Simulation of SiGe:C HBTs using neural network and adaptive neuro-fuzzy inference system for RF applications

In this article, the small-signal equivalent circuit model of SiGe:C heterojunction bipolar transistors (HBTs) has directly been extracted from S-parameter data. Moreover, in this article, we present a new modelling approach using ANFIS (adaptive neuro-fuzzy inference system), which in general has a high degree of accuracy, simplicity and novelty (independent approach). Then measured and model-calculated data show an excellent agreement with less than 1.68?×?10^?5% discrepancy in the frequency range of higher than 300 GHz over a wide range of bias points in ANFIS. The results show ANFIS model is better than ANN (artificial neural network) for redeveloping the model and increasing the input parameters.     

应用于毫米波的共面波导的统一模型及直接提参方法

Coplanar waveguides （CPW） are widely used in mm-wave circuits designs for their good performance. A novel unified model of various on chip CPWs for mm-wave application, together with corresponding direct parameter extraction methodologies, are proposed and investigated, where standard CPW, grounded CPW （GCPW） and CPW with slotted shield （SCPW） are included. Several kinds of influences of different structures are analyzed and considered into the model to explain the frequency-dependent per-unit-length L, C, R, and G parameters, among which the electromagnetic coupling for CPWs with large lower ground or shield is described by a new C-L-R series path in the parallel branch. The direct extraction procedures are established, which can ensure both accuracy and simplicity compared with other reported methods. Different CPWs are fabricated and measured on 90-nm CMOS processes with Short-Open-Load-Through （SOLT） de-embedding techniques. Excellent agreement between the model and the measured data for different CPWs is achieved up to 67 GHz.     

驾驶员自适应神经模糊推理模型的建立与仿真

提出了一类基于自适应神经模糊推理系统(ANFIS)的飞机驾驶员建模方法.首先建立了包含若干待定模糊规则参数的基本驾驶员Takagi-Sugeno模糊模型,将其转换成等效的ANFIS网络系统后,采用驾驶员实际操纵数据和自适应BP算法对模糊规则各个待定参数进行训练并建立最终的模型.进而对已建立的驾驶员模型进行人机闭环系统仿真,结果表明,较之传统的传递函数模型,ANFIS模型与驾驶员实际操作输出之间的拟合程度更加理想.     

太赫兹频段基于NR迭代法的复介电常数提取

伴随着6G通信的发展,雷达遥感、检测成像等多个领域向太赫兹频段拓展,获取材料在该频段的介电常数显得愈发重要。本文基于NR迭代法提取了太赫兹频率下样品的复介电常数,分析了迭代法的初值选取对提取结果的影响。在325～500 GHz频段(Y频段)搭建了一套由矢量网络分析仪(VNA)、扩频模块和四抛物面镜组成的8f准光系统,实现散射参数S₂₁的自由空间测量。由电磁波传输模型推导出复介电常数与S₂₁之间的关系式,利用迭代法提取出了特氟龙(Teflon)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)和聚甲基丙烯酸甲酯(PMMA)样品的复介电常数谱,与其他文献报道的结果一致,验证了系统和方法的有效性。     

An analytical drain current model of short-channel MOSFETs including source/drain resistance effect

In this paper, the DC characteristics of MOSFETs are investigated by means of an analytical approach with considerations of the source/drain parasitic resistance (R _S/R _D). Experimental data of MOS devices for DRAM design and results of TCAD simulation are used to verify the accuracy of theoretical calculation. It is found that both the R _S and R _D can induce a large reduction in the drain current in the linear region, but only the source resistance can cause a large reduction in the drain current in the saturation region. Moreover, the drain current deduction due to the R _S/R _D increases with decreasing channel length and oxide thickness.     

65纳米硅衬底上低损耗带屏蔽的共面波导传输线建模

共面波导传输线可以用作毫米波频段片上的高品质因子的无源器件。在这篇文章里,采用CMOS 65nm工艺设计和制造了加地线屏蔽和不加地线屏蔽的共面波导传输线。本文提出一个基于物理的模型来描述传输线单位长度的频率相关的电感、电容、电阻和电导参数。从基本的共面波导结构出发,模型里加入了慢波效应和底线屏蔽效应的影响。实验数据表明模型有很高的准确度。     

