Showing papers by "Philips published in 1984"

Short-circuit dissipation of static CMOS circuitry and its impact on the design of buffer circuits

Abstract: A simple formula is derived for quick calculation of the maximum short-circuit dissipation of static CMOS circuits. A detailed discussion of this short-circuit dissipation is given based on the behavior of the inverter when loaded with different capacitances. It was found that if each inverter of a string is designed in such a way that the input and output rise and fall times are equal, the short-circuit dissipation will be much less than the dynamic dissipation (<20%). This result has been applied to a practical design of a CMOS driving circuit (buffer), which is commonly built up of a string of inverters. An expression has also been derived for a tapering factor between two successive inverters of such a string to minimize parasitic power dissipation. Finally, it is concluded that optimization in terms of power dissipation leads to a better overall performance (in terms of speed, power, and area) than is possible by minimization of the propagation delay.

Monte Carlo study of the isotropic and nematic phases of infinitely thin hard platelets

Abstract: We present the results of a detailed Monte Carlo study of the phase diagram of infinitely thin hard platelets. A weak first order isotropicnematic transition is observed. The equation of state in the isotropic regime is compared with several current theories, none of which is found to be fully satisfactory. The density dependence of the nematic order parameter is found to be compatible with a ‘critical’ exponent β=0·25. A study of the fluctuations of the order parameter in the isotropic phase casts doubt on the applicability of the Landau-de Gennes expression for the free energy. We observe that the relation between the nematic order parameters and is compatible with the predictions of mean-field theory. Practical aspects of the computation are discussed. A novel method to compute the pressure in a constant-volume Monte Carlo run is presented.

Critical behavior of two-dimensional spin models and charge asymmetry in the Coulomb gas

Abstract: Many two-dimensional spin models can be transformed into Coulomb-gas systems in which charges interact via logarithmic potentials. For some models, such as the eight-vertex model and the Ashkin-Teller model, the Coulomb-gas representation has added significantly to the insight in the phase transitions. For other models, notably theXY model and the clock models, the equivalence has been instrumental for almost our entire understanding of the critical behavior. Recently it was shown that theq-state Potts model and then-vector model are equivalent to a Coulomb gas with an asymmetry between positive and negative charges. Fieldlike operators in these spin models transform noninteger charges and magnetic monopoles. With the aid of exactly solved models the Coulombgas representation allows analytic calculation of some critical indices.

High voltage semiconductor device

Abstract: A field effect transistor, a bipolar transistor, a PIN diode, a Schottky rectifier or other high voltage semiconductor device comprise a semiconductor body having a depletion layer formed throughout a portion in at least a high voltage mode of operation of the device, such as, by reverse biasing a rectifying junction. The known use of a single high-resistivity body portion of one conductivity type to carry both the high voltage and to conduct current results in a series resistivity increasing approximately in proportion with the square of the breakdown voltage. This square-law relationship is avoided by the present invention in which a depleted body portion comprising an interleaved structure of first and second regions of alternating conductivity types carries the high voltage which occurs across the depleted body portion. The thickness and doping concentration of each of these first and second regions are such that when depleted the space charge per unit area formed in each of these regions is balanced at least to the extent that an electric field resulting from any imbalance is less than the critical field strength at which avalanche breakdown would occur in the body portion. The first regions in at least one mode of operation of the device provide electrically parallel current paths extending through the body portion.

The use of a one-stage dynamic programming algorithm for connected word recognition

