Effect of iodine on the laser power of a Cd(II) 441.6-nm line in a positive-column He-Cd+laser

It has been shown that a small amount of iodine added to the He-Cd+ laser discharge increases the laser power of a Cd(II) 441.6- nm line by 30-40 percent and also the electron temperature by a few percent, while the electron density is not changed considerably.     

Thermal effects in double prism dye laser cavities

Output power, beam divergence, and frequency stability in a double-prism dye laser cavity have been investigated as a function of temperature. For rhodamine 6G dye, it has been found that output power decreases by nearly 34 percent, beam divergence increases from 4.5 to 6.5 mrads, and the laser frequency is shifted by as much as 2 cm^-1, for an increase of 10°C above room temperature. The efficiency of the double-prism dye laser oscillator employed here was 18 percent (for N2laser pump) at a linewidth of 0.07 cm^-1(FWHM). Laser linewidth did not vary in the temperature range investigated here.     

ZTE Unveils First 4-Path TD-LTE RRU with 40 MHz and 80 W Capabilities

On September 7, 2011, ZTE announced it had introduced the industry’s first 4-path TD-LTE remote radio unit (RRU). The RRU operates at 40 MHz and has transmitting power of 80 W. The new high-powered, large-capacity RRU support s2×20 MHz TD-LTE     

Cl2/Ar感应耦合等离子体刻蚀Si工艺研究

采用Cl2/Ar感应耦合等离子体（ICP）对单晶硅进行了刻蚀,工艺中用光刻胶作掩膜。研究了气体组分、ICP功率和RF功率等工艺参数对硅刻蚀速率和硅与光刻胶刻蚀选择比的影响,同时还研究了不同工艺条件对侧壁形貌的影响。结果表明,由于物理刻蚀机制和化学刻蚀机制的相对强度受到混合气体中Cl2和Ar比例的影响,硅刻蚀速率随着Ar组分的增加而降低,同时选择比也随之降低。硅刻蚀速率随着ICP功率的增大先增大继而减小,选择比则成上升趋势。硅刻蚀速率和选择比均随RF功率的增大单调增大。在Cl2/Ar混合气体的刻蚀过程中,离子辅助溅射是决定硅刻蚀效果的重要因素。同时,文中还研究分析了刻蚀工艺对于微槽效应和刻蚀侧壁形貌的影响,结果表明,通过提高ICP功率可以有效减小微槽和平滑侧壁。进一步研究了SiO2掩膜下,压强改变对于硅刻蚀形貌的影响,发现通过降低压强,可以明显地抑制杂草的产生。     

Radiative efficiencies of radio frequency sulfur discharges

The radiative efficiencies of RF sulfur discharges under various conditions of power loading, sulfur vapor pressure, and argon buffer pressure have been determined. The highest CW efficiency was 11 percent for a sulfur density of6.3 times 10^{16}cm^-3and 20 torr argon buffer. The results of pulsed operation show that the efficiency increases slightly to 13 percent for a sulfur density of8.8 times 10^{16}cm^-3.     

Scattering of Ultrasound by Blood

The ultrasonic volumetric scattering cross section of the erythrocyte has been measured over a range of frequencies by comparing the rms value of the gated backscattered signal from the blood with that of a wave reflected from a flat reflector with known reflection coefficient. It is found to be proportional to the fourth power of the frequency predicted by the wave scattering theory for small particles in the frequency range from 5 MHz to 15 MHz. The relation between the scattering coefficient and the hematocrit is also examined up to a hematocrit of 45 percent. This coefficient is found to increase along with the hematocrit until it reaches a maximum around hematocrit = 26 percent and then decreases as the hematocrit increases. Twersky's wave scattering theory is applied to describe this result.     