Effects of electromagnetic near-field stress on SiGe HBT’s reliability

In this paper, a reliability damage mechanism was presented in SiGe Heterojunction Bipolar Transistor (HBT). This new stress methodology differs from conventional SiGe, HBT device reliability associated with other stresses, since it was obtained by applying electromagnetic near-field aggression. The near-field set-up is used to disturb with electromagnetic field the Device Under test (DUT) on a localized area. Degradations in the base current and the current gain are identified. They are induced by a large base current leakage due to hot carrier which introduces generation/recombination trap centers at the silicon–oxide interface of the emitter–base spacer. By using the S-parameters measurements, we find that both forward transmission scattering parameter (S₂₁) and the input scattering parameter (S₁₁) are affected by this stress. In addition the power characteristics of DUT are also affected by stress. A Direct Power Injection (DPI) method is used to understand the near-field stress behaviour.     

An accurate, analytical, and technology-mapped definition of the surface potential at threshold and a new postulate for the threshold voltage of MOSFETs

A novel approach of defining the threshold voltage for long channel MOSFETs has been presented in this paper, where it has been proposed that it corresponds to the gate-to-source voltage for which the drift and diffusion components of the total drain current become equal to each other. In order to avoid the greater computation time associated with the numerical solution of these two components, an analytical expression of the surface potential, corresponding to the threshold condition, is given here, which has the same functional form as the one proposed by Tsividis. The fuzzy parameter n, appearing in this expression of the surface potential, is expressed as a function of the substrate doping density (N_A) and the oxide thickness (t_ox). The threshold voltage values, obtained analytically from the relation between the surface potential at the threshold condition and the closed-form technology-mapped expression of the fuzzy parameter n, show an excellent match with those obtained from SILVACO simulations for a wide range of N_A and t_ox, with the maximum error being only about 4%. The comparison of the percent error values of the threshold voltage obtained from this proposed model with those obtained from the other two recently proposed methods, all with respect to SILVACO simulation results, further verifies the validity of our completely analytical, mathematically simple, and straight-forward approach, proposed in this work here.     

Concentration dependence of the band gap of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>In<Subscript>2</Subscript>S<Subscript>4</Subscript> alloys on their composition

The transmittance spectra of MnIn₂S₄ and FeIn₂S₄ ternary compounds and Mn _x Fe_{1 − x} In₂S₄ alloys in the fundamental absorption edge region are studied. The samples were grown by planar melt crystallization. From the experimental spectra, the band gaps of the compounds and their alloys are determined, and the concentration dependence of the alloy band gap on the component content is established. It is found that the band gap nonlinearly varies with the composition parameter x and can be described by a quadratic function.     

ALFC of hybrid multi-generation power system using UC and TCPS by ANFIS control technique

ABSTRACT

This paper reveals the impact of an ultra-capacitor (UC) and thyristor control phase shifter (TCPS) on frequency stability of large hybrid interconnected power system. The impact of UC and TCPS has been studied for general purpose hybrid generated multi areas power system. Further to this, an adaptive neuro fuzzy inference system (ANFIS) is is proposed for automatic load frequency control (ALFC). Thermal and reheat thermal plants are connected in Area-1 and area-2, whereas area-3 has hydro plant and area-4, 5, 6 consists of nuclear power plant, diesel power and gas turbine plant, respectively. A micro grid based on Solar Photovoltaic (PV) system and fleet of electric vehicle (EV) system is developed and integrated with load side of area-1 for load management in interconnected grid. Effect of Small load change and large load change are discussed in separate cases. The controllers are tuned by adding sliding surface to enhance the performance. A comparison between ANFIS and PI-based control approaches with and without UC and TCPS exhibits the superiority of ANFIS controller by integrating UC and TCPS. The results of the proposed control technique are compared with already published results.     

Modeling and simulation of combinational CMOS logic circuits by ANFIS

In this paper, application of adaptive neuro-fuzzy inference system (ANFIS) in modeling of CMOS logic gates as a tool in designing and simulation of CMOS logic circuits is presented. Structures of the ANFIS are developed and trained in MATLAB 7.0.4 program. We have used real hardware data for training the ANFIS network. A hybrid learning algorithm consists of back-propagation and least-squares estimation is used for training. Influence of the structure of the proposed ANFIS model on accuracy and network performance has been analyzed through some combinational circuits. For the comparison of the ANFIS simulation results, we have simulated the circuits in HSPICE environment with 0.35 μm process nominal parameters. The comparison between ANFIS, HSPICE, and real hardware shows the feasibility and accuracy of the proposed ANFIS modeling procedure. The results show the proposed ANFIS simulation has much higher speed and accuracy in comparison with HSPICE simulation and it can be simply used in software tools for designing and simulation of complex CMOS logic circuits.     

