ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 16 Oct 2019 14:33:53 GMT2019-10-16T14:33:53Z501351- Improved cross-coupled quad transconductor cellhttps://scholarbank.nus.edu.sg/handle/10635/114513Title: Improved cross-coupled quad transconductor cell
Authors: Lim, Y.C.; Lai, W.H.; Zhang, X.W.; Li, M.F.
Abstract: Simple modifications to the cross-coupled CMOS transconductor cell that reduce the quiescent currents while maintaining comparable linearity are described. SPICE simulation results show that using BSIM models and a ± 5 V power supply, the linearity error is less than 0.6% over a differential input voltage range of ± 1.3 V in the case of single-ended output, and less than 0.3% over a differential input voltage range of ± 2.4 V in the case of differential output. The cut-off frequency and power consumption are 130 MHz and 5.2 mW in the case of single-ended output, and 80 MHz and 6.1 mW in the case of differential output. In both cases, the THD for a differential input voltage of 1Vpp at 1 kHz is 1.3%.
Tue, 01 Feb 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1145132000-02-01T00:00:00Z
- Comment on the computational complexity of sliding FFThttps://scholarbank.nus.edu.sg/handle/10635/80328Title: Comment on the computational complexity of sliding FFT
Authors: Farhang-Boroujeny, B.; Lim, Y.C.
Abstract: The sliding fast Fourier transform (FFT) is reviewed and is shown to have the computational complexity of N complex multiplications per sample, as opposed to the well-cited assumption of (N/2) log2 N complex multiplication per sample reported in [1].
Tue, 01 Dec 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/803281992-12-01T00:00:00Z
- An efficient algorithm for the design of weighted minimax M-channel cosine-modulated filter bankshttps://scholarbank.nus.edu.sg/handle/10635/61797Title: An efficient algorithm for the design of weighted minimax M-channel cosine-modulated filter banks
Authors: Goh, C.-K.; Lim, Y.-C.
Abstract: This correspondence presents an efficient algorithm for the design of M-channel cosine-modulated filter banks. Our algorithm needs only a few iterations to obtain a weighted minimax solution and provides flexible control of the ripples in the filter's stopband, the overall filter bank transfer function, and the aliasing components. © 1998 IEEE.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/617971998-01-01T00:00:00Z
- Pipelined recursive filter with minimum order augmentationhttps://scholarbank.nus.edu.sg/handle/10635/80988Title: Pipelined recursive filter with minimum order augmentation
Authors: Lim, Y.C.; Liu, Bede
Abstract: Pipelining is an efficient way for improving the average computation speed of an arithmetic processor. However, for an M-stage pipeline, the result of a given operation is available only M clock periods after initiating the computation. In a recursive filter, the computation of y(n) cannot be initiated before the computations of y(n - 1) through y(n - N) are completed. H. B. Voelcker and E. E. Hartquist (1970) and P. M. Kogge and H. S. Stone (1973) independently devised augmentation techniques for resolving the dependence problem in the computation of y(n). However, the augmentation required to ensure stability may be excessively high, resulting in a very complex numerator realization. A technique which results in a minimum order augmentation is presented here. The complexity of the resulting filter design is very much lower. Various pipelining architectures are presented. It is demonstrated by an example that when compared to the prototype filter, the augmented filter has a lower coefficient sensitivity and better roundoff noise performance.
Wed, 01 Jul 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/809881992-07-01T00:00:00Z
- An efficient bit-serial FIR filter architecturehttps://scholarbank.nus.edu.sg/handle/10635/61799Title: An efficient bit-serial FIR filter architecture
Authors: Lim, Y.C.; Evans, J.B.; Liu, B.
Abstract: A new bit-serial architecture for implementation of high order FIR filters is introduced, as well as example FPGA and CMOS realizations. This structure exploits the simplicity of coefficients that consist of two power-of-two terms to yield efficient implementations. Quantization effects are discussed and a simple block scaling method for reducing rounding and truncation noise in high order filters is also presented. © 1995 Birkhäuser.
Fri, 01 Sep 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/617991995-09-01T00:00:00Z
- Efficient height reduction over-the-cell channel routerhttps://scholarbank.nus.edu.sg/handle/10635/62111Title: Efficient height reduction over-the-cell channel router
Authors: Shew, P.-W.; Hsiao, P.-Y.; Lim, Y.-C.
Abstract: The authors present a new algorithm for both two-layer and three-layer over-the-cell channel routing in the standard cell VLSI design. The approach exploits vacant terminals on the channel boundary effectively. It considers the following factors simultaneously to select net segments for routing over the cells: density distribution in the channel, the longest path in the vertical constraint graph, elimination of cycles in the vertical constraint graph and reduction in maximum cliques in the horizontal constraint graph. With respect to the PRIMARY 1 benchmark examples, the router achieved a 41.3% improvement over the Greedy channel router (one Without using over-the-cell area) for a two-layer routing model and a 61.0% improvement for a three-layer routing model. This outperforms all previous algorithms.
Sat, 01 Jul 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/621111995-07-01T00:00:00Z
- Practical design rules for minimax linear phase diamond-shaped 2-d fir low-pass filtershttps://scholarbank.nus.edu.sg/handle/10635/62643Title: Practical design rules for minimax linear phase diamond-shaped 2-d fir low-pass filters
Authors: Lim, Y.C.
