Miniaturized filters for channel translator units by means of LC-technology

This paper presents methods for the design and the realization of high-quality miniaturized LC filters. The use of nonminimum phase networks in order to compensate delay, the implementation of tapped inductors as well as the application of miniaturized coils with improved material, new capacitor types and a new compression technique for the coil winding yield economical solutions with improved performance and reduced size. An example taken from the area of frequency-division-multiplex systems illustrates the effectiveness of the described design and realization methods.     

Variable cut-off digital ladder filters

This paper presents a now class of transformations whose implementation to doubly terminated LC ladder filters results in variable cut-off frequency digital filters. It is shown that using this transformation and the concept of generalized delay, from a given prototype ladder structure, we can construct low-pass, high-pass, band-pass and band-stop filters with variable cut-off frequency and bandwidth. Thu resulting variable filters are canonical in the sense that a minimum number of multipliers in the prototype filter need to be adjusted. Two examples are worked out to illustrate the application of this method.     

Design of nonseparable 3-D filter banks/wavelet bases usingtransformations of variables

The authors present a technique to design two-channel filter banks in three dimensions where the sampling is on the FCO (face centred orthorhombic) lattice, The ideal 3-D sub-band is of the truncated octahedron shape. The design technique is based transformation of variable method equivalent to the generalised McClellan transformation. The filters are FIR, have linear phase and achieve perfect reconstruction. Although the sub-band shape is quite complicated, the ideal frequency characteristics are well approximated. This is illustrated with an example. The technique provides the flexibility of controlling the frequency characteristics of the filters with ease. The filters can be implemented quite efficiently due to the highly symmetrical nature of the coefficients of the transformation. The authors also modify and extend the basic design technique to impose the zero property (the number of zeros of the filter transfer function at the aliasing frequency) on the sub-band filters. This property is important when the filter bank is used iteratively in a tree-structured manner as a discrete wavelet transform system and the issue of regularity arises. Several design examples are presented to illustrate the design technique     

Digital Laguerre filter design with maximum passband-to-stopband energy ratio subject to peak and Group delay constraints

In this paper, we formulate a general design of transversal filter structures with maximum relative passband-to-stopband energy ratio subject to complex frequency response constraints in the passband and the stopband as well as additional constraints such as constraints. These constraints are important for applications where the suppression of noise at certain frequencies are important. Additional constraints are introduced allowing approximately linear phase and constant group delay in the passband. For a given set of basis functions, the design problem can be formulated as a semi-infinite quadratic optimization problem in the filter coefficients, which are the decision variables to be optimized. In this paper, we focus on the design of digital Laguerre filter and digital finite impulse response (FIR) filter structures. A modified bridging algorithm is developed for searching for the optimum pole of the Laguerre filters. Design examples are given to demonstrate the effectiveness of the proposed algorithm.     

Optimal Design of Frequency-Response Masking Filters With Reduced Group Delays

In this paper, a new method for the design of optimal finite-impulse response frequency-response masking (FRM) filters with reduced passband group delays is proposed. To meet the prescribed magnitude response and group delay, the proposed design method takes into account both the magnitude error and the group delay error. The key step is the derivation of the group delay and its gradient with respect to the filter coefficients, based on which an explicit group delay constraint is formulated. By incorporating the group delay constraint into the overall optimization, FRM filters with better approximation to the prescribed reduced group delay can be obtained in comparison with a recent method by Lu and Hinamoto in 2003, as illustrated by two design examples.      

Closed-Form Design of Half-Sample Delay IIR Filter Using Continued Fraction Expansion

In this paper, the closed-form design of half-sample delay infinite-impulse response (IIR) filter is presented. First, the continued fraction expansion (CFE) and its recursive computation are reviewed briefly. Then, the CFE of square root function is applied to design half-sample delay IIR filters with various orders. The comparisons with conventional maximally flat half-sample delay all-pass and Lagrange filters are made and implementation issue is also addressed. Next, the designed half-sample delay filter is used to reduce the approximation error of the conventional IIR Simpson integrator, to design half-band and diamond shaped filters, and to magnify the digital image. Finally, several numerical examples are illustrated to demonstrate the effectiveness of the proposed design method     

A Direct Synthesis Approach for Microwave Filters With a Complex Load and Its Application to Direct Diplexer Design

This paper presents a direct synthesis approach for general Chebyshev filters terminated with a complex load. The new approach is based on the fact that the polynomial functions for synthesizing the filters are composed for any matched loads. By normalizing the polynomial functions with assumed complex matched load impedance by a real reference load impedance using power waves normalization, a set of new polynomial functions for the same filter, but with real load impedance, can be formulated, from which the coupling matrix for the physical filter design can be obtained using a standard direct filter synthesis approach. This new direct synthesis approach can find many applications. A practical application is the direct diplexer design with a realistic junction model being taken into account. With the diplexer design is concerned, a fast-converged iterative scheme is proposed. The effectiveness and the validation of the proposed scheme are demonstrated by two design examples     

