Growth of GaN Films on Si (100) Buffered with ZnO by Ion-Beam-Assisted Filtered Cathodic Vacuum Arc Technique

GaN films have been fabricated on Si (100) substrates with ZnO buffer layers by an ion-beam-assisted filtered cathodic vacuum arc (I-FCVA) technique at␣450°C. GaN films are highly (002)-oriented with a hexagonal structure examined by X-ray diffraction. The room-temperature photoluminescence spectrum of the GaN film exhibits a strong and sharp band-edge emission peak at 3.36 eV. The obtained results demonstrate the potential of the I-FCVA technique for the fabrication of high-quality GaN layers on Si substrates.     

一种应用于EEPROM的片上电荷泵电路设计

设计了一种应用于EEPROM的片内电荷泵电路系统。该电路基于Dickson电荷泵结构,通过使用稳定的参考电压驱动压控振荡电路,从而产生了占空比小于50%的精确时钟,提高了电荷泵升压速度;通过使用调压电路,限制并稳定了输出电压。HSPICE仿真结果显示:在5 V电源电压下,时钟频率高达2.085 MHz。电荷泵仅需要56.256μs就可以输出15.962 V的高压。电荷泵的电压上升时间快,性能优越。     

Characterization,Cathodoluminescence, and Field‐Emission Properties of Morphology‐Tunable CdS Micro/Nanostructures

High‐quality, uniform one‐dimensional CdS micro/nanostructures with different morphologies—microrods, sub‐microwires and nanotips—are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field‐emission properties are systematically investigated. Microrods and nanotips exhibit sharp near‐band‐edge emission and broad deep‐level emission, whereas sub‐microwires show only the deep‐level emission. A significant decrease in a deep‐level/near‐band‐edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high‐resolution transmission electron microscopy. Field‐emission measurements show that the nanotips possess the best field‐emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn‐on field of 5.28 V µm^?1 and the highest field‐enhancement factor of 4 819. The field‐enhancement factor, turn‐on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.     

Design of an ultra fast pipelined wavelength scheduler for optical burst switching

Optical Burst Switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over DWDM links without encountering O/E/O conversion. In OBS, before the transmission of a data burst, a burst header is transmitted through an electronic control path, setting up and tearing down optical paths on-the-fly. Data bursts can remain in the optical domain and pass through the OBS network transparently. Unfortunately, system performance will be greatly degraded, if burst scheduling requests cannot be processed in time. This article quantitatively studied the negative impact of control path overloading on the performance of OBS networks. Results have shown that control path overloading greatly affects the performance of the OBS routers, especially for systems with large WDM channel counts. In order to remove this performance bottleneck, we have designed and implemented an ultra fast pipelined burst scheduler that is able to process a burst request every two clock cycles, regardless of the number of WDM channels per link. The design has been implemented in Verilog HDL and synthesized to FPGAs. Circuit level simulation results confirm the correctness of the design. The circuit has achieved 100 MHz in Altera Cyclone II devices, allowing the scheduler to process a burst request every 20 ns. To the authors’ best knowledge, this is the fastest implementation of burst scheduling algorithms.     

防空兵火控雷达综合抗干扰能力评估

对防空兵火控雷达面临的主要干扰及其所采取的主要抗干扰措施进行了分析,建立了防空兵火控雷达综合抗干扰能力评估模型,并对防空兵火控雷达综合抗干扰能力进行了评估。     

基于MAX197的高精度数据采集系统

模数（A/D）转换芯片广泛应用于数据采集和信号检测中,其精度一般在8～24位之间。主要以MAXIM公司的MAX197模数转换芯片和ATMEL公司的AT89S52单片机设计的12位精度数据采集系统为例,详细说明了单片机高精度数据采集系统的设计方法及单片机数字滤波的方法。     

基于GaAs STATZ模型的RF MOSFET DC建模技术

STATZ模型是表征GaAsMESFET特性的常用模型,具有表达式简洁、参数少的优点。通过尝试将STATZ模型用于表征射频MOSFET的直流特性,提取并在ADS软件中优化了STATZ直流模型的参数。为了提高仿真精度,模型必须考虑晶体管漏极与源极的寄生电阻,根据MOSFET处于强反型区且漏-源电压为零时的等效电路模型提取了晶体管的漏极和源极的寄生电阻。在ADS软件中利用STATZ模型对MOSFET的直流特性进行了仿真,测量的MOSFET直流曲线与仿真曲线一致性很好,验证了模型的良好的精确度,证明了GaAs STATZ模型可以用于表征射频MOSFET的直流特性。晶体管采用中芯国际的0.13μm RF CMOS工艺制作。     

A wavelength division multiplexer based on plastic surfacerelief grating applied to local area communication network

A plastic surface-relief grating as a wavelength division multiplexer is designed and fabricated with the conventional mould pressing technique using the transmission-type fused quartz phase grating as mask pattern and polycarbonate as basal material.The experiment results show that in an optimizing process,the plastic surface-relief grating has the highest firstorder diffraction efficiency under adequate groove depth and incident angle,and can be used as the best optical path for wavelength division multiplexing(WDM).We also establish the experiment setup for testing the WDM performance of the plastic surface-relief grating based wavelength division multiplexer.The results show that the proposed wavelength division multiplexer has the high-stability temperature characteristics,the low insertion loss of less than 5 dB,the large isolation of greater than 20 dB,the low polarization-dependent loss(PDL) of less than 0.4 dB and the relatively steep pass-band characteristics.It is a WDM device with good performance,which can be applied in short distance communication.     

无线激光通信图像去噪技术

无线激光通信是指利用激光束作为载波在空间（陆地或太空）直接进行语音、数据、图像信息双向传送的一种技术。本文主要研究图像信号的去噪技术。无线激光通信过程由于电子线路噪声,背景光,以及大气湍流的影响,其传输的信息必然会含有很多噪声。图像的噪声有很多,其中包括有高斯噪声,本文主要以它为例,在空域滤波法中,找到一种简单、有效的去除噪声方法。在实验的基础上,证明了用中值滤波算法结合拉普拉斯算子,消除椒盐噪声效果比较理想。     

应用纵向分区彩虹全息术合成断层图像的三维消色像

报道了应用纵向分割多狭缝曝光彩虹全息术合成多幅断层图像为三维消色像的方法及其实验结果。通过将主全息图记录狭缝按纵向分割并结合使用循环分割和色散补偿光栅 ,实现了在较高的分辨率和较低色模糊的多幅断层像的白光三维消色像的合成 ,并提高了再现像的视觉亮度、视场和立体感。