Second-order Filter Research Articles

Asumu Fractional Derivative Applied to Edge Detection on SARS-COV2 Images

Edge detection consists of a set of mathematical methods which identifies the points in a digital image where image brightness changes sharply. In the traditional edge detection methods such as the first-order derivative filters, it is easy to lose image information details and the second-order derivative filters are more sensitive to noise. To overcome these problems, the methods based on the fractional differential-order filters have been proposed in the literature. This paper presents the construction and implementation of the Prewitt fractional differential filter in the Asumu definition sense for SARS-COV2 image edge detection. The experiments show that these filters can avoid noise and detect rich edge details. The experimental comparison show that the proposed method outperforms some edge detection methods. In the next paper, we are planning to improve and combine the proposed filters with artificial intelligence algorithm in order to program a training system for SARS-COV2 image classification with the aim of having a supplemental medical diagnostic.

Hardware-Aware Design of Multiplierless Second-Order IIR Filters With Minimum Adders

In this work we optimally solve the problem of multiplierless design of second-order Infinite Impulse Response filters with minimum number of adders. Given a frequency specification, we design a stable direct form filter with hardware-aware fixed-point coefficients where all multiplications are replaced by bit shifts and additions. The coefficient design, quantization and implementation, typically conducted independently, are now gathered into one global optimization problem, modeled through integer linear programming and efficiently solved using generic solvers. The optimal filters are implemented within the FloPoCo IP core generator and synthesized for field programmable gate arrays (FPGAs) and application specific integrated circuits (ASICs). With respect to state-of-the-art three-step filter design methods, our one-step design approach achieves, on average, 48% reduction in number of lookup tables, 27% delay reduction and 57% reduction in power on FPGAs. ASICs experiment illustrate similar 48% reduction in circuit area, 27% delay reduction and 65% power reduction for a 14 nm ASIC.

Polynomial Filtering Algorithms under Quadratic Nonlinearities in System and Measurement Equations: Comparison with Extended and Second-Order Kalman Filters1

The paper considers the filtering problem under quadratic nonlinearities both in system and measurement equations. A polynomial filter, which is a Kalman-type recursive algorithm, is proposed. The similarities between this algorithm and other Kalman-type algorithms such as extended and second-order Kalman filters are discussed. The procedure for estimating the performance and comparing the algorithms is presented. The advantages of proposed algorithm are illustrated using a navigation data processing example

A novel low-complexity state-of-energy estimation method for series-connected lithium-ion battery pack based on “representative cell” selection and operating mode division

In this paper, we present a novel low-complexity state-of-energy (SOE) estimation method for series-connected lithium-ion battery pack based on “representative cell” selection and operating mode division. Firstly, an “ohmic resistance”-based “representative cell” selection method is proposed to determine the freshest cell and the oldest cell among all in-pack cells reliably and rapidly. Subsequently, according to the cell inconsistences degree, battery cell operating mode is artificially divided into two classes. In mode 1, only the oldest cell's SOE needs to be online tracked, which can be directly seen as battery pack's estimated SOE because of the low cell inconsistences degree. In mode 2, a second-order extended Kalman filter is designed to estimate the SOE difference between the freshest cell and the oldest cell under macro time-scale to further compute the freshest cell's SOE. With the freshest cell's and the oldest cell's estimated SOE, battery pack's SOE in mode 2 can be finally obtained by the adaptive weighted strategy. The validation results through sophisticated driving simulation show that the developed method can achieve accurate SOE estimation for battery pack, where the SOE error bands after convergence by two different data are limited within −2% and 0, and within −3% and 0, respectively. • A low-complexity SOE estimation method for lithium-ion battery pack is presented. • An “ohmic resistance”-based “representative cell” selection method is proposed. • Cell operating mode is artificially divided into two classes to reduce complexity. • A dual estimation framework is proposed to track the oldest cell's states. • The chosen two cells' SOE difference is estimated under macro time-scale in mode 2.

