Low-pass Output Research Articles

Analysis and Optimization of Output Low-Pass Filter for Current-Source Single-Phase Grid-Connected PV Inverters

In this study, the design of output low-pass capacitive–inductive (CL) filters is analyzed and optimized for current-source single-phase grid-connected photovoltaic (PV) inverters. Four different CL filter configurations with varying damping resistor placements are examined, evaluating performance concerning the output current’s total harmonic distortion (THD), the power factor (PF), and power losses. High-frequency harmonics are effectively attenuated by a second-order CL filter with the damping resistor placed parallel to the filter inductor. In addition, this filter type achieves the best performance by minimizing power loss. A systematic design methodology using filter normalization techniques allows to determine the optimum filter parameters based on the specified cut-off frequency (500 Hz), power loss (5% of rated power), and target THD (<5%). The analysis, simulations, and experiments show that under various operating conditions, this approach meets the grid connection standards (current THD < 5%, power factor between 0.8 leading and 0.95 lagging) while improving efficiency.

Unknown input observer based neuro-adaptive fault-tolerant control for vehicle platoons with sensor fault and output quantization

Sensor fault and output quantization are common issues acting on vehicle platoon, and they may lead to performance deterioration, instability and even insecurity of the platoon. Therefore, this paper investigates the fault-tolerant control (FTC) problem of vehicle platoons with regard to the above two issues. Considering the probabilistic sensor fault and quantized measurement signals, an unknown input observer (UIO) based fault detection algorithm with adaptive threshold is developed for sensor health status monitoring. Then, an augmented vehicle platoon model is constructed by introducing a low-pass output filter, and a robust UIO is established for state reconstruction. Based on the above results, a fault-tolerant control scheme is exploited by employing the back-stepping control method and adaptive radial basis function neural network (RBF NN) approximation technique, which is proved to be capable of achieving the time-domain string stability (TSS) of vehicle platoons in the presence of sensor fault and output quantization. Simulation results demonstrate the effectiveness of the proposed algorithms.

Design of Low-Cost Full W-Band 8th Harmonic Mixers for Frequency Extension of Spectrum Analyzer

High-order harmonic mixer is popular for frequency extension of spectrum analyzer (SA) from microwave to millimeter-wave or even terahertz band. The manufactures of SA usually offer expensive harmonic mixers where frequency extension is needed. In this work, low-cost designs of 2-port and 3-port W-band 8th harmonic mixers covering 75–110 GHz are proposed, and design method of two port mixer without frequency diplexer to separate local oscillator (LO) and intermediate frequency (IF) signals are first presented. These two kinds of mixers are compatible with almost all the current SAs with frequency extension options, which provides LO for the external harmonic mixer. The mixers are designed with planar microstrip lines and antiparallel Schottky diodes. The circuit of 2-port mixer includes the input broadband bandpass filter, diodes, output lowpass filter, and matching circuits. As for 3-port mixer, only an extra diplexer is needed to separate the IF signal and LO signal. The diplexer is composed of a planar semi-lumped lowpass and a highpass filter. The planar circuits are easily fabricated with low-cost print circuit board process on polytetrafluoroethylene substrate. The measured conversion loss of 2-port 8th harmonic mixer is from 20 to 26 dB, and 23 to 28 dB for 3-port mixer at full W-band. The good measured results indicate the proposed mixers are simple and effective.

Multi-Band Power Amplifier Module with Back-Off Efficiency Improvement using Ultra-Compact 3D Vertical Stack Multi-Chip Package for Cellular Handsets.

A highly integrated multi-mode multi-band (MMMB) power amplifier module (PAM) using hybrid bulk complementary metal oxide semiconductor (CMOS), gallium arsenide (GaAs) heterojunction bipolar transistor (HBT), and silicon-on-insulator (SOI) technologies for low band (LB, 824-915 MHz) and high band (HB, 1710-1980 MHz) is proposed. The hybrid MMMB PAM integrates a bulk CMOS controller die, a GaAs HBT power amplifier (PA) die and a SOI switch die on a six-layer laminate. To simultaneously obtain both highly efficient and highly linear characteristics over a wide range of input power levels, a parallel dual-chain PA strategy has been adopted to provide vary bias current and gain for low-power mode (LPM) and high-power mode (HPM) operation. Additionally, a broadband two-section low-pass output matching network design based on the suppression of high-order harmonics is proposed for enhanced efficiency and linearity. In order to achieve further miniaturization, a three-dimensional (3D) die stack multi-chip module (MCM) packaging structure, where the presented CMOS controller die is stacked vertically on the GaAs HBT PA die, is implemented. The measurement results show that the fabricated MMMB PAM achieves 26.1-27 dB of power gains and 38-38.4% of PAEs at an output power (Pout) of 28 dBm in the HPM, and 20.4-20.9 dB of power gains and 12.4-13.8% of PAEs at Pout of 17 dBm in the LPM over LB. For HB, power gains of 24.3-26.7 dB while maintaining PAEs of 38.2-39.9% at Pout of 28 dBm, and power gains of 15.9-17.5 dB while maintaining PAEs of 12.3-12.8% at Pout of 17 dBm are realized in the HPM and LPM, respectively. The fabricated PAM covering five frequency bands and operating at two power modes only occupies a 5 × 3.5 mm2 area. To the best of the authors' knowledge, this work is the first demonstration of a MMMB PAM adopting an ultra-compact 3D vertical stack MCM package with favorable RF performance.

