Showing papers in "International Journal of Electronics in 1990"
TL;DR: In this article, a random pulse-width modulation technique for voltage-controlled power inverters is proposed, which is based on the non-repetitiveness of the switching pattern, simplicity of the hardware, and uncommonly high limits of switching frequency.
Abstract: As an alternative to the existing deterministic pulse-width modulation methods, a random pulse-width modulation technique for voltage-controlled power inverters is proposed. Advantages of the technique include non-repetitiveness of the switching pattern, simplicity of the hardware, and uncommonly high limits of switching frequency. A prototype random pulse-width modulator is described and experimental results are presented.
110 citations
TL;DR: In this article, the electrical conductivity of metal-CuPc-metal sandwich structures has been extensively studied, particularly with regard to their electrical conductivities and its variation on exposure to various gases.
Abstract: Evaporated copper phthalocyanine (CuPc) thin films in the form of metal-CuPc-metal sandwich structures have been extensively studied, particularly with regard to their electrical conductivity and its variation on exposure to various gases. In the present work, CuPc thin films doped by prolonged exposure to oxygen have been incorporated into asymmetric sandwich structures using ohmic gold and blocking aluminium electrodes. DC conduction processes identified depend both on the polarity and on the electric field strength. Under forward bias (gold electrode positive), conductivity was ascribed to space-charge-limited conductivity controlled by an exponential trap distribution at lower fields and by a single dominant level at higher fields, in accordance with prior work on comparable organic films. Under reverse bias, currents were identified with Schottky emission over a potential barrier of approximate height 1 eV and thickness 200 nm. Additional work on annealed samples showed broadly similar behaviour unde...
40 citations
TL;DR: In this article, a scanning tunnelling microscope was used to investigate the topography and potential distribution of metal-insulator-metal diodes with voltage controlled negative resistance.
Abstract: Electroformed metal-insulator-metal diodes showing voltage controlled negative resistance are investigated with a scanning tunnelling microscope. The topography and the potential distribution are recorded simultaneously at various voltages applied across the sample. The sharp potential drop in the microslit suggests a layer model with current carrying filaments between the layers. Material transport in the vicinity of the potential drop may be an indication of the existence of hot spots.
36 citations
TL;DR: The University of Sydney's GYROTRON IV is a single CW source of low-power millimetre-submillimetre radiation that can be tuned across a broad frequency range from below 100 GHz to above 500 GHz as mentioned in this paper.
Abstract: The University of Sydney's GYROTRON IV is a single CW source of low-power millimetre-submillimetre radiation that can be tuned across a broad frequency range from below 100 GHz to above 500 GHz. The higher frequencies are obtained when the gyrotron operates at the second harmonic of the electron cyclotron frequency. The conditions for achieving second harmonic operation are discussed.
33 citations
TL;DR: In this paper, a wide lead phthalocyanine (PbPc) thickness range (d ~ 0.5-5.0 µm) was made for DC electrical measurements.
Abstract: DC electrical measurements have been made for a wide lead phthalocyanine (PbPc) thickness range (d ~ 0.5–5.0 µm). Measurements of capacitance as a function of inverse thickness revealed a low frequency relative permittivity (∊ r ~ 3.9), slightly higher than in copper phthalocyanine. At low voltages Ohm's law was followed, with a thermally-activated hole concentration of (1 · 1–21) × 1016 m-3. Above a threshold voltage Vt, a power-law dependence of current density on applied voltage was observed, indicating space-charge-limited conductivity, Vt varied in the range 0.4–20 V and was approximately proportional to d2, providing further evidence for this effect. The results were accounted for in terms of an exponential distribution of traps of total concentration 2.8 × 1025 m−3 within the bandgap, as observed in similar organic materials.
26 citations
TL;DR: In this paper, a simple method of analysis for a generalized state-space system of electronic circuits using the single-term Walsh series (STWS) approach is presented, which can be obtained both in block pulse form and in discrete form.
Abstract: This paper presents a simple method of analysis for a generalized state-space system of electronic circuits using the single-term Walsh series (STWS) approach. The input may conveniently and easily be expanded in STWS. The solution is obtained both in block pulse form and in discrete form. The simple and direct method presented here can easily be implemented with a digital computer.
24 citations
TL;DR: A high speed multiplier design is presented using redundant binary signed-digit number representation internally while the input operands and the output product are in two's complement form to create a multiplier that is suitable for VLSI implementation.
Abstract: A high speed multiplier design is presented using redundant binary signed-digit number representation internally while the input operands and the output product are in two's complement form. The design of a carry free redundant binary signed-digit (RBSD) adder cell is presented. The multiplication algorithm uses bit-pair recording to generate the partial products. The partial products are added in the form of a binary tree using carry free RBSD adder cells. The regular structure of these adder cells results in a multiplier design that is suitable for VLSI implementation. The increased speed is achieved through the carry free addition of partial products using redundant signed-digit numbers. The use of a recoding scheme will reduce the number of rows of partial products by a factor of two. The proposed multiplier design has a multiplication time of order O(log2 n) and area-time complexity of order O(n2 log2 n) for a word length of n.