Wideband MIMO Antenna Isolation Enhancement Using 4th-Order Cross-Coupled Decoupling Circuit

This article presents a new fourth-order stub-based decoupling circuit for isolation improvement in a wideband tightly coupled multiple-input–multiple-output (MIMO) antenna array. The proposed decoupling circuit uses a fourth-order coupling-resonator filter effect and is designed using the structure’s admittance parameter. In the decoupling circuit, the pair of dual-band second-order stub-based filters is used for the desired band’s lower and upper frequencies. Finite transmission zeros provide cross-coupling, which helps maintain the admittance slope stopband between these bands and reduces coupling among MIMO elements. The proposed fourth-order decoupling circuit concept can be utilized for different wideband MIMO antenna applications to redesign the targeted band and cross-coupling scenario properly. In addition, to demonstrate the proposed decoupling circuit concept’s influence in achieving good wideband isolation in a compact dimension of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$45\times 40\times1.6$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , octagonal- and circular-shaped patch MIMO antennas are analyzed. To analyze the impact of the proposed decoupling circuit of the dimension <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11.3\times11$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the design, edge-to-edge separation between MIMO elements is kept at a minimum of 0.2 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0035\lambda _{0 \thinspace }$ </tex-math></inline-formula> at 5.4 GHz, WLAN band). This demonstrates that the decoupling circuits are antenna-independent and can be applied to other MIMO antennas. The measured S-parameters of the proposed wideband MIMO antenna present high isolation (>20 dB) between the antenna elements. Moreover, the proposed solutions’ radiation behavior and diversity performance are evaluated. The MIMO antenna element measured radiation efficiency is increased from 50% to 75%. It demonstrates good properties that make it a suitable contender for advanced scientific applications.

0.5 V Differential Difference Transconductance Amplifier and Its Application in Voltage-Mode Universal Filter

This paper presents an innovative CMOS structure for Differential Difference Transconductance Amplifiers (DDTA). While the circuit operates under extremely low voltage supply 0.5 V, the circuit’s performance is improved thanks to using the multiple-input MOS transistor (MI-MOST), the bulk-driven, self-cascode and partial positive feedback (PPF) techniques. As a result, the DDTA structure is less complex, with high gain of 93 dB, wide input voltage range nearly rail-to-rail, and wide transconductance tunability. As an example of application, a second-order voltage-mode universal filter using three DDTAs and two 6 pF integrated capacitors is presented. The filter is designed such that no matching conditions are required for the input and passive components, and the input signals need not be inverted. The natural frequency and the quality factor can be set orthogonally while the natural frequency can be electronically controlled. The circuit was designed and simulated in Cadence environment using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18 \mu \text{m}$ </tex-math></inline-formula> TSMC technology. The simulation results including intensive Monte-Carlo (MC) and process, temperature, voltage (PVT) analysis confirm the stability and the robustness of the design to process, mismatch variation and PVT corners.

Design of Second-Order Multifunction Filter IC Based on Current Feedback Amplifiers With Independent Voltage Gain Control

This paper presents the integrated circuit (IC) design and implementation of the voltage-mode (VM) second-order gain-controlled multifunction filter (GMF), which consists of three current feedback amplifiers (CFAs), two grounded capacitors and four resistors. The design and implementation of the chip are based on a 0.18 &#x03BC;m process technology, and offers the attractive advantages of high efficiency, high reliability, low voltage, low power consumption, small size and good performance. The VM-GMF chip implements low-pass (LP), inverting band-pass (IBP) and band-stop (BS) filtering functions, and can independently control the gain of LP, IBP and BS filtering functions. The chip operates with a wide input voltage of 1.2 V_pp at &#x00B1;0.9 V supply voltage, and has a figure-of-merit (FOM) of 66.7%. The on-chip measured input power at 1-dB compression point (IP1dB) is about 7.5 dBm with good linearity and the measured power dissipation (PD) is 5.4 mW with low voltage and low power consumption. The measured phase noise (PN) at an offset frequency of 1 kHz is -100.61 dBc/Hz. The measured value of the third-order intermodulation distortion (IMD3) is -57.38 dBc and the third-order intercept point (TOI) is 21.77 dBm. Simulations and on-chip experimental measurements demonstrate the theoretical analysis of the proposed VM-GMF.

Small area purification and recognition of network intrusion signals based on the second-order matching filter detection

Small area purification and recognition of network intrusion signals based on the second-order matching filter detection

A 5LCHB Inverter for PV Transformerless Applications With Reduced Leakage Ground Current

The transformerless inverters for photovoltaic systems are widely used as it features low cost, volume, and weight. Thus, in recent years, its study has been of great interest to the research community. In this paper a transformerless cascade multilevel inverter for photovoltaic applications with leakage ground current compensation capability is presented. The proposed solution involves a second-order LC output filter with a particular connection, which is referred to as the DC-link-tied LC output filter. This solution is aimed to deal with the leakage-ground current issue, regardless of the considered PWM strategy. The mathematical model of the system involving such a particular LC output passive filter configuration is presented, out of which, both the differential-mode and the common-mode models are obtained. These models are used to explain the leakage-ground current improvement of the proposed DC-link-tied LC output filter. This hardware solution is evaluated under different modulation schemes to contrast the converter output response and the leakage-ground current performance. Finally, simulation and experimental results are performed using a 1 kW academic prototype to assess the performance of the proposed DC-link-tied LC output filter used in a transformerless inverter application.

