Showing papers by "Philips published in 1979"

The Vivaldi Aerial

Abstract: The Vivaldi Aerial is a new member of the class of aperiodic continuously scaled antenna structures and, as such, it has theoretically unlimited instantaneous frequency bandwidth. This aerial has significant gain and linear polarisation and can be made to conform to a constant gain vs. frequency performance. One such design has been made with approximately 10 dBI gain and ?20 dB sidelobe level over an instantaneous frequency bandwidth extending from below 2 GHz to above 40 GHz.

High voltage thin layer devices (RESURF devices)

Abstract: The application of a somewhat unusual diode structure opens the possibility to make novel kinds of high voltage devices even with very thin epitaxial or implanted layers. In the new structures crucial changes in the electric field distribution take place at or at least near the surface. The acronym RESURF (REduced SURface Field) was chosen.

Intermetallic compounds of rare earths and non-magnetic metals

Abstract: A review is given of the physical properties, composition and crystal structure of intermetallic compounds formed between rare-earth elements and non-magnetic metals, with emphasis on the magnetic properties. Included are the properties of compounds in which the non-rare-earth component is a 4d or 5d transition element. Special consideration is given to the properties of pseudo-binary compounds. Results of magnetisation measurements, neutron diffraction and neutron scattering are discussed together with results derived from NMR, ESR and Mossbauer effect spectroscopy. An evaluation is given of the relevance of the experimental results with respect to different types of exchange interactions in this class of intermetallics. Special consideration is also given to the influence of crystal field effects on the magnetic properties and, furthermore, to the occurrence of intermediate valences in several of the compounds of Ce, Sm, Eu and Yb.

The SIS tunnel emitter: A theory for emitters with thin interface layers

Abstract: Silicon n-p-n transistors are made with emitters consisting of a polycrystalline and monocrystalline region with a thin (20-60-A) "insulating" interfacial layer in between (SIS structure). These transistors show a remarkable increase in emitter efficiency with emitter Gummel numbers up to 7 × 1014s.cm-4, and a low positive or even negative temperature coefficient of the current gain. A model is proposed to explain the mechanism in terms of tunneling through the interfacial layer. The electrical characteristics are measured in the temperature range 290-415 K. From the measurements it is deduced that the tunnel probability for holes (P h ) is 10-2to 10-3and that for electrons (P e ) is >10-5. There also exists a band bending of 30-90 mV at the interfaces with the interfacial layer.

The structure of lithium, sodium and potassium germanate glasses, studied by Raman scattering

Abstract: Polarized and depolarized Raman spectra of alkali germanate glasses are given, together with Raman powder spectra of the crystalline compounds Li2O · 2 GeO2; 3 Li2O · 8 GeO2; 2 Li2O· 9 GeO2; Li2O · 7 GeO2; 2 Na2O · 9 GeO2; K2O · 2 GeO2; K2O · 4 GeO2 and K2O · 8 GeO2. The alkali germanate glasses: xA2O (1−x) GeO2 are studied in the composition range 0 < x < 0.333. The vibrational modes observed in the high energy range of the Raman spectra of the crystalline compounds are interpreted in terms of symmetrical and antisymmetrical O-Ge-O and Ge-O− stretch vibrations. The molecular structure of the germanate glasses is deduced from a comparison of the Raman spectra of the glasses with those of the crystalline compounds, together with a study of the polarization properties of the glass spectra. It is observed that 6-coordinated Ge atoms occur in a network structure which resembles the structures occurring in the crystalline compounds 2 Li2O · 9 GeO2 and 2 Na2O · 9 GeO2. In the region of 0.18 < x < 0.33 it is found that tetrahedra with one non-bridging oxygen atom are formed. These tetrahedra are probably present in a network as occurs in the crystalline digermanates Li2O · 2 GeO2 and K2O · 2 GeO2.

Multilayer information disc

Abstract: The invention relates to a multilayer information disc, in particular a video disc, which is read by laser light. The disc comprises at least two radiation-reflecting optical structures each having a relief-like information track of regions situated alternately at a higher and a lower level which is read in reflection and on the basis of phase differences. Each of the optical structures is covered with a reflection layer at least one of which partially transmits the reading radiation so that upon reading the other optical structure or structures, the radiation passes through the structure provided with the partially transmitting reflection layer. The coefficients of reflection of the various reflective layers are preferably matched to each other in a manner such that upon reading the same amount of light returns from each optical structure. A suitable material for the partially reflective layer is a dielectric which has no light absorption.

