Modeling differential via holes

In this paper, we present a method to characterize differential via holes in printed circuit boards in a both fast and accurate way. The via hole is modeled as a cascade of capacitances and inductances. We use FASTCAP to compute the values of the capacitances, and a closed form formula to obtain the inductance values. The numerical predictions are compared with experimental data     

System failure-frequency analysis using a differential operator

A method for obtaining the failure frequency of any system whose structure function is coherent is introduced. The relationship of the availability to the failure frequency can be expressed as a unique differential operator. In this way, regardless of the form of expression, the failure frequency can be obtained by applying the differential operator to the availability expression. Some reduction techniques are shown to be useful in evaluating failure frequency by means of this differential operator. If the reduction formulas are approximate rather than exact, it is generally difficult to apply the operator. This operator is tested on a special type of approximate reduction (the quadrilateral-star transformation). A numerical example for this reduction is presented     

Prediction of short cardiovascular variability signals based on conditional distribution

A new approach measuring the predictability of a process is proposed. The predictor is defined as the median of the distribution conditioned by a sequence of L - 1 previous samples (i.e., a pattern). A function referred to as the corrected mean squared predictor error is defined to prevent the perfect adequacy to the data (i.e., the decrease to zero of the prediction error), thus avoiding to divide the whole set of data in learning and test sets. This function exhibits a minimum and this minimum is taken as a measure of predictability of the series. The use of the minimization procedure avoids to fix a priori the pattern length L. This approach permits one a reliable measure of predictability on short data sequences (around 300 samples). Moreover, this method, in connection with a surrogate data approach, is useful to detect nonlinear dynamics. The analysis indicates that, in simulated and real data, predictability and nonlinearity measures provide different information. The application of this approach to the analysis of cardiovascular variability series of the heart period (RR interval) and systolic arterial pressure (SAP) shows: 1) SAP series is more predictable than RR interval series; 2) predictability of the RR interval series is larger during tilt, during controlled respiration at 10 breaths/min (bpm) and after high-dose administration of atropine; 3) SAP series is dominated by linear correlation; 4) RR interval series exhibits nonlinear dynamics during controlled respiration at 10 bpm and after low-dose administration of atropine, while it is linear during sympathetic activation produced by tilt and after peripheral parasympathetic blockade caused by high-dose administration of atropine.     

Active all-pass filter using a differential operational amplifier

A circuit is presented for a first-order active all-pass filter using a single differential operational amplifier. The form of the transfer function is T(p) = (1 ? p)/(1 + p).     

Synchronized per survivor MLSD receiver using a differential Kalmanfilter

A synchronized per survivor processing (PSP) maximum likelihood sequence detection (MLSD) receiver is presented for a fast frequency-selective Rayleigh fading channel and large carrier frequency offset. It is shown that, by incorporating the synchronization parameters (the timing error, carrier frequency and phase offsets) into the channel-impulse response (CIR) and modifying the resulting state-space model by a differential approach, the time-varying carrier frequency offset can be effectively tracked using a simple least mean square (LMS) estimator. New criteria are proposed based on the smoothness of the estimated channel derivatives. New criteria are proposed based on this fact that, for smoothly time-varying CIR and frequency offset, the magnitude of the CIR time derivative compared with the magnitude of CIR should be very small. It is illustrated that the new criteria and the conventional mean square error (MSE) are complementary     

Resistive RAM variability monitoring using a ring oscillator based test chip

Common problems with Oxide-based Resistive Random Access Memory (so-called OxRRAM) are related to high variability in operating conditions and low yield. Although research has taken steps to resolve these issues, variability remains an important characteristic for OxRRAMs. In this paper, a test structure consisting of an OxRRAM matrix where each memory cell can be configured as a ring oscillator is introduced. The oscillation frequency of each memory cell is function of the cell resistance. Thus, the test structure provides within-die accurate information regarding OxRRAM cells variability. The test structure can be used as a powerful tool for process variability monitoring during a new process technology introduction but also for marginal cells detection during process maturity.     

Modeling three-dimensional scatterers using a coupled finiteelement-integral equation formulation

Finite-element modeling has proven useful for accurately simulating scattered or radiated fields from complex three-dimensional objects whose geometry varies on the scale of a fraction of a wavelength. To practically compute a solution to exterior problems, the domain must be truncated at some finite surface where the Sommerfeld radiation condition is enforced, either approximately or exactly. This paper outlines a method that couples three-dimensional finite-element solutions interior to a bounding surface with an efficient integral equation solution that exactly enforces the Sommerfeld radiation condition. The general formulation and the main features of the discretized problem are first briefly outlined. Results for far and near fields are presented for geometries where an analytic solution exists and compared with exact solutions to establish the accuracy of the model. Results are also presented for objects that do not allow an analytic solution, and are compared with other calculations and/or measurements     

Modeling accuracy of a fiber-optics test bed using MGF method

The absolute accuracy of modeling a high bit rate optical transmitter-receiver test-bed by using moment generating functions is investigated with extensive system measurements and component characterizations. We achieved a 0.5-dB average optical signal-to-noise ratio accuracy for a 10-Gb/s return-to-zero fiber-optics test bed. The methodology shown here can be very useful for both efficient and accurate component or system engineering.     

