Advanced Materials Research Vols. 588-589

Abstract: The design method of software and hardware was introduced about speech signal acquisition and process based on DSP chip TMS320C64X produced by TI company in this paper. The principle figure of the system, hardware interface circuits, software flow chart as well as relational experiment data and waves were also present.

Abstract: In order to enable engineers to assess the impact of harmonic currents produced by the 12-pulse rectifier unit on the grid. In this paper, through experimental and theoretical reasoning, I discusses in detail the harmonic calculation parameters required of rectifier unit and calculate the filter capacity which reached the filtering standards for single-tuned filter capacitor. Through this method, we can make a good assessment of the harmonics generated by the project and propose effective control measures for the harmonic excess in the beginning of the project construction.

Abstract: A low temperature coefficient, high voltage detection circuit used in Power over Ethernet is proposed. This circuit realizes the detection comparison without utilizing an extra voltage reference circuit and comparator while the temperature coefficient of the threshold voltage is as low as that of a regular bandgap reference. The proposed detection circuit is implemented in CSMC 0.5μm 60V BCD process, Cadence Spectre simulation results show that the temperature coefficient of the threshold voltage is 66.5 ppm/°C over the temperature range of -40°C to 125°C, and the maximum variation of the threshold voltage is 2.7% under all corners.

Abstract: Due to the uncertainties that exist in the running of the analog circuits, the traditional hidden Markov model (HMM) approach is improved through replacing the state transition probability (STP) matrix of the traditional model by time-varying one. An updating control factor is introduced for avoiding the excess updating of the STP in the initial stage of each state. The experimental results indicate that the improved HMM has better fault recognition and diagnosis capability.

Abstract: Compared with traditional three-level neutral-point-clamped (NPC) converter, the recently proposed three-level active NPC (ANPC) converter has the ability to overcome the unbalanced loss distribution, and therefore result in increased output power or switching frequency. In industrial applications, fault tolerance ability of power converters is very important considering system availability, safety and reliability. This paper introduced the control schemes to get stable and continuous output under single device fault for both open-circuit and short-circuit fault cases. By analyzing the phase relationship of reference voltage and load current, the loss calculation method under fault tolerant operation was proposed. Calculation results show that the devices junction temperatures under fault tolerant operation are within the safe operation area (SOA) even they are a little bit higher compared to normal operation, which also confirm the effectiveness of the fault tolerant control schemes.

Abstract: This paper presents a theoretical study of the vertical coherence of ocean ambient noise as the source is the windy ocean surface on the ray theory. At low frequencies less than 2 kHz, the sensitivity of stratified fluid seabed to the vertical coherence of ambient noise in shallow water is analyzed under the condition of distance-irrespective stratified ocean. Using ambient noise data from Chinese north shallow water seabed geo-acoustics parameters are obtained, and the research results show that the inverted method is effective.

Abstract: Passive tuner is the core component of high-power load pull measurement system. To overcome the leakage of electromagnetic field to the outer space and decrease the insertion loss, a structure of waveguide and diaphragm with the choke structure is adopted to design the 25-40GHz tuner. The simulation results of HFSS (High Frequency Simulator Structure) software show that the structure can meet the requirements of the tuning ratio and decrease the insertion loss, and it can be used in the load and source pull measurement system successfully.

Abstract: A systematic study has been undertaken to quantify the effects of jet Mach number and nozzle size on the noise radiated by supersonic jets. All the tests were carried out at an experimental bench of the supersonic jet. Results indicate that the field distribution of supersonic jet screech tones is characterized with very strong directivity. Under the textual experimental conditions, if the jet Mach number remain unchanged, the diameter of nozzle throat increases gradually from 5mm to 8mm or 10mm, and the amplitude values of both the turbulent mixing noise and broadband shockwave correlated noise increase by 2-5dB, and the amplitude value change of the whistler type noise is not obvious, and the occurrence frequency of the whistler type noise decreases by more than 2000Hz; if the jet Mach number increases to 3.0 from 2.0, the amplitude value of the whistler type noise increases by more than 2dB, and the occurrence frequency of the whistler type noise decreases obviously. The experimental measurements of supersonic jet noise provide the sound production mechanism research on the supersonic jet noise with data supports and references and provide the numerical modeling of the supersonic jet noise with validation criteria.

Abstract: This paper introduces the the basic principle of i_p-i_q harmonic detection algorithm and puts forward a method of harmonic detection for the single-phase circuit. This method eliminates the three-phase to two-phase and two-phase to the three-phase coordinate transformation, thus effectively reduces the computation ; moreover it has the advantages of good real-time performance and makes the digital control easy. Matlab simulation results show that this method can detect the harmonic component of single-phase and three-phase current accurately and in real-time.

Abstract: A design of 10 Gbps Vertical Cavity Surface Emitting Laser (VCSEL) driver using 0.18µm CMOS technology is presented in this paper. The core unit of the driver consists of pre-amplify stage and output stage circuit. Technique of three stages differential amplifier with low impedance load and active feedback are employed in pre-amplify stage, and technique of C3A is adopted in output stage to get low power consume and high speed. The simulation results show that the circuit can work at the speed rate of 10 Gbps and maximum of 13 Gbps with a 1.8V power supply. The output modulation current is up to 12.5mA and the power dissipation is 77mW. The chip size is 0.45mm  0.47mm.