Abstract: Diamond-shaped filters are used as antialiasing filters in the conversion between images sampled on the rectangular and quincunx sampling grids. In this brief, we investigate some characteristics of the linear phase diamond-shaped low-pass filters and present a set of design rules applicable to the design of such filters optimal in the minimax error sense. The design rules provide good estimates for the minimum filter support size required to satisfy a given set of specifications. In most cases, the difference between the estimated minimum filter support size and the actual minimum filter support size is less than 5%. © 1997 IEEE.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/626431997-01-01T00:00:00Z
- A low-voltage CMOS OTA with rail-to-rail differential input rangehttps://scholarbank.nus.edu.sg/handle/10635/80274Title: A low-voltage CMOS OTA with rail-to-rail differential input range
Authors: Li, M.F.; Dasgupta, U.; Zhang, X.W.; Lim, Y.C.
Abstract: This paper describes a novel circuit design technique for a low-voltage CMOS operational transconductance amplifier (OTA) where the output current versus the input voltage relationship is linear for differential input voltage range extended from rail to rail. The input transconducting CMOS transistors operate in the nonsaturation region. A pair of complementary n-type input OTAN and p-type OTAP circuits in conjunction with n-MOS and p-MOS output current mirrors are connected in parallel to implement the rail-to-rail voltage input and push-pull current output. The transconductances gmn and gmp of the OTAN and the OTAP are tuned by biasing voltages VDSN and VDSP, respectively. A masterbias generator (with VDSP as input) is used to generate VDSN as output so as to satisfy gmn = gmp. The circuit is capable of operating at supply voltage larger than two times the MOS transistor threshold voltage VT. When the supply voltage is 2 V and the MOS transistor threshold voltage is 0.7 V, using SPICE level 3-2 μm CMOS technology device parameters, the simulation result of the output current deviation from perfect linearity is less than 0.3% for rail-to-rail differential input voltage range. © 2000 IEEE.
Sat, 01 Jan 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/802742000-01-01T00:00:00Z
- An efficient weighted Lp algorithm for the design of quadrature mirror filtershttps://scholarbank.nus.edu.sg/handle/10635/80290Title: An efficient weighted Lp algorithm for the design of quadrature mirror filters
Authors: Goh, C.K.; Lim, Y.C.
Abstract: In this letter, we present an efficient weighted Lp algorithm for the design of quadrature mirror filters. The filterbank design process is formulated as an iterative weighted least-squares optimization problem. Our algorithm minimizes the pth power of the error function, where p may vary in different frequency bands. Good designs are obtained, typically, in a few iterations.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/802901997-01-01T00:00:00Z
- Design of weighted minimax quadrature mirror filtershttps://scholarbank.nus.edu.sg/handle/10635/62022Title: Design of weighted minimax quadrature mirror filters
Authors: Lim, Y.C.; Yang, Rong Huan; Koh, S-N.
Abstract: Quadrature mirror filters have been used extensively for splitting speech signals into subbands which result in no aliasing problem when the subband signals are decimated and then interpolated and recombined. In this paper, we introduce a novel and efficient optimization method for the design of quadrature mirror filters optimum in the weighted least squares sense. By a suitable choice of the least squares weighting function, the weighted minimax quadrature mirror filter is produced. The minimax tolerance weighting function can be arbitrarily defined.
Sat, 01 May 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620221993-05-01T00:00:00Z
- An efficient algorithm to design weighted minimax perfect reconstruction quadrature mirror filter bankshttps://scholarbank.nus.edu.sg/handle/10635/61798Title: An efficient algorithm to design weighted minimax perfect reconstruction quadrature mirror filter banks
Authors: Goh, C.-K.; Lim, Y.C.
Abstract: An efficient algorithm is presented in this paper to design lattice structure two-channel perfect reconstruction quadrature mirror filter (PR-QMF) banks. We formulate the filter bank design problem as an unconstrained weighted least squares problem with respect to the coefficients of the lattice structure. The proposed iterative algorithm optimizes the lattice coefficients and provides flexible control of the filters' stopband ripple profiles. Typically only a few iterations of the algorithm are needed to obtain an optimal solution in the weighted minimax sense. We include a set of practical design rules for use with our algorithm. These rules allow very good estimation of important filter bank characteristics such as the filter length and the number of signed digits for quantization of the lattice coefficients into canonic signed digit representation to meet a given set of PR-QMF bank specifications. © 1999 IEEE.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/617981999-01-01T00:00:00Z
- Frequency-response masking approach for digital filter design: complexity reduction via masking filter factorizationhttps://scholarbank.nus.edu.sg/handle/10635/62220Title: Frequency-response masking approach for digital filter design: complexity reduction via masking filter factorization
Authors: Lim, Y.C.; Lian, Yong
Abstract: It has been reported in several recent publications that the frequency response masking technique is eminently suitable for synthesizing filters with very narrow transition-width. The major advantages of the frequency response masking approach are that the resulting filter has a very sparse coefficient vector and that the resulting filter length is only slightly longer than that of the theoretical (Remez) minimum. The system of filters produced by the frequency response masking technique consists of a sparse coefficient filter with periodic frequency response and one or more pairs of masking filters. Each pair of the masking filters consist of two filters whose frequency responses are similar except at frequencies near the band-edges. In this paper, we present three methods for reducing the complexity of the masking filters. The success of our technique is due to the fact that each pair of the masking filters can be realized as a cascade of a common subfilter and a pair of equalizers.
Mon, 01 Aug 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622201994-08-01T00:00:00Z
- Improved weighted least squares algorithm for the design of quadrature mirror filtershttps://scholarbank.nus.edu.sg/handle/10635/62323Title: Improved weighted least squares algorithm for the design of quadrature mirror filters
Authors: Goh, C.-K.; Lim, Y.C.; Ng, C.S.
