氧化硅在改善双极型晶体管特性上的作用

提出了一种改善npn和横向pnp晶体管放大倍数、扩散致窄电阻(受EB和CB结结深影响的基区电阻)阻值而又不影响其他器件特性的方法.不连续的SiOx可以作为宽禁带半导体材料加在多晶硅和单晶硅的界面处来提高横向pnp晶体管的放大倍数,使其从目前的23提高到30;连续的SiOx作为优秀的绝缘材料覆盖在发射极多晶硅表面,可以确保As在快速热处理后的分布,结果表明npn型晶体管的放大倍数从170降低到110的同时增加了扩散致窄电阻的阻值.这种方法的优点在于利用了极易制造的SiOx改善了半导体器件特性,具有极高的实际应用价值.     

基于人工噪声预编码的多天线中继安全性能分析

为提升存在窃听者的中继网络的安全性能,在多天线放大转发中继端采用人工噪声预编码(ANP)和特征波束形成(EB)安全传输策略,推导了ANP和EB的可达安全速率(EASR)闭合表达式。在中继配置大规模天线时,推导了ANP的EASR下界,并在高信噪比和低信噪比情况下研究了渐近性能。分析和仿真结果显示,在中高信噪比区域,ANP相比于EB可获得显著的性能增益,而在低信噪比区域,EB优于ANP。当信噪比增加时,EB的EASR接近一个与第1跳无关的常数。在高信噪比区域,ANP的最优功率分配方案是将一半左右的功率分配给人工噪声。     

Demonstration of CSRZ Signal Generator Using Single‐Stage Mach‐Zehnder Modulator and Wideband CMOS Signal Mixer

In this paper, we demonstrate an electrically band‐limited carrier‐suppressed return‐to‐zero (EB‐CSRZ) signal generator operating up to a 10 Gbps data rate comprising a single‐stage Mach‐Zehnder modulator and a wideband signal mixer. The wideband signal mixer comprises inverter stages, a mixing stage, and a gain amplifier. It is implemented by using a 0.13 μm CMOS technology. Its transmission response shows a frequency range from DC to 6.4 GHz, and the isolation response between data and clock signals is about 21 dB at 6.4 GHz. Experimental results show optical spectral narrowing due to incorporating an electrical band‐limiting filter and some waveform distortion due to bandwidth limitation by the filter. At 10 Gbps transmission, the chromatic dispersion tolerance of the EB‐CSRZ signal is better than that of NRZ‐modulated signal in single‐mode fiber.     

Performance analysis of linear precoding based on field trials results of MIMO-OFDM system

We use field trial results obtained from a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) wireless system with two transmitter and three receiver antennas (2/spl times/3), to first validate the properties of the transmit correlation matrix in a macro-cellular environment. We find that approximately 20% of the locations have well-defined transmit correlation matrices. Furthermore, the eigenvectors of the transmit correlation matrix vary slowly over distance with 60% of the locations having eigenvector variation of less than 1 dB over a distance of 20 m. Next, we quantify the performance of the optimal statistical linear precoding (OSLP) , and statistical one-dimensional (1-D) eigenbeamforming (SEB) based on transmit correlation matrices, and the 1-D eigenbeamforming (EB)-based on perfect channel knowledge at the transmitter. We find that the OSLP and SEB schemes obtain array gain over the Alamouti scheme at lower signal-to-noise ratio (SNR) with a median gain of 2.0 (1.5) dB at the 1.0-(3.5) km cell-radii. However, the SEB scheme (unlike the OSLP scheme) looses diversity order at higher SNR that leads to a performance loss. The EB scheme provides the best performance over the Alamouti scheme, at the expense of increased feedback requirements.     

