune the synchronous feedforward controller adaptively, are proposed and compared. Finally, simulations and experiments are carried out to demonstrate the validness of the adaptive control methods in an MSCMG test rig. The proposed control strategy does not need an accurate MSR model, and the methods of adaption to parameter variations in the amplifier model are suitable for various applications according to the elimination precision and computational effort.
TL;DR: Investigations illustrate that the location of the stop bands not only can be adjusted by varying the length of gold strips, but also can be dynamically controlled by tuning the Fermi energy level of graphene, and deep modulation is acquired through designing the carrier mobility.
Abstract: Dynamically tunable band stop filter based on metal-graphene metamaterials is proposed and numerically investigated at mid-infrared frequencies. The proposed filter is constructed by unit cells with simple gold strips on the stack of monolayer graphene and the substrate of BaF2. A stable modulation depth up to −23.26 dB can be achieved. Due to the cooperative effect of the “bright-bright” elements, the amount of the gold strips in each unit cell determines the number of the stop-bands, providing a simple and flexible approach to develop multispectral devices. Further investigations illustrate that the location of the stop bands not only can be adjusted by varying the length of gold strips, but also can be dynamically controlled by tuning the Fermi energy level of graphene, and deep modulation is acquired through designing the carrier mobility. With the sensitivity as high as 2393 nm/RIU of the resonances to the varieties of surrounding medium, the structure is also enabled to be an index based sensor. The results will benefit the on plane or integrated micro-structure research with simple structure and flexible tunability, and can be applied in multi-band stop filters, sensors and other graphene-based multispectral devices.
TL;DR: In this paper, a CPW-fed UWB filter-antenna with sharp and high rejection multiple band notches for band-notched UWB communication applications is presented, which is achieved by employing a sharp bandstop filter (BSF) with multiple reject bands using only one element meander line resonator at the bottom layer through theoretical calculations and parametric studies.
Abstract: This paper presents a CPW-fed UWB filter-antenna with sharp and high rejection multiple band notches for band-notched UWB communication applications. The band notch operation is achieved by employing a sharp bandstop filter (BSF) with multiple reject bands using only one element meander line resonator at the bottom layer through theoretical calculations and parametric studies. The adjustment of the notched bands is successfully accomplished by loading the meander line with open ended stubs to modify the harmonic frequencies to the desired bands. The structure of the proposed BSF is simple and compact so that the proposed filter-antenna is achieved with the same size of the reference UWB antenna without an extra area. Measurement results show that the proposed filter-antenna has two notches at the WiMAX systems operating in the 5.8 GHz (5.725–5.85 GHz) and at the international telecommunication union (ITU) operating in the 8.2 GHz (8.025–8.4 GHz). Also, it has sharp rejection characteristics at the edges of the federal communication commission (FCC) band for UWB communications. The experimental measurements are in good agreement with theoretical and simulation results for the BSF and the filter-antenna. Moreover, the filter-antenna exhibits stable omnidirectional radiation patterns except at the notched bands.
TL;DR: A simple method for power-line interference (PLI) removal based on the wavelet decomposition, without the use of thresholding techniques that can be used for PLI removal in ECG signals with superior performance than thresholding and notch filter techniques.
Abstract: Introduction The analysis of electrocardiogram (ECG) signals allows the experts to diagnosis several cardiac disorders. However, the accuracy of such diagnostic depends on the signals quality. In this paper it is proposed a simple method for power-line interference (PLI) removal based on the wavelet decomposition, without the use of thresholding techniques. Methods This method consists in identifying the ECG and noise frequency range for further zeroing wavelet detail coefficients in the subbands with no ECG coefficients in the frequency content. Afterward, the enhanced ECG signal is obtained by the inverse discrete wavelet transform (IDWT). In order to choose the wavelet function, several experiments were performed with synthetic signals with worse Signal-to-Noise Ratio (SNR). Results Considering the relative error metrics and runtime, the best wavelet function for denoising was Symlet 8. Twenty synthetic ECG signals with different features and eight real ECG signals, obtained in the Physionet Challenge 2011, were used in the experiments. Results show the advantage of the proposed method against thresholding and notch filter techniques, considering classical metrics of assessment. The proposed method performed better for 75% of the synthetic signals and for 100% of the real signals considering most of the evaluation measures, when compared with a thresholding technique. In comparison with the notch filter, the proposed method is better for all signals. Conclusion The proposed method can be used for PLI removal in ECG signals with superior performance than thresholding and notch filter techniques. Also, it can be applied for high frequencies denoising even without a priori frequencies knowledge.