Digital echo cancellation for baseband data transmission

Abstract: In analogy with analog speech transmission, simultaneous two-way ("full-duplex") transmission of data signals over two-wire circuits can, in principle, be achieved by the application of hybrid couplers. In practice the resulting imperfect isolation between transmitter and receiver at the same end of a connection is disastrous for the detection of the data from the other end and has to be nullified in some way. A solution to this problem can be found in echo cancellation by means of an adaptive digital filter. In this paper an integrated circuit realized in 4Φ-dynamic NMOS technology is presented which has been designed especially for echo cancellation in baseband modems. In the design a number of aspects have extensively been accounted for. These are the choice of adaptation algorithm, the interaction between the digital filter and its analog environment, interpolation, finite precision implementation, and the natural occurrence of an effect akin to dithering. These subjects receive full attention in this paper. The realized IC can be used for the economical upgrading of existing baseband modems to full-duplex service and can pave the way to the use of similar circuits in the local area of the future digital telephone.

The effect of fading and shadowing on channel reuse in mobile radio

Abstract: Co-channel interference probabilities are calculated for mobile radio systems operating in a Rayleigh fading lognormal shadowing environment with inverse fourth power law dependence of area mean signal level on range. Interference levels are shown to be high even with generous reuse distances. The results are used to calculate spectrum utilization using reasonable but tentative estimates of protection ratio and channel spacing for SSB systems. On this basis SSB offers a higher spectral efficiency than current 25 kHz spaced FM systems.

Superfluorescence: Quantum-mechanical derivation of Maxwell-Bloch description with fluctuating field source

Abstract: For a pencil-shaped extended medium with Fresnel number equal to 1, we have quantum mechanically derived a description of the initiation of superfluorescence in terms of Maxwell-Bloch equations with a fluctuating source due to the zero-point fluctuations of the vacuum field. By the introduction of classical behavior, these equations are extended to include nonlinear behavior due to decreasing atomic inversion. The principal assumption in the derivation is that the main features of superfluorescence are governed by the interaction of atoms with field modes inside two small solid angles around the pencil axis. The delay ${\ensuremath{\tau}}_{D}$, defined as the time at which the mean-squared tipping angle of the collective Bloch vector attains the value 1, turns out to be given by ${\ensuremath{\tau}}_{D}=(\frac{{\ensuremath{\tau}}_{R}}{4}){[\mathrm{ln}{(2\ensuremath{\pi}N)}^{\frac{1}{2}}]}^{2}$, where ${\ensuremath{\tau}}_{R}$ is the radiation time for collective decay and $N$ is the number of atoms. The corresponding effective initial tipping angle roughly equals $\frac{2}{{(N)}^{\frac{1}{2}}}$. A Fokker-Planck equation is derived to describe the statistics of the initial development of the tipping angle. The variance $\ensuremath{\Delta}{\ensuremath{\tau}}_{D}$ of the delay of the superfluorescence pulse satisfies approximately $\ensuremath{\Delta}{\ensuremath{\tau}}_{D}=\frac{2.3}{\mathrm{ln}N}$. A brief comparison with previous treatments of superfluorescence is given.

Valence change and phase stability of 3 d -doped BaTi O 3 annealed in oxygen and hydrogen

Abstract: BaTi${\mathrm{O}}_{3}$ ceramics doped with several iron-group elements up to 2.0 mole% were identically prepared and afterwards annealed at 700\ifmmode^\circ\else\textdegree\fi{}C in ${\mathrm{O}}_{2}$ at 150 bar or in ${\mathrm{H}}_{2}$-${\mathrm{H}}_{2}$O with an oxygen partial pressure of ${10}^{\ensuremath{-}22}$ bar. The valence states of the dopants were determined by magnetic-susceptibility measurements, and the phase-transition temperatures were established by dielectric measurements. The transition temperatures and the charge of the Cr, Mn, and Co dopants were found to change reversibly upon annealing at different oxygen partial pressures whereas both remained constant for Fe, Ni, Zn, and Ga dopants. The change of the concentration of oxygen vacancies, which proved to be inherently connected with valence changes, was investigated gravimetrically.