Small area purification and recognition of network intrusion signals based on the second-order matching filter detection

Small area purification and recognition of network intrusion signals based on the second-order matching filter detection

Robust Delay Compensation Strategy for LCL-Type Grid-Connected Inverter in Weak Grid

Capacitor-current-feedback active damping has been widely adopted in digitally controlled LCL-type grid-connected inverters (GCIs). However, their digital control delay causes the system stability to deteriorate within a negative damping range. Particularly, in a weak grid, such GCIs are prone to be unstable against the grid impedance variation. To address the above problem, a delay compensation strategy is proposed for an LCL-type GCI, in which a second-order low-pass filter (LPF) is inserted into the capacitor-current-feedback path. This increases the virtual-positive-resistance-region from one-sixth of the sampling frequency to almost within the Nyquist frequency. Therefore, the robustness of the grid-connected inverter can be significantly enhanced against the grid impedance variation. Furthermore, to ensure the system stability and improve the injecting current tracking performance, a proportional complex integral (PCI) strategy is adopted. More specifically, a robustness analysis is conducted under discrete domain. Finally, a 2-kW prototype is constructed, and the experimental results confirm the effectiveness of the theoretical expectations.

Frequency-Tunable Absorptive Bandpass Filter Using Substrate-Integrated Waveguide Structure

This work, for the first time, presents an absorptive frequency-tunable substrate-integrated waveguide (SIW) filter. For the filter design, an absorptive bandpass filter prototype tailored to an SIW structure has been formulated. The proposed absorptive bandpass filter prototype is capable of having a return loss larger than 20 dB at all frequencies although it has a simple matching circuit. The filter prototype has been attained by comprehensive formula-based synthesis of a new matching circuit equivalent to an existing one. To validate our filter prototype, a second-order absorptive bandpass filter that can alter its center frequency has been designed, fabricated, and measured. This article demonstrates approaches to find physical dimensions by comparing each section of the filter structure with the corresponding part of the prototype. The fabricated absorptive bandpass filter has a compact structure by virtue of its simple matching section. The frequency-tunable SIW resonators allow our absorptive bandpass filter to adjust its center frequency from 1.76 to 2.69 GHz while having absorptive performance. The measured reflection of the filter centered at 2.50 GHz is smaller than -10 dB between 1.56 and 3.27 GHz (2.10:1). It is shown that theory, simulation results, and measured responses are in good agreement.

Performance and Security Analysis of Parameter-Obfuscated Analog Circuits

In this article, key-based obfuscation of the transistor dimensions is proposed to mask the biasing conditions of an analog circuit and, therefore, protect the circuit against intellectual property (IP) piracy. Vector- and mesh-based obfuscations are developed that provide different degrees of circuit security with tradeoffs in design complexity and area. An algorithm for the selection of an obfuscation transistor and a satisfiability modulo theory (SMT)-based algorithm that searches the design space to determine the dimensions of the obfuscation transistors are developed to reduce the computational complexity of designing and implementing the proposed parameter obfuscation techniques. The parameter obfuscation techniques, along with the developed algorithms, are implemented on an active inductor-based second-order bandpass filter (BPF) and an operational amplifier (op-amp). The results from the analysis of the obfuscated BPF and op-amp indicate that the critical circuit performances are properly locked with at least 15% variation from the target circuit parameters when setting incorrect transistor sizes. A simulation-based optimization algorithm is proposed to tune the biasing conditions and transistor body voltages, which mitigates the effects of both the parasitic impedance of the circuit and any variation due to the implementation of the obfuscation circuitry. The proposed simulation-based optimization algorithm determines the biasing conditions and body voltages of the BPF in 500 iterations and the op-amp circuit in 70 iterations, which provides a significant reduction in the design time and the number of circuit recycles. Implementing the parameter obfuscation technique with the proposed algorithms provides an efficient means to secure analog circuits while reducing the design time to implement security features.

