Advanced Materials Research Vols. 712-715

Abstract: This paper analyzes the advantages of the direct digital frequency synthesis (DDS) in signal generator applications, introduces the basic principles and characteristics of AD9850, a cost-effective chip, shows the overall scheme of a signal source design based on DDS and implements the hardware system. Experimental results show the signal generator can produce sine wave signals scoping from 100Hz to 5MHz, clock signals and triangular wave signals and can display frequency on the LCD.

Abstract: Power MOSFET is develop in power savings, high efficiency, small size, high reliability, fast switching, low noise. Power MOSFET can be used high-speed switching transistors devices. Recently attention to the motor and the application of various technologies. Power MOSFET is devices the voltage-driven approach switching devices are design to handle on large power, power supplies, converters, motor controllers. In this paper, design the 400 V Planar type, and design the trench type for realization of low on-resistance. Trench Power MOSFET Vth : 3.25 V BV : 484 V Ron : 0.0395 Ohm has been optimized.

Abstract: The high accuracy modeling is a prerequisite to study UTC-PD matching circuit design and power combining. This paper presents the high accuracy modeling method of UTC-PD photodiode. The measured frequency response curve of photoelectric conversion was used as a benchmark, and the model of the equivalent circuit was modified consistently in order to make the frequency response curve of the model fit the measured frequency response curve. This method addressed effectively the modeling issues of UTC-PD photodiode.

Abstract: A new CMOS bandgap reference which is optimized by adaptive GA(genetic algorithm) is presented in this paper. During the optimization of the parameters, according to the different specifications, the idea which looks on secondary targets as the boundary restrictions is proposed, so that the problem of multi-objective normalization is solved. The secondary optimizing method about coarse adjusting initially, meticulous adjusting successively is proposed in the optimization based on adaptive Genetic Algorithm. The simulation results which have reached the leading standard of industry indicate the advantage and validity of the method comparing with other method used in the design of bandgap references.

Abstract: In complex and severe electromagnetic environment with more electric aircraft (MEA) and aircraft missions diversity, the power supply quality analysis and its corresponding circuit design is a key technology for the design of automatic power distribution system on airborne platform. By analyzing the structure and the characteristics of automatic power distribution system and its executive component – SSPC, this paper improves the power supply quality through paralleling RC circuit to MOSFET to absorb current shock and voltage fluctuation,and gives the calculating method of the RC components. By experiments with principle prototype, it is verified that the method can reduce the dynamic voltage fluctuation of the power supply system.

Abstract: Based on CO2 gas shielded arc welding of short circuit transfer welding current waveform changes with microcontroller core control with TTL counter as a basic circuit, the design an arc welder monitoring system the high-speed camera composition trigger circuit to solve the high-speed camera shutter trigger open the question of and actual monitoring system is verified.

Abstract: In this paper, fully monolithic tunable millimeter-wave filters using defected ground structures (DGS) are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. In the first order tuning, the 3-dB cut-off frequency changes from 8.2GHz to10.5GHz, and the second order tuning is 8.2GHz to 16.8GHz. The tested results show that the pass-band ripple is less than 1.2dB and the maximal out-of-band rejection is better than 27dB. The chip size of the low-pass filter is 2.5mm×1.2mm.

Abstract: As the increasing applications of laser diodes in laser cladding and laser hardening, the single laser diode 0ptical power can not meet the actual requirements. An improvement of the power and Power densty necessary and it can be achieved by beam shaping and beam combination such as polarization coupling the polarization coupling technology is used to couple two laser beams with thin film plate polarizer In this paper two 880 nm vertical stacked arrays with an output power of l600 W was achieved After fast axils and slow axis collimated, the polarization direction of one stacked arrays is rotated 90 degree through a half wave plate, thus, the polarization directions of two laser stack are vertica1. The beams of two lasers are incident on the p1ate po1arizer, one transmits through it, and the other is reflected on it. Finally, two beams combine to one. Polarization coupling of two bars increases the power by a factor of 1.6, and the output power is 2500 W, electro optical conversion efficiency is more than 48%. The spot size is about2 mm x 2 mm. This laser can be directly applied to cladding, surface hardening and other fields.

Abstract: A bistable model is established including the effect of spontaneous emission in a vertical cavity semiconductor optical amplifier (VCSOA). The sensitivities to the amplified spontaneous emission (ASE) of the bistable characteristics in a VCSOA and a traditional edge emitting SOA are compared by numerical analysis. The control of the bistable characteristics and the degeneration of the bistability hysteresis are also analyzed by utilizing the modified model.

Abstract: We propose wave shape transformers using slab transformation media which can transform planar wave shapes to convex or concave ones. By finite embedded coordinate transformations, a transformation is established from a parabola to a plane and the constitutive parameters of slabs are obtained. Numerical simulations are given to validate the performance of the theoretical design. Using such transformers, Gaussian beam collimation and focusing can be realized.