Tunable frequency versatile filters implementation using minimum number of passive elements

Two new universal active current-mode filters are proposed, one topology of which is with three inputs and one output, the other prototype is with single input and three outputs counterpart. One proposed circuit employs two current conveyors, two grounded capacitors and two resistors, wherever the other proposed circuit employs two current conveyors, two grounded capacitors and two multi-input, multi-output Operational Transconductance Amplifiers(OTA) as variable resistor for tuning the cutoff frequency of realized filters. Without changing the passive elements, the proposed circuits employ features of multifunctional, convenient for integration, low sensitivities and simple in structure.     

A design and implementation of fully programmable switched-currentIIR filters

An approach to switched-current filter design based on digital multiply-accumulator and delay blocks is presented. The characteristics of the filter are made fully programmable by simply changing the ratios of the coefficient transistors. To reduce the effect of switch charge injection and channel-length modulation, a high-performance, single-ended differential, switched-current memory cell is developed and used as a basic building block. To reduce the chip area and to maintain the required accuracy of the coefficients, an array consisting of three different sizes of transistors is designed instead of using a unit transistor array as coefficient transistors. An experimental prototype infinite impulse response filter array consisting of six second-order switched-current sections is designed and fabricated with a standard 1.2-μ CMOS process technology. A hard-wiring technique is used to program the filters. The test results show that the characteristics of the filters satisfy the design requirements     

On design and implementation of a decimation filter for multistandard wireless transceivers

In this work, we deal with the design and implementation of a decimation filter to be used in wideband radio-frequency receiver. The paper outlines architecture considerations for multistandard wireless transceivers. Also, it describes the design steps and the tradeoffs concerning the hardware implementation. GSM and DECT standards specifications are met by the proposed filtering cascade structure. The filter processes six-bit data stream input from a fourth-order sigma-delta modulator and has been prototyped in a field-programmable gate array device.     

CSDC: a new complexity reduction technique for multiplierless implementation of digital FIR filters

We present a computation reduction technique called computation sharing differential coefficient (CSDC) method, which can be used to obtain low-complexity multiplierless implementation of finite-impulse response (FIR) filters. It is also applicable to digital signal processing tasks involving multiplications with a set of constants. The main component of our proposed CSDC method is to combine the strength of the augmented differential coefficient approach and subexpression sharing. Exploring computation reuse through algorithmic equivalence, the augmented differential coefficient approach greatly expands the design space by employing both differences and sums of filter coefficients. The expanded design space is represented by an undirected and complete graph. The problem of minimizing the adder cost (the number of additions/subtractions) for a given filter is transformed into a problem of searching for an appropriate subexpression set that leads to a minimal adder cost. A heuristic search algorithm based on genetic algorithm is developed to search for low-complexity solutions over the expanded design space in conjunction with exploring subexpression sharing. It is shown that up to 70.1% reduction in the adder cost can be obtained over the conventional multiplierless implementation. Comparison with several existing techniques based on the available data shows that our method yields comparable results for multiplierless FIR filter implementation.     

Development of compact and low-crosstalk PLC-WDM filters for hybrid-integrated bidirectional optical transceivers

This paper reports on the development of planar-lightwave-circuit wavelength-division-multiplexing (PLC-WDM) filters based on double polynomial curve directional couplers, which will be integrated into compact and low-cost bidirectional optical transceivers for FTTx systems. Silica-based PLC-WDM filters smaller than 5 mm/spl times/100 /spl mu/m for Ethernet passive optical network (E-PON) applications were designed and fabricated to have low bidirectional crosstalk (lower than -40 dB) as well as low insertion losses (lower than 1 dB) within the operating temperatures of -40 to 80/spl deg/C. Several features and design guides that can reduce the size of directional couplers and improve the level of bidirectional crosstalk are discussed.     

Reference current computation methods for active power filters: accuracy assessment in the frequency domain

This paper focuses on the steady-state response of existing methods for computing the reference current of active power filters. For each class of methods, the main source of discrepancy between the load harmonic current and the computed reference current is identified and the frequency spectrum of the resulting error is analytically determined. Although this topic has been partially addressed in previous publications, the proposed frequency-domain approach provides valuable qualitative information about how the errors are produced and distributed, which is masked when the analysis is carried out in the time domain. First, the frequency-domain formulation is separately presented for each method. Then, a comparison of the resulting errors is performed on a case study. Finally, some experimental results are given to validate the proposed frequency-domain analysis.     

OBS边缘节点突发收发卡的设计与实现

研究光突发交换(OBS:Optical Burst Switching)网络中边缘节点收发卡的设计与实现,在FPGA内部设计实现了基于空间过采样技术的百兆光突发数据的恢复与接收,同时通过控制激光器驱动电路实现了光路数据的突发发送.实验结果表明,该方案可以实现突发数据的正确发送和接收,并可以避开相位锁定、时钟恢复所需的等待时间.从而减少突发包头的同步码开销,提高了带宽利用率.     

Use of comb filters for efficient VLSI implementation of reducedclock frequency noise shapers

The use of comb filters as an elegant means of reduced clock frequency noise-shaping without excessive hardware overhead is presented. The significance of the method is illustrated using second order noise-shaping characteristics. A 256 times oversampled and noise-shaped bit-stream sequence is obtained by running a second order noise shaper at a clock frequency four times lower than that of the bit-stream sampling rate, in association with an in-loop multi-bit to four single bit transformation at a tolerable hardware overhead     

An algebraic technique for designing active filters in the frequency domain for control and signal processing

This paper presents a straightforward algebraic method for designing feedback loops in the frequency domain. The emphasis here is on control system design, but the technique is applicable to active filter design as well. The object is to produce a practical analog filter with a minimum of design effort. The algebraic solution to the design problem is presented, and several examples are explored.     