THE PERFORMANCE ANALYSIS OF DISCRETE-TIME DETECTION AND ESTIMATION IN COLOR GAUSSIAN NOISE

The paper investigates the relation between the sample number and the perormances ofsignal detection and parameter estimation in color Gaussian noise in fixed time T.It points out that if theautocorrelation coefficient between the neighbour samples is in the range of 0.1—0.2,the GSNR S~2[T(X_L)]will approach to the GSNR limit S~2(T).The paper also points out that the sample sequence of the solution of asecond-order differential equation is not an AR(2)model.But when the sample interval △ approaches zero,the sample sequence can be described by AR(2).Therefore we can calculate S~2(T)easily.At the end of thepaper,the relation between the likelihood ratio detection and the maximun.likelihood estimation is discussed.     

Tunable/adaptive second-order IIR notch filter

A modified second-order infinite impulse response (IIR) notch filter with constrained poles and zeros is presented to eliminate or retrieve sinusoids embedded in a broadband signal. Such a filter is ideally suited to either parallel or cascaded implementation. Two classes of problems are considered. The first is where the sinusoidal frequencies are known a priori. For this case a straightforward design procedure based on a set of design characteristic graphs is used to select tunable notch filter parameters. An interesting property of the notch filter model is that it can be converted to a line enhancer by interchanging the position of the poles and zeros. The second type of problem arises when the sinusoidal frequencies are unknown and possibly varying with time. This means that an adaptive solution is required and an important consideration is the parameter estimation accuracy. For this purpose, the paper derives the Cramer–Rao lower bound for the adaptive cascaded notch filter using a frequency-domain approach. Some simulation results are included to demonstrate the effectiveness of the proposed adaptive notch filter.     

Cross‐layer design for MIMO systems over spatially correlated and keyhole Nakagami‐m fading channels

Cross‐layer design is a generic designation for a set of efficient adaptive transmission schemes, across multiple layers of the protocol stack, that are aimed at enhancing the spectral efficiency and increasing the transmission reliability of wireless communication systems. In this paper, one such cross‐layer design scheme that combines physical layer adaptive modulation and coding (AMC) with link layer truncated automatic repeat request (T‐ARQ) is proposed for multiple‐input multiple‐output (MIMO) systems employing orthogonal space‐‐time block coding (OSTBC). The performance of the proposed cross‐layer design is evaluated in terms of achievable average spectral efficiency (ASE), average packet loss rate (PLR) and outage probability, for which analytical expressions are derived, considering transmission over two types of MIMO fading channels, namely, spatially correlated Nakagami‐m fading channels and keyhole Nakagami‐m fading channels. Furthermore, the effects of the maximum number of ARQ retransmissions, numbers of transmit and receive antennas, Nakagami fading parameter and spatial correlation parameters, are studied and discussed based on numerical results and comparisons. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel digital predistorter technique using an adaptive neuro-fuzzy inference system

This letter presents a novel digital predistorter technique using an adaptive neuro-fuzzy inference system (ANFIS). The proposed approach employs real-time input and output signals of a nonlinear power amplifier as inputs to the ANFIS, so as to approximate the inverse functions of the power amplifier. The antecedent and consequent parameters of the FIS constructed by the ANFIS are tuned using backpropagation and least squares algorithms. Simulation shows that this novel technique has improved the linearity of a WCDMA signal by a further 4 dBc compared to a conventional look-up table (secant) approach. Moreover, this proposed technique is capable of adapting to instantaneous variation in the power amplifier response through time, which is a topic often omitted by researchers in this area.     

An adaptive hierarchical control approach of vehicle handling stability improvement based on Steer-by-Wire Systems

This paper proposes a novel adaptive hierarchical control approach for Steer-by-Wire (SbW) vehicles to improve the handling stability. The high-level stability control scheme contains a variable steering ratio (VSR) strategy based on the adaptive-network-based fuzzy inference system (ANFIS) and an active front steering (AFS) controller designed with the integral sliding mode method by tracking the expected yaw rate, in which the desired front wheel angle is generated to enhance the cornering stability performance. Besides, an adaptive tracking controller (ATC) for the SbW system is designed by using the adaptive sliding mode control method to achieve desired steering performance in the lower level. The proposed adaptive control strategy is validated with different driving circles from ISO standards in simulation tests and hardware-in-the-loop (HiL) experiments. The results demonstrate that the designed control approach improve the vehicle handling stability significantly, even in some extreme driving conditions.     