Abstract: This paper presents an improved weighted least squares (WLS) algorithm for the design of quadrature mirror filters (QMF's). First, a new term is incorporated into the objective function that effectively prevents an optimization algorithm from producing suboptimal QMF's. These suboptimal QMF's exhibit transition band anomaly; the frequency responses of the filters have large oscillatory components in the transition band. The new term can be applied to the WLS design of any FIR filter to prevent similar transition band anomaly. Next, we present the algorithm to obtain the QMF coefficients that minimizes the objective function incorporating the new term. The computational requirement of this algorithm is also briefly discussed. Last, we include a set of practical design rules for use with our algorithm. These rules simplify the design process by providing good estimation of the design parameters, such as the minimum filter length, to meet a given set of QMF specifications.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/623231999-01-01T00:00:00Z
- New approach for deriving scattered coefficients of pipelined IIR filtershttps://scholarbank.nus.edu.sg/handle/10635/80790Title: New approach for deriving scattered coefficients of pipelined IIR filters
Authors: Lim, Y.C.
Abstract: The synthesis of a particular class of pipelined IIR digital filter requires the denominator of the z-transform transfer function to be expressed in scattered form. The existing technique for deriving the scattered coefficient values requires finding the zeros of the denominator polynomial. In this correspondence, we present a new approach for deriving the scattered coefficient values that does not require the evaluation of the zeros of the transfer function's denominator polynomial.
Sun, 01 Oct 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/807901995-10-01T00:00:00Z
- Single-precision multiplier with reduced circuit complexity for signal processing applicationshttps://scholarbank.nus.edu.sg/handle/10635/81191Title: Single-precision multiplier with reduced circuit complexity for signal processing applications
Authors: Lim, Y.C.
Abstract: When two numbers are multiplied, a double-wordlength product is produced. In applications where only the single-precision product is required, the double-wordlength result is rounded to single-precision. Hence, in single-precision applications, it is not necessary to compute the least significant part of the product exactly. Instead, it is only necessary to estimate the carries generated in the computation of the least significant part that will ripple into the most significant part of the product. This will produce a single-precision multiplier with significantly reduced circuit complexity. Three novel methods for realizing this class of reduced complexity single-precision multipliers are introduced and their performance analyzed.
Thu, 01 Oct 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/811911992-10-01T00:00:00Z
- Parallel and pipelined implementations of injected numerator lattice digital filtershttps://scholarbank.nus.edu.sg/handle/10635/80932Title: Parallel and pipelined implementations of injected numerator lattice digital filters
Authors: Lim, Y.C.
Abstract: Parallel and pipelined implementations are effective measures for improving the maximum permissible sampling rate of a digital filter if all the data required by the arithmetic units are immediately available on demand. This implies that parallel access to the data should be possible and that for any loop in the signal flow graph the total number of series delay elements should be at least equal to the total number of pipelined stages in that loop. In the conventional lattice form IIR digital filter, the feedback loops are single-delay loops. As a consequence, the conventional lattice form IIR filter does not benefit significantly from parallel and pipelined implementation scheme. In this paper, we introduce a new lattice form IIR filter structure where the number of delay elements in the loops can be set arbitrarily. This renders the new lattice form IIR filter amenable to parallel and pipelined implementation.
Sat, 01 Jul 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/809321995-07-01T00:00:00Z
- Forward-backward LMS adaptive line enhancerhttps://scholarbank.nus.edu.sg/handle/10635/80449Title: Forward-backward LMS adaptive line enhancer
Authors: Lim, Y.C.; Ko, C.C.
Abstract: A new LMS (least-mean-square) adaptive line enhancer algorithm is presented. It makes use of forward and backward prediction errors to update the coefficient values. For a given feedback factor, the algorithm converges to the optimal Wiener solution with the same speed as for the LMS algorithm, but requires about twice the number of multiplications and additions. However, in the situation when the order of the enhancer is at least a few times larger than the number of sinusoids to be enhanced, or when the frequencies of the sinusoids to be enhanced are not close to 0 or 0.5, the misadjustment of the new algorithm is approximately half that of the LMS algorithm.
Sun, 01 Jul 1990 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/804491990-07-01T00:00:00Z
- Optimum design of one and two-dimensional FIR filters using the frequency response masking techniquehttps://scholarbank.nus.edu.sg/handle/10635/80919Title: Optimum design of one and two-dimensional FIR filters using the frequency response masking technique
Authors: Lim, Y.C.; Lian, Yong
Abstract: In the frequency response masking technique, the impulse response of a prototype filter and that of its complement are up-sampled (by inserting zeros) by a factor of M and then cascaded to a pair of interpolators. The prototype filter itself may again be synthesized using the frequency response masking technique producing a multistage frequency response masking design. In this paper, we derive an expression for the impulse response up-sampling ratio M, which will produce a minimum complexity design. We show that 1) M approaches e (the base of the natural algorithm) as the number of frequency response masking stages increases, 2) in a K-stage design the complexity of the filter is inversely proportional to the (K+1)th root of the transition width, 3) the frequency response masking technique is effective if the normalized transition width is less then 1/16, and 4) the frequency response masking technique is more efficient than the interpolated impulse response technique if the square root of the normalized transition width is less than the arithmetic mean of the normalized passband edge and stopband edge. We also derive an expression for the multistage frequency response ripple compensation. An optimum design relationship for the interpolated impulse response technique is also derived. The design of narrow-band two-dimensional filters using the frequency response masking technique is also presented.
