Photosensitivity and Scanning of Silicon Image Detector Arrays

The first part of this paper deals with the basic photodiode unit, its principle of operation, and the factors that affect the photodiode and array sensitivity. Experimental results of the planar Si p/sup +/-n photodiode are presented. Design and layout considerations including the integration time are also given. The second part of this paper deals with scanning of photodiode arrays. Detail design considerations are given for a static MOST ring counter. A dynamic shift register with clocked loads for integral scanning is also considered. Design considerations of a realized photosensing matrix with integral scanning are given. Finally, scanning problems of large arrays are briefly considered.     

The IFR/DFR property of the forward recurrence-time distribution

When a failure or replacement process is modeled as a renewal process, the residual life of the unit in use at a given time is generally referred to as the forward recurrence time (RT). Distributional properties of this random variable are critically important in many applications. This paper investigates the extent to which the failure-rate function monotonicity of a life distribution is inherited by the forward RT distribution at time s of its renewal process. For DFR life distributions, the forward RT distribution is also DFR for every s⩾0. However, the corresponding property does not necessarily hold for IFR life distributions. The forward RT distribution is IFR in the limit as s→0 and as s→∞. For IFR Weibull life distributions, we demonstrate numerically that the forward RT distribution is IFR for small s. As s is increased, it alternates between being IFR and non-IFR in an interesting cyclical pattern, and remains IFR beyond a large enough s     

Increasing the clock frequency of switched-capacitor filters

The time constant ? of a switched-capacitor (s.c.) integrator is C/(fcCR), where CR is the value of the s.c., C the integrating capacitor and fc the clock frequency. For a given ?, if fc is to increase, C/CR must increase proportionately. Since a large capacitor ratio C/CR is inconvenient to implement in an integrated circuit, most s.c. filters are clocked at the Nyquist rate. Since higher clock rates reduce switching delays, a technique of enabling higher clock frequencies without the need for large capacitor ratios has been developed.     

Analysis of the threshold characteristics of the uniform Josephsonflux shuttle

A general method for calculating the mode boundaries of a uniform flux shuttle and numerical techniques for computing these thresholds are presented. A number of examples of practical interest are given, including the current distribution in a shuttle due to a single vortex, and static margins of directly injected two-phase shift registers and magnetically clocked three-phase shift registers. Comparison with dynamic circuit simulations shows that the static thresholds are good approximations over a wide range of junction parameters     

New single-clock CMOS latches and flipflops with improved speed andpower savings

New dynamic, semistatic, and fully static single-clock CMOS latches and flipflops are proposed. By removing the speed and power bottlenecks of the original true-single-phase clocking (TSPC) and the existing differential latches and flipflops, both delays and power consumptions are considerably reduced. For the nondifferential dynamic, the differential dynamic, the semistatic, and the fully static flipflops, the best reduction factors are 1.3, 2.1, 2.2, and 2.4 for delays and 1.9, 3.5, 3.4, and 6.5 for power-delay products with an average activity ratio (0.25), respectively. The total and the clocked transistor numbers are decreased. In the new differential flipflops, clock loads are minimized and logic-related transistors are purely n-type in both n- and p-latches, giving additional speed advantage to this kind of CMOS circuits     

Failure Time for a Redundant Repairable System of Two Dissimilar Elements

The distribution of time to failure for a system consisting of two dissimilar elements or subsystems operating redundantly and susceptible to repair is discussed. It is assumed that the times to failure for the two system elements are independent random variables from possibly different exponential distributions, and that the repair times peculiar to each element are independently distributed in an arbitrary fashion. For this basic model a derivation is given of the Laplace-Stieltjes transform of the distribution function of time to system failure, i.e, the time until both elements are simultaneously down for repair, measured from an instant at which both are operating. An explicit formula is given for the mean or expected time to system failure, a natural approximation to the latter is exhibited, and numerical comparisons indicate the quality of this approximation for various repair time distributions. In a second model the possibility of system failures due to overloading the remaining element after a single element failure is explicitly recognized. The assumptions made for the basic model are augmented by a stochastic process describing the random occurrence of overloads. Numerical examples are given. Finally, it is shown how the above models may be easily modified to account for delays in initiating repairs resulting from only occasional system surveillance, and to account for random catastrophic failures.     

The Distribution of Sums of Path Gains in the IEEE 802.15.3a UWB Channel Model

When multipath arrival times and gains are specified by the IEEE 802.15.3a ultra-wideband (UWB) channel model, formulas are derived for the characteristic function of the sum of gains arriving in a given time window. These formulas are first used to determine structural properties of the corresponding distributions and densities. The formulas are then used to compute the distribution and density functions by numerically inverting the characteristic function. For small time windows, the densities of the path-gain sums are bimodal and therefore highly non-Gaussian     

Analysis and Parameterization of Methodologies for the Conversion of Rain-Rate Cumulative Distributions from Various Integration Times to One Minute

The conversion of rain-rate cumulative distributions from any integration time, T, to one minute is a viable option whenever local one-minute data (time series or cumulative distribution functions) are not available for microwave system design. This paper reviews some of the most common rain-rate cumulative-distribution conversion methods. For selected models, it provides a complementary set of coefficients for regional and global application by performing regression to a measurements database. The performance of each model is analyzed, together with its adaptability to various climatic regions. Finally, recommendations with regard to the global applicability of models are given.     

