Showing papers on "Voltage-controlled filter published in 2002"

A novel Kalman filter for frequency estimation of distorted signals in power systems

Abstract: A simple and novel approach in the design of an extended Kalman filter (EKF) for the measurement of power system frequency has been presented in this paper. The design principles and the validity of the model have been outlined. The performance of this filter has been compared with some of the existing methods for estimating the frequency of a signal under noisy conditions. The feasibility of the proposed filter has been tested in the laboratory under worst-case measurement and network conditions, which might occur in a typical power system. Also, the proof of the stability for the proposed filter has been discussed for a single sinusoid. It has been found that the proposed algorithm is suitable for real-time applications especially when the frequency changes are abrupt and the signal is corrupted with noise and other disturbances due to harmonics.

Control and performance of a fully-digital-controlled shunt active filter for installation on a power distribution system

Abstract: This paper presents a fully-digital-controlled shunt active filter for harmonic termination of a power distribution system. The main purpose of the active filter based on voltage detection is not to compensate for current harmonics but to damp out harmonic propagation caused by line inductors and shunt capacitors for power factor correction. However, time and phase delays inherent in digital controllers might lead to unsatisfactory harmonic-damping performance although digital controllers are preferable to analog controllers. This paper deals with the design and implementation of a digital controller for a shunt active filter based on voltage detection. Experimental results obtained from a laboratory system developed in this paper verify the viability and effectiveness of the fully-digital-controlled active filter.

A medium-voltage transformerless AC/DC power conversion system consisting of a diode rectifier and a shunt hybrid filter

Abstract: This paper proposes a 3.3-kV transformerless AC-to-DC power conversion system consisting of a three-phase six-pulse diode rectifier and a shunt hybrid filter. The hybrid filter is formed by a single tuned LC filter per phase and a small-rated three-phase active filter, which are directly connected in series without any matching transformer. The required rating of the active filter is much smaller than that of a conventional standalone active filter be. In addition, no additional switching-ripple filter is required for the hybrid filter because the LC filter functions not only as a harmonic filter tuned at the seventh harmonic frequency but also as a switching-ripple filter around 10 kHz. Experimental results obtained from a 200-V 5-kW laboratory system and simulation results of a 3.3-kV 300-kW system confirm the validity and effectiveness of the system.

Design and implementation of an inverter output LC filter used for dv/dt reduction

Abstract: This paper presents the design and analysis of a LC output filter for use with IGBT-based motor drive inverters. The LC filter is used to limit the rate of rise of the inverter output voltage and reduce common mode noise to the motor. In typical applications where dv/dt is limited to 100-500 V//spl mu/s, the resonant frequency of the filter is above the switching frequency. A diode bridge must therefore be used to clamp the resonant voltage. Resistors are also used to help dissipate the energy stored in the resonant circuit. Crucial to the design of the filter is the handling of the additional losses in the filter. The paper describes the design considerations for such a filter for use in a 460 V induction motor drive. The losses in the circuit are estimated to show the limitations of the filter. Experimental results illustrate the control of dv/dt at the inverter terminals, and the reduced peak voltage at the motor end of a long cable.

A tunable filter and method of tuning a filter

Abstract: A bandpass filter is tuned by converting the filter into an oscillator using a negative resistance circuit, tuning the oscillator by using conventional tuning techniques such as tuning a varactor via a phase locked loop, sampling and holding the tuning signal and switching off the negative resistance circuit to convert the oscillator back into a bandpass filter.

Implementation and performance of automatic gain adjustment in a shunt-active filter for harmonic damping throughout a power distribution system

Abstract: This paper discusses automatic gain adjustment in a fully-digital-controlled shunt active filter. This is the first step in cooperative control of the multiple active filters based on voltage detection for harmonic damping throughout power distribution systems. In general, the active filter should be equipped with an optimal control gain corresponding to the characteristic impedance of a distribution line. However, it is difficult to know circuit parameters of a real distribution line having various shunt capacitors and loads. Therefore, a main purpose of the gain adjustment is to make the active filter damp out harmonic propagation without considering the circuit parameters. In addition, the gain adjustment can reduce the compensating currents and losses in the active filter, and moreover it can avoid over-damping performance. Experiment results obtained from a 200-V, 20-kW laboratory system verify the effectiveness of the active filter equipped with automatic gain adjustment.