Mon, 01 Feb 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/809191993-02-01T00:00:00Z
- Design rules for rectangular 2-D FIR low-pass filtershttps://scholarbank.nus.edu.sg/handle/10635/62023Title: Design rules for rectangular 2-D FIR low-pass filters
Authors: Low, S.-H.; Lim, Y.-C.
Abstract: Rectangular-shaped low-pass filters are used in image processing applications. In this paper, we investigate some characteristics of the linear phase rectangular-shaped low-pass filter. A set of design rules applicable for the design of such filters optimal in the minimax error sense is formulated.
Tue, 01 Oct 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620231996-10-01T00:00:00Z
- Novel approach for the design of two channel perfect reconstruction linear phase fir filter bankshttps://scholarbank.nus.edu.sg/handle/10635/80831Title: Novel approach for the design of two channel perfect reconstruction linear phase fir filter banks
Authors: Goh, C.K.; Lim, Y.C.
Abstract: -This correspondence presents a novel approach for the design of two channel perfect reconstruction (PR) linear phase finite-impulse response (FIR) filter banks. A broad class of even and odd filter length PR filter bank cases can be obtained by simply re
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/808311998-01-01T00:00:00Z
- Frequency-domain modeling of continuous-time systems using the lattice algorithms.https://scholarbank.nus.edu.sg/handle/10635/62219Title: Frequency-domain modeling of continuous-time systems using the lattice algorithms.
Authors: Lim, Y.C.; Parker, S.R.
Abstract: Two frequency-domain methods for modeling continuous-time system using the lattice algorithms are presented. In one of the methods, the frequency-domain data are sampled at a nonuniformly spaced frequency grid. This method is suitable for applications where the frequency response of the continuous-time systems can be measured explicitly. In the other method, the frequency-domain data are sampled at a uniformly spaced frequency grid. This method is suitable for applications where the frequency spectrum of the input and output signals are computed from the input and output time-domain data using the FFT (fast Fourier transform).
Wed, 01 Mar 1989 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622191989-03-01T00:00:00Z
- Design of cascade form FIR filters with discrete valued coefficientshttps://scholarbank.nus.edu.sg/handle/10635/62013Title: Design of cascade form FIR filters with discrete valued coefficients
Authors: Lim, Yong Ching; Liu, Bede
Abstract: The authors show that by cascading two direct-form FIR filters, each with coefficients that are the sum or difference of two power-of-two terms, it is possible to achieve very small peak ripple. An iterative equalization strategy is used in the design of the cascaded filter. The success of the method depends on the initial prototype filter being used. Two equally effective methods are presented for selecting the prototype filter; each yields a final design with good roundoff noise property.
Tue, 01 Nov 1988 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620131988-11-01T00:00:00Z
- A width-recursive depth-first tree search approach for the design of discrete coefficient perfect reconstruction lattice filter bankhttps://scholarbank.nus.edu.sg/handle/10635/54853Title: A width-recursive depth-first tree search approach for the design of discrete coefficient perfect reconstruction lattice filter bank
Authors: Lim, Y.C.; Yu, Y.J.
Abstract: The lattice structure two-channel orthogonal filter bank structurally guarantees the perfect reconstruction (PR) property. Thus, It Is eminently suitable for hardware realization even under severe coefficient quantization condition. Nevertheless, its frequency response is still adversely affected by coefficient quantization. In this paper, a novel recursive-in-width depth-first tree search technique is presented for the design of lattice structure PR orthogonal filter banks subject to discrete coefficient value constraint. A frequency-response deterioration measure is developed to serve as a branching criterion. At any node, the coefficient which will cause the largest deterioration in the frequency response of the filter when quantized is selected for branching. The improvement in the frequency response ripple magnitude achieved by our algorithm over that by simple rounding of coefficient values differs widely from example to example ranging from a fraction of a decibel to over 10 dB.
Sun, 01 Jun 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/548532003-06-01T00:00:00Z
- A polynomial-time algorithm for designing FIR filters with power-of-two coefficientshttps://scholarbank.nus.edu.sg/handle/10635/81904Title: A polynomial-time algorithm for designing FIR filters with power-of-two coefficients
Authors: Li, D.; Lim, Y.C.; Lian, Y.; Song, J.
Abstract: This paper presents a polynomial-time algorithm for designing digital filters with coefficients expressable as sums of signed power-of-two (SPT) terms. Our proposal is based on an observation that under certain circumstances, the realization cost of a filter with SPT coefficients depends only on the total number of SPT terms, regardless of how the terms distribute among the coefficients. Therefore, the number of SPT terms for each coefficient is not necessarily limited to a fixed number. Instead, they should be allowed to vary subject to a given number of total SPT terms for the filter. This provides the possibility of finding a better set of coefficients. Our algorithm starts with initializing all the quantized coefficient values to zero. It chooses one SPT term at a time and allocates it to the currently most deserving coefficient to minimize the L ∞ distance between the SPT coefficients and their corresponding infinite wordlength values. This process of allocating the SPT terms is repeated until the total number of SPT terms for the filter is equal to a prescribed number. For each filter gain, the time complexity is a second-order polynomial in the number of coefficients to be optimized and is a first-order polynomial in the filter wordlength.
Thu, 01 Aug 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/819042002-08-01T00:00:00Z
- Extrapolated impulse response FIR filtershttps://scholarbank.nus.edu.sg/handle/10635/62176Title: Extrapolated impulse response FIR filters
Authors: Lim, Y.C.; Liu, B.
