Y. Liu

Hong Kong Polytechnic University

33Publications

14H-index

492Citations

Publications 33

Newest*
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Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

In this paper, a general optimum full-band, high-order discrete-time differentiator design problem is formulated as a peak-constrained least squares optimization problem. That is, the objective of the optimization problem is to minimize the total weighted square error of the magnitude response subject to the peak constraint of the weighted error function. This problem formulation provides great flexibility for the tradeoff between the ripple energy and the ripple magnitude of the discrete-time d...

Estimated H-index: 1

Estimated H-index: 1

Estimated H-index: 44

In this brief, a near-allpass strictly stable minimal-phase real-valued rational infinite-impulse response filter is designed so that the maximum absolute phase error is minimized subject to a specification on the maximum absolute allpass error. This problem is actually a minimax nonsmooth optimization problem subject to both linear and quadratic functional inequality constraints. To solve this problem, the nonsmooth cost function is first approximated by a smooth function, and then our previous...

Optimal PWM Control of Switched-Capacitor DC–DC Power Converters via Model Transformation and Enhancing Control Techniques*
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Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

This paper presents an efficient and effective method for an optimal pulsewidth-modulated (PWM) control of switched-capacitor dc-dc power converters. Optimal switching instants are determined based on minimizing the output ripple magnitude, the output leakage voltage and the sensitivity of the output load voltage with respect to both the input voltage and the load resistance. This optimal PWM control strategy has several advantages over conventional PWM control strategies: 1) it does not involve...

Efficient Algorithm for Solving Semi-Infinite Programming Problems and Their Applications to Nonuniform Filter Bank Designs*
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Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

An efficient algorithm for solving semi-infinite programming problems is proposed in this paper. The index set is constructed by adding only one of the most violated points in a refined set of grid points. By applying this algorithm for solving the optimum nonuniform symmetric/antisymmetric linear phase finite-impulse-response (FIR) filter bank design problems, the time required to obtain a globally optimal solution is much reduced compared with that of the previous proposed algorithm

Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

This correspondence considers a design of magnitude responses of optimal rational infinite impulse response (IIR) filters. The design problem is formulated as an optimization problem in which a total weighted absolute error in the passband and stopband of the filters (the error function reflects a ripple square magnitude) is minimized subject to the specification on this weighted absolute error function defined in the corresponding passband and stopband, as well as the stability condition. Since...

Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

This correspondence considers the optimized design of interpolative sigma delta modulators (SDMs). The first optimization problem is to determine the denominator coefficients. The objective of the optimization problem is to minimize the passband energy of the denominator of the loop filter transfer function (excluding the dc poles) subject to the continuous constraint of this function defined in the frequency domain. The second optimization problem is to determine the numerator coefficients in w...

Estimated H-index: 9

Estimated H-index: 16

Estimated H-index: 14

The development of efficient time optimal control strategies for coupled spin systems plays a fundamental role in nuclear magnetic resonance (NMR) spectroscopy. In particular, one of the major challenges lies in steering a given spin system to a maximum of its so-called transfer function. In this paper we study in detail these questions for a system of two weakly coupled spin-½ particles. First, we determine the set of maxima of the transfer function on the special unitary group SU(4). It is sho...

Estimated H-index: 20

Estimated H-index: 9

Estimated H-index: 44

The Davies transformation is a method to transform the steering vector of a uniform circular array (UCA) to one with Vandermonde form. As such, it allows techniques such as spatial smoothing for direction-of-arrival (DOA) estimation in a correlated signal environment, developed originally for uniform linear arrays, to be applied to UCAs. However, the Davies transformation can be highly sensitive to perturbations of the underlying array model. This paper presents a method for deriving a more robu...

Estimated H-index: 4

Estimated H-index: 44

Estimated H-index: 14

In this paper, we establish several oscillatory criteria for even order neutral differential equations with distributed deviating arguments, which generalize and improve some known results.

Estimated H-index: 10

Estimated H-index: 15

Estimated H-index: 44

This correspondence considers an optimum nonuniform finite impulse response (FIR) transmultiplexer design problem subject to specifications in the frequency domain. Our objective is to minimize the sum of the ripple energy for all the individual filters, subject to the specifications on amplitude and aliasing distortions, and to the passband and stopband specifications for the individual filters. This optimum nonuniform transmultiplexer design problem can be formulated as a quadratic semi-infini...

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