Replacing Cryptographic Keys in AMI Mesh Networks with Small Latency

Advanced Metering Infrastructures (AMI) facilitate efficient and reliable exchange of electricity information between the homes and utilities. Their unique characteristics (e.g., connecting millions of smart meters; accessing customers’ private information), however, make them a lucrative target for adversaries. For example, an attacker might try to compromise the head-end of an AMI and send “remote disconnect commands” to the smart meters, disconnecting a large number of customers. To implement message authentication and protect message integrity and confidentiality, a number of cryptographic keys are being utilized. A “command key”, for example, signs messages that are sent from the head-end to the meters. Such keys, however, introduce their own set of problems if they ever get compromised. A stolen command key would allow an adversary to continuously send malicious commands to the meters. Hence, the compromised keys must be revoked and replaced as quickly as possible. This paper proposes an efficient and reliable key distribution framework for the AMI mesh networks based on the connected dominating set approach. The keys are replaced with minimal latency through our “hexagon-tile coloring scheme”, which allows the maximum number of keys to be transmitted in parallel, free of collision.     

Small-signal gain calculations for electrostatically focused klystrons

The small-signal gain of an electrostatically focused klystron (ESFK) will be different from that of a conventional klystron because the drift tube is not dc field free and the RF bunching process is altered. A method for calculating the small-signal gain of an ESFK, based on a space-charge wave analysis of the lens cell, is presented. Calculated and measured values of small-signal gain for several different ESFK's are given.     

Temperature stabilized transistor amplifiers

A design procedure is evolved based on emitter-base voltage V/SUB EB/ and collector-base voltage V/SUB CB/ as stability parameters with the aim of achieving a gain stabilized transistor amplifier against temperature variations. Silicon transistors have been operated with a fairly stabilized gain in the temperature range from -15/spl deg/ to 270/spl deg/C. The voltage and power gains of this amplifier are found to be reasonably stable against unit to unit replacements. The circuits designed according to this approach are particularly suited for operation of long duration at elevated temperatures. The role of the leakage currents in affecting the operation of a several hour duration at elevated temperatures is investigated experimentally and it is found that the low I/SUB CB0/ units are better suited for such an operation. Further experimentations include the study of the gain stability characteristics of the amplifiers using Darlington pairs, CE-CE tandem connections, two stage RC-coupled amplifier, and the different amplifier.     

Dependence of the efficiency-bandwidth product on electrical volumeof small dielectric loaded antennas

The efficiency fractional efficiency bandwidth product (EB) that is expressed as a ratio of the radiation resistance to the absolute value of an input reactance of an antenna is used as a performance measure for small dielectric-loaded monopole antennas (DLMAs). The dependence of the efficiency bandwidth (EB) on the permittivity of the dielectric loading (i.e., the electrical volume) is experimentally investigated for the first time after we succeeded in measuring the small radiation resistance of the DLMAs precisely on the basis of the Wheeler cap method. As a result, it was found that the EBs of some DLMAs were enhanced over a bare monopole antenna and an EB characteristic curve has a maximum point. This result suggests the presence of the optimum electrical volume for the dielectric loading in order to obtain the best EB performance. A calculation by the finite-difference time-domain (FDTD) method was also conducted to confirm the presence of the maximum EB value under a certain condition. A general reason for the existence of the peak value is also explained using a mathematical deduction     

A simple model of the free electron laser oscillator from low intohigh gain

An investigation of the Compton free electron laser (FEL) oscillator from the low into the high gain regime is presented. The one-dimensional Maxwell-Pendulum equations, describing the radiation-electron beam evolution in an FEL, are used to develop a simple, computationally efficient method of modeling the radiation evolution. The maximum efficiency for a range of values of the gain parameter G is calculated     

High-sensitivity FSK signal detection with an erbium-doped fiberpreamplifier and Fabry-Perot etalon demodulation

A report is presented on a 622-Mb/s optical transmission system with demodulation of alternate mark invert (AMI) encoded frequency shift keying (FSK) signals by a Fabry-Perot etalon. A 25-dB gain erbium-doped fiber preamplifier gave a receiver sensitivity of -40 dBm at 10^-9 BER, which was improved to -44 dBm with the addition of a narrowband optical filter. The theoretical sensitivity of the preamplified receiver and the effect of the etalon on the amplified spontaneous emission beat noise are discussed and related to experiment     