Abstract: An FIR filter structure with reduced hardware complexity is presented. It makes use of the quasi-periodic nature of the impulse response samples of low-pass and high-pass filters to extrapolate the filter length. Because of the reduced number of multipliers, it has lower roundoff noise power compared to the direct-form structure. In this technique, one period of the impulse response is realized accurately and the other periods with smaller magnitudes are realized as scaled versions of that period.
Sat, 01 Dec 1990 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/621761990-12-01T00:00:00Z
- Genetic algorithm approach for the optimization of multiplierless sub-filters generated by the frequency-response masking techniquehttps://scholarbank.nus.edu.sg/handle/10635/70423Title: Genetic algorithm approach for the optimization of multiplierless sub-filters generated by the frequency-response masking technique
Authors: Yu, Y.J.; Lim, Y.C.
Abstract: In this paper, the genetic algorithm (GA) is applied to optimize the discrete coefficient values of very sharp linear phase FIR digital filters generated by frequency-response masking (FRM) technique. The discrete coefficient space is the signed power-of-two (SPT) space. Since the genetic algorithm optimizes all the sub-filters' coefficients simultaneously, it overcomes the drawback existing in linear optimization technique that optimizes the sub-filters individually. If the genetic algorithm starts from the continuous solution obtained by using non-linear joint optimization algorithm, the obtained overall ripple magnitude of the discrete solution is very close to that of the continuous solution. Great improvement is achieved compared to the discrete coefficient filters obtained by rounding the coefficient values of the continuous solutions. © 2002 IEEE.
Tue, 01 Jan 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/704232002-01-01T00:00:00Z
- FRM based FIR filter design - The WLS approachhttps://scholarbank.nus.edu.sg/handle/10635/70386Title: FRM based FIR filter design - The WLS approach
Authors: Yu, Y.J.; Lim, Y.C.
Abstract: Frequency-response masking (FRM) technique produces a filter network which comprises several sub-filters with very sparse coefficient values. If the sub-filters are optimized seperately, the overall filter network will be suboptimal. In this paper, an unconstrained weighted least squares algorithm for simultaneously optimizing the sub-filters generated by the frequency-response masking technique is presented. Simulation runs show that our proposed technique produces significant reduction in the effective filter length.
Tue, 01 Jan 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/703862002-01-01T00:00:00Z
- Linear-phase digital audio tone control using multiplication-free FIR filterhttps://scholarbank.nus.edu.sg/handle/10635/62384Title: Linear-phase digital audio tone control using multiplication-free FIR filter
Authors: Lian, Yong; Lim, Yong Ching
Abstract: A new linear-phase FIR filter system for digital audio tone control applications is presented. The system is based on the multiplication-free fourth-order low-pass FIR filter. The arithmetic complexity of the system is very low. It only needs 24 summation operations per sample.
Fri, 01 Oct 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/623841993-10-01T00:00:00Z
- LINEAR-PHASE DIGITAL AUDIO TONE CONTROL.https://scholarbank.nus.edu.sg/handle/10635/62385Title: LINEAR-PHASE DIGITAL AUDIO TONE CONTROL.
Authors: Lim, Y.C.
Abstract: A new linear-phase three-way filter system for digital audio tone-control application is presented. Approximately 80% of its coefficient values are zero. The remaining nonzero coefficient values are 0. 5 and 0. 25. Thus the filter system is essentially multiplication free. When the high-frequency and low-frequency gain weightings are unity, the filter system acts as a pure delay producing no frequency response distortion.
Thu, 01 Jan 1987 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/623851987-01-01T00:00:00Z
- Linearity improvement of CMOS transconductors for low supply applicationshttps://scholarbank.nus.edu.sg/handle/10635/62383Title: Linearity improvement of CMOS transconductors for low supply applications
Authors: Li, M.F.; Chen, X.; Lim, Y.C.
Abstract: A new CMOS transconductor circuit is proposed. It incorporates a current bootstrapping loop to improve the linearity without using a large source follower and high supply voltage.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/623831993-01-01T00:00:00Z
- New natural selection process and chromosome encoding for the design of multiplierless lattice QMF using genetic algorithmhttps://scholarbank.nus.edu.sg/handle/10635/71131Title: New natural selection process and chromosome encoding for the design of multiplierless lattice QMF using genetic algorithm
Authors: Yu, Y.J.; Lim, Y.C.
Abstract: A new natural selection process and chromosome encoding for the design of signed power-of-two (SPT) coefficient lattice structure quadrature mirror filter (QMF) bank using genetic algorithm (GA) is presented in this paper. In the design of filters using genetic algorithms, in general, genetic operations may render the SPT representation of a value non-canonical. In this paper, a new encoding scheme is introduced to encode the SPT values. In this new scheme, the canonical property of the SPT values is preserved under genetic operations. Additionally, a new feature which drastically improves the performance of our GA is introduced. The new feature is: the probability of mutation for each codon of a chromosome is weighted by the reciprocal of its effect. Owing to the new feature, the performance of our new GA outperforms conventional GA. © 2001 IEEE.
Mon, 01 Jan 2001 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/711312001-01-01T00:00:00Z
- A novel genetic algorithm for the design of a signed power-of-two coefficient quadrature mirror filter lattice filter bankhttps://scholarbank.nus.edu.sg/handle/10635/54610Title: A novel genetic algorithm for the design of a signed power-of-two coefficient quadrature mirror filter lattice filter bank
Authors: Yu, Y.J.; Lim, Y.C.