TL;DR: In this article, a hybrid transformer-based CMOS tunable duplexer with a single-ended blocker-tolerant low-noise amplifier (LNA) is proposed for a highly integrated reconfigurable RF front-end architecture.
Abstract: A hybrid transformer-based CMOS tunable duplexer with a single-ended blocker-tolerant low-noise amplifier (LNA) is proposed for a highly integrated reconfigurable RF front-end architecture. The proposed LNA adopts $Q$ -enhanced $LC$ notch filter at the source of the cascode device and $LC$ bandpass filter at the load. It improves the blocker tolerance and linearity of the receiver by rejecting unwanted out-of-band blockers and transmitter (TX) leakage signals. The duplexer with the notch-filtered LNA was fabricated in a 65-nm CMOS process. It has a voltage gain of 24.2 dB from the antenna to the LNA output with 28-dB notch filtering, cascaded noise figure of 6.4 dB, TX insertion loss of 3.8 dB, and IIP3FD of 52.4 dBm. It can also cover a mid-band range from 1.6 to 2.2 GHz in cellular applications. It draws an average current of 8 mA from a supply voltage of 1.2 V and has an active area of 1.19 mm2.
TL;DR: Filter-based solutions are appropriate and a new procedure for tuning the notch filter is proposed, however, this procedure requires that the resistance of the inductors is known and a novel filter-based solution is proposed that uses lag filters.
Abstract: LCL -filter-based grid-tie inverters require damping for the current-loop stability. There are only software modifications in active damping, whereas resistors are added in passive damping. Although passive damping incurs in additional losses, it is widely used because of its simplicity. This paper considers the active damping in medium-voltage parallel inverters for wind turbines. Due to cost reasons, only minimal software changes are allowed and no extra sensors can be used. The procedure must be robust against line-inductance variations in weak grids. Double-update mode is needed so the resonance frequency is under the Nyquist limit. The bandwidth reduction when using active damping is also required to be known beforehand. Moreover, the design procedure should be simple without requiring numerous trial-and-error iterations. In spite of the abundant literature, the options are limited under these circumstances. Filter-based solutions are appropriate and a new procedure for tuning the notch filter is proposed. However, this procedure requires that the resistance of the inductors is known and a novel filter-based solution is proposed that uses lag filters. The lag filters displace the phase angle at the resonance frequency so that the Nyquist stability criterion is fulfilled. Simulations and experiments with a 100-kVA prototype validate the analysis.
TL;DR: A dual band and low phase noise Ku-band voltage-controlled oscillator (VCO) using 180-nm CMOS technology that employs a switched notch filter that can operate in the low and high band and has a quality factor that is higher than that of a conventional inductor–capacitor (LC) resonator.
Abstract: A dual band and low phase noise Ku-band voltage-controlled oscillator (VCO) using 180-nm CMOS technology is presented in this brief. The proposed VCO employs a switched notch filter that can operate in the low and high band, which depends on the state of nmos transistor and has a quality factor that is higher than that of a conventional inductor–capacitor (LC) resonator. The proposed resonator doubles the quality factor compared to LC in the technology and reduces the total die area. The first band is realized by the switched interdigital resonator when a nMOS transistor is in the off state. Furthermore, the second band is realized by turning nmos transistor to the on state, which is located between two fingers in the proposed resonator. The chip is implemented in 180-nm CMOS technology, and found that the proposed VCO operates from 15.5 to 16.7 Hz (low band) and 16.6 to 17.4 GHz (high band). At 1.8-V power supply, the power consumption of the oscillator core is 5.4 and 7.2 mW in the low- and high-frequency bands, respectively. The measured phase noise is −107 dBc/Hz at 1 MHz offset from 16.7-GHz carrier frequency.
01 Jan 2018
TL;DR: The results show that LMS filter provides superior results in comparison to other methods for de-noising of ECG signals, both in frequency and time domain.