Site percolation in randomly packed spheres

Abstract: Three-dimensional structures of equal-sized randomly packed hard spheres (RPHS) have been built on a computer, and the site-percolation threshold has been calculated. The mean coordination of RPHS is 6 and we find a site-percolation threshold of 0.310 (\ifmmode\pm\else\textpm\fi{}0.005). This value of the percolation threshold is the same as the simple cubic lattice, which has an exact coordination of 6. Expressing the percolation threshold for randomly packed hard spheres, in terms of the volume of occupied space, gives a critical-volume fraction of 0.183 (\ifmmode\pm\else\textpm\fi{}0.003).

Perceptions of dentofacial morphology by laypersons, general dentists, and orthodontists

Abstract: Line drawings of facial profiles and color photographs of dentitions were evaluated by laypersons and professionals. Eleven drawings of facial profiles and 11 photographs of dentitions were evaluated by parents, general practitioners of dentistry, and orthodontists for normality and for the necessity for orthodontic treatment. A three-point scale was used.

Hydrogen absorption in various zirconium- and hafnium-based intermetallic compounds

Abstract: The interaction with hydrogen gas of sixteen intermetallics containing zirconium or hafnium at a concentration of at least 50 at.% was studied. It was found that reversible hydrogen absorption involving the formation of a ternary hydride occurred for all the hafnium compounds and for the zirconium compounds of 50 at.% Zr composition. For all compounds of higher zirconium content hydrogen absorption was found to be irreversible because of the formation of the binary hydride ZrH2. Lattice parameters are given for the intermetallic compounds of hafnium before and after charging with hydrogen gas.

Electrophoretic display devices

Abstract: An electrophoretic display device comprises a cell in which a colloidal suspension of pigment particles is contained between associated electrodes and means are provided for the establishment of a potential between the electrodes for the selective transport of pigment particles. This potential permits changing the spatial distribution of pigment particles in specifically defined regions of the display cell. The device also comprises a light transmissive plate associated with the cell, whereby illumination received in the plate is internally reflected, with light coupling between the illumination and selected regions of the cell at which such particles are suitably disposed. The coupled illumination is transmitted by the cell to the observer. The cell regions at which the particles are disposed are switchably selectable.

Method and apparatus for detecting the presence of caries in teeth using visible luminescence

Abstract: A method and apparatus for detecting the presence of caries in human teeth using visible luminescence. A region to be examined is excited with a beam of monochromatic light. The intensity of the visible light emitted from the region is measured at two predetermined wavelengths, one where the intensity dependence of the spectra is about the same for caries and noncaries and the other where the relative intensity increases significantly in the presence of caries. A signal corresponding to the difference in the two intensities is obtained and then displayed. By first determining the magnitude of the difference signal at a nondecayed region, any increases in the magnitude as other regions are probed indicate the presence of caries. The invention is based on the discovery that the visible luminescence spectra for decayed and nondecayed regions of a human tooth are substantially different and that the differences are such that visible luminescence from teeth can be used to detect the presence of caries.

Static and dynamic noise margins of logic circuits

Abstract: Explaining four basic types of noise, and by showing the various methods, together with boundary conditions, which can be used to find the worst case noise margins A flip-flop setup is advised which can be used for measurements and computer simulations, both for static and dynamic noise margins Also configurations with fan-in and fan-out larger than 1 can be handled with this flip-flop method In general, it is found that the dynamic noise margins increase for shorter noise pulses; a first-order explanation of this phenomenon is given Also, energy noise margins are considered The theoretical considerations are completed with computer simulations and measurements of the static and dynamic noise margins of integrated Schottky logic (ISL), as an example

