Order Low Pass Research Articles

Innovative viscoelastic material selection strategy based on dma and mini-shaker tests for spacecraft applications

With the increase of payload sensitivity (such as high precision optics for sub-metric imager), micro-vibration disturbances generated by spinning actuators, if not controlled, may affect on-board instruments and may worsen the quality of pictures taken by an Earth observation imager. For the last two decades, viscoelastic materials have been gradually used in isolators designed for space applications. Their attractiveness comes from their ability to act as a second order low pass filter to minimise micro-vibration forces. In this study, an innovative viscoelastic material pre-selection process has been developed to assess the mechanical and thermal properties of viscoelastic isolators during early design stages. In order to characterise the viscoelastic isolators, tests have been performed at viscoelastic material level (material characterisation) and at viscoelastic isolator level (isolator characterisation). A qualitative correlation has been established between the master curves (material characterisation) and the transmissibility curves (isolator characterisation) which leads to a possible prediction of expected isolation performances of a viscoelastic material during early design stages.

Current mode MOSFET-only third order Butterworth low pass filter with DTMOS tuning technique

A new low-voltage, MOSFET-only, third order low-pass filter is proposed. The circuit employs only MOSFETs operating in saturation region. The transconductance gains and the parasitic gate to source capacitances of the MOSFETs represent resistive and capacitive elements of the filter. Using TSMC 0.18 µm technology parameters the circuit is simulated, non-ideal effects have been investigated and dynamic threshold voltage MOS tuning technique has been developed for the filter circuit to suppress the non-idealities. In this tuning technique, bulk terminals of MOS transistors are used to adjust the biasing point of the circuit by changing the threshold voltages of the MOS transistors. This gives the designers more flexibility than conventional tuning methods and allows low voltage operation when several transistors are stacked over each other. The resulting circuit is capable of operation at high frequencies with low power consumption due to the usage of significantly less number of transistors than conventional active block-based filtering circuits.

EVALUATION OF INTEGRATED ANALOG RC FILTER STRUCTURES FOR MULTISTANDARD TRANSCEIVERS / INTEGRINIŲ ANALOGINIŲ RC FILTRŲ STRUKTŪRŲ DAUGIASTANDARČIAMS SIŲSTUVAMS-IMTUVAMS TYRIMAS

Multistandard transceivers usually have high order low pass filters in their receiver chains. Different filter topologies may have various component variation tolerances and different output noise. In this work, three 6th order filter with different topologies are analyzed for use in multistandard transceivers. Filters are designed in 0.18 µm and 65 nm CMOS technologies and simu-lated using Cadence software. The results show, that the filter frequency response variation in integrated circuits does not de-pend on the filter topology. Simulation results also show that the Leapfrog filter topology has the smallest integrated output noise in the filter bandwidth and is most suited for low noise applications. Daugiaustandarčiuose siųstuvuose-imtuvuose naudojami aukštesnės eilės žemųjų dažnių filtrai. Skirtingos filtrų struktūros gali būti nevienodai jautrios jas sudarančių elementų nuokrypiams ir daryti skirtingą įtaką daugiastandarčių siųstuvų-imtuvų triukšmams. Darbe pateikti trijų šeštosios eilės skirtingų struktūrų aktyviųjų RC filtrų, skirtų daugiaustandarčiams siųstuvams-imtuvams, tyrimo rezultatai. Filtrų struktūros modeliuojamos naudojant 0,18 μm ir 65 nm KMOP integrinių grandynų gamybos technologijas ir Cadence Virtuoso programinę įrangą. Iš imitacijos rezultatų matyti, kad moderniose integrinių grandynų technologijose filtrų dažninių amplitudės charakteristikų (DACh) parametrų nuokrypis beveik nepriklauso nuo filtro struktūros. Tarp analizuotų filtrų struktūrų mažiausia praleidžiamųjų dažnių juostoje integruota išėjimo triukšmo vidutinė kvadratinė vertė gaunama naudojant šuolinių grįžtamųjų ryšių struktūros filtrus.

Instrument current transducer for measurements in asymmetrical conditions in three-phase circuits with upper harmonics

The theme of the article is protection of electrical circuits against negative sequence currents both with sinusoidal and trapezoidal waveforms. The suggested solution is enhancement of instrument current transducers used in industrial relaying and control applications. The instrument negative sequence current transducer connected to Rogowski coils designed by the authors is presented in the article. To protect circuits with extremely non-sinusoidal currents (such as trapezoidal waveforms), instrument transducers with 2nd order low pass filter are suggested. In the presence of higher-order harmonics in the protected three-phase circuit the low pass filter will reduce the THD in the output voltage of instrument negative sequence current transducer (as compared to harmonics in currents of the protected circuit) and compensate for the differentiation effect typical of such transducer schemes.The paper may be of interest for investigators and engineers engaged in research, design and commissioning of protection and control equipment, current instrument and measurement devices used in industrial applications, and also for undergraduate and postgraduate students in electrical engineering.