GaAs MESFET低温性能实验

本文介绍了在低温下,对GaAs MESFET(包括12GHz低噪声器件、双栅器件、功率器件及振荡用器件)所进行的性能测量与分析。在218K(-55℃)下,上述各类器件的跨导g_m相对于室温可增加5～8％,器件的C_(gs)可减少20～50％,器件的寄生电阻R_s和R_d可减少15～40％,R_g也存在缓慢下降的趋势。 文章还给出了低温下低噪声GaAs MESFET放大器的噪声、增益—温度曲线。在218K下,放大器的噪声相对室温可下降1dB左右,单级增益相对室温可增加1～1.5dB,即在低温表现出良好的微波性能。     

High efficiency CW transferred-electron oscillator with optimized doping profile

This study is aimed at helping to design X-band CW transferred-electron oscillators with higher performance. Temperature rise in devices operating in the accumulation layer mode is analyzed both with heat sink negative and heat sink positive. Efficiencies and output powers in both polarities are calculated and compared. The calculation shows efficiency in CW operation is drastically improved by quantitatively controlling the doping profile to account for the temperature profile and further governed by carrier concentration times layer thickness (n × l) product and diode size. For the heat sink negative, output power over 800 mW is predicted from a single-mesa conventional structure, using a wafer with an n × l product of 2.0 × 10¹²cm^-2and doping profile increasing, toward the substrate (away from the heat sink), by 30-35 percent across the active layer. For the heat sink positive, an almost flat profile is suitable and output power over 1.5 W is predicted for a diode with a doping increase of 10 percent across the active layer toward the substrate. The calculations are substantiated experimentally by diodes with n × l products of 1.5-2.3 × 10¹²cm^-2and doping increases of 20-70 percent across the active layer toward the substrate heat sink negative operation.     

Near-infrared high-power LED's with Ga1-xAlxAs epitaxially grown junctions

This paper reports on a study of several techniques of fabricating an efficient Ga1-xAlxAs IRED with high power. Smooth epitaxial layers are grown on a substrate containing a thick Ga1-xAlxAs epitaxial layer which is used to form a hemispherical emitting surface. This is achieved by using a melting-back technique without up-heating. An effect of the AlAs molefraction ratio between n- and p-type regions was clearly found by measurement of a large number of diode chips, and the best performances were obtained on the junctions with the ratioX_{n}/X_{p} simeq 1.5. Ohmic contacts to the p and n regions were applied on the same surface of the wafer using only one metallic source for the vacuum deposition. A cerium-oxide film serves as an antireflection coating when deposited on the hemispherical surface and increases the optical output power by more than 30 percent. External quantum efficiencies of 28 percent (current density: 400 A/ cm²) and optical output power of 96 mW (drive current: 300 mA, current density: 1500 A/cm²) have been observed from diodes emitting at 8300 Å under dc operation at room temperature.     

Low power and high speed multiplier design with row bypassing and parallel architecture

This paper presents a low power and high speed row bypassing multiplier. The primary power reductions are obtained by tuning off MOS components through multiplexers when the operands of multiplier are zero. Analysis of the conventional DSP applications shows that the average of zero input of operand in multiplier is 73.8 percent. Therefore, significant power consumption can be reduced by the proposed bypassing multiplier. The proposed multiplier adopts ripple-carry adder with fewer additional hardware components. In addition, the proposed bypassing architecture can enhance operating speed by the additional parallel architecture to shorten the delay time of the proposed multiplier. Both unsigned and signed operands of multiplier are developed. Post-layout simulations are performed with standard TSMC 0.18 μm CMOS technology and 1.8 V supply voltage by Cadence Spectre simulation tools. Simulation results show that the proposed design can reduce power consumption and operating speed compared to those of counterparts. For a 16×16 multiplier, the proposed design achieves 17 and 36 percent reduction in power consumption and delay, respectively, at the cost of 20 percent increase of chip area in comparison with those of conventional array multipliers. In addition, the proposed design achieves averages of 11 and 38 percent reduction in power consumption and delay with 46 percent less chip area in comparison with those counterparts for both unsigned and signed multipliers. The proposed design is suitable for low power and high speed arithmetic applications.     