Abstract: A novel genetic algorithm (GA) for the design of a canonical signed power-of-two (SPT) coefficient lattice structure quadrature mirror filter bank is presented in this paper. Genetic operations may render the SPT representation of a value noncanonical. In this paper, a new encoding scheme is introduced to encode the SPT values. In this new scheme, the canonical property of the SPT values is preserved under genetic operations. Additionally, two new features that drastically improve the performance of our GA are introduced. (1) An additional level of natural selection is introduced to simulate the effect of natural selection when sperm cells compete to fertilize an ovule; this dramatically improves the offspring survival rate. A conventional GA is analogous to intracytoplasmic sperm injection and has an extremely low offspring survival rate, resulting in very slow convergence. (2) The probability of mutation for each codon of a chromosome is weighted by the reciprocal of its effect. Because of these new features, the performance of our new GA outperforms conventional GAs.
Wed, 01 May 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/546102002-05-01T00:00:00Z
- A Novel Integrated CMOS Switch Circuit for High Precision Sample-and-Hold Techniquehttps://scholarbank.nus.edu.sg/handle/10635/54616Title: A Novel Integrated CMOS Switch Circuit for High Precision Sample-and-Hold Technique
Authors: Li, M.F.; Yep, S.Y.; Lim, Y.C.
Abstract: A new CMOS switch circuit is proposed for the implementation of high precision sample-and-hold. The switch includes a current mirror and switching action is controlled by current pulses. This reduces charge injection due to clock feedthrough and the charge injection is input signal independent, resulting in a greatly improved sample-and-hold accuracy.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/546161997-01-01T00:00:00Z
- An iterative method for optimizing FIR filters synthesized using the two-stage frequency-response masking techniquehttps://scholarbank.nus.edu.sg/handle/10635/69346Title: An iterative method for optimizing FIR filters synthesized using the two-stage frequency-response masking technique
Authors: Yu, Y.J.; Saramäki, T.; Lim, Y.C.
Abstract: An efficient technique for drastically reducing the number of multipliers and adders in narrow-transition band linear-phase finite-impulse response filters is to use one-stage or multistage frequency-response masking (FRM) approaches as originally introduced by Lim. It has been observed recently that for the one-stage FRM approach the filter complexity can be considerably reduced by iteratively optimizing the periodic filter and masking filters by properly sharing the frequency-response-shaping responsibilities in their respective frequency regions. In this paper, a similar iterative method is applied to the two-stage FRM structure to reduce the filter complexity even more. An example taken from the literature is included illustrating that the number of adders and multipliers for the resulting filters are less than 75 percent compared with the original designs.
Wed, 01 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/693462003-01-01T00:00:00Z
- Decomposition of binary integers into signed power-of-two termshttps://scholarbank.nus.edu.sg/handle/10635/61994Title: Decomposition of binary integers into signed power-of-two terms
Authors: Lim, Yong Ching; Evans, Joseph B.; Liu, Bede
Abstract: Previous work has shown that approximation of digital filter coefficients using sums of signed power-of-two terms yields significant area/speed advantages in custom implementations, at the expense of a slight frequency response deterioration. The completeness, uniqueness, and resolving power of signed powers-of-two representations are studied, and circuits for extracting a prescribed number of signed power-of-two terms whose sum is the closest approximation to a given integer are presented. Examples of implementation of these circuits in a CMOS process are given.
Sat, 01 Jun 1991 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/619941991-06-01T00:00:00Z
- Design of discrete-coefficient-value linear phase FIR filters with optimum normalized peak ripple magnitudehttps://scholarbank.nus.edu.sg/handle/10635/62014Title: Design of discrete-coefficient-value linear phase FIR filters with optimum normalized peak ripple magnitude
Authors: Lim, Y.C.
Abstract: Four methods are presented for optimizing filters in the normalized peak ripple magnitude (NPRM) sense. Two of the methods belong to the passband gain sectioning technique. The other two methods make use of the objective function f = δ - αb. Several heuristic methods for determining α are also presented. The NPRM is an important performance measure; the absolute peak ripple magnitude and passband gain are less important. In these applications, the passband gain need not be fixed at unity but should be a continuous variable to be optimized. Nevertheless, an upper and a lower bound on the passband gain should be imposed to satisfy overflow and roundoff noise performance requirements.
Sat, 01 Dec 1990 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620141990-12-01T00:00:00Z
- Design of sharp linear-phase fir bandstop filters using the frequency-response-masking techniquehttps://scholarbank.nus.edu.sg/handle/10635/50460Title: Design of sharp linear-phase fir bandstop filters using the frequency-response-masking technique
Authors: Yang, R.; Lim, Y.-C.; Parker, S.R.
