Order Low Pass Filter Research Articles

Improved droop control strategy for grid-connected inverters

Abstract An improved control strategy for grid-connected inverters within microgrids is presented in this paper. The strategy is based on the classical P − ω and Q − V droop method. The improvement in the proposed control strategy is twofold: Firstly, the transient response of the droop controller is improved by replacing the traditional method of measuring average power, which is based on using a first order low pass filter, by a real time integration filter. This is shown to reduce the imported transient energy when connecting to the grid. Secondly, the steady state output current quality is improved by utilising a virtual inductance, which is shown to reject grid voltage harmonics disturbance and thus improve the output current THD. A small signal model of the inverter based on the transfer function approach is developed to analyse its stability and determine droop gains. Simulation and experimental results are presented to validate the model and demonstrate the controller capabilities.

Improved Virtual-Flux-Linkage Observation Method of PWM Rectifier

In order to improve the virtual flux oriented vector control performance of PWM rectifier, an improved observation method of virtual flux-linkage is proposed. To avoid the relevant problems of pure integrator, and to achieve the accurate observation of the grid voltage’s phase, three first order low-pass filters are cascaded to displace the pure integrator. Based on the SVPWM modulation module and the presented algorithm, grid voltage sensorless control system of three-phase PWM rectifier is given. Simulation results have shown that: either in rectifying or inverting status, the amplitude and phase of virtual flux-linkage can be observed accurately, i.e. the control system of PWM rectifier can operate reliably without the grid voltage sensors; the presented estimation method of virtual flux-linkage is effective.

Digital self-excited loop for a superconducting linac

A self-excited loop based RF control with signal processing carried out primarily in the digital domain, has been developed for the amplitude and phase stabilization of RF fields in the superconducting resonators of BARC-TIFR linac, having a resonant frequency of 150MHz. The system employs direct sampling and the subsequent signal processing has been carried out in a Field Programmable Gate Array. The signal processing has all been carried out in the baseband using the in-phase and the quadrature components only. Limiter, one of the key elements of the signal processing, has been implemented as a feedback loop, which keeps the magnitude of its output constant without affecting the phase. Using a first order low pass filter with gain as the controller, good steady state and adequate dynamic characteristics have been obtained for the limiter. The paper describes the signal processing modules with emphasis on the analysis of the limiter. The test results with the BARC-TIFR linac are presented. The results are encouraging and establish the suitability of the signal processing scheme for this and similar systems.

Sliding-Mode Observer for Speed and Position Sensorless Control of Linear-PMSM

Abstract The paper presents a sliding-mode observer that utilizes sigmoid function for speed and position sensorless control of permanent-magnet linear synchronous motor (PMLSM). In conventional sliding mode observer method there are the chattering phenomenon and the phase lag. Thus, in order to avoid the usage of the low pass filter and the phase compensator based on back EMF, in this paper a sliding mode observer with sigmoid function for detecting the back EMF in a PMLSM is designed to estimate the speed and the position of the rotor. Most of conventional sliding mode observers use sign or saturation functions which need low pass filter in order to detect back electromotive force (back EMF). In this paper a sigmoid function is used instead of discontinuous sign function to decrease undesirable chattering phenomenon. By reducing the chattering, detecting of the back EMF can be made directly from switching signal without any low pass filter. Thus the delay time in the proposed observer is eliminated because of the low pass filter. Furthermore, there is no need to compensate phase fault in position and speed estimating of linear-PMSM. Advantages of the proposed observer have been shown by simulation with MATLAB software.

Data set preprocessing methods for the artificial intelligence-based diagnostic module

The paper presents the application of statistical (econometrics-originated) methods to process learning and testing data sets used by the artificial intelligence (AI) methods in the diagnostics of analog systems. Before the training and evaluation of the intelligent module is performed, the measurement data are analysed to minimize the number of attributes (symptoms) required to distinguish between different states of the System Under Test (SUT). This way the knowledge extracted from the set is simplified, increasing the operation speed and minimizing the threat of overlearning. Also, elimination of unnecessary symptoms from the set allows for decreasing the set of test points where measurements are taken (which is economically desirable). Preprocessing operations include elimination of constant or quasi-stationary symptoms and finding their minimal set, allowing for the efficient fault detection or parameter identification. The paper focuses on the Hellwig and Multiple Correlation Coefficient methods adjusted to the technical diagnostics applications. They are implemented to optimize data sets obtained from simulation of the fifth order lowpass filter. Their usefulness is tested using the artificial neural network (ANN) and Rough Sets (RS) classifiers responsible for detection, and identification of parametric faults.