Impacts of Quadrature Signal Generation-Based PLLs on Low-Frequency Oscillation in an Electric Railway System

The low-frequency oscillation (LFO) issue has occurred frequently in single-phase electric train and traction network interactive systems (hereinafter train-network systems). On a single-phase electric train, the quadrature signal generation-based phase-locked loop (QSG-PLL) has been widely used to achieve unit power factor operation. The bandwidth of the single-phase PLL is close to the frequency of the LFO, but its impacts on the LFO are not considered fully in previous works. In this article, three typical QSG-PLLs are studied in depth, and their unified model is derived in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> frame. Furthermore, the impacts of the QSG-PLL structure and parameters on the LFO are revealed. The analysis results indicate that the QSG part plays an important role in the LFO analysis, but the parameters of the PLL part have slight impacts on the train’s impedance under the low-power operation mode. Three different QSGs can all be regarded as providing a second-order low-pass filter (LPF) to generate the virtual <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> component in the single-phase system. The higher damping ratio of the second-order LPF can increase the magnitude of the train’s impedance, which is beneficial to enhance the stability of the train-network system. Finally, experimental results via hardware in loop (HIL) are employed to verify the correctness of the theoretical analysis results.

Dual-Bandstop Substrate-Integrated-Coaxial Tunable and Static RF Filters

This letter discusses the RF design and practical realization of dual-bandstop filters (BSFs) with compact size and two independently controlled rejection bands. They are based on miniaturized substrate-integrated-coaxial (SIC) resonant stages that are made from two capacitively loaded posts and a thru-line. Each of the stages creates two transmission zeros (TZs) that can be exploited for the realization of dual-bandstop RF filters with approximately half the size of conventional single-post series-cascaded SIC filter configurations. Further miniaturization is achieved by tuning the center frequency of the bands. For proof-of-concept validation purposes, three prototypes were designed, manufactured, and measured. They include a static (rejection bands centered at 4 and 4.5 GHz) and a tunable (between 3.6–4.6 GHz) dual-bandstop second-order RF filters and a third-order dual-bandstop RF filter with bands centered at 4 and 4.4 GHz.

Ladder-Based Synthesis and Design of Low-Frequency Buffer-Based CMOS Filters

Buffer-based CMOS filters are maximally simplified circuits containing as few transistors as possible. Their applications, among others, include nano to micro watt biomedical sensors that process physiological signals of frequencies from 0.01 Hz to about 3 kHz. The order of a buffer-based filter is not greater than two. Hence, to obtain higher-order filters, a cascade of second-order filters is constructed. In this paper, a more general method for buffer-based filter synthesis is developed and presented. The method uses RLC ladder prototypes to obtain filters of arbitrary orders. In addition, a set of novel circuit solutions with ultra-low voltage and power are proposed. The introduced circuits were synthesized and simulated using 180-nm CMOS technology of X-FAB. One of the designed circuits is a fourth-order, low-pass filter that features: 100-Hz passband, 0.4-V supply voltage, power consumption of less than 5 nW, and dynamic range above 60 dB. Moreover, the total capacitance of the proposed filter (31 pF) is 25% lower compared to the structure synthesized using a conventional cascade method (40 pF).

On the Design of Power Law Filters and Their Inverse Counterparts

This paper presents the optimal modeling of Power Law Filters (PLFs) with the low-pass (LP), high-pass (HP), band-pass (BP), and band-stop (BS) responses by means of rational approximants. The optimization is performed for three different objective functions and second-order filter mother functions. The formulated design constraints help avoid placement of the zeros and poles on the right-half s-plane, thus, yielding stable PLF and inverse PLF (IPLF) models. The performances of the approximants exhibiting the fractional-step magnitude and phase responses are evaluated using various statistical indices. At the cost of higher computational complexity, the proposed approach achieved improved accuracy with guaranteed stability when compared to the published literature. The four types of optimal PLFs and IPLFs with an exponent α of 0.5 are implemented using the follow-the-leader feedback topology employing AD844AN current feedback operational amplifiers. The experimental results demonstrate that the Total Harmonic Distortion achieved for all the practical PLF and IPLF circuits was equal or lower than 0.21%, whereas the Spurious-Free Dynamic Range also exceeded 57.23 and 54.72 dBc, respectively.