Abstract: This paper is of tutorial nature and describes a one-stage dynamic programming algorithm for file problem of connected word recognition. The algorithm to be developed is essentially identical to one presented by Vintsyuk [1] and later by Bridle and Brown [2] ; but the notation and the presentation have been clarified. The derivation used for optimally time synchronizing a test pattern, consisting of a sequence of connected words, is straightforward and simple in comparison with other approaches decomposing the pattern matching problem into several levels. The approach presented relies basically on parameterizing the time warping path by a single index and on exploiting certain path constraints both in the word interior and at the word boundaries. The resulting algorithm turns out to be significantly more efficient than those proposed by Sakoe [3] as well as Myers and Rabiner [4], while providing the same accuracy in estimating the best possible matching string. Its most important feature is that the computational expenditure per word is independent of the number of words in the input string. Thus, it is well suited for recognizing comparatively long word sequences and for real-time operation. Furthermore, there is no need to specify the maximum number of words in the input string. The practical implementation of the algorithm is discussed; it requires no heuristic rules and no overhead. The algorithm can be modified to deal with syntactic constraints in terms of a finite state syntax.

The influence of feedback intensity on longitudinal mode properties and optical noise in index-guided semiconductor lasers

Abstract: Theory and experiments on optical feedback effects in index-guided single-mode semiconductor lasers are presented. Evidence is found for the existence of a characteristic parameter C which indicates the relative strength of the optical feedback. Near the transition ( C \approx 1.0 ) from low to high feedback, the feedback-induced low-frequency intensity noise shows a maximum. At higher feedback hysteresis and instabilities are dominant, whereas the feedback-induced noise is low again.

Spread spectrum radio transmission system

Abstract: A communications system wherein an intelligence signal modulates the spacing of relatively narrow pulses of a fixed rate pulse train, and these pulses key on a transmitter which employs a pair of series connected avalanche mode operated transistors. These are repetitively powered via a charged coaxial delay line, and the output, appearing across a resistive load, is fed directly, or through a shaping filter, to a discone transmitting antenna. At a receiving location, the received signal is amplified by a wide band amplifier and fed through a reverse contoured filter (of the transmitting filter, if one is employed). The signal is detected via synchronous detection which locks onto the received pulse train, after which the modulation evidence by the pulse train is recovered by a low pass filter.

Short-range order and thermal stability in amorphous alloys

Abstract: Amorphous alloys of the types Zr1-xNix, Zr1-xCox, Zr1-xFex and Zr1-xCux were prepared by melt-spinning and studied by means of differential scanning calorimetry and X-ray diffraction. The crystallisation temperatures (Tx) and the activation energies for crystallisation ( Delta E) were determined. The former values were found to vary only slightly with concentration while the latter show a marked concentration dependence, which is particularly pronounced in Zr1-xNix. The occurrence of compositional short-range ordering (CSRO) in amorphous systems is discussed with respect to its consequences for the hole model proposed earlier. It is shown that the predictions of the hole model are only slightly affected by the occurrence of CSRO, owing to a gross cancellation of the effects of a decreasing hole formation enthalpy and decreasing configuration entropy. The relatively strong temperature dependence of the configurational entropy expected for alloy compositions with strong CSRO leads to an increase in the experimental values of the apparent activation energies. From the concentration dependence of the experimental activation energies indications can be obtained about the concentration dependence of CSRO. It appears that the regions with a maximum CSRO do not, in general, correspond to the concentrations at which intermetallic compounds occur, nor do they correspond in all cases to regions located around the deepest eutectic composition.

Model Studies with the Inversely Calculated lsochrones of Ventricular Depolarization

Abstract: This paper describes experimental studies on the influence of inhomogeneities in the volume conductor, and model errors and measurement errors on the inversely calculated isochrones of ventricular depolarization. The results indicate that in the inverse problem the use of inhomogeneous models is essential, that knowledge of the exact heart geometry (shape and orientation) is important, and that signal error (noise) as encountered in normal ECG recordings is not critical. The number of (measurement) leads required is found to be on the order of 64.

Hydrodynamics of small tubular pumps

Abstract: Miniature tubular pumps are used to emit droplets from ink-jet matrix heads. This paper deals with the simulation of the behaviour of a viscous and compressible liquid in such pumps. The response of the liquid in the frequency and time domain is analysed.An approximate method is given to determine the droplet speed and size.