유도 부하에 적합한 넓은 입력 전압 범위와 높은 역률의 2단 AC-AC 컨버터 설계

In this paper, a two-stage AC-AC power supply is designed to specifically handle the operation and performance improvements of the power system with highly inductive loads. The proposed power supply scheme includes an input interleaved power factor correction (PFC) stage to improve the input power factor (PF) and regulate the DC bus voltage required for the second stage, which is a voltage source inverter (VSI) with an output low pass filter to adjust the load harmonics contents and regulate the load voltage and frequency to the specified AC load values. The small-signal models of the PFC and VSI stages are obtained, and optimal voltage and current control loops for both stages are designed based on the obtained models to improve the required system power performance and stability. PSIM simulation is used to examine the performance of the proposed power supply under various input-output operation conditions. This work achieves a 500VA, (180-260)V RMS Power supply with an input PF of 99%, better output voltage regulation, and a lower THD value for the purpose of supplying industrial inductive loads.

MOSFET-C current mode filter for secure communication applications

In this paper, a dual output current-mode biquad filter with band-pass and low-pass outputs using MOS transistors and capacitors is presented. In these type of filters MOSFETs operating in saturation mode are used instead of standard active elements and transconductances of these transistors are utilized instead of resistors. In the study a voltage controlled current source (VCCS) based core filter circuit is presented. This circuit is used as a starting point for the complete filter design. After VCCSs are replaced by MOSFETs biased for operating in saturation region, a resistorless MOSFET-C type filter circuit is obtained with only seven transistors and two grounded capacitors. Also, an agile filter application for secure communication is given to illustrate the functionality.

Single-input multiple-output voltage-mode shadow filter based on VDDDAs

This paper presents a voltage-mode shadow filter with single-input multiple-output (SIMO) configuration using voltage differencing differential difference amplifiers (VDDDAs). In this design, the low-pass and high-pass output functions of the single-input three-output second order filter are feedback via the voltage amplifier. The proposed filter consists of three VDDDAs, one grounded resistor and two grounded passive elements. The proposed filter uses grounded elements which is attractive for integrated circuit (IC) fabrication. It can simultaneously provide low-pass (LP), high-pass (HP), band-pass (BP), band-reject (BR) and all-pass (AP) responses without matching condition. The proposed circuit has high input impedance. The natural frequency (ω0) and quality factor (Q) can be independently and electronically tuned by changing the external DC bias currents. The effect of the non-ideal and parasitic elements of the VDDDA is studied and investigated. The PSpice simulation and experimental results using CMOS technology and commercially available active devices are given to confirm the workability of the proposed filter.

Reconstruction of membrane current by deconvolution and its application to membrane capacitance measurements in cardiac myocytes.

Correct detection of membrane currents under whole-cell patch–clamp conditions is limited by the transfer function of a recording system. The low-pass output filter of a recording amplifier alters the time course of membrane current and causes errors in relevant descriptors. To solve these problems, we developed a practical procedure for reconstruction of the time course of membrane currents based on deconvolution of recorded currents in frequency domain. The procedure was tested on membrane capacitance estimates from current responses to step voltage pulses. The reconstructed current responses, in contrast to original current records, could be described exactly by an adequate impedance model of a recorded cell. The reconstruction allowed to increase the accuracy and reliability of membrane capacitance measurements in wide range of cell sizes and to suppress the cross-talk errors well below the noise. Moreover, it allowed resolving the instabilities in recording conditions arising from parasitic capacitance and seal resistance variation. Complex tests on hardware models, on simulated data sets, and on living cells confirmed robustness and reliability of the deconvolution procedure. The aptitude of the method was demonstrated in isolated rat cardiac myocytes by recording of spontaneous vesicular events, by discerning the formation of a fusion pore, and by revealing artefacts due to unstable seal resistance.

