我校"信号与系统"课程的改革与建设

信号与系统是电气信息类专业重要的技术基础课程。近年来,课程组对“信号与系统”课程进行了全面的改革与建设,造就了一支高素质的教师队伍,提出了具有鲜明时代特征的教育教学思想,重构了课程体系,更新了教学内容,出版了高水平教材,改革了教学方法与手段,取得了丰硕成果,2003年被评为国家精品课程。     

Harmonic extraction from high-efficiency avalanche diodes

A novel harmonic-extraction method for operation of high-efficiency avalanche diodes has been demonstrated. It has been shown that high-efficiency power output can be obtained not only at the trapped-plasma frequency, but also at harmonic frequencies with respect to the trapped-plasma frequency. Second-harmonic powers of 110 W at 2.67 GHz with 22-percent efficiency from L-band diodes, and 64 W at 4.85 GHz with 15-percent efficiency from S-band diodes have been obtained. Third-harmonic extraction has extended the power output into the lower X-band frequency. Microstrip circuits for harmonic-extraction have been developed and analyzed. The circuit impedance requirements at the diode terminals have been computed. The circuit has been discussed in terms of a multiple-reflection triggering process. Useful information for circuit design has been deduced from a series of harmonic-extraction experiments. The voltage waveforms have been measured and have shown evidence of harmonic extraction and its association with the trapped plasma mode.     

单电子晶体管的制备、集成与电路研究

我们制备出了高温Si单电子晶体管,研究了单电子晶体管的集成原理,实现了14个单电子晶体管的串联集成和2个单电子晶体管的并联集成。同时也研究了单电子晶体管与传统高迁移率晶体管的集成和技术,发现可用单个电子来调控传统晶体管的栅对源漏极电流的控制能力（跨导）,利用单电子晶体管的集成方法,建立了对电荷超敏感的探测技术（包括超敏感的库尔计）,实现了单电子存储器中的单电子过程的探测,并设计了一种新型的多值存储器。     

光谱吸收光纤气体传感技术探讨

简述了光纤气体传感器的基本特性.介绍了几种光谱吸收光纤气体传感的方法.详细阐述了各种传感原理.分析了影响光谱吸收光纤气体传感精度的因素.     

Wide-Band Reflection-Type Transferred Electron Amplifiers

Stable CW and pulsed linear-reflection-type amplification at C- and X-band frequencies using epitaxial-GaAs transferred electron devices is described. These devices have a doping density-length product (nl) greater than 5 x 10/sup 11/cm/sup -2/. Criteria for avoiding the normal instabilities are discussed with specific regard for the circuit impedance, operating bias-voltage material characteristics, and the device temperature. The active impedance of a stable device has been measured, along with the effects of the package parasitic. These data were utilized to design multiple-tuned wide-band circulator-coupled coaxial-amplifier networks. Instantaneous CW bandwidths of nearly 1 octave have been measured in C-band, and instantaneous bandwidths of 4 GHz have been measured in X-band with single-stage Iinear gains from 6 to 12 dB. A -1-dB gain compression power output of 250 mW, with a saturated power output approaching 1 watt, has been realized from a single device. The noise figure of a single-stage amplifier has been found to be 15 dB. The phase response of a typical amplifier has been found to be linear with a differential phase shift of less than 20/spl deg/ /GHz. The amplitude linearity has been related to third-order intermodulation distortion and found to be comparable to that obtainable from traveling-wave-tube amplifiers (TWTAs). In a two-stage configuration a small-signal gain of 22 dB and a fractional bandwidth of 35 percent have been realized in C-band. A novel scheme for studying the gain response of pulse-biased devices using swept-frequency techniques has been developed. Pulsed amplification has been obtained with a power output of 2 watts at a 5-percent duty cycle with a conversion efficiency of 6 percent and a bandwidth of 1 GHz.     

Analytical modeling of flicker and thermal noise in n-channel DG FinFETs

A compact physics-based thermal and flicker noise model has been developed for n-channel Double Gate FinFETs with varying structural parameters. The effects of mobility degradation due to velocity saturation, carrier heating and channel length modulation have been incorporated for an accurate modeling of noise. The mobility fluctuations dependent on the inversion carrier density have been considered and a characteristic of the flicker noise different from that of Bulk MOSFETs was observed. This has been validated by the experimental results. Based on the proposed thermal and flicker noise model, a compact expression of the corner frequency has been derived and the effects of the structural parameters such as the length and the thickness of the channel have been analyzed. Finally, the model has been applied for p-channel devices and noise behavior in accordance with experimental data has been obtained.     

