Lucian Stanciu

Digital audio equalizers with flat frequency response

In this paper a design method of the digital audio equalizers with small ringing impulse responses, by using symmetric B-spline functions and spline polynomials, is presented. It is important to have a flat frequency response for the audio equalizer. The solution is to approximate the response of each frequency band by using spline functions, that insures continuous superior order derivatives. These small ringings give a natural audition. A tradeoff between frequency band independence, small ringings of the impulse response and desired frequency response, must be made.

Optimal grouped B-spline windows for power spectral density estimation

The solution, of minimizing the effect known as spectral leakage into the sidelobe of a window function is to obtain a continuous waveform, which results in lesser sidelobe level. Conventional windows are able to control these characteristics by only one parameter. To suppress the spectral leakage, a window function in the time domain is used to shape the finite time sampled measurement data. The higher order of continuity of the of the time window function can be obtained by using grouped B-spline functions with three control parameters for power spectral density estimation.

B-spline approach for the design of quadrature mirror filters

In this paper a design method of the optimum quadrature mirror filters (QMF), by using symmetric B-spline functions, is presented. It was shown that linear phase FIR filters cannot exactly satisfy the condition that the squared amplitude frequency responses are mirror images of each other about the line ω= π /2 which has led to the name quadrature mirror flters. It is important to have a flat frequency response for the filters. The solution is to approximate the response of each frequency band by using B-spline functions, that insures continuous superior order derivatives. In the proposed method, the prototype filter is optimized with the novelty of using spline functions in the transition band.

Continuous polynomials combination for the design of quadrature mirror filters

This material proposes an efficient method for the design of the two channel quadrature mirror filters (QMF) bank, by using continuous polynomial functions. It is important to know that linear phase FIR filters cannot exactly satisfy the power complementarity condition. The proposal is to approximate the amplitudes of the two frequency transition bands by using continuous polynomial functions. The result is a good frequency selectivity. In the proposed approach, the prototype filter is optimized, by using continuous polynomials in the transition band. Many simulation results are presented to sustain the proposed method.

Efficient FPGA implementation of the DCD-RLS algorithm for stereo acoustic echo cancellation

The development of teleconferencing systems has allowed the communication using two acoustic channels (stereo configuration). The corresponding standard acoustic echo cancellation process requires four adaptive filters with a considerable usage of hardware resources. In this context, the dichotomous coordinate descent (DCD) - recursive least-squares (RLS) algorithm, using the widely linear (WL) model, was proposed as an efficient alternative to the classical RLS solution. In this paper, an efficient Field Programmable Gate Array (FPGA) implementation of the DCD-RLS method is presented, with attractive numerical properties and good performance.

Grouped B-spline functions for the design of Quadrature Mirror Filters

The design of two channel Quadrature Mirror Filter (QMF) banks is considered with constraints on the peaks of the reconstruction error and that of the subband filter ripple sizes. In this paper a design method of the optimum quadrature mirror filters (QMF), by using grouped B-spline functions in each transition band, is presented. It was shown that linear phase FIR filters cannot exactly satisfy the condition that the squared amplitude frequency responses are mirror images of each other about the line ω = π / 2, which has led to the name quadrature mirror filters. It is important to have a flat frequency response for the filters. The solution is to approximate the response of each frequency band by using grouped B-spline functions, that insures continuous superior order derivatives.

FPGA implementation for power spectral estimation using grouped B-Spline windows

Spectrum sensing is an essential component in radio systems such as cognitive networks, which aim for opportunistic usage of unutilized radio spectrum. In order to perform an accurate estimation and reduce spectral leakage, grouped B-Spline windows can be used. The amplitude of the windows can be modified using three control parameters. A hardware implementation solution is presented and the performance of the proposed system is verified. The analyzed structure is attractive for hardware implementations with spectral sensing features.

Grouped B-spline windows for power spectral density estimation

The power spectral density of a signal can be estimated most accurately by using a window that can attain a narrower main lobe width and a higher decay rate. Conventional windows are able to control these characteristics by only one parameter, so there is a trade-off problem. To reduce the effect of spectral leakage, a window function can be used whose amplitude tapers smoothly and gradually toward zero at both ends. The spectral methods are accurate for smooth functions and we propose using grouped B-spline windows with three control parameters for power spectral density estimation and analyze its characteristics.

Spline windows for power spectral density estimation

The power spectral density of a signal can be estimated most accurately by using a window with a narrow bandwidth and large sidelobe attenuation. Conventional windows generally control these characteristics by only one parameter, so there is a trade-off problem. To reduce the effect of spectral leakage, a window function can be used whose amplitude tapers smoothly and gradually toward zero at both ends. To overcome this problem, we propose using grouped spline windows with two control parameters for power spectral density estimation and analyze its characteristics.

Electromagnetic compatibility analysis of the printed circuits boards using finite element method

Due to many significant advances in computer modeling occurred in the past 30 years, there is now possible to approach many EMC problems in a completely numerical way. EMC problems can be formulated in terms of Partial Differential Equations (PDE) to be solved numerically by means of some discretization techniques such as the Finite Element Method (FEM), the Finite Difference Time Domain Method (FDTD) or they can be formulated in terms of Integral Equations (IE) to be solved numerically by application of the Method of Moments (MOM). In this paper some aspects regarding the possibility to use the FEM to analysis and compute the disturbance field produced by signal and supply traces of a printed circuit board (PCB) are presented.