In some applications, it is required to have continuous-time low-pass analog filtering systems which simultaneously possess a constant group delay in the passband and a narrow transition band. Usually, these systems are implemented by adding to the output of a filter with steep-amplitude selectivity (an elliptic filter, for instance) an all-pass filter which compensates the unfavorable run of the group delay response of the first filter. However, this compensation process will also increase the duration of the transient response of the resulting filtering system. This paper presents a new class of delay-compensated parameter-varying lowpass elliptic filters with a transient response of short duration. This improvement is achieved by means of a temporary change in the value of the filter parameters when a steplike transition with a minimum amplitude is detected in the input signal. As a consequence of the control strategy used to induce parameter variations in the proposed class of filters, its behavior is nonlinear in nature. Therefore, its stability properties (and particularly their bounded-input bounded-output stability) are also assessed. Simulations verifying the effectiveness of the new class of filters are presented and compared to the performance of delay-compensated and delay-uncompensated elliptic filters which were chosen as study cases.
Linear time-varying (LTV) systems have found a niche of their own in the processing of continuous-time signals. In this brief, it is shown how the reduction of the duration of the transient response of a class of continuous-time LTV filters may be seen as the combined effect of the increased dampening of its amplitude response and the increase of the instantaneous frequency of its damped oscillations. For this aim, an LTV system whose damping factor and the damped frequency of its oscillations may be specified as functions of time is used as a vehicle of study. Time-varying eigenvalues are used to assess the behavior of the proposed system. Simulation results are used to verify the proposed mechanism behind the reduction of the duration of the transient response in the LTV filters under study.
Newton-Raphson DC analysis of large-scale nonlinear circuits may be an extremely time consuming process even if sparse matrix techniques and bypassing of nonlinear models calculation are used. A slight decrease in the time required for this task may be enabled on multi-core, multithread computers if the calculation of the mathematical models for the nonlinear elements as well as the stamp management of the sparse matrix entries is managed through concurrent processes. In this paper it is shown how the numerical complexity of this problem (and thus its solution time) can be further reduced via the circuit decomposition and parallel solution of blocks taking as a departure point the Bordered-Block Diagonal (BBD) matrix structure. This BBD-parallel approach may give a considerable profit though it is strongly dependent on the system topology. This paper presents a theoretical foundation of the algorithm, its implementation, and numerical complexity analysis in virtue of practical measurements of matrix operations.
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