Multiple access communications system

Abstract: A multiple-access communications system for an unlimited user population wherein a system controller continuously transmits Aloha signals on a slot-by-slot basis giving an updated number of time slots available whereby a calling party can select any one of the designated time slots at random. The calling party checks the time slot immediately preceding its selected time slot to ascertain if the current Aloha number is zero (or an equivalent thereof). If it is zero then the calling party reverts to listening for a time slot containing an Aloha number greater than zero. Alternatively if it is not zero the calling party apparatus sends a signal to the system controller in its selected time slot. Multipurpose signalling in each time slot can be carried out by the system controller thereby reducing the overhead on the system and speeding-up the setting-up of calls which may be off-air or non off-air.

Transdermal dosimeter and method of use

Abstract: A transdermal dosimeter, a device used to monitor exposure to chemical agents is disclosed. The device is attached to the skin surface and functions by causing the uptake of compounds that are excreted through the skin.

Dynamic RHEED observations of the MBE growth of GaAs

Abstract: Detailed measurements have been made of the specular beam intensity in RHEED patterns from static and growing GaAs surfaces. The basic parameters investigated were substrate temperature and electron beam azimuth. The results have provided further understanding of growth dynamics and surface disorder, respectively. There is a significant trend away from two-dimensional growth at the higher temperatures, which also correspond to more Ga-rich surface structures. Conversely, surface disorder is apparently greater during growth at the lower temperatures, where the structure is As-rich. The static As-stable 2×4 surface is, however, the most ordered and the most closely two-dimensional. It has also been shown that ordered, two-dimensional growth can be initiated from excess Ga adatom populations.

The densification of monolithic gels

Abstract: The densification of gels to glasses with composition SiO 2 and 8Al 2 O 3 92SiO 2 has been studied as a function of heat treatment between 120 and 1200°C using Raman spectroscopy together with measurements of density and specific surface area. Monolithic dry gels are prepared at 120°C. In the case of SiO 2 these have a density of 1.39 g/cm 3 , a specific surface area of 790 m 2 /g and a mean pore radius of 10 A. In the case of 8Al 2 O 3 92SiO 2 gels these values are 0.76 g/cm 3 , 535 m 2 /g and 50 A, respectively. The Raman spectra of monolithic dry SiO 2 gels, measured as a function of temperature, show that both surface and bulk SiOH groups are present. The relative concentration of these groups is temperature dependent. The total OH content decreases with increasing temperature. The combined results of Raman, density and specific surface area measurements show that during densification two, partly related, processes occur, viz. pore collapse and the condensation of surface SiOH groups to SiOSi bonds.

Connected components in binary images: The detection problem

Abstract: From the Publisher: Concerns the separation of objects from their background--a major problem in pattern recognition. This unique monograph outlines--down to the code level--an algorithmic approach to the real-time detection of connected components in binary pictures acquired in a raster-scan fashion.

Kinetic limitations to surface segregation during MBE growth of III–V compounds: Sn in GaAs

Abstract: The incorporation of Sn as a dopant in GaAs has been studied in the temperature range of 500°–650° C, over a wide range of Ga and As fluxes, the latter being incident as either As4 or As2 molecules. The results are explained in terms of a surface segregation model in which the behaviour at high growth temperatures (above ∼600 °C) approaches thermal equilibrium, but growth at lower temperatures involves a kinetic limitation to the segregation process.

Multi-pulse excitation linear-predictive speech coder

Abstract: A multi-pulse excitation linear-predictive speech coder operates in accordance with an analysis-by-synthesis method for determining the excitation. The coder (10) comprises an LPC-analyzer (11), a multi-phase excitation generator (13), means (12, 14) for forming an error signal representative of the difference between an original speech signal (s(n)) and a synthetic speech signal (s(n)), a filter (15) for perceptually weighting the error signal and means (16) responsive to the weighted error signal (e(n)) for generating pulse parameters controlling the excitation generator (13) so as to minimize a predetermined measure of the weighted error signal. The LPC-parameters and the pulse parameters of the excitation signal (x(n)) are encoded for efficient storage or transmission. The bit capacity required for pulse position encoding of the excitation signal (x(n)) is considerably reduced by arranging the excitation generator (16) for an excitation signal (x(n)) which in each excitation interval (L) consists of a pulse pattern having a grid of a predetermined number (q) of equidstant pulses and by arranging the control means (16) for generating pulse parameters characterizing the grid position (k) relative to the beginning of the excitation interval (L) and the variable amplitudes (bk (j), 1≦j≦q) of the pulses of the grid.