Design of efficient M-band coders with linear-phase andperfect-reconstruction properties

This paper presents a new design technique for obtaining M-band orthogonal coders where M=2ⁱ. The structures obtained using the proposed technique have the perfect reconstruction property. Furthermore, all filters that constitute the subband coder are linear-phase FIR-type filters. In contrast with conventional design techniques that attempt to find a unitary alias-component matrix in the frequency domain, we carry out the design in the time domain, based on time-domain orthonormality constraints that the filters must satisfy. The M-band design problem is reduced to the problem of finding a suitable lowpass filter h₀(n). Once a suitable lowpass filter is found, the remaining (M-1) filters of the coder are obtained through the use of shuffling operators on the lowpass filter. This approach leads to a set of filters that use the same numerical coefficient values in different shift positions, allowing very efficient numerical implementation of the subband coder. In addition, by imposing further constraints on the lowpass branch impulse response h₀(n), we are able to construct continuous bases of M-channel wavelets with good regularity properties. Design examples are presented for four-, eight-, and 16-band coders, along with examples of continuous wavelet bases that they generate     

Design of some 2-D filters through the transformation technique

The transformation technique is a powerful tool for designing 2-D FIR filters. However, it is not useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types of filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along a straight line passing through the origin. The transformation technique is further extended to yield such directional filters. Design and application examples for both these filters are also presented     

Printed Circuit Coupled-Line Filters for Bandwidths Up to and Greater Than an Octave

The realization of edge-coupled-line filters as printed circuits has generally been assumed to be confined to filters with fractional bandwidths of 30 percent or less. However, the design technique described herein has eliminated the 30-percent restriction and such filters may now be constructed for fractional bandwidths up to approximately 100 percent. Instead of constraining the physical realization to be a cascade of coupled lines, the technique allows the realization to consist of coupled lines and simple lengths of line cascaded in such a way that resultant circuit dimensions are practicable for the bandwidth specified. Practical examples are specified.     

A Delay Partitioning Approach to H �� Filtering for?Continuous Time-Delay Systems

This paper investigates the problem of delay-dependent H _∞ filter design for continuous time-delay systems. Attention is focused on the design of linear filters guaranteeing a prescribed noise attenuation level in an H _∞ sense. The admissible filters can be obtained from the solution of a convex optimization problem in terms of linear matrix inequalities (LMIs), which can be readily solved via standard software. The crucial issue for solving the filter design problem is the utilization of the delay partitioning idea, which proves to be less conservative than most of the existing results, and the conservatism could be notably reduced by thinning the delay partitioning. Numerical examples are provided to show the effectiveness and the advantage of the proposed filter design method.     

Single Filter Frequency Masking High-Speed Recursive Digital Filters

For recursive filter the maximal sample frequency is bounded by the recursive loops in the filter. [In this paper, it is understood that recursive filters are infinite-length impulse response (IIR) filters.] In this work, a filter structure based on the use of the frequency masking approach is presented that increases the maximal sample frequency for narrowband and wideband filters by introducing more delay elements in the recursive loops. By using identical subfilters (except for the periods), the subfilters can be mapped using folding to a single pipeline/interleaved arithmetic structure yielding an area-efficient implementation. The filters are potentially suitable for low-power implementation by using power supply voltage scaling techniques. In this work, the design of the filters is discussed and estimations of the ripples are derived. Two examples show the viability of the proposed method.     

多通带低群延迟误差FIR滤波器设计的迭代算法

常数低群延迟有限冲击响应（FIR）滤波器在通信等领域得到了广泛应用,尤其是要求无波形失真、信号延迟小的场合。而低群延迟的FIR滤波器,其相位响应只能做到近似线性相位,其群延迟只能做到近似常数。为了减小与期望常数群延迟之间的误差,最近提出的通过迭代更新相位误差上界函数来逐步减小群延迟误差的方法,只考虑了单通带滤波器的minimax设计。本文将把该方法推广至多通带FIR滤波器的minimax设计和约束最小二乘设计,先对各通带单独处理使每个通带的最大群延迟误差有效降低后,再考虑各通带之间平衡,对各子带的最大群延迟误差进行折中,进而使整个通带上的最大群延迟误差继续减小。对约束最小二乘设计还特别考虑了通过修改收敛参数来解决相位误差约束过紧时设计问题无解的问题。仿真实例表明,该方法能有效减小多通带滤波器的最大群延迟误差。      

Design of oversampled nonuniform filter banks with arbitrary rational frequency partitioning

Among the theory and design of oversampled nonuniform filter banks (NUFBs), most of the existing works only consider the cases with integer decimators, and up to now the issue with rational sampling factors has not been discussed yet. In this paper, we generalize the partial modulation technique to realize arbitrary rational frequency partitioning of oversampled NUFBs with highly desired linear-phase (LP) property. Further for the subbands with sampling factors violating the guard band restriction, a phase-modification scheme is derived to avoid uneliminable large aliasing and meanwhile preserving the LP characteristics of shifted analysis/synthesis filters. By using the proposed method, the design issue of LP oversampled NUFBs can be reduced to that of several prototypes, decreasing the design complexity largely. As illustrated by examples, the proposed algorithm is more general in terms of arbitrary rational decimation and thus has broad application prospects.     