A fully differential LC-VCO using a new varactor control structure

This paper presents a fully differential inductor-capacitor voltage-controlled oscillator (LC-VCO) with a new differentially-tuned varactor structure. The proposed LC-VCO has lower phase noise and better robustness to the injected common-mode noise than the differentially-tuned LC-VCO using the previous antiparallel structure. The LC-VCO implemented using 0.5-/spl mu/m SiGe BiCMOS technology is tunable from 4.251 to 4.428 GHz and the measured phase noise is -119 dBc/Hz at 1-MHz offset over the entire tuning range. Its core current is only 1.7 mA at 2.5-V supply voltage.     

Simulated inductors using differential amplifiers

A novel circuit for the simulation of high-quality inductors is described. The circuit is based on differential amplifiers and can use standard integrated circuits; in initial tests, it has given very large effective inductances with high Qfactors at very low frequencies.     

Modeling inefficiencies in a reliability system using stochastic frontier regression

For some reliability systems, it is possible to have the system reliability smaller than the reliability obtained using the configuration of the components. This may be due to the inefficiency of the system. By inefficiency, we mean any tendency or attribute that will bring down the performance of the system from the level the configuration is capable of or expected to provide or designed for. This sets a maximum limit (or frontier) for the performance of the system. Therefore, deviation of the observed level from this limit would then be an indicator of the inefficiency. In this paper, we have made an attempt to model inefficiencies in the working of a reliability system, and to define an inefficiency index. The paper discusses the practical estimation of the coefficient of inefficiency in the system performance. The stochastic frontier regression methods are used to estimate the inefficiency. The validity of the methodology has been assessed for an exponential model, using a limited simulation study. The inefficiency indices proposed in this paper are simple, as they must be to be useful to engineers. We found that the suggested indices & their estimation procedures work well.     

High-speed GaAs dynamic frequency divider using a double-loopstructure and differential amplifiers

GaAs 2.0-8.0-GHz and 6.0-10.5-GHz dynamic frequency dividers have been developed. These dynamic dividers have a double-loop structure using a differential amplifier for high-speed and stable operation despite supply-voltage fluctuations. This structure operates from a single voltage supply. An advanced WSi self-aligned gate process technology (0.1-μm long gate) was used to improve the high-frequency characteristics of the FET     

A fully differential comparator using a switched-capacitordifferencing circuit with common-mode rejection

A fully differential comparator is described. It uses a switched-capacitor differencing circuit that provides common-mode rejection. The comparator has been tested by building a 3-b flash analog-to-digital converter (ADC) in a 2-μm CMOS process. With a supply voltage of 3.3 V, a sampling rate of 25 MHz, and full-scale sinusoidal inputs up to 7 MHz, the signal-to-distortion ratio of the ADC when the input is single ended is about 1-2 dB less than when the input is differential. In a 2-μm CMOS process, the comparator occupies 0.25 mm² and dissipates 1.05 mW     

Modeling video traffic using wavelets

In this letter we establish a wavelet model for video traffic. Different from the existing methods which model the video traffic in the time domain, we model the wavelet coefficients in the wavelet domain. The strength of the wavelet model includes: (1) an unified approach to model both the long-range and the short-range dependence in the video traffic simultaneously; (2) a computationally efficient method for developing the model and generating high quality video traffic; and (3) feasibility of performance analysis using the model     

Modeling and analysis of stochastic differential equations driven by point processes

The modeling and analysis of nonlinear systems described by differential equations driven by point process noise are considered. The stochastic calculus of McShane is generalized to include such differential equations, and a more general canonical extension is defined. It is proved that this canonical extension possesses the same desirable properties for point process noise that it does for the noise processes, such as Brownian motion, considered by McShane. In addition, a new stochastic integral with respect to a point process is defined; this alternative integral obeys the rules of ordinary calculus. As a special case of the analysis of such systems, linear systems with multiplicative point process noise are investigated. The consistency of the canonical extension is studied by means of the product integral. Finally, moment equations and criteria for the stochastic stability of linear systems with multiplicative Poisson noise are derived.     

Active all-pass filter using differential amplifier

The relationship between a recently described active all-pass filter using a differential amplifier and one described in an earlier paper is discussed. A method of using either circuit to produce an all-pass function of any degree is also indicated.     

Modeling and investigation of a geometrically complex UWB GPR antenna using FDTD

A detailed analysis of ultrawide-band (UWB), dual-polarized, dielectric-loaded horn-fed bow-tie (HFB) antennas is carried out using the finite-difference time-domain (FDTD) method. The FDTD model includes realistic features of the antenna structure such as the feeding cables, wave launchers, dielectric loading, and resistive-film loading. Important antenna characteristics that are usually difficult to obtain via measurements can be obtained more directly from this FDTD model. Since the HFB antennas under consideration are intended for ground penetrating radar (GPR) applications, the effects of the half-space medium are also investigated. The simulated results serve to verify the performance of the HFB antenna design, and to optimize various antenna parameters.