Shunt active power filter synthesizing resistive loads

Abstract: The paper discusses the use of a shunt active power filter to compensate for the line current distortion and to improve the power factor. The advantages of the resistive load synthesis over the sinusoidal current synthesis when the filter is used in a system where the voltage is not perfectly sinusoidal are presented. The control circuit is based on analogic multipliers, and the currents follow the same waveforms of the respective line voltages. Experimental results of connecting a three-phase active power filter to a nonsinusoidal grid are presented.

Ultra-selective 22-pole 10-transmission zero superconducting bandpass filter surpasses 50-pole Chebyshev filter

Abstract: An ultra-selective filter for third-generation (3G) and fourth-generation wireless application is presented. The demonstrated filter consists of 22 resonators and five cross couplings that produce ten transmission zeros. The filter was designed at 1950-MHz center frequency with a 20-MHz bandwidth to meet existing 3G wireless applications. The measured filter data shows excellent selectivity, better than 30-dB/100-kHz skirt slopes, and 90 dB of rejection at 350 kHz from the band edge. This filter performance surpasses the performance of a 50-pole Chebyshev filter. In order to fit a large number of resonators into a limited wafer area, a new compact resonator was developed. The filter was fabricated using a YBCO thin film on a 2-in MgO wafer.

An efficient and simple method for designing prototype filters for cosine-modulated pseudo-QMF banks

Abstract: We present a new method to design prototype filters for conventional cosine-modulated pseudo-quadrature mirror filter (QMF) banks. This method is based on windowing, and sets the 3-dB cutoff frequency of the filter obtained at /spl pi//2M. In this way, the filter bank performance can be significantly improved compared to other existing design methods.

Ripple feedback filter suitable for analog/digital mixed-mode audio amplifier for improved efficiency and stability

Abstract: A new ripple feedback filter is presented for analog/digital mixed-mode amplifier (MMA) among audio applications. MMA is composed of two amplifiers: one is analog amplifier responsible for high fidelity and the other is digital switching amplifier in charge of high efficiency. To improve both total harmonic distortion (THD) and efficiency, a passive RLC filter is needed at the output side of the digital switching amplifier. A conventional filter, however, causes phase delay, which worsens current loop stability and makes the normal operation of MMA impossible. A ripple feedback filter is newly suggested to solve this problem, obtaining excellent efficiency and low THD.

A high-speed, programmable, CSD coefficient FIR filter

Abstract: A new high-speed, programmable FIR filter is presented, which is a multiplierless filter with CSD encoding coefficients. We propose a new programmable CSD encoding structure to make CSD coefficients programmable. Compared with the conventional FIR structure with Booth multipliers, this coding structure improves the speed of filter and decreases the area. We design a 10-bits, 18-taps video luminance filter with the presented filter structure. The completed filter core occupies 6.8 /spl times/ 6.8 mm of silicon area in 0.6 /spl mu/m 2P2M CMOS technology, and its maximum work frequency is 100 MHz.

Frequency spectrum based low-area low-power parallel FIR filter design

Abstract: Parallel (or block) FIR digital filters can be used either for high-speed or low-power (with reduced supply voltage) applications. Traditional parallel filter implementations cause linear increase in the hardware cost with respect to the block size. Recently, an efficient parallel FIR filter implementation technique requiring a less-than linear increase in the hardware cost was proposed. This paper makes two contributions. First, the filter spectrum characteristics are exploited to select the best fast filter structures. Second, a novel block filter quantization algorithm is introduced. Using filter benchmarks, it is shown that the use of the appropriate fast FIR filter structures and the proposed quantization scheme can result in reduction in the number of binary adders up to 20%.