Trellis codes for partial-response magnetooptical direct overwriterecording

The authors present conditions on the error sequences between channel input sequences which guarantee certain lower bounds on the free Euclidian distance at the output of a partial-response (PR) class I or II channel. From these expressions, trellis codes are derived which improve performance of binary signaling over noisy PR channels with reduced complexity maximum-likelihood sequence detection. They are shown to be compatible with the input restriction caused by the magnetooptical resonant coil direct overwrite recording scheme. The codes achieve high signal-to-noise ratio coding gains of 3 dB (on PR class I) and 2.2 dB (on PR class II) with rates as close to, but strictly less than, the capacity of the initial input restriction as desired. The performance of these codes is analyzed with an optical channel simulation system which shows that one code has the rare but highly desirable property that its maximum-likelihood sequence detector (MLSD) is less complex than the MLSD of the reference system and still achieves an error rate performance gain of 1.8 dB     

Empirical Bayes Approach to Reliability Estimation for the Exponential Distribution

In the empirical Bayes (EB) approach to a reliability estimation for the exponential distribution, a prior distribution is placed on the family of prior gamma distributions to produce an EB estimator. The EB estimator is asymptotically optimal and admissible. The results of a Monte Carlo study are presented to demonstrate the favorable risk behavior of the EB estimator as a Bayes estimator if the sample size is large.     

Independent control of EDFA gain shape and magnitude usingexcited-state trapping

Controlled use of excited-states of erbium are used to decouple the magnitude and shape of the gain spectrum of an erbium-doped fiber amplifier (EDFA) containing a low phonon energy glass. This makes it possible to operate a single EDFA at multiple gains without the gain flatness degradation referred to as dynamic gain-tilt. Dynamic gain-tilt free operation is demonstrated in the long-wavelength portion of the erbium gain spectrum using an erbium-doped ZBLAN fiber     

Removal of the eye-blink artifacts from EEGs via STF-TS modeling and robust minimum variance beamforming

A novel scheme for the removal of eye-blink (EB) artifacts from electroencephalogram (EEG) signals based on a novel space-time-frequency (STF) model of EEGs and robust minimum variance beamformer (RMVB) is proposed. In this method, in order to remove the artifact, the RMVB is provided with a priori information, namely, an estimation of the steering vector corresponding to the point source EB artifact. The artifact-removed EEGs are subsequently reconstructed by deflation. The a priori knowledge, the vector corresponding to the spatial distribution of the EB factor, is identified using the STF model of EEGs, provided by the parallel factor analysis (PARAFAC) method. In order to reduce the computational complexity present in the estimation of the STF model using the three-way PARAFAC, the time domain is subdivided into a number of segments, and a four-way array is then set to estimate the STF-time/segment (TS) model of the data using the four-way PARAFAC. The correct number of the factors of the STF model is effectively estimated by using a novel core consistency diagnostic- (CORCONDIA-) based measure. Subsequently, the STF-TS model is shown to closely approximate the classic STF model, with significantly lower computational cost. The results confirm that the proposed algorithm effectively identifies and removes the EB artifact from raw EEG measurements.     

Nanostructure fabrication using electron beam and its applicationto nanometer devices

Nanofabrication developed by using electron beam (EB) are described. Ten-nm structures of organic positive and negative resist patterns have been achieved by using a commercially available EB lithography system with energy of 30-50 keV. The self-developing properties of an AlF₃-doped LiF inorganic resist have been studied for sub-10-nm lithography. By optimizing the inorganic resist film quality, 5-nm linewidth patterns with 60-nm periodicity were directly delineated under a 30-keV EB. Moreover, EB-induced deposition is described as an interesting method for nanofabrication. An novel approach for nanolithography using de Broglie wave has been developed. Line and dot patterns with 100-nm periodicity were exposed on a PMMA resist by EB holography with a thermal field-emitter gun and an electron biprism. This technique allows us to produce nanoscale periodic patterns simultaneously. Furthermore, the possibility of nanostructure fabrication by atomic-beam holography has been demonstrated by using a laser-trap technique and a computer-generated hologram made by EB lithography. As applications of EB nanolithography to nanodevices, a 40-nm-gate NMOS Si device and a high-temperature-operation single-electron transistor (SET) are described     