Note: Electronic damping of microphonics in superconducting resonators of a continuous wave linac

The paper presents an implementation technique to damp the microphonics in superconducting resonators utilizing the coupling between the electromagnetic and the mechanical modes of a resonator. In the technique used the resonant frequency variations are fed back to modulate the field amplitude through a suitable transfer function. Of the two transfer functions used in the experiments, one emulates a derivative action and is placed in a negative feedback configuration. The other transfer function is essentially a parallel combination of second order low pass filters and is used in a positive feedback configuration. Experiments with the Quarter Wave resonators of IUAC, New Delhi linac demonstrate that the damping of some of the modes increases significantly with the introduction of this feedback leading to a reduction in power required for field stabilization and quieter operation of the RF control system.

On Efficient Design of High-Order Filters With Applications to Filter Banks and Transmultiplexers With Large Number of Channels

This paper proposes a method for designing high-order linear-phase finite-length impulse response (FIR) filters which are required as, e.g., the prototype filters in filter banks (FBs) and transmultiplexers (TMUXs) with a large number of channels. The proposed method uses the Farrow structure to express the polyphase components of the desired filter. Thereby, the only unknown parameters, in the filter design, are the coefficients of the Farrow subfilters. The number of these unknown parameters is considerably smaller than that of the direct filter design methods. Besides these unknown parameters, the proposed method needs some predefined multipliers. Although the number of these multipliers is larger than the number of unknown parameters, they are known a priori. The proposed method is generally applicable to any linear-phase FIR filter irrespective of its order being high, low, even, or odd as well as the impulse response being symmetric or antisymmetric. However, it is more efficient for filters with high orders as the conventional design of such filters is more challenging. For example, to design a linear-phase FIR lowpass filter of order 131071 with a stopband attenuation of about 55 dB, which is used as the prototype filter of a cosine modulated filter bank (CMFB) with 8192 channels, our proposed method requires only 16 unknown parameters. The paper gives design examples for individual lowpass filters as well as the prototype filters for fixed and flexible modulated FBs.

40MHz의 대역폭과 개선된 선형성을 가지는 Active-RC Channel Selection Filter

본 논문에서는 40MHz의 대역폭과 개선된 선형성을 가지는 active-RC channel selection filter (CSF)가 제안된다. 제안되는 CSF는 5차 butterworth 필터로써 한 단의 1차 low pass 필터와 두 단의 biquad 기반의 2차 low pass 필터, 그리고 DC offset 제거를 위한 DC 피드백 회로로 구성된다. CSF의 선형성을 개선하기 위해 스위치로 사용되는 MOSFET의 body를 source 노드로 연결한다. 설계된 CSF의 대역폭은 10MHz, 20MHz, 그리고 40MHz로 선택될 수 있으며, 전압 이득은 0dB에서 24dB까지 6dB의 단위로 조정된다. 제안된 CSF는 1.2V 40nm의 1-poly 8-metal CMOS 공정에서 설계된다. 설계된 CSF가 40MHz의 대역폭과 0dB의 gain을 가질 때, OIP3는 31.33dBm이고 in-band ripple은 1.046dB, IRN는 39.81nV/sqrt(Hz)로 시뮬레이션 검증되었다. CSF의 면적과 전력소모는 각각 <TEX>$450{\times}210{\mu}m^2$</TEX>와 6.71mW 이다. An active-RC channel selection filter (CSF) with the bandwidth of 40MHz and the improved linearity is proposed in this paper. The proposed CSF is the fifth butterworth filter which consists of a first order low pass filter, two second order low pass filters of a biquad architecture, and DC feedback circuit for cancellation of DC offset. To improve the linearity of the CSF, a body node of a MOSFET for a switch is connected to its source node. The bandwidth of the designed CSF is selected to be 10MHz, 20MHz and 40MHz and its voltage gain is controlled by 6 dB from 0 dB to 24 dB. The proposed CSF is designed by using 40nm 1-poly 8-metal CMOS process with a 1.2V. When the designed CSF operates at the bandwidth of 40 MHz and voltage gain of 0 dB, the simulation results of OIP3, in-band ripple, and IRN are 31.33dBm, 1.046dB, and 39.81nV/sqrt(Hz), respectively. The power consumption and layout area are <TEX>$450{\times}210{\mu}m^2$</TEX> and 6.71mW.