Preparation of loading information for reliability simulation

Many decisions regarding the design with a system using sockets are made using a point estimate (often from a standard or accepted practice) of the compressive load. The components of a CLGA assembly were analyzed using Monte Carlo simulation methods to determine the distribution of the compressive loads that are applied to the component socket. The components of the assembly that impact the resulting load were identified and their individual distributions defined. The relationship between the height of the components and the compression provided by the springs was determined and used to estimate a load distribution. The load distribution thus estimated can be used as an input to further virtual qualification efforts. For example, the estimated load distribution from this analysis was used with other manufacturing parameters and FEA models to estimate the IC socket contact compression. The results showed that the minimum compression required for a good electrical contact was achieved over 99.9% of the time. Therefore, information that is obtained from virtual qualification was shown to be of great value in the determination of proper test conditions and design decision making.     

Clocked molecular quantum-dot cellular automata

Quantum-dot cellular automata (QCA) is an approach to computing that eliminates the need for current switches by representing binary information as the configuration of charge among quantum dots. For molecular QCA, redox sites of molecules serve as the quantum dots. The Coulomb interaction between neighboring molecules provides device-device coupling. By introducing clocked control of the QCA cell, power gain, reduced power dissipation, and computational pipelining can be achieved. We present an ab initio analysis of a simple molecular system, which acts as a clocked molecular QCA cell. The intrinsic bistability of the molecular charge configuration results in dipole or quadrupole fields that couple strongly to the state of neighboring molecules. We show how clocked control of the molecular QCA can be accomplished with a local electric field.     

Time distribution characteristics of cat-eye reflected light from moving optical target

By using the Collins diffraction formula and expanding the aperture function into a finite sum of complex Gaussian functions, an analytical formula of the time light intensity distribution for oblique Gaussian beams passing through a moving cat-eye optical lens and going back along the entrance way is deduced.By numerical computation,the variation laws of the time intensity distributions of the cat-eye reflected light with the viewing angle,imaging distance,aperture and instantaneous field of view are given.The results show that the relationship between the light intensity at the return place and the detection time is linear,and it is of inverse proportion only when the viewing angle is very large.For the staring imaging optical lens, the nonlinear extent of the time distribution curve becomes larger with the decrease of the viewing angle.For the instanta- neous imaging optical lens,there is still some cat-eye reflected light when the detection system is out of the viewing field of the target lens.     

Pulse Regeneration in the Gigabit-Per-Second Range Using a Diode Differential Regenerator

A clocked pulse regenerator circuit (diode differential regenerator (DDR)) is described which employs a modified hybrid tee, step recovery diodes, and bipolar transistors. For the first time a hybrid tee is used in ultra broad-band digital applications. Signal pulses with bit rates up into the gigabit-per-second range are regenerated, the shape of the input pulses having no direct influence on the shape of the output pulses. Only the charge of the input signals determines the amplitudes of the output pulses. At a signal bit rate of 1 Gbit/s an insertion voltage gain of 20 dB was obtained. Operating the DDR in a push-pull mode the voltage gain is doubled to 26 dB. Because the output pulses of the DDR are very narrow the circuit can be used in time-division multiplexers providing output pulse streams with bit rates up to 16 Gbit/s and amplitudes of several volts across a load of 50 Omega. The internal behavior of the DDR is analyzed, among other things by the results of computer simulations. Calculations for optimizing the employed components are given.     

The superposition of periodic cell arrival streams in an ATMmultiplexer

The authors consider the queue arising in a multiservice network using ATM (asynchronous transfer mode) when a superposition of periodic streams of constant-length cells is multiplexed on a high-speed link. An exact closed formula is derived for the queue length distribution in the case where all streams have the same period, and tight upper and lower bounds are obtained on this distribution when the periods are different. Numerical results confirm that the use of a Poisson approximation (i.e. the M/D/1 queue) can lead to a significant overestimation of buffer requirements, particularly in the case of heavy loads. Buffer requirements for a mixture of different period streams can be accurately estimated from the upper bound on the queue length distribution. For given load, requirements increase with the number of long-period (i.e. low-bit rate) sources. The results are deduced from a novel characterization of the single-server constant service time queue, which should be useful in other applications     

Applying Bayesian mixtures-of-experts models to statistical description of smart power semiconductor reliability

Reliability prediction of semiconductor devices gains importance, since demand increases and resources, e.g. time, are restricted. Normally, methods focusing on technology aspects are applied. This work presents a more mathematical approach by using Bayesian statistics. Physical failure inspection and past research indicate that the data follow a bimodal distribution. Therefore, we suggest using a heteroscedastic mixture of two normal distributions to model the given data. To incorporate the dependency on different test settings, linear models are used for the means and the mixing proportion. Gamma distributions are proposed as priors for the model parameters, due to the physical restrictions concerning the sample space. For the variances hierarchical inverse gamma priors are applied. Sampling from the posterior is done by using Monte Carlo Markov Chain methods. The proposed mixtures-of-experts model shows good adaption to the behavior of the measurements as well as good prediction quality.     

