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The classical stereophonic acoustic echo cancellation (SAEC) scheme requires the identification of four echo paths using the same number of adaptive algorithms. The SAEC setup can be reinterpreted by employing the widely linear (WL) model, which recasts the two-input/two-output system with real random variables as a single-input/single-output system with complex random variables. The WL model improves...
The design of the finite impulse response (FIR) digital filters with linear phase is considered by cascading a prototype filter with complementary comb filters. The minimum attenuation in the stop band is increased and the complexity of implementation is reduced, because the complementary comb filters contain only adders and storage units. The prototype filter is designed by using grouped B-spline...
This paper presents a design method of the audio digital appodizing filters, by using B-spline and continuous polynomial functions in the transition frequency band. It is known that an appodizing filter can be used to control the time smear for a recording and a reproducing chain. The choice of the frequency response above 20 kHz can reduce the time extent of the impulse response. In the proposed...
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...
Radio resources have had higher demand in the last years. The frequency band licenses for most of the radio spectrum are sold for long periods of time and give exclusive rights to the owner. By using such an approach the spectrum seems overcrowded, but the reality shows that many frequency areas are actually used in a very small degree. We have demonstrated in [4] that cognitive radio (CR) technology...
A fast technique for designing prototype filters for modulated filter banks is proposed. This technique is based on using the grouped B-spline windows for designing the prototype filter and also spline functions in the transition band to approximate ideal filters. The main advantage of the proposed design scheme is that it lowers the computational complexity when compared with other existing techniques...
In this paper, we analyze the numerical properties of the recently proposed joint-optimized normalized least-mean-square (JO-NLMS) algorithm. This algorithm was developed in the context of a time-variant system model, using an iterative procedure for adjusting the system model parameter. Due to these features, the JO-NLMS algorithm behaves like a variable step-size adaptive filter, leading to both...
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...
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,...
The paper deals with the domain of CDMA communications systems affected by narrowband interferences, noise and flat fading. The spectrum used by some CDMA wireless systems is frequently utilized by other systems and the probability of radio-frequency interferences is relatively high in the vicinity of airports, broadcast towers and office buildings. This work researches the performances of several...
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...
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...
This paper presents a design method of the optimum quadrature mirror filters (QMF), by using spline polynomial functions. It is known 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. The solution is to approximate the response...
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...
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 amplitudefrequency 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...
In this paper a design method of the optimum digital audio equalizers with small ringing impulse responses, by using symmetric B-spline functions 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...
In this paper a design method of the optimum digital audio equalizers with small ringing impulse responses, by using symmetric B-spline functions 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...
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...
A complete computer program for audio restoration using an autoregressive algorithm and two-pass split-window filtering is presented. Methods of clicks detection in old recordings are analyzed. Experimental results are presented.
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