On The Optimization of Fractional Order Low-Pass Filters

This paper presents three different optimization cases for normalized fractional order low-pass filters (LPFs) with numerical, circuit and experimental results. A multi-objective optimization technique is used for controlling some filter specifications, which are the transition bandwidth, the stop band frequency gain and the maximum allowable peak in the filter pass band. The extra degree of freedom provided by the fractional order parameter allows the full manipulation of the filter specifications to obtain the desired response required by any application. The proposed mathematical model is further applied to a case study of a practical second- generation current conveyor (CCII)-based fractional low-pass filter. Circuit simulations are performed for two different fractional order filters, with orders 1.6 and 3.6, with cutoff frequencies 200 and 500 Hz, respectively. Experimental results are also presented for LPF of 4.46 kHz cutoff frequency using a fabricated fractional capacitor of order 0.8, proving the validity of the proposed design approach.

Feature Extraction Method for Improving Speech Recognition in Noisy Environments

The paper presents a feature extraction method, named as Normalized Gammachirp Cepstral Coefficients (NGCC) that incorporates the properties of the peripheral auditory system to improve robustness in noisy speech recognition. The proposed method is based on a second order low-pass filter and normalized gammachirp filterbank to emulate the mechanisms performed in the outer/middle ear and cochlea. The speech recognition performance of this method is conducted on the speech signals in real-world noisy environments. Experimental results demonstrate that method outperformed the classical feature extraction methods in terms of speech recognition rate. The used Hidden Markov Models based speech recognition system is employed on the HTK 3.4.1 platform (Hidden Markov Model Toolkit).

Performance evaluation of a new signal processing system design to improve CANDU SDS1 trip response during large break LOCA events

ABSTRACTPerformance of a recently developed signal processing system for CANDU (Canada Deuterium Uraniu) reactor shutdown system 1 (SDS1) is evaluated in this paper. The evaluation is carried out in MATLAB/Simulink software environment as well as with an existing power measurement and signal processing system. The new signal processing algorithm is obtained based on the synthesis of several first order low pass filters with different delayed time constants. Throughout this paper, a special attention has been paid to compare the new signal processing system with the existing one. The dynamic behavior of the new signal processing system in the practical large loss of coolant accidents (LLOCA) events has also been examined. Simulation results show that during the LLOCA event, the reactor trip time, as well as the peak power, is decreased remarkably. Through the simulation studies, it has convincingly demonstrated that the new signal processing system has significant advantages over the existing system in terms of the improved trip response and accommodation of the spurious trip immunity. This advantage will significantly enhance the safety margin, or will bring economical benefits to nuclear power plants.

Comparing Equivalent Dead-Time Compensators

Abstract: The paper deals with evaluation of some new aspects in dead-time compensators design for the first order time delayed plant. It considers several alternative solutions to the Smith predictor employing higher order low pass filters. Nominally they should yield the same dynamics. Evaluation by real time control of an Arduino based thermal plant aims to show if they are equivalent also in non-ideal practical applications. Another tested question is, if the introduction of higher order filters brings some advantages. Due to introduction of a disturbance reference model, the new modifications of the Smith predictor keep its original dynamics also under an explicit stabilizing controller. They may be derived both for input and output measurable disturbances. However, since a disturbance observer for reconstruction of non measurable output disturbances by a parallel plant model is applicable just to stable plants, from the beginning the comparison shows non identical properties of the treated solutions. The carried out experiments show also their differences in noise attenuation.

Variational Multiscale Element Free Galerkin Method Coupled with Low-Pass Filter for Burgers’ Equation with Small Diffusion

Variational multiscale element free Galerkin (VMEFG) method is applied to Burgers’ equation. It can be found that, for the very small diffusivity coefficients, VMEFG method still suffers from instability in the presence of boundary or interior layers. In order to overcome this problem, the high order low-pass filter is used to smooth the solution. Three test examples with very small diffusion are presented and the solutions obtained are compared with exact solutions and some other numerical methods. The numerical results are found in which the VMEFG coupled with low-pass filter works very well for Burgers’ equation with very small diffusivity coefficients.