Abstract: Heart rhythms can be recorded and electrically displayed using Electrocardiogram (ECG) signal with non-stationary properties. However, such recordings can be corrupted by different types of proximity noise including power line interference (PLI). The corruption can cause variation in amplitude and/or duration of signal leading to diagnostic errors. Traditional notch filters are ineffective against such noise due to non-static nature of PLI frequency. In this paper, we study ECG signal de-noising technique using the traditional notch filter, band stop filter, Least-Mean-Square (LMS) filter. Results are compared both in frequency and time domain. The program is written using Signal Processing Toolbox (MATLAB). Our results show that LMS filter provides superior results in comparison to other methods for de-noising of ECG signals.
TL;DR: Because the TGMR and guided mode resonance (GMR) filters are placed independently in the THz beam path, both tunable and fixed resonances can be obtained at the same time in the spectrum.
Abstract: A variable grating period made of quartz has been applied to fabricate a tunable guided mode resonance (TGMR) filter with transverse-electric (TE) and –magnetic (TM) modes in the terahertz (THz) region. We prepared three TGMR filters with grating periods of 5.0, 3.3, and 1.7 μm/mm over the length of the filter. For the 5.0 μm/mm, the resolution of resonance frequency shift of the TE0,1, TE1.1, and TM0,1 was 3.6, 4.0, and 3.4 GHz/mm, respectively. With a metal slit spacing of 2 mm located in front of the TGMR filter, the movable range of the TGMR was 24 mm, and the resonance frequency could be shifted up to 87, 96, and 82 GHz, where the center frequencies of each resonance were 0.402, 0.579, and 0.460 THz, for the TE0,1, TE1.1, and TM0,1, respectively. Furthermore, because the TGMR and guided mode resonance (GMR) filters are placed independently in the THz beam path, both tunable and fixed resonances can be obtained at the same time in the spectrum.
TL;DR: It is expected that the optical tunable filter strategies could become one of the key parts of laser-based Raman spectroscopy, fluorescence, life science devices, optical communication systems, astronomical telescopes, and so forth.
Abstract: Spatially continuous tunable optical notch and band-pass filter systems that cover the visible (VIS) and near-infrared (NIR) spectral ranges from ∼460 nm to ∼1,000 nm are realized by combining left- and right-handed circular cholesteric liquid crystal (CLC) wedge cells with continuous pitch gradient. The notch filter system is polarization independent in all of the spectral ranges. The band-pass filter system, when the left- and right-handed CLCs are arranged in a row, is polarization independent, while when they are arranged at right angles, they are polarization dependent; furthermore, the full-width at half-maximum of the band-pass filter can be changed reversibly from the original bandwidth of 36 nm to 16 nm. Depending on the CLC materials, this strategy could be applied to the UV, VIS, and IR spectral ranges. Due to the high performance in the broad spectral range, cost-effective facile fabrication process, simple mechanical control, and small size, it is expected that our optical tunable filter strategies could become one of the key parts of laser-based Raman spectroscopy, fluorescence, life science devices, optical communication systems, astronomical telescopes, and so forth.
TL;DR: In this paper, a frequency and bandwidth-tunable bandstop filter using substrate-integrated wave-guide (SIW) resonators has been proposed, which can be tuned from 0 (all-pass) to 96 MHz reaching the attenuation level of 44 dB.
Abstract: This paper presents a frequency- and bandwidth-tunable bandstop filter using substrate-integrated wave- guide (SIW) resonators. For designing such a filter, this paper also presents a tunable coupling structure between a microstrip line and an SIW resonator for obtaining the bandwidth tuning capability. The coupling structure has two coupling slots between the microstrip line and the resonator, and the phase shift between the two slots determines the overall external coupling value of the resonator. This external coupling value can be controlled by making use of a phase shifter, which in turn makes it possible to adjust the bandwidth of a bandstop filter. A thorough mathematical analysis is shown using the equivalent circuit model of the presented coupling structure, and it has been verified by measuring an SIW resonator containing the presented structure. The presented tunable coupling structure has also been applied to a design of bandstop filter that can be tuned from 2.8 to 3.4 GHz. The measured results at 3.1 GHz show that the bandwidth can be tuned from 0 (all-pass) to 96 MHz reaching the attenuation level of 44 dB.