Time-Interleaved Multirate Sigma–Delta Modulators

A time-interleaved (TI) implementation of multirate sigma-delta modulators (SDMs) is proposed. In multirate SDMs, the first integrator is clocked at a rate that is lower than that of the rest of the integrators. In the proposed architecture, each integrator clocked at a high rate is replaced by two parallel integrators operating in interleaved mode and clocked at the same low rate as the first one. The new architecture has several nice features. First, every integrator operates at the same low rate, which simplifies the clock circuitry when compared to the original multirate modulator. Second, there are no delayed cross paths, which is typical of TI-SDMs. Third, no high-rate sample-and-hold at the input of a TI-SDM is required. Finally, as time interleaving is not applied to the first integrator, the proposed modulator is robust against circuit mismatches, unlike other TI architectures. The same strategy can be applied to continuous time (CT) modulators. To the authors' knowledge, this is the first TI-CT-SDM ever reported     

An application of informational divergence to Huffman codes

A classification of all probability distributions over the finite alphabet of an information source is given, where the classes are the sets of distributions sharing the same binary Huffman code. Such a classification can be used in noiseless coding, when the distribution of the finite memoryless source varies in time or becomes gradually known. Instead of applying the Huffman algorithm to each new estimate of the probability distribution, if a simple test based on the above classification is passed, then the Huffman code used previously is optimal also for the new distribution.     

Theory of a multiply fed and loaded insulated linear antenna in air

Analytic expressions are derived for the input admittance and the current distribution along the multiply fed and loaded insulated antenna in air which is excited across feed gaps of nonzero widths. The Wiener-Hopf type analysis for a center fed insulated antenna is combined with the axial field discontinuity (AFD) method to develop the current and admittance expression. This AFD method considers the metallic surface of the linear antenna as a series combination of longitudinal, electric-field surface functions that exist due to feeding and/or loading. The analysis, which does not employ superposition of even and odd distributions of sources and loads, yields final expressions in terms of the excitation location, its aperture electric field within the feed gaps, impedance locations, and their values. The current distribution for cases of unity dielectric constant shows an excellent agreement with data based on the moment method. The input admittances and current distributions are reported for different multiple excitations and loads and dielectric constants of the insulator     

The Effect of the System Specification on the Optimal Selection of Clocked Storage Elements

This paper represents a departure from the conventional methods of design and analysis of clocked storage elements that rely on minimizing a fixed energy-delay metric. Instead it establishes a systematic comparison in the energy-delay design space based on the parameters of the surrounding blocks. We define the composite energy-efficient characteristic over all storage element topologies and identify the most efficient storage element depending on its position on the composite characteristic relative to other topologies within a pipeline stage. Thus, we show that an optimal design could use a mixed variety of clocked storage elements (CSEs) depending on their placement in the pipeline and critical path. Since a well-designed system has hardware intensities balanced for a given cycle, a CSE choice will be made depending on the pipeline and path intensities. We show that a meaningful comparison can be carried out only by acknowledging that the optimal design and choice of the clocked storage elements depends heavily on the application, and by analyzing the energy and delay of the clocked storage elements in context of this application. The analysis in the energy-delay space allows us to understand some intuitive design choices in a quantitative way and to identify the optimal storage element topologies for an arbitrary system specification     

Higher Order Nested Wigner Distributions: Properties and Applications

The concept of Wigner distribution (WD) is extended to higher-order nested Wigner distributions. The nested ambiguity function (NAF) is also derived naturally by employing the known interrelation between the WD and the ambiguity function (AF). These distributions are obtained by nesting a function within itself a number of times. The definitions of these new multidimensional distributions are given in analogy to the standard first-order 2-D distributions in both temporal/spatial and spectral forms and follow the definitions of quartic distributions presented in and . Some important properties are derived and discussed, including interrelationships between the various representations, marginals, correlations, and uncertainties, as well as their geometrical characteristics. The second-order nested Wigner distribution (NWD) is used to showcase the power of such distributions in potential application areas, such as signal estimation, signal separation, and radar signal analysis. For such signal processing tasks, it is demonstrated that the NWDs can be successful in situations where the standard 2-D distributions have proved to be inadequate