Abstract: A novel computationally efficient realization of sharp linear-phase finite impulse response (FIR) bandstop filters is proposed. The synthesis scheme for the bandstop filters is derived from variations of the frequency-response-masking technique. Five realization structures are presented in this paper for the synthesis of five different classes of bandstop filters. Approximate expressions for the optimal value of the impulse response up-sampling ratio (M) and the corresponding number of multipliers are derived.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/504601998-01-01T00:00:00Z
- Synthesis of linear-phase multirate frequency-response-masking filtershttps://scholarbank.nus.edu.sg/handle/10635/50471Title: Synthesis of linear-phase multirate frequency-response-masking filters
Authors: Lim, Yong-Ching; Yang, Rui
Abstract: The application of the frequency-response-masking technique for the synthesis of computationally efficient sharp filters has been discussed widely in the literatures. However, all of the previously reported frequency-response-masking methods are efficient for synthesizing filters operating in the single rate environment only. In this paper, we extend the frequency-response-masking technique into the design of multirate filters. Our method is eminently suitable for the synthesis of anti-aliasing and anti-imagining filters for interpolation and decimation operations.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/504711997-01-01T00:00:00Z
- Design of sharp FIR bandstop filters using quadrature masking filtershttps://scholarbank.nus.edu.sg/handle/10635/50468Title: Design of sharp FIR bandstop filters using quadrature masking filters
Authors: Yang, Rui; Lim, Yong-Ching; Bellanger, Maurice
Abstract: A novel computationally highly efficient realization of sharp symmetrical bandstop FIR filter is proposed. The new structure is derived using the frequency-response-masking technique, where the bandedge-shaping filter is derived from half-band filter by substituting each delay of the half-band filter by M delays. The masking filters are unconventional. They are quadrature filters derived from linear combinations of the masking filters in the conventional frequency-response-masking technique. Approximate expressions for the optimal value of M and the corresponding number of multipliers are derived.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/504681997-01-01T00:00:00Z
- Design of cascaded FIR filtershttps://scholarbank.nus.edu.sg/handle/10635/50467Title: Design of cascaded FIR filters
Authors: Lim, Yong-Ching; Yang, Rui; Liu, Bede
Abstract: Many filtering operations require the use of more than one filter connected in cascade. The stopband response of each of these filters must meet a given minimum attenuation requirement, whereas the overall passband peak ripple magnitude must be within a pre-specified tolerance limit. Generally, the design approaches require the passband ripple magnitude of each of the filters to be smaller than that of the overall filter. However, if the filters are jointly optimized so that the passband ripples of the filters are 180° out of phase, then the passband ripple magnitudes of the individual filters may be allowed to be very much larger than the maximum allowable overall ripple magnitude without violating the tolerance limit of the overall passband ripple magnitude. In this paper, we present a linear-programming technique for jointly optimizing the filters.
Mon, 01 Jan 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/504671996-01-01T00:00:00Z
- DIGITAL FILTER BANK FOR DIGITAL AUDIO SYSTEMS.https://scholarbank.nus.edu.sg/handle/10635/62041Title: DIGITAL FILTER BANK FOR DIGITAL AUDIO SYSTEMS.
Authors: Lim, Y.C.
Abstract: The design of a linear-phase digital filter bank for audio system frequency response equalization is shown. This filter bank uses frequency-response masking and complementary filtering principles to achieve a sharp frequency response for each band; unity gain at all frequencies with no ripple when all gain weightings of the filter bank outputs are unity; and low hardware complexity.
Fri, 01 Aug 1986 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620411986-08-01T00:00:00Z
- Grid density for design of one- and two-dimensional FIR filtershttps://scholarbank.nus.edu.sg/handle/10635/62263Title: Grid density for design of one- and two-dimensional FIR filters
Authors: Yang, R.H.; Lim, Y.C.
Abstract: The frequency response of a digital filter is often optimised to meet a given set of specifications on a dense grid of frequency points. The density of the frequency grid points must be sufficiently high so that the frequency response of the filter does not violate the specifications at frequencies in between the grid points. However, the computational complexity of the design process and the storage requirements of the computer increase with the number of frequency grid points. In this a detail study of the grid density requirement for the design of FIR filters is presented. The study leads to a useful design rule.
Tue, 01 Jan 1991 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622631991-01-01T00:00:00Z
- Frequency-response masking approach for the synthesis of sharp two-dimensional diamond-shaped filtershttps://scholarbank.nus.edu.sg/handle/10635/62222Title: Frequency-response masking approach for the synthesis of sharp two-dimensional diamond-shaped filters
Authors: Lim, Y.C.; Low, S.H.
Abstract: The frequency-response masking (FRM) technique is an efficient method for realizing sharp one-dimensional (1-D) filters. Sharp 1-D filters realized using the FRM technique have considerably lower complexity than those realized in the direct form. In this paper, we present an extension of the FRM technique to the synthesis of sharp two-dimensional (2-D) diamondshaped (DS) filters. The new technique, based upon dividing the frequency spectrum into four complementary components and the utilization of four masking filters, achieves large reductions in filter implementation complexity when the transition width of the desired DS filter is very narrow. An expression for the impulse response up-sampling ratio that produces the design with the least complexity is derived. Extensions of the technique for the synthesis of 2-D filters other than the DS filters are also discussed. © 1998 IEEE Publisher Item Identifier S 1057-7130(98)08504-8.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622221998-01-01T00:00:00Z
- Frequency grid density for the design of 2-D FIR filtershttps://scholarbank.nus.edu.sg/handle/10635/62216Title: Frequency grid density for the design of 2-D FIR filters
Authors: Low, S.H.; Lim, Y.C.
Abstract: In the design of a digital 2-D FIR filter, the frequency response is often optimised to satisfy a given set of specifications on a dense grid of frequency points. The accuracy of a filter design improves when there are more grid points, but this is at the expense of higher computational resources. The authors present the relationship between the accuracy and the frequency grid density in 2-D filter designs. A new formula for determining the frequency grid spacing is also proposed.
Thu, 01 Aug 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622161996-08-01T00:00:00Z
- Forward-backward LMS adaptive line enhancerhttps://scholarbank.nus.edu.sg/handle/10635/62210Title: Forward-backward LMS adaptive line enhancer
Authors: Lim, Y.C.; Ko, C.C.