Novel one-dimensional and two-dimensional forward discrete wavelet transform 5/3 filter architectures for efficient hardware implementation

We implemented a more efficient circuit for one-dimensional (1-D) forward discrete wavelet transform (DWT) 5/3 filter. Our design utilizes processing and memory resources that are wasted in some other state-of-the-art solutions and is at least 33% simpler in terms of used registers, is 17% simpler in terms of used logic elements, has 7% higher maximum operating frequency and has 2% lower total power dissipation than previously published designs. The advantages of our design are achieved by a novel non-stationary filter topology which reuses the same registers for generating both low-pass and high-pass output coefficients, in different time slots, due to feed-forward and feedback paths. Our design is suitable for image compression systems which use 5/3 filter, e.g., JPEG 2000. We also proposed two-dimensional (2-D) DWT 5/3 architecture which uses implemented 1-D DWT filter design. The proposed 2-D DWT architecture outperforms all previously published architectures in terms of required memory capacity, which is at least 20% lower than memory capacity in any other reported solution.

Prediction-based Deadbeat Control for Grid-connected Inverter with L-filter and LCL-filter

—In this article, an improved deadbeat control algorithm suitable for digital signal processor-based circuit implementation is proposed. The control algorithm allows the derivation of a nearly sine wave output current with a fixed switching frequency of a current-controlled voltage source inverter. Two low-pass output filters configurations are considered in this study: a simple inductance filter and an LCL-filter. By taking advantage of prior knowledge of the state variables’ shape, the improved deadbeat control algorithm is based on a simple prediction model to derive the expected duty cycle needed to switch on and off the power switches. The control study of the grid-connected inverter with L and LCL output filters has been considered using a co-simulation approach with (Powersim Inc., Rockville, Maryland, USA) and MATLAB software (The MathWorks, Natick, Massachusetts, USA). The obtained results show the improvement of both shape quality and tracking accuracy of the output current quantified by low ripple content and a nearly unity power factor.

A Low-Power Interface for Capacitive Sensors With PWM Output and Intrinsic Low Pass Characteristic

A compact, low power interface for capacitive sensors, is described. The output signal is a pulse width modulated (PWM) signal, where the pulse duration is linearly proportional to the sensor differential capacitance. The original conversion approach consists in stimulating the sensor capacitor with a triangular-like voltage waveform in order to obtain a square-like current waveform, which is subsequently demodulated and integrated over a clock period. The charge obtained in this way is then converted into the output pulse duration by an approach that includes an intrinsic tunable low pass function. The main non idealities are thoroughly investigated in order to provide useful design indications and evaluate the actual potentialities of the proposed circuit. The theoretical predictions are compared with experimental results obtained with a prototype, designed and fabricated using 0.32 μm CMOS devices from the BCD6s process of STMicroelectroncs. The prototype occupies a total area of 1025× 515 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and is marked by a power consuption of 84 μW. The input capacitance range is 0-256 fF, with a resolution of 0.8 fF and a temperature sensitivity of 300 ppm/°C.

MOS-only second order current-mode LP/BP filter

In this study, a current-mode dual output low-pass and band-pass filter is presented using only six MOSFET transistors in its core. Transconductances and gate-to-source capacitances of the MOS transistors are employed instead of passive resistors and capacitors. The proposed circuit exhibits important features such as simplicity, low-voltage/power operation, reduced chip area and wide frequency range compared to classical analog circuits that require active elements with large number of transistors. Simulations are performed to verify the theoretical results.

Amplificador classe d para subwoofer

Este artigo apresenta uma topologia de amplificador Classe D de potência adequado para operar com sub-woofer. A estrutura proposta não necessita de fonte de alimentação estabilizada e filtro passa baixas de saída como ocorre com os amplificadores Classe D tradicionais. Um protótipo de 1 kW foi implementado em laboratório obtendo-se rendimento superior a 90 % e THD inferior a 1 %. Roteiro de projeto, princípio de operação e estratégia de controle também são apresentados.

Universal current-mode filter with multiple inputs and one output using MOCCII and MO-CCCA

In this paper, by introducing a current-controlled current amplifier with multi-outputs (MO-CCCA), two new multi-input and single-output (MISO) universal filtering circuits are proposed. Each circuit just contains two second-generation current conveyors with multiple outputs (MOCCIIs), one MO-CCCA and four grounded RC elements. They can realize low-pass, band-pass, high-pass, band-stop and all-pass filtering outputs. The characteristic parameters natural frequency ( ω 0 ) and quality factor ( Q ) can be tuned independently by bias current of MO-CCCA. Compared to other similar circuits, the circuits in this paper have simpler structures and independent tuning characteristics of ω 0 and Q. Moreover, a filter with a high Q can be obtained by adjusting the ratio of MO-CCCA's bias currents.

