Charge-Line Dual-FET High-Repetition-Rate Pulsed Laser Driver

Most modern pulsed laser systems require versatile laser diode drivers. A state-of-the-art pulsed laser driver should provide precise peak power regulation, high repetition rate, and pulse duration control. A new, charge line dual-FET transistor circuit structure was developed to provide all these features. The pulsed modulation current is adjustable up to Imax = 1.2 A, with the laser diode forward voltage acceptable up to UF max = 20 V. The maximum repetition rate is limited by a charge line circuit to frep max = 20 MHz. Compared to the conventional single transistor drivers, the solution proposed in this paper allows a precise, high resolution width regulation to be obtained, whereas a low pulse jitter is ensured. In the solution, two separate, out-of-phase signals are used to trigger the individual Field Effect Transistors (FET). The resultant pulsed modulation current full-width-at-half-maxima (FWHM) is regulated from ~200 ps up to 2 ns. All control and timing signals are generated with a popular Field-Programmable Gate Array (FPGA) digital circuitry. The use of standard FPGA devices ensures the low cost and high reliability of the circuit, which are not available in laser drivers consisting of sophisticated analogue adjustable delay circuits.

Simulation and Analysis of the Neutral Resistance Grounding of 1140V Power System in Coal Mine

The neutral grounding mode through resistance and the grounding resistance value of 1140V coal mining distribution system are studied and simulated in this paper. According to the 1140V power supply system parameter of the underground mining area of a coal mine, the PACAD software is used to establish the simulation model of power system. The single-phase ground fault caused by the insulation deterioration of the load equipment is simulated through setting single-phase ground fault in charge line of load side. The advantage of neutral grounding mode through resistance is analyzed through the simulation result. According to the distributed capacitance over the ground of simulation data and power network, the value range of the neutral point grounding resistance can be obtained.

Line Force, Charge, and Dislocation in Anisotropic Piezoelectric Composite Wedges and Spaces

Two-dimensional problems of anisotropic piezoelectric composite wedges and spaces are studied. The Stroh formalism is employed to obtain the basic real-form solution in terms of two arbitrary constant vectors for a particular wedge. Explicit real-form solutions are then obtained for (i) a composite wedge subjected to a line force and a line charge at the apex of the wedge and (ii) a composite space subjected to a line force, line charge, line dislocation, and an electric dipole at the center of the composite space. For the composite wedge the surface traction on any radial plane θ = constant and the electric displacement Dθ normal to the radial plane θ = constant vanish everywhere. For the composite space these quantities may not vanish but they are invariant with the choice of the radial plane.