Comparison of $$(1+\alpha )$$ ( 1 + α ) Fractional-Order Transfer Functions to Approximate Lowpass Butterworth Magnitude Responses

Three fractional-order transfer functions are analyzed for differences in realizing ($$1+\alpha $$1+?) order lowpass filters approximating a traditional Butterworth magnitude response. These transfer functions are realized by replacing traditional capacitors with fractional-order capacitors ($$Z=1/s^{\alpha }C$$Z=1/s?C where $$0\le \alpha \le 1$$0≤?≤1) in biquadratic filter topologies. This analysis examines the differences in least squares error, stability, $$-$$-3 dB frequency, higher-order implementations, and parameter sensitivity to determine the most suitable ($$1+\alpha $$1+?) order transfer function for the approximated Butterworth magnitude responses. Each fractional-order transfer function for $$(1+\alpha )=1.5$$(1+?)=1.5 is realized using a Tow---Thomas biquad a verified using SPICE simulations.

Approximated Fractional-Order Inverse Chebyshev Lowpass Filters

In this paper we use a least-squares fitting routine to approximate the stopband ripple characteristics of fractional-order inverse Chebyshev lowpass filters which have fractional-order zeros and poles. MATLAB simulations of $$(1+\alpha )$$(1+�)-order lowpass filters with fractional steps from $$\alpha =0.1$$�=0.1 to $$\alpha =0.9$$�=0.9 are given as examples. SPICE simulations of 1.2-, 1.5-, and 1.8-order lowpass filters and experimental results of a 1.5-order filter using approximated fractional-order capacitors in a Multiple-Input Biquad circuit validate the implementation of these circuits.

PID controller for automatic voltage regulator using teaching–learning based optimization technique

Abstract The present work presents teaching–learning based optimization (TLBO) algorithm as an optimization technique in the area of tuning of the classical controller installed in automatic voltage regulator (AVR). The proposed TLBO algorithm is applied with an aim to find out the optimum value of proportional integral derivative (PID) controller gains with first order low pass filter installed in the AVR. The voltage response of the AVR system, as obtained by using the proposed TLBO based PID controller with first order low pass filter, is compared to those offered by the other algorithms reported in the recent state-of-the-art literatures. The advantage of using this control strategy may be noted by providing good dynamic responses over a wide range of system parametric variations. For on-line, off-nominal operating conditions, fast acting Sugeno fuzzy logic technique is applied to obtain the on-line dynamic responses of the studied model. Furthermore, robustness analysis is also carried out to check the performance of the designed TLBO based PID controller. An analysis, based on voltage response profile, has been investigated with the variations of the model parameters. The simulation results show that the proposed TLBO based PID controller is a significant optimization tool in the subject area of the AVR system. The essence of the present work signifies that the proposed TLBO technique maybe, successfully, applied for the AVR of power system.

MICROSTRIP LOW PASS FILTER DESIGNS USING DEFECTED GROUND STRUCTURE

The microwave filters play an important role in most RF/microwave applications. They are designed to remove undesired harmonics to reduce the system noise or to remove spurious mixing products. DGS slot with an interdigital shape are introduced here in two elliptic low pass filter designs. Here a fifth order low pass filter was designed, simulated and fabricated for a cut off frequency of 3GHz. Finally a prototype model were designed based on the simulation results obtained. These prototype filter designs have more than 20 dB of stop band rejection and a good return loss in the pass band. The fabricated results proved to be better than the simulation results. In the first low pas filter design the central aperture was replaced with the interdigital slot structure which improved the stop band response at the resonant frequency around 7.8 GHz. To improve the stop band rejection two interdigital structures were introduced in the bottom layer (Ground).

Design of Low Power, High Gain PLL using CS-VCO on 180nm Technology

This paper investigates the design and performance of the PLL (Phase Locked Loop). The proposed PLL designed with PFD (Phase Frequency Detector), CP (Charge Pump), first order Low Pass Filter and CS-VCO (Current Starved-Voltage Control Oscillator), in this paper the designed PFD used for proposed PLL is free from dead zone. The VCO used for the designed PLL shows larger tuning range and high gain as compares to previous work, i.e. tuning range (167MHz – 1.711GHz) and VCO gain (2.21GHz/V or 13.875*10 radians/s*V). In the proposed work, the designed PLL has higher pull-in range 950MHz (50MHz – 1GHz) with maximum jitter 9.8ps. Power dissipation for proposed PLL system is low, i.e. 277.2 μW with maximum pull-in time is 265ns at 1GHz. The proposed PLL circuit is implemented on CADENCE UMC0.18um process technology file with supply voltage 1.8V. All simulations are done using cadence spectre simulator.