基于LTCC工艺双频GPS陶瓷微带天线研究

在空腔模型理论基础上,利用微扰法对切角矩形微带天线进行严密的数学推论.并设计了GPS双馈点双频圆极化陶瓷微带天线.根据设计公式计算出结构参数,在Ansoft-HFSS软件中建立天线模型,通过参数优化得到天线参数,并利用LTCC工艺进行样品制作.结果表明:样品天线工作在1575 MHz和1 227 MHz时,10 dB带宽均大于10 MHz,回波损耗均小于-15 dB,轴比均小于4 dB,仿真结果与测试结果相似.总结了天线小批量生产的经验,提出了进一步小型化的研究方向.     

铌酸锂定向耦合器的优化设计

分析了定向耦合器几个参数的相互关系,设计了钛扩散铌酸锂定向耦合器的仿真方案,用BPM软件对不同耦合间距的定向耦合器对工艺的容差进行了模拟计算,得到了几种耦合间距/串音变化的组合.     

Sinh-Domain linear transformation filters

A new systematic method for designing Sinh-Domain linear transformation (LT) filters is introduced in this article. For this purpose, a substitution scheme containing the Sinh-Domain LT equivalent of each passive prototype has been introduced. The proposed equivalents have been realised by employing appropriate Sinh-Domain building blocks with low-voltage operation capability. As an example, a third-order Sinh-Domain elliptic LT filter has been designed and its performance has been evaluated through simulation results. In addition, a detailed comparison with the corresponding Sinh-Domain and log-domain counterparts has been performed and the obtained results have been further discussed.     

Mode coupling at arc-fusion splices in graded-index fibers

Mode coupling at an arc-fusion splice has been investigated theoretically and experimentally. It has been certified experimentally that fiber parameters change at an arc-fusion splice. A mode transfer matrix has been derived which describes mode coupling at splices with fiber parameter changes along the fiber axis. The mode-coupling effects on the frequency response of spliced graded-index fibers have been investigated. Length dependence of 3 dB bandwidth has been measured for 10 km long graded-index fiber both with and without a splice. It has been clarified that the mode-coupling effect at the splice broadens the 3 dB bandwidth by 10 percent in the long fiber link in comparison with that for the fiber without a splice.     

重油隧道窑的红外温度测量

在分析重油隧道窑工况的基础上，分析了窑内烟气、燃烧物发射率、窑墙效应、环境温度对红外测温的影响以及热电偶测温的缺点，采取了相应的措施。利用中国发现专科实现了传感器输出信号的一致性。给出了传感器在重滑隧道窑现场使用２．５年后的复校数据。最后，估算出了用红外温度计替代热电偶测窑温产生的经济效益。     

Nanoscale germanium MOS Dielectrics-part I: germanium oxynitrides

In this paper, nanoscale germanium (Ge) oxynitride dielectrics are investigated for Ge MOS device applications. The synthesizing methodology and physical properties of these oxynitride films have been examined first. Basic electrical characteristics have been acquired on metal-gated MOS capacitors with Ge oxynitride dielectric on substrates with different dopant types and crystal orientations. Using an optimized oxidation and nitridation recipe, high-quality Ge MOS capacitors with a minimal frequency dispersion and capacitance-voltage hysteresis have been demonstrated. In addition, the Ge oxynitride dielectric-substrate interface has also been analyzed with the combined low-frequency-high-frequency capacitance method that revealed a substantial reduction of interface trap density after the forming gas anneal. An asymmetric interface trap density distribution within the Ge bandgap has been mapped out, which might explain the inferior n-channel Ge MOSFETs with oxynitride dielectric. An abnormality in the general gate leakage behavior has been observed and found to originate from a transient charge-trapping effect.     

A circular crossed-field amplifier for in situ measurements, studyof reentrant beam effects, and comparison with numerical simulation

A low frequency, injected beam, circular format crossed-field amplifier has been designed and constructed for the purpose of studying electron-radio frequency wave interaction in reentrant devices. The device has been designed to allow in situ diagnostic probe measurements in the space between the anode and sole. The device has been operated in nonreentrant, fully reentrant, and reentrancy controlled configurations. Details of the design and operating parameters are described. Device characteristics are examined with respect to the amount of circulating charge or degree of reentrancy. A large increase in gain has been achieved from nonreentrant to the fully reentrant format. A gain of 7.2 dB has been obtained for the latter whereas only 3.8 dB has been obtained for the former with 30 mA of injected beam current. A maximum gain of 14.4 dB has been achieved for the fully reentrant configuration. Electron beam and noise measurements versus the degree of reentrancy have also been examined. Results from the nonreentrant amplifier performance have been directly compared with the MASK simulation code and good agreement has been obtained. These experiments will provide the basis for more detailed investigations on the effect of reentrancy on CFA operation and will also allow for the development of more accurate computer models of the reentrant system for numerical simulation of CFA operation     

An Optimum Design Methodology for Planar-Type Coaxial Probes Applicable to Broad Temperature Permittivity Measurements