Input filter interactions in peak-current-mode-controlled buck converter operating in CICM

Abstract: Peak-current-mode (PCM) control is a widely used method to control switched-mode converters. Most often an input filter is necessary to meet electromagnetic interference requirements. The input filter can cause instability and degradation of input and output dynamics if not properly designed. The input filter design from the output dynamics viewpoint has been addressed in numerous papers, resulting in well-agreed results in the case of direct duty-ratio control. The same methods and criteria have also been applied to PCM control, but the results have turned out to be conflicting. This paper shows that the adverse effect of the input filter on the output performance of a peak-current-controlled buck converter in continuous inductor-current mode is insignificant. The input performance is, however, significantly affected, necessitating the use of proper damping. It is also shown that the instability is caused solely by the instability of the input filter under negative incremental resistance. The methods used are unified in nature, but the results obtained in this study cannot be generalized to be valid for types of converters other than a buck converter.

The Variable Structure Filter

Abstract: This paper presents a new strategy for estimation of state variables. The strategy may be applied to linear systems and is referred to as the Variable Structure Filter. The filter is considered for discrete-time systems subject to random disturbances and measurement noise. A proof of stability for the filter is provided. For stability, this filtering concept requires a specification of an upper bound for the random disturbances and measurement noise. The filter requires a parametric model and can be formulated to accommodate model uncertainties. The application of this filter to a third order linear system is demonstrated.Copyright © 2002 by ASME

Directly tuned filter and method of directly tuning a filter

Abstract: A Method for filter tuning using direct digital sub-sampling is provided. The tuning is accomplished in the digital domain by determining the filter characteristics from the shape of the transfer function. The input signal (1) is passed through the filter (3) and is then sub-sampled by and Analog-to-digital Converter (ADC) (5). The sub-sampled signal (6) is then processed in the digital domain using a digital circuit (7) that is used to determine the center frequency (Fc) and Quality factor (Q) and/or other important filter parameters. The Fc, Q and/or other important filter parameters are then adjusted by generating digital control signals (8) that can be converted to analog signals (10) using Digital-to-analog Converters (DACs) (9).

Diplex circuit forming bandstop filter

Abstract: A bandstop filter for use in CATV applications is formed by a pair of diplexers, a lowpass filter and a highpass filter. Signals having a frequency range of, e.g., 0-3 GHz enter at a first node connected to the inputs of both the lowpass and highpass filters. Signals having frequencies below a first, predetermined value pass through the lowpass filter, and signals having frequencies above a second, predetermined value pass through the highpass filter with signals having frequencies between the first and second values being blocked, i.e., “stopped.” The outputs of both the lowpass and highpass filters are connected to the second diplexer at a second node which is connected to the single output.

Controllable broad-spectrum harmonic filter (cbf) for electrical power systems

Abstract: A broad-spectrum harmonic filter is developed. This filter is to be connected in series ahead of the load which generates harmonics. This filter basically consists of 3 fixed elements, i.e. a series reactor and a shunt reactor in series with a capacitor. It can function to completely filter out 5th harmonic current in 3 phase systems (or 3rd harmonic current in single phase systems) and to reduce other harmonic components by high percentages say, typically close to 70%. Thus the portions of various harmonics flowing toward the electrical power source can be held within acceptable limits.

An adaptively-pipelined mixed synchronous-asynchronous digital FIR filter chip operating at 1.3 GigaHertz

Abstract: A high-throughput low-latency digital finite impulse response (FIR) filter has been designed for use in partial-response maximum-likelihood (PRML) read channels of modem disk drives. The filter is a hybrid synchronous-asynchronous design. The speed critical portion of the filter is designed as a high-performance asynchronous pipeline, sandwiched between synchronous input and output portions, making it possible for the entire filter to be dropped into a clocked environment. A novel feature of the filter is that the degree of pipelining is dynamically variable, depending upon the input data rate. This feature is critical in obtaining a very low filter latency throughout the range of operating frequencies. The filter was fabricated in a 0.18 /spl mu/m CMOS process. Resulting chips were fully functional over a wide range of supply voltages, and exhibited throughputs of over 1.3 Giga items/second, and latencies as low as four clock cycles. The internal asynchronous pipeline was estimated to be capable of significantly higher throughputs, around 1.8 Giga items/second. With these performance metrics, the filter has better performance than that reported for existing digital read channel filters.