Design analysis of a gain-stabilized transistor amplifier at elevated temperatures using passive elements

The decrease of the emitter-base and collector-base junction voltages of a transistor with temperature and the effect of the external circuit resistances on these voltages are studied theoretically and experimentally. The influence of the shifting of the operating point with temperature on the gain is discussed. A new design approach based on V/SUB EB/ and V/SUB CB/ as the stability parameters is given using only passive components. It is found that this approach definitely leads to better gain stability with temperature than other design techniques using NTC elements. Although work in the early stages was concentrated on germanium transistors (-15 to +115/spl deg/C), already some encouraging results have also been attained in the study of silicon transistors.     

Resolution improvement of acoustic microimaging by continuous wavelet transform for semiconductor inspection

Acoustic microimaging (AMI) is used as an important non-destructive tool in semiconductor reliability evaluation and failure analysis. As advanced microelectronic packages are being produced smaller and thinner, detection of the internal features and defects in the packages is approaching the resolution limits for conventional AMI. To meet this challenge, an acoustic time–frequency domain imaging technique is proposed in this paper, which utilizes the excellent time–frequency localization characteristics of the continuous wavelet transform (CWT) to improve the axial resolution of AMI, without increasing acoustic frequencies.The proposed technique is compared to time domain AMI, frequency domain AMI and sparse signal representation based AMI (SSRAMI) with respect to both axial resolution and robustness. Simulation results show that the proposed technique has superior performance compared to time domain and frequency domain AMI techniques, and has close performance to SSRAMI but with less computation load.     

Low Voltage Digitally Controlled CMOS Current Conveyor

In this paper, a digitally controlled current conveyo(DCCC) is presented. The proposed DCCC is based on rail-to-rail folded cascode implementation with a current division network (CDN). The CDN is used to provide control on the current gain of the DCCC. The CDN uses a novel current division technique based on differential pairs. The proposed DCCC can operate from ±1.5 V supply voltages. Applications of the proposed DCCC such as variable gain amplifiers (VGA) and digitally tunedfilters have been investigated. PSpice simulations based on the AMI 1.2 µm N-well level 3 parameters are in agreement with the presented work.     

Performance analysis of exponential backoff

New analytical results are given for the performance of the exponential backoff (EB) algorithm. Most available studies on EB focus on the stability of the algorithm and little attention has been paid to the performance analysis of EB. In this paper, we analyze EB and obtain saturation throughput and medium access delay of a packet for a given number of nodes N. The analysis considers the general case of EB with backoff factor r; binary exponential backoff (BEB) algorithm is the special case with r=2. We also derive the analytical performance of EB with maximum retry limit M (EB-M), a practical version of EB. The accuracy of the analysis is checked against simulation results.     

Empirical Bayes Estimators of Reliability for Lognormal Failure Model

Empirical Bayes (EB) procedures are considered for estimating the reliability R(t;?,?) = gaufc[(ln t -?)/?] for the lognormal failure model. EB estimators are obtained for the 2 cases: i)? is unknown and ? is known, and both ? and ? are unknown. The empirical Cdf of the maximum likelihood estimators of the parameters is used to obtain the EB estimators. ii) A smooth EB estimator of R(t;?,?) is developed when ? is unknown and ? is known. A modification of this estimator is proposed for both ? and ? unknown. In both cases, EB estimators are obtained for complete samples at each testing stage. Monte Carlo simulations are presented to compare the EB estimators and the maximum likelihood (ML) estimators of R(t;?,?). The simulations indicate that the smooth EB estimators have smaller mean squared errors than the other EB estimators or the ML estimators.