Donor-acceptor pair bands in ZnSe

Abstract: The donor-acceptor pair (DAP) bands have been studied in single crystals of ZnSe grown by vapor-phase epitaxy, from solutions of Ga, and In, and also by liquid-phase epitaxy. The temperature dependence of both steady-state photoluminescence and time-resolved spectra was used to identify the DAP bands ${R}_{0}$, ${Q}_{0}$, ${P}_{0}$ associated with Li and Na dopants. The DAP band ${Q}_{0}$ at 2.695 eV was already identified by Merz et al. as due to ${\mathrm{Al}}_{\mathrm{Zn}}^{+}$-${\mathrm{Li}}_{\mathrm{Zn}}^{\ensuremath{-}}$. We have associated the DAP band ${P}_{0}$ due to transitions involving ${\mathrm{Al}}_{\mathrm{Zn}}^{+}$ donor and ${\mathrm{Na}}_{\mathrm{Zn}}^{\ensuremath{-}}$ acceptor and the DAP band ${R}_{0}$ due to transitions involving a shallow donor and ${\mathrm{Li}}_{\mathrm{Zn}}^{\ensuremath{-}}$ acceptor, respectively. This shallow donor level seems to be associated with the presence of Li in ZnSe and could be ${\mathrm{Li}}_{\mathrm{int}}^{+}$. From these studies we obtain the acceptor level due to ${\mathrm{Na}}_{\mathrm{Zn}}$, 124\ifmmode\pm\else\textpm\fi{}2 meV, and the shallow donor associated with ${\mathrm{Li}}_{\mathrm{int}}$ as \ensuremath{\approx} 26 meV, respectively. This study suggests that compensation in ZnSe may be related to background donor impurities such as ${\mathrm{Li}}_{\mathrm{int}}$ rather than native defects.

Mammogram Inspection by Computer

Abstract: We have considered the problem of computerized picture processing of mammographic images for the early detection of breast cancer by determination of the very significant microcalcifications. Brightness measures, gray-level statistics, and a compactness measure are applied in a decision tree to characterize the candidate objects. A verification technique was evaluated to differentiate between significant groups of microcalcifications and isolated objects as well as false alarms. Feasibility of the microcalcification detection algorithm was demonstrated in experiments using 132 mammogram subareas, each consisting of 512 ×512 picture elements.

Detachable connector for optical fibres

Abstract: A detachable connector, for coupling the ends of optical fibers, comprising two connector portions, each connector portion having fixing means, for detachably connecting the connector portions to each other, and at least one rotationally symmetrical housing having a bore which is coaxial to a central axis. The housing has a reference face at one end and adjusting means secured in the bore at an opposite end. The adjusting means enables an optical axis, of an end of an optical fiber to be secured in a tube, and to be adjusted parallel to the central axis of the housing. When the two interconnected connector portions contact each other by way of the reference faces, the optical axes of the fibers in each connector portion are parallel to one another.

Portable element for receiving, storing, displaying and outputting digital data, and a reservation device for use in a reservation system

Abstract: A portable element shaped as a card, for receiving, storing, displaying and outputting data in numerical or alphanumerical characters, for temporarily communicating with a locally present reservation system and to exchange data therewith. The reservation system communicates with a service facility which is not locally present such as a transport vehicle. On the basis of an actual or forecast staus of the service facility, reservation data are applied to the portable element, and are displayed thereon, and also applied to the service facility. The contactless communication between portable element and reservation device can be initiated by a proximity signal.

Inductively coupled plasma-atomic emission spectroscopy: Its present and future position in analytical chemistry