Least squares approximation of perfect reconstruction filter banks

Designing good causal filters for perfect reconstruction (PR) filter banks is a challenging task due to the unusual nature of the design constraints. We present a new least squares (LS) design methodology for approximating PRFBs that avoids most of these difficult constraints. The designer first selects a set of subband analysis filters from an almost unrestricted class of rational filters. Then, given some desired reconstruction delay, this design procedure produces the causal and rational synthesis filters that result in the best least squares approximation to a PRFB. This technique is built on a multi-input multi-output (MIMO) system model for filter banks derived from the filter bank polyphase representation. Using this model, we frame the LS approximation problem for PRFBs as a causal LS equalization problem for MIMO systems. We derive the causal LS solution to this design problem and present an algorithm for computing this solution. The resulting algorithm includes a MIMO spectral factorization that accounts for most of the complexity and computational cost for this design technique. Finally, we consider some design examples and evaluate their performance     

Design of 1-D Stable Variable Fractional Delay IIR Filters

In this brief, a two-stage approach for the design of 1-D stable variable fractional delay infinite-impulse response (IIR) digital filters is proposed. In the first stage, a set of fixed delay stable IIR filters are designed by minimizing a quadratic objective function, which is defined by integrating error criterion with IIR filter stability constraint condition. Then, the final design is determined by fitting each of the fixed delay filter coefficients as a 1-D polynomial. Two design examples are given to show the effectiveness of the proposed design method     

Quadratic filters for signal processing

Polynomial (or Volterra) filters are introduced, and the quadratic filters are presented as the simplest example of such filters. The principle aspects and properties of quadratic filters are derived in the framework of the discrete Volterra expansion. Fixed as well as adaptive filters are considered in one-dimensional and multidimensional environments. Such issues as design and efficient realizations are thoroughly addressed, and standard and advanced adaptation algorithms are presented. Several examples of signal processing applications requiring quadratic filters are discussed     

A Multimode Transmultiplexer Structure

This paper introduces a multimode transmultiplexer (TMUX) structure capable of generating a large set of user-bandwidths and center frequencies. The structure utilizes fixed integer sampling rate conversion (SRC) blocks, Farrow-based variable interpolation and decimation structures, and variable frequency shifters. A main advantage of this TMUX is that it needs only one filter design beforehand. Specifically, the filters in the fixed integer SRC blocks as well as the subfilters of the Farrow structure are designed only once. Then, all possible combinations of bandwidths and center frequencies are obtained by properly adjusting the variable delay parameter of the Farrow-based filters and the variable parameters of the frequency shifters. The paper includes examples for demonstration. It also shows that, using the rational SRC equivalent of the Farrow-based filters, the TMUX can be described in terms of conventional multirate building blocks which may be useful in further analysis of the overall system.     

GlitchLess: Dynamic Power Minimization in FPGAs Through Edge Alignment and Glitch Filtering

This paper describes GlitchLess, a circuit-level technique for reducing power in field-programmable gate arrays (FPGAs) by eliminating unnecessary logic transitions called glitches. This is done by adding programmable delay elements to the logic blocks of the FPGA. After routing a circuit and performing static timing analysis, these delay elements are programmed to align the arrival times of the inputs of each lookup table (LUT), thereby preventing new glitches from being generated. Moreover, the delay elements also behave as filters that eliminate other glitches generated by upstream logic or off-chip circuitry. On average, the proposed implementation eliminates 87% of the glitching, which reduces overall FPGA power by 17%. The added circuitry increases the overall FPGA area by 6% and critical-path delay by less than 1%. Furthermore, since it is applied after routing, the proposed technique requires little or no modifications to the routing architecture or computer-aided design (CAD) flow.      

TDAT-time domain analysis tool for EEG analysis

An interactive design and analysis tool for displaying and quantifying multiple channels of data is presented. The system allows one to easily visualize multiple data channels and simultaneously observe the effects of filters on the data and to evaluate signal detection algorithms. The software is designed for a workstation environment; it will find application in a variety of applications where one needs to simultaneously visualize multiple data channels. TDAT is being used for the design and evaluation of filters and detection algorithms for electroencephalogram (EEG) waveforms, and it is serving as a prototype of a paperless system to be used by electroencephalographers. This paper describes the general software structure of the system and illustrates many of the system features with examples.