微弱信号在数字信号处理器上的检测与实现

本文首先介绍了微弱信号的检测理论,包括自相关检测和互相关检测.虽然模拟电路对于信号处理的实现比较简单,但是对于容易被噪声掩盖的微弱的有用信号的检测并不是十分理想,而对于数字电路来说,设计和实现方式上相对于模拟电路的实现比较复杂,但是对于提取微弱信号效果较为明显,容易在噪声干扰下检测出微弱信号.针对模拟电路处理微弱信号存在的问题,本文提出了采用数字电路进行微弱信号处理的过程以及在DSP上的软件、硬件的数字实现过程.     

基于TD的3G无线网性能测试评估体系

结合国家重要专项测试项目对网络的评估要求,从TD-SCDMA网络评估内容与测试方法出发,详细介绍了TD-SCDMA网络所需要评估的内容,以及评估指标的定义。最后,对TD-SCDMA网络指标的量化评估进行了研究分析,结合网络和项目实际情况,选取了若干个关键网络指标,通过加权平均的方法建立网络评估模型。     

通用雷达杂波仿真系统的设计与实现

以雷达电子战系统仿真与评估为应用背景,基于信号级建模仿真方法和通用化、模块化设计思想,构建了适用于多种雷达电子战系统仿真应用的通用雷达杂波仿真系统,介绍了系统的设计与实现方法,给出了其中的关键仿真模型。该系统能够对固定平台和运动平台下雷达所接收的地/海杂波以及气象杂波进行信号级模拟。最后给出了仿真结果,验证了该系统的有效性。     

Noise limit in heterodyne Interferometer demodulator for FBG-based sensors

This paper reports the results of a recent investigation on the noise-limited performance in heterodyne interferometric demodulation systems for fiber Bragg grating strain sensors. Theoretical and simulation results are presented and compared with experimental results.     

Effective Periodic Poling in Optical Fibers

The distributions of electric field and induced second‐order nonlinearity are analyzed in the periodic poling of optical fibers. A quasi‐phase matching efficiency for the induced nonlinearity is calculated in terms of both the electrode separation distance between the applied voltage and generalized electrode width for the periodic poling. Our analysis of the quasi‐phase matching efficiency implies that the conversion efficiency can be enhanced through adjusting the separation distance, and the electrode width can be maximized if the electrode width is optimized.     

路由选择的智能方法

本文利用模糊理论来对通信网中的路由进行动态选择。文中首先讨论了路由选择所要考虑的一些因素,然后利用模糊综合评判理论评估出路由选择的量化综合指标,再通过模糊图中的最强路法选择出两点间的最佳路由。最后把该法同已有方法进行仿真比较,发现该法比较的方法能较大地提高接通率,且性能未受损害。     

High-nonlinearity fiber optical parametric amplifier with periodicdispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength λ_p far from the fiber zero-dispersion wavelength λ₀ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for λ_p=1542 and λ₀=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber     

Performance of thin-film transistors with ultrathin Ni-MILCpolycrystalline silicon channel layers

High-performance, low-temperature processed thin-film transistors (TFTs) with ultrathin (30-nm) metal induced laterally crystallized (MILC) channel layers were fabricated and characterized. Compared with the MILC TFTs with thicker (100 nm) channel layers, the ones with the 30-nm channel layers exhibit lower threshold voltage, steeper subthreshold slope, and higher transconductance. Furthermore, the comparatively lower off-state leakage current and the higher on-state current of the “thin” devices also imply a higher on/off ratio. At a drain voltage of 5 V, an on/off ratio of about 3×10 ⁷ was obtained for the 30-nm TFTs, which is about 100 times better than that of the 100-nm TFT's. No deliberate hydrogenation was performed on these devices     

Adhesion strength of leadframe/EMC interfaces

Cu-based leadframe sheets were oxidized in alkaline solutions to produce brown and/or black oxide on the surfaces, and molded with epoxy molding compound (EMC). The adhesion strength of leadframe/EMC interface was measured using sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens. Results showed that the adhesion strength of leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates. The presence of smooth-faceted Cu₂O on the surface of the leadframe gave close to zero fracture toughness (G_C) and suitable pull strength (PS). A direct correlation between G_C and PS showed that PS can be a measure of G_C only in a limited range.     

A New Digital Sense Multiple Access (DSMA) Protocol for High-Speed Wireless Networks

In this paper, we propose a new digital sensemultiple access with delayed transmission (DSMA/DT)protocol for reverse channel in high-speed wirelessnetworks. The new protocol is motivated by theobservation that the existing DSMA protocol does not yieldsatisfactory throughput for long round-trip propagationand processing delay, which occurs in outdoor high-speedenvironments or when the receiver hardware requires long signal processing time. The newDSMA/DT protocol is intended to reduce the performanceimpacts of the round-trip delay. Look-ahead busy/idleflag, seizure queueing, and reserved time slots are also devised for the new protocol. Whilerequiring at most two additional status bits on theforward channel and no additional hardware capability,these features further enhance the protocol performance and enable constant-bit-rate service withlittle added complexity in control. The channelthroughput of the DSMA/DT protocol and the optionalfeatures are analyzed. Closed-form expressions for thethroughput are obtained. For non-negligible round-tripdelay relative to packet transmission time, ournumerical results show that the new protocol improvesthe throughput by as much as 60% when compared to theexisting DSMA protocol. For superior performance andsimplicity, the DSMA/DT protocol will be appropriate foruse in high-speed wireless networks.