Experimental studies of the O/O2/CS2CW CO chemical laser

Experimental studies of a CW transverse-flow chemical laser are reported. These studies include investigation of gas flow and mixing lengths, densities of chemical species in the reacting flow stream, and gas-additive effects on laser emission. This device has yielded the highest performance yet observed for CO chemical lasers with a specific output power of 65.5 J/g (29.7 kJ/1b) and a minimum chemical efficiency of 21 percent. It was found that additional chemical species are present in the flow stream beyond those predicted by a simple three-reaction model of the chemical kinetics. Gas additives have been found to give increases in total output power, and can also be used to enhance either high or low bands in the output spectrum.     

PowerNap: an efficient power management scheme for mobile devices

We present PowerNap, an OS power management scheme, which can significantly improve the battery life of mobile devices. The key feature of PowerNap is the skipping of the periodic system timer ticks associated with the operating system. On an idle device, this modification increases the time between successive timer interrupts and enables us to put the processor/system into a more efficient low power state. This saves the energy consumed by workless timer interrupts and the excess energy consumed by the processor in less efficient low power states. PowerNap is tightly integrated with the kernel and is designed for optimal control of the latency and energy associated with transitioning in and out of the low power states. We describe an implementation of PowerNap and its impact on system software. Experiments with IBM's WatchPad verify the ability of PowerNap to extend battery life. An analytical model that quantifies the ability of the scheme to reduce power is also presented. The model is in good agreement with experimental results. We apply the model to small form-factor devices which use processors that have a PowerDown state. In such devices, PowerNap may extend battery life by more than 42 percent for small processor workloads and for background power levels below 10 mW.     

A cyclotron-wave rectifier for S-band and X-band

A device for converting microwave power into either dc power or low-frequency ac power has been investigated both theoretically and experimentally. Rotational energy is stored in an electron beam by a Cuccia coupler, then converted to longitudinal energy by interaction with a space-dependent dc magnetic field, and finally recovered as electric energy by a depressed collector. A simple kinematic analysis demonstrates that the Cuccia coupler can convert large amounts of microwave power into electron beam rotation. Limits on the electric field strength and asynchronism between signal frequency and cyclotron frequency are established for both classical and relativistic coupler operation. Efficiency analyses of the process of conversion from orbital energy to dc electric energy, both classical and relativistic, indicate that the efficiency exceeds 95 percent for a particular range of operating conditions. As an ac power supply, the device responds to the modulating frequency of the signal. Theory predicts near-negligible harmonic distortion as well as flatness of frequency response from dc to about 1.0 MHz modulating frequency. Four tubes and a prototype (with "artificial" coupler) were tested experimentally. The first three tubes exhibited efficiencies up to 22 percent, being hindered by reflection of electrons into the coupler. Certain design changes were tested on the prototype, where efficiencies from 36 percent to 75 percent were obtained. Incorporating these design changes into the fourth tube yielded measured efficiencies up to 34 percent, or when corrected to disregard unusually large cavity losses, up to 59 percent. Experimental tests of the tube as an ac converter yielded excellent frequency response and about 20 percent second-harmonic distortion. It is concluded that the theoretical foundation of efficiency predictions has thus far been based on too optimistic assumptions.     

S/N and error rate performance in AlGaAs semiconductor laser preamplifier and linear repeater systems

The applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement. Experiments were carried out with the Fabry-Perot cavity laser amplifiers whose characteristics are improved by reducing the input mirror reflectivity to 6 percent. The use of a preamplifier improves the minimum detectable power by 7.4 dB over the Si-APD direct detection level when the received signal is amplified by 30 dB before photodetection. The use of two linear repeaters increases the regenerative repeater gain by 37 dB. These experimental results are in good agreement with theoretical predictions based on the photon statistic master equation analysis.     