不連続的インピーダンス変化特性を有した薄膜ＧＭＩセンサと微分回路を組合せた磁界検出方法に関する検討

A giant magnetoimpedance sensor with a step-like impedance property was obtained in the case of amorphous Co85Nb12Zr3 soft magnetic thin film in a rectangle shape with an in-plane uniaxial easy axis in a direction nearly 60 degrees relative to the width direction of the element. It was shown experimentally that the magnetic field in which the step-like impedance change occurs has an almost constant value with a standard deviation in the microtesra (μT) range. The magnetic field in which the step-like change occurs includes information on the external magnetic field. To realize a magnetic field sensor with an accuracy of nT/Hz1/2 by using this step-like phenomenon, a differential circuit was studied in combination with an alternating bias field in the kilohertz (kHz) frequency range. The aim of the differential circuit was to make the driving circuit into a digital logic circuit, by using pulse signals timed to coincide with the step-like changes. The alternating bias field increases the sampling number, because of the step-like changes in the bias frequency. The aim of the ac bias is to improve the sensor accuracy by using an averaging effect. This paper reports a first trial of the method. As a result, a high-linearity sensor without hysteresis was obtained, which had a linearity error of less than 0.5% in the range of ±100 μT. A measurement accuracy of 460 nT was achieved with a 20 Hz time constant of the output low pass filter (LPF).

Mitigation of Bearing Electro-Erosion of Inverter-Fed Motors Through Passive Common-Mode Voltage Suppression

In recent years, investigations of bearing current caused by voltage source inverters (VSIs) have emphasized the effect of steep wavefronts and high carrier frequencies. Such investigations have led to suggested bearing current mitigation techniques incorporating frequency-dependent devices such as low-pass VSI output filters and low-inductance ground paths. Alternatively, others have addressed the problem from an electrostatic standpoint within the motor and have offered solutions such as shaft grounding brushes, insulated bearings, and electrostatically shielded stator windings. This paper examines VSI-output common-mode voltage as the driving source of bearing currents and develops, from a system level, the electrostatic circuit approach as a device to give insight into the technique of reducing common-mode voltage at the motor terminals and thus at the rotor. The technique is passive, low-cost, and retrofittable where allowed by electrical codes and is capable of reducing common-mode voltage by levels of magnitude. Such reductions can profoundly extend bearing service life by reducing the electro-erosion of the bearing surfaces.

A highly efficient CDMA power amplifier based on parallel amplification architecture

A highly efficient code division multiple access power amplifier of parallel amplification architecture exhibits power added efficiency of 17% and adjacent channel power ratio less than -51 dBc at an output power of 16 dBm. The output impedances of the low/high-power amplifier chains are very low because the collector impedances of the OFF-state power heterojunction bipolar transistors are low and the low impedances are transformed into even lower ones by low-pass output matching circuits. The low impedances are boosted up using a compact lumped /spl lambda//4 transmission line and the chains are operated independently without producing any significant performance degradation.

A 71-MHz CMOS IF-baseband strip for GSM

An intermediate-frequency (IF) baseband strip for a superheterodyne GSM receiver developed in a 0.25-/spl mu/m CMOS technology is presented. It contains a 71-MHz IF amplifier, programmable between -20 and +60 dB in 2-dB steps; a quadrature demodulator; and two low-pass output filters for channel selection. Measurements show an overall maximum gain of 89 dB and a noise figure of 3.8 dB. Phase and amplitude mismatches of the demodulator are below 10 and 0.1 dB, respectively. The high linearity required by the blocking and intermodulating signals, which are not completely suppressed by the IF filter, has been achieved using 4.7 mA from the 2,5-V power supply.

A versatile current-mode biquad using operational amplifiers

A versatile current-mode biquadratic filter using three operational amplifiers and nine passive elements is proposed. By suitably choosing the output branch, lowpass, bandpass, highpass, bandstop and allpass transfer functions are realized simultaneously without changing the circuit configuration and elements. Two circuits, one is for low frequency application and the other for high frequency, are proposed. The center frequency, quality factor and gain constants of the circuit can be tuned independently. Simulated results show that the circuits work successfully.

Speaker excursion control system

A speaker excursion control circuit for driving relatively small diameter speakers at their maximum output while assuring minimum distortion of acoustical output from such transducers detects signals which may cause over excursion and dynamically controls the amplitude of signals applied to the power amplifier coupled to the speakers. In one embodiment of the invention a single state-variable filter is employed with a voltage controlled amplifier controlled by a low pass output of the state-variable filter to provide the speaker signal control. In another embodiment, a pair of state-variable filters are employed with the first of such filters defining a model for the speaker cone excursion and providing control output signals to a second state-variable filter which dynamically shifts its filtering characteristics causing increased signal attenuation when the control signals indicate that speaker over excursion may occur.