Inductorless filters: a survey II. Linear active and digital filters

In this two-part survey the author has attempted to review the main methods of inductorless filter design being pursued at the present time. These filters are of particular interest because they may provide the replacement for the LC filters that are being eliminated from electronic equipment as a result of the trend toward microminiaturization. This month's installment discusses inductorless filters of both the linear active and digital types.     

Synthesis and performance of a new class of implementation forhigh-order recursive digital filters

The authors investigate a new class of approaches to the synthesis of high-order recursive digital filters. These are all characterised by partitioning the overall filter into a set of parallel subfilters, each of which is of moderate order. The subfilters may be any of the classical implementations: direct form, parallel, cascade or lattice. The authors investigate cascade and lattice implementation of the subfilters. The investigation includes selection of the number of subfilters to use, how to derive their coefficients and theoretical noise calculations. This is supported by simulation testing of a variety of real and synthetic filters using maximal length binary sequences (MLS) as input as this provides information on both the linear and nonlinear errors involved. It is found that particularly when filter order is 50 or more, the new structures have reduced quantisation noise and improved tolerance to quantisation than their classical counterparts     

The dual-X current conveyor (DXCCII): a new active device for tunable continuous-time filters

In this work, a new active device, namely the dual-X current conveyor is proposed for linear tunable continuous-time filtering. The proposed device avails tunability with the aid of triode MOSFETs, while keeping large-signal linearity high. Besides linearity enhancement, the dual-X structure of the active device brings interesting features, which help reduce the required number of active devices and MOSFET resistors in a MOSFET-C continuous-time filter. Also, unlike most MOSFET-C filter structures, there does not exist a matching requirement for the utilized MOSFETs. A CMOS implementation and two application examples (a current mode Tow-Thomas biquad and a current-mode sinusoidal oscillator) are supplied and simulated to reveal the important advantages.     

A new control technique for active power filters using a combinedgenetic algorithm/conventional analysis

In this paper, the computational problems associated with the optimization techniques used to evaluate the switching patterns for controlling variable-characteristics active power filters are presented and critically analyzed. Genetic algorithms (GAs) are introduced in this paper to generate a fast and accurate initial starting point in the highly nonlinear optimization space of mathematical optimization techniques. GAs tend to speed up the initialization process by a factor of 13. A combined GA/conventional technique is also proposed and implemented to reduce the associated computational burden associated with the control and, consequently, increasing the speed of response of this class of active filters. Comparisons of these techniques are discussed and presented in conjunction with simulation and practical results for the filter operation     

CAD of microwave integrated active filters by the real frequency — computer program FREELCD

This article presents synthesis and optimization for active and integrated microwave filters. The method is based on the real frequency theory. Gain, bandwidth, vswrand group delay are the optimized characteristics. Optimization is done with the J.J. More subroutine which is an improvement of the Levenberg- Marquardt algorithm. These integrated active low- pass and bandpass filters are used in the field of telecommunications area. Applications are given with one or several fet,several equalizers and attenuation poles which are necessary for broadband filters. Theory is favourably extended to distributed domain with transmission lines and stubs. Low- pass and bandpass examples are given up to 14 GHz in localised and distributed domains. Responses of filters can have asymmetric frequency characteristics. A cadprogram has been written and named freelcd.We give the different subroutines and say that freelcdis useful for microwave integrated active filters.     

The triamplifier, a new circuit element, and its use in active filters

A new operational amplifier circuit building block-the triamplifier-is described. This is basically a symmetrical amplifier with three inputs and three outputs. The triamplifier can be used to realize high-performance floating inductors, and appears to offer significant advantages over alternative circuits.     

Circuit optimization: the state of the art

The authors review the current state of the art in circuit optimization, emphasizing techniques suitable for modern microwave CAD (computer-aided design). The main thrust in the field is currently the solution of realistic design and modeling problems, addressing such concepts as physical tolerances and model uncertainties. A unified hierarchical treatment of circuit models forms the basis of the presentation. It exposes tolerance phenomena at different parameter/response levels. The concepts of design centering, tolerance assignment, and postproduction tuning in relation to yield enhancement and cost reduction suitable for integrated circuits are discussed. Suitable techniques for optimization oriented worst-case and statistical design are reviewed. A generalized l_p centering algorithm is proposed and discussed. Multicircuit optimization directed at both CAD and robust device modeling is formalized. Tuning is addressed in some detail, both at the design stage and for production alignment. State-of-the-art gradient-based nonlinear optimization methods are reviewed with emphasis given to recent, but well tested, advances in minimax, l₁, and l₂ optimization     

PWM regenerative rectifiers: state of the art

New regulations impose more stringent limits on current harmonics injected by power converters that are achieved with pulsewidth-modulated (PWM) rectifiers. In addition, several applications demand the capability of power regeneration to the power supply. This work presents the state of the art in the field of regenerative rectifiers with reduced input harmonics and improved power factor. Regenerative rectifiers are able to deliver energy back from the dc side to the ac power supply. Topologies for single- and three-phase power supplies are considered with their corresponding control strategies. Special attention is given to the application of voltage- and current-source PWM rectifiers in different processes with a power range from a few kilowatts up to several megawatts. This paper shows that PWM regenerative rectifiers are a highly developed and mature technology with a wide industrial acceptance.