Abstract: This review (with 179 references) is mainly intended to facilitate judgements about the present and future position of inductively coupled plasma-atomic emission spectrometry (ICP-AES) among both various “established” spectroscopic methods and AES methods based on novel plasma sources for liquid analysis. It is considered that a thorough and critical comparison of the capabilities and cost of ICP-AES with those of the existing outfit of a laboratory must be made in each individual situation separately to judge whether ICP-AES as a supplement to or a replacement of one or more established techniques is an economic proposition. From this point of view ICP-AES is reviewed as a relatively new method for the analysis of liquids and dissolved solids. The principle of the method and the basic instrumentation are briefly outlined. The distinction between low-power argon ICPs and high-power nitrogen-argon ICPs is pointed out and the viability of both approaches in the analysis of real samples is noted. Analytical performance is discussed in terms of detection limits, precision, accuracy and dynamic range. Applications of real-sample analysis are given as illustrative examples. A list is included of the best detection limits of 67 elements in aqueous solutions as reported for argon ICPs operated with pneumatic and ultrasonic nebulizers. Detection limits of 15 elements in oil are given to illustrate the potentials of low-power argon ICPs in the field of organic liquid analysis. The detection limits of As, Sb, Bi, Se and Te as achieved by combining hydride generation with an argon ICP, are presented to demonstrate recent progress in the determination of elements for which the detection power was hitherto less satisfactory than desired. With regard to precision, the behaviour of ICPs is pointed out as fluctuation-nose limited systems that are dominated by a relative standard deviation (RSD) of ≤ 1 % in both background and net signals as generated in the source. The dependence of the RSD in the eventually measured net signals (gross signal minus background signal) on the ratio of concentration to detection limit is discussed. An extensive discussion of accuracy incorporates detailed reference to factors such as spectral interferences and reagent impurities, nebulization and transport interferences, “solute vaporization” interferences, and ionization interferences, which may affect the accuracy attained in ICP-AES. It is shown that ICP-AES is relatively free from interferences so that a fair degree of accuracy can be reached, if proper precautions are taken, which, in comparison with AES methods using other excitation sources, or AAS, are not excessive. It is added, however, that the measures needed to ensure fair accuracy will become increasingly severe as the analyte concentration approaches the detection limit more closely or the composition of the sample becomes more complex. It is noted that under these conditions the problems that arc spectroscopists had to face in trace analysis using dc arc spectrography are again encountered, in particular as regards the correct isolation of a net line signal from a background spectrum whose structure depends on the sample composition. The advantages of the large linear dynamic range of three to five orders of magnitude are mentioned. The numerous applications of ICP-AES reported in literature are illustrated with a list of classes of materials for which analyses were described recently. Spectrometers enter into the discussion as indispensable parts of ICP equipment that are necessary for complete analytical instruments and the price of which may be a multiple of that of the ICP source itself. Alternative spectrometers for ICP-AES are grouped into three categories depending on the type of analysis problem: 1) general survey analysis, 2) routine multielement analysis and non-routine multielement analysis with limited flexibility, and 3) flexible single-element analysis. This classification, which fits in with general cost and performance considerations, is used as a convenient basis in the subsequent assessment of the position of ICP-AES among “established” spectroscopic methods. This assessment encompasses comparisons of the capabilities of ICP-AES, flame AES, flame and furnace atomic absorption spectrometry (AAS), de arc AES, spark AES, and X-ray fluorescence spectrometry (XRFS). The position of ICPs with respect to alternative novel plasma sources for liquid analysis by AES is discussed in the light of the historic development. This eventually led to the present situation in which there are at least twelve manufacturers of spectroscopic equipment that are marketing ICP apparatus and one marketing a dc plasma source for liquid analysis, while a renewed commercialization of a capacitively coupled microwave plasma (CMP) is stimulating new interests in CMPs. As to microwave-induced plasmas (MIP), attention is drawn in particular to the TM010 cavity that permits the generation of atmospheric pressure plasmas in helium. These have excellent characteristics as element-selective detectors in gas chromatography and also have many potential applications in multielement and single-element analysis in general, especially for the analysis of microsamples, if these are separately evaporated and atomized, e.g. by electrothermal means, prior to their introduction into the MIP.

Brushless direct current motor

Abstract: A brushless D.C. motor has electrical power switched between the phase windings by means of a circuit which includes a plurality of hall effect switches. The hall effect switches are operated by a plurality of arcuate commutating magnets which are radially polarized and are disposed axially adjacent to field magnets which are also radially polarized. Ordinarily, the direction of radial polarization of the commutating magnets and the field magnets will be opposite.

Curved array of sequenced ultrasound transducers

Abstract: An array of ultrasound transducers for pulsed sector-scan operation includes a plurality of transducer elements disposed on an arc of a circle and oriented to emit and receive ultrasound radiation in the direction of the center of the arc. A group of adjacent transducers within the array is active for each ultrasound pulse. The position of the group in the array is incrementally shifted along the arc, one transducer at a time, to effect scanning. The inherent focussing effect of a curved group of transducers is compensated with time delays or a negative lens to provide a parallel, sector-scanned radiation beam.

Optical record carrier and apparatus for reading it

Abstract: A record carrier is disclosed having an optically readable information structure comprising trackwise arranged information areas, as well as an apparatus for reading said record carrier. By using two mutually perpendicularly polarized beams components for reading and by giving the information areas of adjacent track portions a different geometries such that areas of one geometry can be read in an optimum manner by only one of the beam components and is virtually not observed by the other beam component, the track distance can be reduced without increasing the crosstalk, so that the information content of the record carrier is increased.