A Novel Algorithm of Fundamental Positive Sequence Voltage Detector under Unbalanced and Distorted Voltages

This paper presented a new algorithm for the performance improvement of fundamental positive sequence voltage extraction under unbalanced and distorted conditions. In this algorithm, an improved software phase-locked loop (SPLL) with a second order low-pass filter was proposed and analyzed, completely eliminating the phase detection errors of the unbalanced and distorted source voltages. The paper began with a description of the proposed fundamental positive sequence extraction method, and then a detailed analysis of the designed SPLL was introduced. The proposed algorithm improved the sinusoidal current control strategy of active power filter (APF) which was based on the classical power theories for obtaining an optimal extraction of the fundamental positive sequence current. To verify the feasibility of the algorithm in real-time applications, the simulation model was established in MATLAB-Simulink environment. Then, the algorithm was implemented in DSP using the TMS320F28335 development board. The results indicated that the proposed algorithm is feasible and effective, and it could be directly used in the practical applications.

Realistic model of compact VLSI FitzHugh–Nagumo oscillators

In this article, we present a compact analogue VLSI implementation of the FitzHugh–Nagumo neuron model, intended to model large-scale, biologically plausible, oscillator networks. As the model requires a series resistor and a parallel capacitor with the inductor, which is the most complex part of the design, it is possible to greatly simplify the active inductor implementation compared to other implementations of this device as typically found in filters by allowing appreciable, but well modelled, nonidealities. We model and obtain the parameters of the inductor nonideal model as an inductance in series with a parasitic resistor and a second order low-pass filter with a large cut-off frequency. Post-layout simulations for a CMOS 0.35 μm double-poly technology using the MOSFET Spice BSIM3v3 model confirm the proper behaviour of the design.

Second Order Low-Pass and High-Pass Filter Designs Using Method of Synthetic Immitance Elements

The paper briefly describes the basics of frequency filter design method using synthetic immittance elements with current conveyors. An introduction of the paper explains the advantages and also disadvantages of using this method. Other chapters briefly introduce a design process of simple second order low-pass and high-pass filter. A theory of current conveyors is discussed too, because they are the basic building blocs of proposed synthetic element and also active frequency filters. Finally, the particular solutions of low-pass and high-pass filters are given and verified by OrCAD PSpice simulations.

CCII based fractional filters of different orders

This paper aims to generalize the design of continuous-time filters to the fractional domain with different orders and validates the theoretical results with two different CCII based filters. In particular, the proposed study introduces the generalized formulas for the previous fractional-order analysis of equal orders. The fractional-order filters enhance the design flexibility and prove that the integer-order performance is a very narrow subset from the fractional-order behavior due to the extra degrees of freedom. The general fundamentals of these filters are presented by calculating the maximum and minimum frequencies, the half power frequency and the right phase frequency which are considered a critical issue for the filter design. Different numerical solutions for the generalized fractional order low pass filters with two different fractional order elements are introduced and verified by the circuit simulations of two fractional-order filters: Kerwin–Huelsman–Newcomb (KHN) and Tow-Tomas CCII-based filters, showing great matching.

Fully differential DDA-based fifth and seventh order Bessel low pass filters and buffers for DCR radio systems

In this letter the design, fabrication and measurements of fully differential filters and buffers in a 180 nm CMOS process for direct conversion receivers (DCRs) applications are reported. The fully differential fifth and seventh order Bessel low pass filters and buffers are completely based on a differential difference amplifier with common mode feedback capability. In particular, the filters have been designed with a tunable 100 kHz---1 MHz 6 dB bandwidth, in two steps, in order to allow the DCR radio to operate with a 100 Kbit/s---1 Mbit/s data rate. The circuits operate at a 3.3 V supply voltage. The whole chip power consumption, implementing four buffers, two-fifth and two-seventh order low pass filters, is only 6 mW, being particularly suitable for portable apparatus.

Charge Pump, Loop Filter and VCO for Phase Lock Loop Using 0.18µm CMOS Technology

This paper presents a Low power charge pump, second order low pass filter and voltage controlled oscillator for low power phase lock loop. The paper contains the detailed circuit diagram of charge pump, loop filter and voltage control oscillator with 1.8v power supply. The design has been realized using 0.18um CMOS technology. Here current starved voltage control oscillator is use for phase lock loop.

Design of Ota-C Filter for Biomedical Applications

This paper presents design of operational transconductance amplifier is to amplify the ECG signal having low frequency of 300Hz, with the supply voltage of 0.8v. To reduce the power dissipation of 779nW, by using fifth order low pass filter. The OTA-C filter is to eliminate noise voltage and increases the reliability of the system. A chip is fabricated in a 0.18μm CMOS process is simulated and measured to validate the system performance using HSPICE.