Abstract: A new LMS (least-mean-square) adaptive line enhancer algorithm is presented. It makes use of forward and backward prediction errors to update the coefficient values. For a given feedback factor, the algorithm converges to the optimal Wiener solution with the same speed as for the LMS algorithm, but requires about twice the number of multiplications and additions. However, in the situation when the order of the enhancer is at least a few times larger than the number of sinusoids to be enhanced, or when the frequencies of the sinusoids to be enhanced are not close to 0 or 0.5, the misadjustment of the new algorithm is approximately half that of the LMS algorithm.
Sun, 01 Jul 1990 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622101990-07-01T00:00:00Z
- FREQUENCY-RESPONSE MASKING APPROACH FOR THE SYNTHESIS OF SHARP LINEAR PHASE DIGITAL FILTERS.https://scholarbank.nus.edu.sg/handle/10635/62221Title: FREQUENCY-RESPONSE MASKING APPROACH FOR THE SYNTHESIS OF SHARP LINEAR PHASE DIGITAL FILTERS.
Authors: Lim, Yong Ching
Abstract: If each delay element of a linear-phase, low-pass digital filter is replaced by M delay elements, an (M plus 1)-band filter is produced. The transition-width of this (M plus 1)-band filter is 1/M that of the prototype low-pass filter. A complementary filter can be obtained by subtracting the output of the (M plus 1)-band filter from a suitably delayed version of the input. The complementary filter is an (M plus 1)-band filter whose passbands and stopbands are the stopbands and passbands, respectively, of the original (M plus 1)-band filter. If the frequency responses of the original (M plus 1)-band filter and its complementary filter are properly masked and recombined, a narrow transition-band filter can be obtained. This techniques can be used to design sharp low-pass, high-pass, bandpass, and bandstop filters with arbitrary passband bandwidth.
Tue, 01 Apr 1986 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/622211986-04-01T00:00:00Z
- Fast vicinity-upgrade algorithm for rectilinear Steiner treeshttps://scholarbank.nus.edu.sg/handle/10635/62190Title: Fast vicinity-upgrade algorithm for rectilinear Steiner trees
Authors: Chua, J.K.; Lim, Y.C.
Abstract: A new algorithm for rectilinear Steiner trees (RST) is presented. The proposed algorithm is based on successively constructing a vicinity structure from a rectilinear minimum spanning tree (MST) and generating a refined RST. The algorithm achieves an 8.5-10% average cost improvement over the rectilinear MST at a time complexity of O(n log n). To address specifically the linear programming approach of global routing, the algorithm is modified to generate K trees.
Tue, 01 Jan 1991 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/621901991-01-01T00:00:00Z
- Pipelined recursive filter with minimum order augmentationhttps://scholarbank.nus.edu.sg/handle/10635/62626Title: Pipelined recursive filter with minimum order augmentation
Authors: Lim, Y.C.; Liu, Bede
Abstract: Pipelining is an efficient way for improving the average computation speed of an arithmetic processor. However, for an M-stage pipeline, the result of a given operation is available only M clock periods after initiating the computation. In a recursive filter, the computation of y(n) cannot be initiated before the computations of y(n - 1) through y(n - N) are completed. H. B. Voelcker and E. E. Hartquist (1970) and P. M. Kogge and H. S. Stone (1973) independently devised augmentation techniques for resolving the dependence problem in the computation of y(n). However, the augmentation required to ensure stability may be excessively high, resulting in a very complex numerator realization. A technique which results in a minimum order augmentation is presented here. The complexity of the resulting filter design is very much lower. Various pipelining architectures are presented. It is demonstrated by an example that when compared to the prototype filter, the augmented filter has a lower coefficient sensitivity and better roundoff noise performance.
Wed, 01 Jul 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/626261992-07-01T00:00:00Z
- Parallel and pipelined implementations of injected numerator lattice digital filtershttps://scholarbank.nus.edu.sg/handle/10635/62578Title: Parallel and pipelined implementations of injected numerator lattice digital filters
Authors: Lim, Y.C.
Abstract: Parallel and pipelined implementations are effective measures for improving the maximum permissible sampling rate of a digital filter if all the data required by the arithmetic units are immediately available on demand. This implies that parallel access to the data should be possible and that for any loop in the signal flow graph the total number of series delay elements should be at least equal to the total number of pipelined stages in that loop. In the conventional lattice form IIR digital filter, the feedback loops are single-delay loops. As a consequence, the conventional lattice form IIR filter does not benefit significantly from parallel and pipelined implementation scheme. In this paper, we introduce a new lattice form IIR filter structure where the number of delay elements in the loops can be set arbitrarily. This renders the new lattice form IIR filter amenable to parallel and pipelined implementation.
Sat, 01 Jul 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/625781995-07-01T00:00:00Z
- New prefilter structure for designing filtershttps://scholarbank.nus.edu.sg/handle/10635/62482Title: New prefilter structure for designing filters
Authors: Lian, Y.; Lim, Y.C.; Lim, Y.C.
Abstract: A new prefilter structure is presented. The frequency response of the prefilter structure is derived from the combination of two cosine functions. By cascading these prefilters with an appropriate equalizer, low complexity filters with high stopband attenuation can be achieved. The proposed prefilter leads to a significant saving in the number of arithmetic operations in the prefilter-equalizer cascade structure.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/624821993-01-01T00:00:00Z