Yong Lim

Bio: Yong Lim is an academic researcher from National University of Singapore. The author has contributed to research in topics: Digital filter & Rounding. The author has an hindex of 5, co-authored 6 publications receiving 594 citations.

FIR filter design over a discrete powers-of-two coefficient space

Abstract: FIR digital filters with discrete coefficient values selected from the powers-of-two coefficient space are designed using the methods of integer programming. The frequency responses obtained are shown to be superior to those obtained by simply rounding the coefficients. Both the weighted minimax and the weighted least square error criteria are considered. Using a weighted least square error criterion, it is shown that it is possible to predict the improvement that can be expected when integer quadratic programming is used instead of simple coefficient rounding.

Finite word length FIR filter design using integer programming over a discrete coefficient space

Abstract: It is demonstrated that the improvement achieved by using integer programming over simple coefficient rounding in the design of finite impulse response (FIR) filters with discrete coefficients is most significant when the discrete coefficient space is the powers-of-two space or when a specification is to be met with a given coefficient word length by increasing the filter length. Both minimax and least square error criteria are considered.

On the synthesis of IIR digital filters derived from single channel AR lattice network

Abstract: The synthesis of two families of ARMA lattice filters-injected numerator filters and the tapped numerator filters-are presented. For both families of filters, the denominator of the z-transform transfer function is synthesized using the single channel AR lattice. The transfer function's numerator of the injected numerator filter is realized by weighting and injecting the input signal into N + 1 appropriate points of the AR lattice where N is the order of the filter. For the tapped numerator filter, the transfer function's numerator is realized by a weighted sum of the signals tapped from N + 1 appropriate points of the AR lattice. The lattice structure introduced by Gray and Markel is a special case of the tapped numerator design. The injected numerator filters are observed to possess certain overflow properties superior to the tapped numerator filters.

Efficient special purpose linear programming for FIR filter design

Abstract: A high efficiency special purpose linear programming algorithm for FIR filter design is introduced, This algorithm incorporates FFT and FIR zero-phase filters to assist in the computation. Compared to the general purpose linear programming, this special purpose linear programming produces large savings in the computing cost when used to design FIR filters. The savings increase with the length of the filter being designed.

An interpolation technique for computing the DFT of a sparse sequence

Abstract: An interpolation technique for the approximate computation of the DFT of a sparse sequence is presented. This new method is more efficient than FFT pruning, particularly for long sequences where the effectiveness of FFT pruning diminishes. This interpolation method for computing the DFT of a sparse sequence is very useful in filter design and spectrum analysis.

Use of minimum-adder multiplier blocks in FIR digital filters

Abstract: The computational complexity of VLSI digital filters using fixed point binary multiplier coefficients is normally dominated by the number of adders used in the implementation of the multipliers. It has been shown that using multiplier blocks to exploit redundancy across the coefficients results in significant reductions in complexity over methods using canonic signed-digit (CSD) representation, which in turn are less complex than standard binary representation. Three new algorithms for the design of multiplier blocks are described: an efficient modification to an existing algorithm, a new algorithm giving better results, and a hybrid of these two which trades off performance against computation time. Significant savings in filter implementation cost over existing techniques result in all three cases. For a given wordlength, it was found that a threshold set size exists above which the multiplier block is extremely likely to be optimal. In this region, design computation time is substantially reduced. >

Frequency-response masking approach for the synthesis of sharp linear phase digital filters

Abstract: If each delay element of a linear phase low-pass digital filter is replaced by M delay elements, an (M + 1) -band filter is produced. The transition-width of this (M + 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 + 1) -band filter from a suitably delayed version of the input. The complementary filter is an (M + 1) -band filter whose passbands and stopbands are the stopbands and passbands, respectively, of the original (M + 1) -band filter. If the frequency responses of the original ( M + 1) -band filter and its complementary filter are properly masked and recombined, narrow transition-band filter can be obtained. This technique can be used to design sharp low-pass, high-pass, bandpass, and bandstop filters with arbitrary passband bandwidth.

FIR filter design over a discrete powers-of-two coefficient space

Abstract: FIR digital filters with discrete coefficient values selected from the powers-of-two coefficient space are designed using the methods of integer programming. The frequency responses obtained are shown to be superior to those obtained by simply rounding the coefficients. Both the weighted minimax and the weighted least square error criteria are considered. Using a weighted least square error criterion, it is shown that it is possible to predict the improvement that can be expected when integer quadratic programming is used instead of simple coefficient rounding.

An improved search algorithm for the design of multiplierless FIR filters with powers-of-two coefficients

Abstract: An improved algorithm is presented for the discrete optimization of finite-impulse-response (FIR) digital filter coefficients which are represented by a canonic signed-digit (CSD) code, ie, numbers representable as sums or differences of powers-of-two The proposed search algorithm allocates an extra nonzero digit in the CSD code to the larger coefficients to compensate for the very nonuniform nature of the CSD coefficient distribution This results in a small increase in the filter complexity; however, the improvement in the frequency response is substantial The coefficient optimization is performed in two stages The first stage searches for an optimum scale factor and the second stage consists of a local bivariate search in the neighborhood of the scaled and rounded coefficients >

Moving picture coding method and moving picture decoding method

Abstract: A moving picture coding apparatus for performing inter-picture predictive coding for pictures constituting a moving picture is provided with a coding unit for performing predictive error coding for image data; a decoding unit for performing predictive error decoding for an output from the coding unit; a reference picture memory for holding output data from the decoding unit; and a motion vector detection unit for detecting motion vectors on the basis of the decoded image data stored in the memory. When coding a B picture as a target picture, information indicating whether or not the target picture should be used as a reference picture when coding another picture is added as header information. Therefore, in a decoding apparatus for decoding a bit stream Bs outputted from the moving picture coding apparatus, management of a memory for holding the reference picture can be facilitated on the basis of the header information.