Production of very high inrush currents in transformers during energization may create deep voltage sag causing malfunction to electronic and other loads. In high voltage power system star-delta transformers are generally switched in, one by one, producing inrush currents each time. The inrush current may be reduced by sequential phase energization of each transformer with neutral resistors. This paper suggests that sequential phase energization should be carried out on the first transformer only after paralleling the delta secondary of all the transformers. This procedure eliminates inrush currents in all the remaining transformers without too much increase in the inrush of the first transformer.
We propose a subband adaptive chip equalizing (SACE) receiver for high-speed direct-sequence ultra-wideband (DS-UWB) communications to efficiently suppress intersymbol interference (ISI) and multiple-access interference (MAI) in short-range indoor networks. The SACE receiver exploits the pre-whitening effect of the filter banks to reduce the eigenvalue spread of the input signal covariance matrix. Numerical results show that the proposed receiver significantly outperforms the fullband adaptive chip equalizing (FACE) receiver while maintaining a lower complexity.
By applying two techniques to the single stage common gate architecture, a new area optimized reconfigurable LNA for multi-standard applications is presented in this paper. This is achieved by LC tuning of the output LNA capacitors in different frequency bands with an easily reconfigured new integrated differential variable inductor. The input impedance is matched by a capacitive feedback loop which also improves NF and linearity performance of LNA. Using these techniques, a LNA supporting PCS, UMTS and IEEE802.11 b-g standards is designed in 65nm CMOS technology which achieves S11 and NF better than -13dB and 1.9dB in all mentioned bands.
The stability of a new adiabatic stepwise charging circuit with an asymmetric 1D capacitor array is discussed. SPICE simulation shows that this circuit, like the one with a symmetric array, is stable. For the analytical discussion, we derive a matrix that connects charge and voltage in the circuit with the asymmetric 1D-capacitor array and show that the matrix is the positive-definite symmetric one. Using matrix theory, it is proved that the eigen value of the matrix connecting the initial voltage deviation from the step value with that after the charge-recycling process is smaller than 1. Therefore, the voltage deviation becomes zero after many charge-recycling processes.
A simple rate equation model of double pass (DP) Erbium doped fiber amplifier (EDFA) is developed based on the Giles and Desurvire (1991) model of single pass (SP) EDFA. The mathematical equations to calculate stimulated absorption and emission rate between level 1 and 2 of SP EDFA are modified by integrating the reflected backward propagating signal of DP EDFA. Reflection loss of signal by the reflector is included with the backward propagating signal of DP EDFA. A combination of Runge-Kutta and relaxation method is used to numerically solve the developed DP EDFA rate equation model. Considering high gain and low noise figure (NF) by very low remote pump power as main design objective, the design procedure of remotely pumped optimized DP EDFA is described. Finally the robustness and stability of the developed DP EDFA rate equation model are shown by analyzing the numerical results and output shape using various design parameters.
User-specific subspace method, such as CLAFIC concatenates the speech matrices side by side leads to a high dimensional feature space before forming the correlation matrix. We propose an enhanced CLAFIC method in speaker verification, coined as Probabilistic 2D CLAFIC which apply a straightforward 2D speech matrix projection technique for feature dimension reduction and GMM is used to construct the speaker model to boost up the performance. Our results show the superior performance and low computation time in the proposed system.