A planar-type coaxial probe applicable to wide temperature and frequency range has been developed. The probe employs a dielectric with a low coefficient of thermal expansion to minimize the effect of thermal deformation for broad temperature measurements. Additionally, a detailed design methodology has been developed to optimize the probe apertures in an effort to minimize the measurement uncertainty while maximizing the operating bandwidth. For this purpose, thorough sensitivity analysis has been employed to correlate the probe structures and dimensions to the individual sensitivity parameters. The analysis has been validated by parametric experiments. By using the dielectric with a low coefficient of thermal expansion and optimizing the probe dimensions, accurate permittivity measurements have been demonstrated from 30 C to 75 C with 40-GHz bandwidth. With the application of the error-correction method, the measurement temperature range has been further extended all the way up to the boiling temperature of water C). Furthermore, the complex permittivities of methanol have been measured from 30 C to 50 C and the dispersion parameters and full interpolation formulas have been extracted.     

Characterization of V-groove coupled microshield line

A new membrane supported air-filled V-groove coupled microshield has been investigated using finite element method. The even- and odd-mode characteristic impedances and the effective dielectric constants have been computed. The dependence on various dimensions has been studied. The crosstalk levels between adjacent lines have been compared with that in coupled microstrip lines, coupled microstrip lines with lateral ground planes, and V-groove structures with and without metallization in the groove.     

Transfer Functions of Amplitude and Phase Fluctuations and Additive Noise in Varactor Doublers

In order to evaluate the spectral purity degradation produced by varactor doublers, the transfer properties of amplitude and phase fluctuations have been determined with reference to a theoretical analysis developed in a previous work. Quasi-stationary conditions have been assumed and the input and output tuning circuits have been approximated with a linear relation between frequency and reactance. The effect of the bias circuit has been taken into account both for fixed-bias and self-bias conditions. Then the additive-noise contribution of the doubler circuit elements have been obtained. Numerical examples and curves are given for all the evaluated quantities.     

Design and development of a novel high-transconductance pH-ISFET (ion-sensitive field-effect transistor)-based glucose biosensor

A glucose biosensor based on a high-transconductance ISFET transduction element with aspect ratio (channel width/length) of 400 has been developed. This biosensor is an N-channel enhancement mode device with interdigitated drain-source geometry, fabricated by the NMOS process, in which glucose oxidase (GOD) enzyme has been immobilized over the silicon dioxide-silicon nitride dual-dielectric gate. The device has been operated in the active mode by applying a gate voltage through Ag/AgCl reference electrode. Electrical characterization has been performed in terms of I-V characteristics like output characteristics and leakage current. The pH response characteristics have been measured and the pH sensitivity factor has been found to be?≥?50?mV/decade. Device characterization has also been performed by a signal conditioning circuit developed for direct readout of pH from the ISFET device. Temperature behaviour and drift phenomenon have been investigated.

The glucose response characteristics of the ISFET have been determined, without and with the glucose oxidase enzyme layer. Improvement of the glucose sensitivity by deposition of the enzyme layer has been studied and cross-sensitivity of the device towards urea has been examined. The advantage of the high transconductance was evident from the ability of the sensor to detect small glucose concentrations without the enzyme layer. The paper describes the design, fabrication and characterization of the sensor.     

Perturbation theory for the evaluation of the normalised cutoff frequencies in radially inhomogeneous fibres

A simple perturbation theory has been used to study the normalised cutoff frequencies of radially inhomogeneous fibres. The formalism has been developed with a truncated parabolic-index profile as zero-order solution. Numerical calculations have been carried out for ?-profiles and have been found to be in good agreement with more rigorous approaches reported by previous authors.     

多上下文MQ编码器优化与VLSI实现

 MQ(Multiple Quantization)编码器由于效率低下已经成为JPEG2000的性能瓶颈.本文对MQ编码算法中的上下文关系进行了提取,对索引表中的启动态和非暂态进行了分离,并提出一种用于预测索引值的方法.同时,对重归一化运算中出现的大概率事件和小概率事件进行分离,使其可并行对2个上下文完成编码.依据该算法,本文提出了一种多上下文并行处理的MQ编码器VLSI结构.实验结果表明,本文提出的MQ编码器能够工作在286.80MHz,吞吐量为573.60 Msymbols/sec,相比Dyer提出的Brute Force with Modified Byteout结构,本文的吞吐量提升约35%,且面积减小78%.     

Nonlinear theory of long-range-interaction resonant generators

A nonlinear self-consistent theory has been developed for resonant electronic generators of long-range interaction. The theory has been under development for devices whose electrodynamic system has a high Q-factor and a sufficiently rarefied spectrum. In accordance with the initial physical situation, the mathematical model under consideration has been obtained in the form of a system of differential equations, and an algorithm for its numerical solution has been proposed. The maximum amplitude of the generated oscillations in an open cavity with a Gaussian distribution of the field has been calculated analytically.