Kenji Suyama

Design of CSD coefficient FIR filters based on branch and bound method

In this paper, we propose a novel method for a high-speed optimal design of FIR filters with CSD coefficients. The design problem can be formulated as a mixed integer programming problem and can be optimally solved using the branch-and-bound method. Then, in such a method, many feasible solutions with similar objective function values exist, and thus enormous subproblems are generated in the branch operation. It prevents us from fast design of filters. Therefore, it is effective to limit a feasible region in advance. In the proposed method, an approximation solution obtained by the other optimization method is used to omit unnecessary subproblems from the branch operation. That is, the branch-and-bound method is begun with the branch tree constructed based on the approximation solution. As a result, a significant reduction of subproblems can be expected. Several design examples are shown to present an effectiveness of the proposed method.

A 10 GHz frequency-drift temperature compensated LC VCO with fast-settling low-noise voltage regulator in 0.13 µm CMOS

This paper presents an LC voltage controlled oscillator (VCO) with an integrated compensation circuit that reduces oscillation frequency drift due to temperature variations. The temperature compensation circuit consists of MOS inversion varactor as a compensation capacitor, and BJTs and resistors for temperature dependent voltage bias generation, and noise contribution suppression of a bias noise. The effectiveness of this technique is demonstrated in a 10 GHz LC VCO with a frequency divider (divide-by-2), output measurement buffer, and integrated fast-settling low-noise voltage regulator. The VCO achieves current consumption of 21.0 mA, tuning range of 10.68 GHz to 12.40 GHz, phase noise of − 109.9 dBc / Hz at 1 MHz offset from 6.12 GHz carrier. The VCO frequency-drift due to temperature is improved by 82 % with the compensation circuit.

A moving sound source tracking based on two successive algorithms

In this paper, we proposed a novel method for single moving sound source tracking based on two successive algorithms. Although the MUSIC(MUltiple SIgnal Classification) method is well-known as one of the best high resolution methods for the unmoving source, two serious difficulties occur regarding as computational costs to solve the problem when the MUSIC method is applied in such a situation. The first occurs at the signal subspace tracking, which requires the eigen-decomposition and thus needs the enormous computations. The second occurs at a peak search of the MUSIC spectrum function, which involve many complex multiplying operations. In the proposed method, the PAST algorithm is applied to track sequentially the signal subspace without the eigen-decomposition, and the IPLS algorithm is applied to search successively the peak of MUSIC spectrum. Several experimental results in actual room environments are shown to present that more accurate results equivalent to the MUSIC method can be obtained by the proposed method less computational costs than the MUSIC method.

A robust technique for sound source localization in consideration of room capacity

This paper proposes a robust technique for a sound source localization based on the time difference of arrival in noisy or reverberant environments. A nonlinear minimization problem for estimating source positions is formulated as a constrained optimization problem in consideration of room capacity. Then, a penalty function for a feasible region of this problem is used as the objective function. As a result, only estimation results within the room can be obtained. It is shown by several experiments that, by using the technique, estimation accuracy can be improved more than 25%.

An effective allocation of non-zero digits for CSD coefficient FIR filters using 0–1PSO

In this paper, a novel method for effective allocation of non-zero digits in design of CSD (Canonic Signed Digit) coefficient FIR (Finite Impulse Response) filters is proposed. The design problem can be formulated as a mixed integer linear programming problem, which is well-known as a NP-hard problem. Recently, a heuristic approach using the PSO (Particle Swarm Optimization) for solving the problem has been proposed, in which the maximum number of non-zero digits is limited in each coefficient. On the other hand, the maximum number of non-zero digits is limited in total in the proposed method and the 0-1PSO is applied. It enables an effective allocation of nonzero digits and provides a good design. Several examples are shown to present an efficiency of the proposed method.

Multiple sound sources tracking method based on Subspace Tracking

In this paper, we propose a novel method for tracking two talkers. The tracking is performed using a microphone array and is based on algorithms implemented successively, namely, the PAST (Projection Approximation Subspace Tracking) and IPLS (Interior Point Least Square) algorithms. When multiple sound sources exist, the order of eigenvectors estimated by the PAST might change at each point in the time-frequency domain. This prevents us from separating and localizing each source. In addition, the appropriate initial values for the IPLS algorithm are required even for the silent-speech sections or in the low-energy domain because of the sparseness of speech signals. To overcome such difficulties, we propose a new method for assigning eigenvectors in the appropriate order and a method for setting the suitable initial value in the IPLS. Several results of experiments performed in an actual room environment show the effectiveness of the proposed method.

Optimal design of FIR filter with discrete coefficients based on integer semi-infinite linear programs

The purpose of the paper is to propose, a new design method of FIR filters with discrete coefficients considering optimality. In the proposed method, the design problem of FIR filters is formulated as a Mixed Integer Semi-Infinite Linear Programming problem (MISILP), which can be solved by a branch and bound technique. Then, it is possible to obtain the optimal discrete coefficients, and the optimality of the obtained solution can be guaranteed. It was confirmed that optimal coefficients of linear phase FIR filter with discrete coefficients could be designed in reasonable computational time with sufficient precision based on the results of computational experiments.

A new heuristic signed-power of two term allocation approach for designing of FIR filters

In this paper, we consider design problems of linear phase FIR filters with CSD (or SP2) coefficients. When the total number of non-zero SP2 terms is given for the design problem, we have to determine the number of non-zero SP2 terms allocated for each filter coefficient respectively, while maintaining the total number. However, this is considered to be an NP-hard problem. Hence, Lim et al. (1998) developed an heuristic method for this allocation problem. In this paper, we propose a new heuristic method for the problem and compare it with Lims method through numerical experiments.

An ACO approach for design of CSD coefficient FIR filters

In this paper, a design method of FIR (Finite Impulse Response) filters with CSD (Canonic Signed Digit) coefficients using ACO (Ant Colony Optimization) is studied. This design problem is formulated as a combinatorial optimization problem. It requires high computation time to obtain an optimal solution. Instead, several heuristic approaches have been developed for solving this problem in a reasonable computation time. ACO is one of the promising approaches and is appropriate for solving the combinatorial optimization problem. Therefore, we study the design method of CSD coefficient FIR filters using ACO. In the design examples, ACO is compared with the other heuristic approaches. Furthermore, a difference between initial coefficients and optimal coefficients is investigated to reveal differences of algorithm behavior. As a result, it is shown that the ACO approach is effective for the design of CSD coefficient FIR filters.

Multiple sound source tracking by two microphones using PSO

In this paper, a method for multiple sound source tracking by two microphones is proposed. PSO (Particle Swarm Optimization) is used for searching multiple peaks on MUSIC (MUltiple SIgnal Classification) spectrum. In addition, a difficulty which the tracking fails when a speech returns to a utterance period after a silent period is resolved. Then, a penalty function is added in an evaluation function of PSO, in which a weighted histogram of DOA (Direction-Of-Arrival) estimation results in time-frequency region is used as the penalty. Several experiments were conducted in an actual room to evaluate the effectiveness of the proposed method.