New wide-band DC-block cymbal bandpass filter

Abstract: A new low-loss dc-blocking parallel-cascaded bandpass filter is presented. The filter is much easier to use and fabricate, more compact, and simpler to design than the conventional end- or parallel-coupled line filters. The filter has a wide passband with a 2:1 voltage standing-wave ratio bandwidth of around 10% and an insertion loss of 0.5 dB at 10 GHz. Simulated results agree very well with experimental results.

The all phase DFT filter

Abstract: This paper proposes a concept of all phase data space, and, based on the DFT/IDFT filtering a new type of zero-phase filter, called the all phase DFT (APDFT) filter is proposed The APDFT is a new FIR filter design scheme possessing concurrently the merits of the conventional windowing and the frequency sampling This paper gives the custom design method of the APDFT filter and demonstrates some of it's good properties Theoretical analysis and simulation experiment showed that it has the advantage of frequency sampling in the overall filter performance, and can be used to realize strictly and power complementary, sub-band filtering The APDFT filter can be implemented with common convolution structure, and a direct network in frequency domain as well This paper gives the architecture of the network and an associate simplified algorithm This network is not sensitive to the finite word length effect It can constitute a time-varying system, and be easily integrated into a universal zero-phase digital filter with programmable length and frequency response The APDFT digital filter can be extensively adopted in digital signal processing applications

Low-voltage low-power high-Q CMOS RF bandpass filter

Abstract: Based on the gyrator-C inductor topology, a second-order bandpass filter can be realised by adding a series capacitor to the input port of the gyrator. high-Q second-, fourth- and sixth-order fully differential RF bandpass filters operating in the 2.4 GHz Industrial, Scientific and Medical (ISM) frequency band under a 2 V single power supply voltage with low-power dissipation are demonstrated.

An efficient approach for designing nearly perfect-reconstruction low-delay cosine-modulated filter banks

Abstract: A systematic multi-step approach is described for optimizing the stopband response of the prototype filter for low-delay critically sampled cosine-modulated filter banks in the least-mean-square sense subject to the maximum allowable aliasing and amplitude errors. In this approach, filter banks having several channels are designed by starting with a filter bank with a small number of channels. Then, the number of channels is gradually increased and a new prototype filter is optimized using the modified version of the prototype filter of the previous step as a good start-up solution. Several examples are included illustrating the flexibility of the proposed approach for making compromises between the required filter orders, the required filter bank delays, and the aliasing and amplitude errors. These examples show that by allowing very small amplitude and aliasing errors, the stopband performance of the resulting filter bank is significantly improved compared to the corresponding perfect-reconstruction filter bank. Alternatively, the filter bank delay and the order of the prototype filter can be significantly reduced while still achieving practically the same filter bank performance.

Remote control device of acousto-optic tunable filter and optical transmission system containing equalizer using acousto-optic tunable filter and optical transmission system containing optical add/drop multiplexer using acousto-optic tunable filter

Abstract: The invention provides a remote control device of an acousto-optic tunable filter, which comprises an acousto-optic tunable filter interpolated in an optical transmission line, capable of controlling an output state of an input light signal by being supplied with a surface acoustic wave control signal through a control port; a surface acoustic wave control signal source to generate the surface acoustic wave control signal, which is provided at a remote place from the acousto-optic tunable filter; and a control unit that receives an information of the surface acoustic wave control signal from the surface acoustic wave control signal source through remote transmission means, and supplies the surface acoustic wave control signal to the control port of the acousto-optic tunable filter. According to this invention, the scale of the device using the acousto-optic tunable filter becomes enlarged, the power consumption is increased; and the man power required for the maintenance of the devices can be reduced, and the remote control of the acousto-optic tunable filter can be achieved.

