铝基印制板的成型及压板翘工艺

简述铝基板冲板模具的设计、调试的要点及发生问题的解决方案,重点叙述了通过利用压板翘模具得以成功解决铝基板冲板后板翘的问题。     

A 60 GHz Medium Power Amplifier for Radio‐over‐Fiber System

We present the design and fabrication of a 60 GHz medium power amplifier monolithic microwave integrated circuit with excellent gain‐flatness for a 60 GHz radio‐over‐fiber system. The circuit has a 4‐stage structure using microstrip coupled lines instead of metal‐insulator‐metal capacitors for unconditional stability of the amplifier and yield enhancement. The gains of each stage of the amplifier are modified to provide broadband characteristics of input/output matching for the first and fourth stages and to achieve higher gains for the second and third stages to improve the gain‐flatness of the amplifier for wideband.     

Coupling coefficients evaluation of a directional coupler using gain guided and index antiguided fibers

In this paper, we have investigated the mutual and self coupling characteristics of directional couplers using two individual gain guided and index antiguided fibers, which can deliver robust single mode operation with large mode area, respectively owing to the combined adequately large gain coefficients in the core; Some interesting and distinguishing properties from conventional index guided fiber couplers are obtained that: The variations of coupling coefficients are complex-valued and spatially damping oscillated, but not exponential-like decreasing as conventional index guided couplers.     

Investigation of patch antennas based on crossed idiosyncratic PBG structure

The method of finite difference time domain (FDTD) was used, and characteristics of the patch antenna based on drilling periodic air holes in the substrate were studied, the results indicate that the surface waves which propagate along the surface of the substrate can be suppressed by the crossed idiosyncratic PBG (photonic crystal band-gap) structure because of its effect of forbidden-band, that it can radiate most of electromagnetic waves’ energy in the substrate significantly, and that it has lower return loss (S11) compared to the conventional patch antennas, thus, a high gain is attained, its performance is improved. Due to these advantages, the use of photonic crystal patch antennas will be extended in areas such as mobile communication, satellite communication, aviation, etc.     

1～6GHz宽带低噪声放大器的研制

该放大器采用负反馈的设计原理, 利用ＥＥＳＯＦ进行ＣＡＤ设计, 选用噪声较小增益较高的日本ＦＵＪＩＴＵ公司的ＧａＡｓ晶体管（ＦＨＸ１４ 型）。通过精心调试,解决了研制中两个难题, 即多级级联与稳定性和可靠性难题, 从而使该放大器达到满意的性能指标     

A study of green wavelength-division multiplexed optical communication systems using cascaded fiber bragg grating

This paper studies the performance analysis of wavelength-division multiplexed optical communication systems (WDM). First, flat-gain erbium doped fiber amplifiers (EDFAs) are seriously needed to obtain proper and equal amplification of all channels. Such amplifiers can be designed by intrinsically modifying the host material or extrinsically using proper filters. In this research, we benefit from both the intrinsic and extrinsic methods to achieve sharp flat EDFA output gain using cascaded fiber Bragg gratings (FBGs). Second, the performance of our technique has been evaluated through calculating the bit error rate (BER) and signal-to-noise ratio (SNR) of a WDM system embedded with the reported EDFA flattening system. The parametric simulations of the FWHM of FBGs, SNR, optical power and the transmission distance have shown a noticeable improved performance. Sending data via an optical WDM system will be proven from comprehensive simulations to achieve high quality signal transmission spectrums, increased transmission distances and low power consumption. By extension, the reported design using cascaded FBGs can also be generalized to equalize the gain of any arbitrary profile.     

三相交错LLC谐振变换器空载问题的研究

三相LLC谐振变换器在轻载工况运行时,会出现输出侧电压漂高失控的现象,这是由于变压器匝间电容与副边整流管的结电容的存在共同形成寄生电容,在重载时,寄生电容对变换器输出的影响特别小,可以忽略不记,但是在轻载时,寄生电容被充电后放电过程对变换器输出的影响特别大,会改变直流增益曲线的状态,所以要对寄生电容做特殊考虑,以不至于...     

Miniaturized structures based on color centers in lithium fluoride: Optical properties and applications

Research activities concerned with color centers in alkali halide films started recently. The use of versatile, well-assessed, and low-cost fabrication techniques consisting of physical vapor deposition of Lithium Fluoride (LiF) films combined with direct writing lithographic processes allows the realization of miniaturized structures, like broad-band emitters, channel waveguides, optical microcavities and point-light sources emitting in the visible spectral range. Promising results have been obtained in the generation, amplification and waveguiding of visible light in LiF treated by low energy electron beams, where the efficient formation of stable primary and aggregate color centers also induces a local modification of the refractive index. A brief overview of the investigated optical properties is presented together with a short discussion about their perspectives of applications in optoelectronics.     

22 dB all-fiber green amplifier using Er-doped fluoride fiber

We demonstrate a 22 dB all-fiber amplifier at 546 nm using Er³⁺-doped fluoride fiber by forward upconversion pumping of a 974 nm laser diode. The gain saturation effects and the power conversion efficiency of this amplifier are investigated in detail based on gain characteristics and numerical simulations.     

A rain attenuation model for satellite link attenuation predictions incorporating the spatial inhomogeneity of rainrate

A model describing the spatial inhomogeneity of rainrate within a rain cell is derived and incorporated into a specific attenuation model to yield a more exact relationship than has been used heretofore relating rainrate and the attendant attenuation at frequencies above 10 GHz. The resulting unified attenuation model relates terrestrial and slant path attenuation, effective propagation distance and path diversity gain to parameters characterizing the earth-station or stations (e.g. location, height, latitude, elevation angle and baseline distance from another station), the frequency of operation, and the two possible raintypes admitted into the model (i.e. convective rain and residual or debris rain). The model is particularly suited for the theoretical investigation of path diversity gain since this concept owes its existence to spatial inhomogeneity of rainrate. This inhomogeneous rain attenuation model can be interfaced with an appropriate statistical rainrate prediction model, such as the Crane two-component model, to yield more precise attenuation predictions.