Single Cell Microbioreactor for observing Dynamic Gene Expression and Cell Response to Environment in Bacteria

Biological systems have been shown to implement a low-pass filter in order to distinguish high frequency noise from a lower frequency input signal, which is essential to a cellular system to adapt or sustain fitness in fluctuating environment conditions. Gene expression has been shown to exhibit noise leading to phenotypic heterogeneity of a cell population. Many microfluidic techniques have been developed in order to study single cell inducible gene expression, however rely solely on diffusion timescales to effectively alternate between inducer concentrations. In our approach, we developed a microfluidic platform for single cell analysis that allows for dynamic control of a target cell in oscillating well-defined culture media and inducer concentrations. The hydrodynamic trap enables confinement and manipulation of single cells in free solution using the sole action of fluid flow. Automated feedback control is integrated into the device using an “on-chip” valve, which allows for precise confinement of cells in free solution. During observation, cells are confined at a fluid stagnation point generated by planar extensional flow in a cross-slot microfluidic geometry, thereby enabling non-perturbative trapping of cells for long time scales. Using this platform, we investigated the effect of small molecule inducers on gene expression in the lac operon using fluorescent reporter proteins and cell growth rates as a proxy of cellular fitness. We applied our technique to determine the cut-off frequency associated with periodic stimuli for the lac circuit in E. coli, wherein the cut-off frequency in the case of the low-pass filter is the higher frequency when response begins to attenuate. We observed that single cell gene expression depends on the correlation between growth rate and frequency of exposure to inducer concentrations.

Robust Optimal Control of Flexible Space Structures by a Proper Controller Using Displacement Output

This paper considers robust optimal control of flexible space structures with collocated sensors and actuators. First, we introduce a third order low-pass filter of which relative degree is 1, at each input channel. Then, we feed back output of the filter and displacement and velocity output of the space structure to input of the filter, so that we obtain a third order proper controller using only displacement output. By choosing parameters of the proper controller as the controller becomes a phase lead compensator, a closed-loop system becomes robustly stable against uncertainty of characteristic parameters of the structures such as mass, damping, and stiffness. The purpose of this paper is to show the closed-loop system becomes not only robustly stable but also optimal for a quadratic cost function by making two feedback gains contained in the proper controller sufficiently large.

Voltage Flicker Monitoring Based on Virtual Instrument and Wavelet Packet Transform

This paper proposes a new method of monitoring and analyzing voltage flicker based on wavelet packet transform and virtual instrument, and establishes an arithmetic model of the system. First, through the wavelet package transform, we can extract the amplitude modulation waveform, get the accurate time when the voltage flicker occurs and stops, and count the frequency and amplitude of voltage fluctuation. Then, the sensation level weighted filter, square multiplier and first order low pass filter can be designed. Finally, the evaluation indices of short-term flicker severity can be obtained by using statistic sorting algorithms. Experiment results show that this method is very applicable for the detection of non-stationary voltage fluctuating and flicker signals.

Gravitation search algorithm: Application to the optimal IIR filter design

This paper presents a global heuristic search optimization technique known as Gravitation Search Algorithm (GSA) for the design of 8th order Infinite Impulse Response (IIR), low pass (LP), high pass (HP), band pass (BP) and band stop (BS) filters considering various non-linear characteristics of the filter design problems. This paper also adopts a novel fitness function in order to improve the stop band attenuation to a great extent. In GSA, law of gravity and mass interactions among different particles are adopted for handling the non-linear IIR filter design optimization problem. In this optimization technique, searcher agents are the collection of masses and interactions among them are governed by the Newtonian gravity and the laws of motion. The performances of the GSA based IIR filter designs have proven to be superior as compared to those obtained by real coded genetic algorithm (RGA) and standard Particle Swarm Optimization (PSO). Extensive simulation results affirm that the proposed approach using GSA outperforms over its counterparts not only in terms of quality output, i.e., sharpness at cut-off, smaller pass band ripple, higher stop band attenuation, but also the fastest convergence speed with assured stability.

A 160 &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\mu{\rm A}$&lt;/tex&gt;&lt;/formula&gt; Biopotential Acquisition IC With Fully Integrated IA and Motion Artifact Suppression

This paper proposes a 3-channel biopotential monitoring ASIC with simultaneous electrode-tissue impedance measurements which allows real-time estimation of motion artifacts on each channel using an an external μC. The ASIC features a high performance instrumentation amplifier with fully integrated sub-Hz HPF rejecting rail-to-rail electrode-offset voltages. Each readout channel further has a programmable gain amplifier and programmable 4th order low-pass filter. Time-multiplexed 12 b SAR-ADCs are used to convert all the analog data to digital. The ASIC achieves >; 115 dB of CMRR (at 50/60 Hz), a high input impedance of >; 1 GΩ and low noise (1.3 μVrms in 100 Hz). Unlike traditional methods, the ASIC is capable of actual motion artifact suppression in the analog domain before final amplification. The complete ASIC core operates from 1.2 V with 2 V digital IOs and consumes 200 μW when all 3 channels are active.