Analysis and operation of hybrid active filter for harmonic elimination

Abstract: This paper presents a hybrid active filter topology and its control to suppress the harmonic currents from entering the power source. The adopted hybrid active filter consists of one active filter and one passive filter connected in series. By controlling the equivalent output voltage of an active filter, the harmonic currents generated by the nonlinear load are blocked and flow into the passive filter. The power rating of the converter is reduced compared with the pure active filters to filter the harmonic currents. The harmonic current detection approach and DC link voltage regulation are proposed to obtain equivalent voltage of the active filter. The effectiveness of the adopted topology and control scheme has been verified by the computer simulation and experimental results in a scaled-down laboratory prototype.

Integrated tunable filter for broadband tuner

Abstract: A tunable filter circuit includes a first differential pair biased by a first current, a second differential pair biased by a second current, a first capacitor and a second capacitor. The tunable filter circuit of the present invention can be configured as a bandpass filter or a bandstop filter by connecting the input voltage signal to different input nodes of the tunable filter circuit. The tunable filter circuit can be tuned by adjusting the values of the first current and the second current. In an alternate embodiment, frequency tuning is achieved either by switching capacitive loads or changing resistive impedances introduced at the emitter of the differential pairs, which also extends the input voltage range of the filter. This emitter resistance is implemented using MOS switches whose on-resistance can be controlled for a precise tuning within a large frequency range.

Absolutely calibrated periodic filters and sources

Abstract: A method and a system for filtering a user light beam using a periodic filter having a frequency response stabilized at an absolutely calibrated value are provided. A primary light beam is generated by a tunable laser source and portions thereof are filtered by an absolute reference filter and the periodic filter. First the frequency of the laser source is automatically locked on the absolute reference filter, and then the frequency response of the periodic filter is locked relative to the frequency of the laser source. The frequency response of the periodic filter is therefore continuously maintained at the proper calibration. User input and output are provided to pass the user light beam through the stabilized periodic filter independently of the filter stabilization process. A broadband absolutely calibrated optical source and a method for absolutely calibrating an optical spectrum analysis device are also provided.

High speed QPSK MMIC and QAM modulator

Abstract: In a system for modulating an RF carrier, the RF carrier is fed through a lowpass filter and phase shifted approximately −90 degrees The RF carrier is also fed through a high pass filter and phase shifted approximately +90 degrees A switch connected to the output of the lowpass filter and connected to the output of the highpass filter, selects and outputs either the −90 degree phase shifted carrier output from the lowpass filter or the +90 degree phase shifted carrier output from the highpass filter depending on a switching state determined by data bit information received at a data port to produce a BPSK modulated RF carrier Two such BPSK modulators may be combined using lowpass and highpass filters to form a QPSK modulator Two such QPSK modulators may be combined with an attenuator to form a QAM modulator

A cochlear filter implemented with a field-programmable gate array

Abstract: A digital cochlear filter was designed and implemented in hardware using a Xilinx XC4010 field-programmable gate array (FPGA) chip. The filter gives a good fit to biological data. It is a tenth-order recursive filter implemented as a parallel combination of low-order elements. A systematic approach to the design problem enabled us to achieve a good fit to cochlear data with efficiency of hardware usage. This approach can be easily extended to other similar applications.

A phase noise reduction technique in microwave oscillator using high-Q active filter

Abstract: The authors present a 10 GHz oscillator that uses a high-Q active filter to reduce the phase noise. The loaded Q of active filter is obtained at about 500. This oscillator is compared with another oscillator which uses a passive filter. The difference of two oscillators' Q is estimated at 12.5 times the open-loop gain simulation. The measured result of phase noise at 100 kHz offset shows maximum 10 dB reduction with high-Q active filter.