S/N and Error Rate Performance in AlGaAs Semiconductor Laser Preamplifier and Linear Repeater Systems

The applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement. Experiments were carried out with the Fabry-Perot cavity laser amplifiers whose characteristics are improved by reducing the input mirror reflectivity to 6 percent. The use of a preamplifier improves the minimum detectable power by 7.4 dB over the Si-APD direct detection level when the received signal is amplified by 30 dB before photodetection. The use of two linear repeaters increases the regenerative repeater gain by 37 dB. These experimental results are in good agreement with theoretical predictions based on the photon statistic master equation analysis.     

软开关PWM控制器的新型开关电源设计

近年来,电子产品的工作电压不断降低,但是耗电电流却在不断增加。因此,开发大功率开关电源在通信以及军工领域有很大的发展空间。阐述了有源钳位开关的基本原理,基于电流控制型芯片UCC2891设计出了一种3．0V／30A的同步整流有源钳位正激变换器开关电源,给出了电路设计、电路图以及最后的测试结果。实验结果证明,采用ZVS（零电压开关）技术的电源具有较好的稳定性和较高的转换效率,在很宽的输入电流和输出电压的范围内效率仍可高于90％。     

A ten-stage electrostatic depressed collector for improving klystron efficiency

A ten-stage electrostatic depressed collector, designed with the aid of an analog computer, was tested on a 1-kW CW 750-MHz klystron. Excellent correlation was achieved between computed and measured performance under varying conditions of RF drive. At full RF power output approximately 60 percent of the spent beam energy was recovered by use of the depressed collector. The net power conversion efficiency of the tube was raised from its undepressed value of 54.3 percent to approximately 70.9 percent. At one-half full power output, a collector efficiency of 70 percent was measured. At zero RF power output collector efficiency was 80 percent. To achieve these results it was necessary to install a small focusing coil between the final drift tube and the collector. No spurious oscillations or instabilities were detected when collector depression was employed, nor was electron backstreaming increased significantly. Intentional short circuiting of adjacent collector electrode pairs was shown to cause only minor degradation in collector performance.     

EHV transmission in the U.S.S.R. power grid

In 1965, 507 billion kWh of electricity was produced in the Soviet Union, and the total generating capacity of its power stations reached 114 000 MW. The total length of transmission lines, with voltages of 35 kV and higher, ran to 312 000 km. The capacity of the European power interconnections of the U.S.S.R. exceeded 68 000 MW in March 1966. The control of the power industry is centralized under the Ministry of Power and Electrificiation of the U.S.S.R. Ninety-four percent of its electric energy is generated at power stations that are part of interconnected systems. Thermal stations predominate; their generating capacity accounts for 77 percent of the total installed generation. Hydroelectric plants represent 22 percent of the total capacity and 18 percent of the total output. About one percent of the total power production is from nuclear plants. Thirty-six percent of the thermal plants are equipped to transmit heat energy as well as electric power.     

A theoretical analysis and experimental confirmation of the optimally loaded and overdriven RF power amplifier

Although the conventional Class B approach to RF amplifier design yields high output power and reasonable collector efficiency (78.5 percent at maximum output power), neither the power nor the efficiency are optimum, and both are dependent on RF drive level. This paper presents an analysis of appropriately selected collector voltage and current waveforms which determine the load impedance at the fundamental and harmonically related frequencies; these conditions define the ClassB "optimum efficiency" case with 100 percent collector efficiency and 1.27 times the conventional Class B value of output power. If the RF drive level is increased, and the collector voltage and current waveforms are appropriately selected so that the amplifier is overdriven, a different load impedance is determined; these conditions define the "optimum power" case with 1.46 times the conventional Class B value of output power and 88 percent collector efficiency. The "optimum power" case has the added advantage that the output power and collector efficiency are essentially constant over a predetermined range of drive level. Finally, the theory is verified by the construction and testing of a UHF power amplifier having a power output of 46 watts and an over-all dc to RF conversion efficiency of 65 percent with a 1 dB for 10.5- dB insensitivity of output power to RF drive.