Signal generating device

Abstract: An X-Y signal generating device comprises two belts (11,11') extending between and around two pairs of rollers (12,13) and (12',13'). One band moves in the X-direction and one in the Y-direction, and one band is located inside the other. The rollers are mounted on a common block (14). Each band has a strengthened section (17,17') with a slot (18,18') in it. An actuating key (21) is located at the crossover point of the two slots and may be moved freely in any direction, within limits, causing proportionate movement of the two bands around the rollers. XY control signals can be derived independently from the movement of the bands. The XY control signals can be produced by providing the bands with combined resistive/conductive surfaces and using conductive rollers to pass a current through the bands.

A comparative study of methods for thin-film and surface analysis

Abstract: A number of features characteristic of different thin-film analytical methods are reviewed and evaluated. The principles, approach for quantification and prominent problems of the most commonly used methods (ESCA, AES, SIMS, LEIS, RBS and NRA) are discussed. Evaluation of the special advantages and disadvantages of the different methods points out the need for a synergetic multi-method approach in thin-film analysis.

Erasable magneto-optical recording media

Abstract: Magneto-optical storage techniques in amorphous metal films have the advantages of high bit density and contactless write, read and erasure operations. Digital information is stored as a sequence of small magnetic domains; writing and erasure is performed by local temperature rise (AlGaAs laser heating) in combination with a low external magnetic field. In principle, the number of switching cycles is unlimited. Non destructive readout is achieved via magneto-optical effects. Material and system aspects for erasable compact-disk audio application will be reviewed. Disks are vapour-deposited on pregrooved substrates. Binary and ternary alloys of Gd, Tb combined wlth Fe,Co are highly suitable, storage media. For practical use bi- and multilayer structures were used in order to improve the read-out efficiency and lifetime of the disk. Aging effects were studied by measurements of magneto-optical and magnetic properties and SIMS analysis during the lifetime of the disk. Current results of about 45 dB CNR (30 kHz bandwidth) and a lifetime for the disk of more than 5 years opens the discussion of applications in low- and high-density storage in professional and consumer fields.

Electrode configurations for an electrophoretic display device

Abstract: An electrophoretic display device is set forth having various electrode schemes in order to modulate transmission of light through the device. The electrophoretic particles of the suspension form an imaging structure relating to an array of small unit cells or pixels which are turned on or off by appropriate electrical signals. Accordingly, the pigment particles totally cover transparent electrodes, which condition can be changed by applying the appropriate electric field to the opposite electrode. By this structure, various alphanumeric displays can be constructed.

Generalized Tamed Frequency Modulation and Its Application for Mobile Radio Communications

Abstract: Continued investigation of tamed FM (TFM) has led to an extension called generalized tamed FM (GTFM). The very narrow spectral property of a GTFM signal meets the stringent requirements on bandwidth utilization in modern mobile radio applications. The principle of GTFM is first described. It is then shown that the generation of GTFM signals can be made very simple by the use of an ROM table-lookup technique. By an appropriate choice of parameters in GTFM signal generation at the transmitter, a joint optimization for coherent and noncoherent detection with regard to BER performance in the presence of additive white Gaussian noise can be achieved. For mobile radio applications, the robustness of the detection scheme to fast fading is important. A low-complexity noncoherent receiver is presented, Comprising a frequency discriminator and a simple maximum-likelihood sequence estimator. This receiver performs well in a fast fading environment. Computer simulated results of BER performance of this scheme are given. These results are confirmed by experimental measurements.