Performance analysis of equal-gain diversity receivers over generalized Gamma fading channels

Generalized Gamma (GG) distribution is a generic model that covers many well-known fading distributions as special cases. This paper deals with the performance analysis of L-branch equal gain combining (EGC) receivers operating over GG fading channels. For these receivers and by using convergent infinite series approach, the probability of error (P_e) can be formulated in the form of an infinite series. The coefficients of P_e series can be derived by calculating complicated integrations over the fading envelope distribution. In this paper, it is shown that the required integrations for the case of GG distribution have a complex closed-form in terms of Meijer's G function, and then, a new approximation method is developed for computation of them. The proposed method only needs mean and variance of the fading envelope; hence it has low complexity and eliminates the need for calculation of complex functions. The presented numerical examples show that the developed method can approximate the required parameters and also the individual coefficients accurately and this accuracy increases with the increase of L. The proposed method is applied to analyze the probability of error performance of the L-branch EGC receiver with both coherent phase shift keying (CPSK) and frequency shift keying (CFSK) modulation schemes under different GG channel conditions. Also the effect of gain unbalance between diversity branches on the probability of error is investigated.     

On-line parameter identification of SPM motors based on MRAS technique

This article proposes a new parameter estimation method for surface-mounted permanent magnet (SPM) motors by employing the model reference adaptive system (MRAS) technique. The proposed algorithm is applied to an SPM motor used in washing machines. To determine washing and dewatering patterns, a washer tries to detect the size of load in the beginning of the operation. Hence it requires an accurate estimation of system parameters. The proposed estimation method identifies stator inductance and flux-linkage by using d- or q-axis current error, and its value is used for estimation independently with respect to each parameter. Therefore, the proposed scheme can get rid of the instability in inductance and flux estimation caused by the cross-coupling between d- and q- quantities. In this article, the stator resistance is detected by using the recursive least square (RLS) method to reduce measurement noises and to eliminate dead-time effect. Simulation results show that the proposed scheme tracks the parameters well even when there is transient states in rotor speed and the load conditions, and experimental results verify the validity and efficacy of the proposed algorithm.     

Synthesis of Homogeneously Alloyed Cu2−x(SySe1−y) Nanowire Bundles with Tunable Compositions and Bandgaps

Bundles of homogeneously alloyed Cu_2?x(S_ySe_1?y) nanowires with various compositions (0 ≤ y ≤ 1) are controllably prepared via a simple water‐evaporation method under mild conditions. It is found that the nanowire bundles have similar copper contents (0.37 ≤ x ≤ 0.44) and morphologies, and the same face centered cubic (fcc) crystal structure and growth orientation of [110] over the entire composition range of y. To the best of the authors' knowledge, this is the first report on cubic phased ternary Cu_2?x(S_ySe_1?y) compounds. It is found that lattice parameter of the Cu_2?x(S_ySe_1?y) compound changes linearly with the S content. It is also shown that the direct and the indirect bandgaps of the nanowires vary quadratically with the S content and have bowing parameters of 0.20 and 0.21 eV respectively. Energy‐gap‐tuning via compositional change is achieved for both the direct (1.48?1.87 eV) and the indirect (0.50?0.90 eV) bandgaps. The trends of lattice parameter and bandgap variations are consistent with those described by Végard's Law.     

Dynamic Power Saving Mechanism for 3G UMTS System

This paper investigates the power saving mechanism of Universal Mobile Telecommunications System (UMTS). UMTS discontinuous reception (DRX) is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer threshold t _I and the DRX cycle t _D . Analytic analysis and simulation model are proposed to study the optimal t _I and t _D selections that maximize the MS power saving under the given mean packet waiting time constraint. We also devise an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts the t _I and t _D values to enhance the performance of UMTS DRX. Our study quantitatively shows how to select the best inactivity timer and DRX cycle values for various traffic patterns. We also show that DDRX nicely captures the user traffic patterns, and always adjusts the t _I and t _D close to the optimal values.