Integrated Electro-Absorption Modulation DFB Laser Based Optical True Time-Delay Feeder for X-Band Phased Array Antennas

A 4-bit optical true-time-delay feeder incorporating an integrated electro-absorption modulation distributed feedback (DFB) laser for X-band phased array antennas is demonstrated. The integrated electro-absorption modulation DFB laser is an attractive device that provides a very compact, low-cost solution for optical true-time-delay systems. The variable delay line is constructed by cascaded magneto-optic switches, which have fast switching speed. The integrated electro-absorption modulation DFB laser system shows high signal-to-noise ratio up to 58dB, and the transmission performance of the system is relatively good and accredited.     

Optical focusing feature of single element in 128×128 elements electrically controllable cylindrical liquid crystal lens array

<正>A 128×128 elements cylindrical liquid crystal(LC) lens array with electrically controllable focal length is proposed.The cylindrical LC lens array uses transparent indium tin oxide(ITO) films as electrode,avoiding to affect the optical path operating in the voltage-off status.As the top electrode of the cylindrical LC lens array contacts with LC,the operation voltage root-mean-square(RMS) amplitude can be as low as 1.4 V and the response time is about 20-30 ms.The special optical focusing feature of the cylindrical LC lens array is got.And the focal length of this array is about 60-450μm.     

Coverage-dependent kinetics and thermodynamics of carbon monoxide adsorption on a ternary copper catalyst derived from static adsorption microcalorimetry

A reliable method for adsorption systems in equilibrium is established to derive coverage-dependent kinetics and thermodynamics from the volumetric data obtained during the static microcalorimetric measurement of heats of adsorption. The Wigner-Polanyi equation is applied to analyze the pressure change as a function of time during stepwise dosing of the adsorptive until thermodynamic adsorption-desorption equilibrium is established. For carbon monoxide adsorption on a hydrogen-reduced Cu/ZnO/Al2O3 catalyst, the adsorption rate constant (ka) is found to be in the range from 10(-6) to 10(-4) Pa(-1) s(-1), and the desorption rate constant (kd) from 10(-4) to 10(-2) s(-1), both increasing with fractional coverage theta. The kinetically derived equilibrium constant Ktheta is in good agreement with Ktheta obtained from the adsorption isotherm. RT ln(Kp0) and the differential heat of adsorption (qdiff) were found to decrease in parallel, reflecting a normal Temkin-type heterogeneity.     

Observation of a red-blue detuning asymmetry in matter-wave superradiance

We report the first experimental observation of strong suppression of matter-wave superradiance using blue-detuned pump light and demonstrate a pump-laser detuning asymmetry in the collective atomic recoil motion. In contrast to all previous theoretical frameworks, which predict that the process should be symmetric with respect to the sign of the detuning of the pump laser from the one-photon resonance, we find that for condensates the symmetry is broken. With high condensate densities and red-detuned pump light the distinctive multiorder, matter-wave scattering pattern is clearly visible, whereas with blue-detuned pump light superradiance is strongly suppressed. However, in the limit of a dilute atomic gas symmetry is restored.     

Na~+掺杂量对BaBiO_3基陶瓷NTC特性的影响

以BaCO3、Bi2O3为原料,Na2C2O4为掺杂剂,用传统固相法制备了具有NTC特性的BaBi1–xNaxO3陶瓷。用XRD,SEM和ρ-t特性测量仪,研究了Na+掺杂量对该陶瓷的物相、显微结构及电性能的影响。结果表明:BaBi1–xNaxO3陶瓷的B25/85值和室温电阻率ρ25均随着x(Na2C2O4)的增加呈现先减小后变大的趋势;当x(Na2C2O4)为0.050时,获得了具有较好NTC特性的试样,其ρ25为2200?·cm,B25/85值为3365K。     

A 10 GHz high-efficiency and low phase-noise negative-resistance oscillator optimized with a virtual loop model

A virtual loop model was built by the transmission analysis with virtual ground method to assist the negative-resistance oscillator design, providing more perspectives on output power and phase-noise optimization. In this work, the virtual loop described the original circuit successfully and the optimizations were effective. A 10 GHz high-efficiency low phase-noise oscillator utilizing an InGaP/GaAs HBT was achieved. The 10.028 GHz oscillator delivered an output power of over 15 dBm with a phase-noise of lower than -107 dBc/Hz at 100 kHz offset. The efficiency of DC to RF transformation was 35%. The results led to a good oscillator figure of merit of-188 dBc/Hz.The measurement results agreed well with those of the simulations.     

不同微空气桥结构的InP/InGaAs HBT

文章报道了几种具有不同微空气桥结构的InP HBT。由于微空气桥减小了寄生,发射极尺寸为2×12.5 um2 的InP/InGaAs HBT的截止频率和最大震荡频率都接近160GHz。论文将具有不同微空气桥结构的器件高频特性与传统InP HBT进行对比。对比表明,微空气结构明显降低了寄生,且双指微空气桥结构可以更有效的提高器件的射频特性。试验结果同时表明,微空气桥结构对于提高小尺寸发射极InP HBT的高频特性更有潜力。     

AlGaN/GaN HEMT 小信号模型提取方法的改进

The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in largesignal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract Rg. In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S 11 and S 22 is improved, and fT and fmax can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S-parameters in the range of 0.1 to 26.1 GHz.     

A 10 GHz high-efficiency and low phase-noise negative-resistance oscillator optimized with a virtual loop model

A virtual loop model was built by the transmission analysis with virtual ground method to assist the negative-resistance oscillator design, providing more perspectives on output power and phase-noise optimization. In this work, the virtual loop described the original circuit successfully and the optimizations were effective. A 10 GHz high-efficiency low phase-noise oscillator utilizing an InGaP/GaAs HBT was achieved. The 10.028 GHz oscillator delivered an output power of over 15 dBm with a phase-noise of lower than -107 dBc/Hz at 100 kHz offset. The efficiency of DC to RF transformation was 35 %. The results led to a good oscillator figure of merit of-188 dBc/Hz. The measurement results agreed well with those of the simulations.     

The Stage-structured Predator-Prey System with Delay and Harvesting

In this article, we establish a mathematical model of two species with stage structure and the relation of predator-prey, obtain the necessary and sufficient condition for the permanence of two species and the extinction of one species or two species. We also obtain the optimal harvesting and the threshold of harvesting for the sustainable development and increasing delays can cause a bifurcation into periodic solutions. Finally, we give some numerical results and graphs.