A Novel Active Damping Control of a Three-phase PWM Inverter with LC Filter

A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of 2nd order low pass filter(2nd LPF) which has a zero damping ratio. A simple method of implementing 2nd LPF with damping ratio is to add resistor to inductor or capacitor of LC filter. In an industrial application, it is not practical to adopt damping resistor because it results in losses being proportional to square of current flowing through resistor. Instead of using damping resistors, the proposed active damping control(ADC) utilizes all pass filter(APF) and considers inherent processing delay of digital controller. The overall transfer function of the proposed method is the same as a 2nd LPF and its damping ratio is also controllable via control variables. Detailed design and implementation of controller is also presented. Experiments are conducted with a 7.5kVA induction motor drive system controlled by PWM converter and inverter. Test waveforms are also presented to verify the proposed LC filter control algorithm.

Voltage differencing transconductance amplifier based resistorless and electronically tunable wave active filter

This paper presents a systematic approach for the realization of resistorless wave active filter using voltage differencing transconductance amplifier. The proposed filter uses grounded capacitor and also possesses electronic tunability of cut-off frequency via bias current. The functionality of the proposed filter is verified for a 4th order low pass filter through PSPICE simulation using 0.18 µm TSMC CMOS technology parameter. Experimental results using commercially available IC LM13700/NS are also included which corroborate the theoretical and simulated results.

2차 델타 시그마 변조기법을 이용한 고 정밀 및 고 안정 디지털 전자석 전원 장치에 관한 연구

This paper is writing about developing magnet power supply. It is very important for power supply to obtain output current in high precision and high stability. As a switching noise and a power noise are the cause of disrupting the stability of output current, to remove these at the front end, low pass filter with 300Hz cutoff frequency is designed and placed. And also to minimize switching noise of the current into magnet and to stop abrupt fluctuations, output filter should be designed, when doing this, we design it by considering load has high value inductance. As power supply demands the stability of less than 5ppm, high precision 24bit(300nV/bit) analog digital converter is needed. As resolving power of 24bit(300nV/bit) analog digital converter is high, it is also very important to design the input stage of analog digital converter. To remove input noise, 4th order low pass filter is composed. Due to the limitation of clock, to minimize quantization error between 15bit DPWM and output of ADC having 24bit resolving power, ∑-? modulation is used and bit contracted DPWM is constituted. And before implementing, to maximize efficiency, simulink is used.

A Novel Current Controller Scheme for Doubly Fed Induction Generators

This paper presents a novel current control methodology for grid connected doubly-fed induction generator (DFIG) based wind energy conversion systems. Controller is based on a proportional controller with additional first order low pass filter disturbance observer which estimates the parameter dependent nonlinear feed-forward terms. The results in simulations and experimental test bed obviously demonstrate that decoupled control of active and reactive power is achieved without the necessity of additional machine parameter.

Approximated Fractional Order Chebyshev Lowpass Filters

We propose the use of nonlinear least squares optimization to approximate the passband ripple characteristics of traditional Chebyshev lowpass filters with fractional order steps in the stopband. MATLAB simulations of(1+α),(2+α), and(3+α)order lowpass filters with fractional steps fromα = 0.1 toα = 0.9 are given as examples. SPICE simulations of 1.2, 1.5, and 1.8 order lowpass filters using approximated fractional order capacitors in a Tow-Thomas biquad circuit validate the implementation of these filter circuits.

FIR Linear Phase Fractional Order Digital Differentiator Design using Convex Optimization

In this paper, design of linear phase FIR digital differentiators is investigated using convex optimization. The problem of differentiator design is first described in terms of convex optimization with different optimization variables’ options, taken one at a time. The method is then used to design first order low pass differentiators and results are compared with Salesnick’s technique and Parks McClellan algorithm. The designed FIR low pass differentiator has improvement in transition width and flexibility to optimize different parameters. The concept of low pass differentiation is further generalized to fractional order differentiators. Fractional order differentiators are designed by using minmax technique on mean square error. Design examples demonstrate easy design procedure and flexibility in the process as well as improvement over existing fractional order differentiators in terms of mean square error in passband. Finally, fractional order differentiators are designed and used for texture enhancement of color images. Better texture enhancement than existing filtering approaches is established based on average gradient and entropy values. General Terms FIR Filter, Fractional order differentiator, Low pass differentiator, Full band differentiator, Image Enhancement.