Observer-based adaptive neural network control for PEMFC air-feed subsystem

Oxygen excess ratio (OER) tracking of polymer electrolyte membrane fuel cell (PEMFC) air-feed subsystem is an interesting topic to obtain a high energy conversion ratio. The control purpose is challenging due to the unknown nonlinear function, time-varying external disturbance and unmeasured variable. To deal with the above problems, a neural network control scheme based on tracking error observer and disturbance observer is proposed. Firstly, a canonical form of the PEMFC air-feed subsystem is developed based on the input–output feedback linearization method. Meanwhile, a tracking error observer which only uses the system output is developed for the reconstruction of the unmeasured variable. Secondly, the neural network based on a novel adaptive learning law is proposed to approximate the unknown nonlinear function. An identification model with a second-order low-pass filter is designed such that the adaptive learning law is adjusted by the observer error and modeling error, simultaneously. Finally, to reduce the effect caused by compound disturbance including the external disturbance and neural network approximation error, a nonlinear disturbance observer is proposed. The main contribution of this study is not only avoiding the prior knowledge of system uncertainty, external disturbance and the unmeasured variable but also improving the OER tracking performance under the measurement noise. Lyapunov theory analysis shows that the system tracking error is uniformly ultimately bounded. Numerical simulations and hardware-in-loop (HIL) experiments show that the proposed neural network control algorithm can maintain OER at the target value even under external disturbance. The experimental results show that the performance indexes including the mean absolute error (MAE), the root mean square error (RMSE) and the standard deviation (SD) of the proposed controller during the whole process are 0.0213, 0.0547 and 0.0538, respectively. Compared with the proportional–integral–derivative (PID) controller (MAE 0.0466, RMSE 0.0762 and SD 0.0745), robust adaptive radial basis function neural network (RBFNN-H∞) controller (MAE 0.0841, RMSE 0.0839 and SD 0.0813) and hybrid robust adaptive radial basis function neural network (HARBFNN-1st) controller (MAE 0.0255, RMSE 0.0613 and SD 0.0603), the proposed controller performs a better performance.

Compact Differential Diplex Filtenna With Common-Mode Suppression for Highly Integrated Radio Frequency Front-Ends

A compact, differential diplex filtenna (DDF) with common-mode (CM) suppression is presented. A rectangular dual-mode patch is developed that operates in both its TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode and a reshaped TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode to realize two passbands. Two capacitively loaded loop (CLL) resonators that work at different frequencies are combined with the dual-mode patch to enhance its operational bandwidth and to provide a second-order Chebyshev filter response for both passbands. A slot-coupled differential feed is adopted to suppress the harmonic and CM noise and to obtain symmetrical radiation patterns with low cross-polarization levels. The design process, which is based on filter synthesis theory, is detailed. A prototype operating over the 2.4G and 5.8G WLAN bands was fabricated, assembled, and tested. The measured results, in good agreement with their simulated values, confirm that it attains maximum broadside realized gains of 5.45 and 8.5 dBi and −10 dB fractional impedance bandwidths of 2.4% (2.42–2.48 GHz) and 5.2% (5.65–5.95 GHz) for the lower and upper passbands, respectively. Moreover, it exhibits good out-of-band rejection levels of 18 and 29 dB for the lower and upper stopbands, respectively.

Hybrid control of piezoelectric flexible manipulator based on Volterra filtered-xLMS algorithm

To suppress the nonlinear vibration of the flexible manipulator during motion, this article presents a hybrid control strategy based on a servo motor and a piezoelectric actuator. The dynamic model of the piezoelectric flexible manipulator is established first. To realize the trajectory tracking, a proportional derivative control method is used to schedule the control torque. Because the Volterra filter can approximate the nonlinear system model, a Volterra filtered-xLMS algorithm based on a second-order Volterra filter structure is proposed, by which the active nonlinear vibration control of flexible link is realized. Simulation results show that the proposed Volterra filtered-xLMS algorithm can not only make use of the advantages of the classical filtered-xLMS algorithm but also solve the problem of effective modeling of nonlinear secondary path. The proposed hybrid control strategy based on Volterra filtered-xLMS algorithm and proportional derivative control algorithm can improve the position accuracy of joint and effectively suppress the vibration response of the nonlinear flexible link. A piezoelectric flexible manipulator with PZT (lead zirconate titanate) sensor and actuator is designed to demonstrate the validity and efficiency of the proposed method by experiments. Experiment results demonstrate that the attenuation time of vibration response is reduced from 5 s to 1.5 s, the vibration response at the first-order frequency is reduced by 60%, and the proposed methodology has an important advantage in application of active vibration control of piezoelectric flexible manipulator.