24 citations
TL;DR: In this article, the underlying physical principles of electromigration, which is one of the principal wearout mechanisms of the metal conducting tracks in LSI and VLSI circuits, are introduced.
Abstract: The underlying physical principles of electromigration, which is one of the principal wearout mechanisms of the metal conducting tracks in LSI and VLSI circuits, are introduced. Track lifetime is believed to be influenced by the track dimensions, composition and passivation layer. These effects are considered. Different methods for determining the lifetime of a circuit, from simple lifetime tests at elevated temperatures to production-line tests, are also reviewed.
23 citations
TL;DR: Voltage-fed full-bridge series resonant inverters are described in this paper that use static induction transistors, and operate efficiently in the frequency range 100-1000 kHz for high power induction-heating and melting power supplies.
Abstract: Voltage-Fed full-bridge series resonant inverters are described that use static induction transistors, and operate efficiently in the frequency range 100–1000 kHz. Trial inverters are considered for 100 kHz and/or 400kHz high-power induction-heating and melting power supplies. In addition, a quasi-resonant inverter suitable for radio-frequency applications is produced to diminish switching losses operating at 1 MHz or so. Both types of inverter are found to work safely with sufficiently high efficiency, feeding high output power.
22 citations
TL;DR: In this paper, two types of quasi-optical antennas were examined for their suitability as a means of directing the radiation from a tunable gyrotron millimetre-wave source into a plasma for scattering.
Abstract: Two types or quasi-optical antennas are examined for their suitability as a means of directing the radiation from a tunable gyrotron millimetre-wave source into a plasma for scattering. The first type of antenna has a single parabolic reflector. The second has two reflectors; the first elliptical, the second parabolic. This combination has the advantage of focusing the beam into a spot at the centre of the plasma.
20 citations
TL;DR: In this paper, the graphite-like nature of the current paths in metal-insulator-metal devices has been identified by tunnelling spectroscopy and noise measurements, and its consequences reveal a better understanding of the properties of electro-formed metal-informer-metal diodes.
Abstract: The graphite-like nature of the current paths in metal-insulator-metal devices has recently been identified by tunnelling spectroscopy and noise measurements. This and its consequences reveal a better understanding of the properties of electro-formed metal-insulator-metal diodes.
TL;DR: In this article, the influence of charged particles on the nucleation process is studied systematically and experiments are performed on the nearly defect-free cleavage planes of alkali halides along with investigations of surfaces damaged by electron irradiation.
Abstract: In the past, several research groups have studied the nucleation and growth of thin metal films on various substrates. The results may be interpreted using the kinetic nucleation model proposed by Zinsmeister. In this theory the formation of crystallites is described as a two-dimensional polymerization process caused by atoms diffusing on the substrate surface. Biatomic and larger molecules are assumed to be immobile. Velfe et al. and Robins demonstrated a reduction of the number density of crystallites if the bombardment of the substrate surface with charged particles arising from the evaporation source is avoided. In the present paper the influence of charged particles on the nucleation process is studied systematically. Nucleation experiments are performed on the nearly defect-free cleavage planes of alkali halides along with investigations of surfaces damaged by electron irradiation. The results show that the kinetic nucleation model used in the past is not applicable.
TL;DR: In this article, a review of modifications introduced to the original polyfilamentary model for electronic conduction in electroformed insulating films is presented, and the normal distributions of the values of radii and resistivities among the filament population are found to provide a satisfactory basis for determining currentvoltage characteristics for metal/insulator/metal structures.
Abstract: A state-of-art review is presented of modifications introduced to the original polyfilamentary model for electronic conduction in electroformed insulating films. The solution of the one-dimensional heat equation, satisfying some physically realistic boundary conditions, is believed to be the best technique for describing thermal dissipation. New criteria based upon thermal loss through the positively biased electrode are obtained for the occurrence of voltage-controlled negative resistance. Different types of distributions of filamentary parameters are considered, and the normal distributions of the values of radii and resistivities among the filament population are found to provide a satisfactory basis for determining current-voltage characteristics for metal/insulator/metal structures. The experimentally observed shift in the peak of the I(V) characteristics is explained in terms of variations in the statistical parameters characterizing a probability density function for the distributions.
TL;DR: Two new efficient algorithms are proposed to convert the minterms of a switching function to the coefficients of its Reed-Muller polynomial with fixed polarities based on the use of boolean matrix representation.
Abstract: Two new efficient algorithms are proposed to convert the minterms of a switching function to the coefficients of its Reed-Muller polynomial with fixed polarities. The conversion procedure is based on the use of boolean matrix representation. The first algorithm is applied to generate all the generalized Reed-Muller expansions of the related switching function and select the optimum solution from them. The second algorithm is applied to generate directly the minimal generalized Reed-Muller expansion for a given switching function without undertaking all possible fixed polarity realizations. The two algorithms can also be applied to generate the minimal Exclusive-OR realization in fixed polarity for the incompletely specified functions. Two fast and efficient computer simulations for the proposed algorithms have been developed using BASIC programming language, these computer programs accept the number of the function variables and the minterms of a switching function and return the minimal Reed-Muller expan...
TL;DR: A new algorithm is described for calculation of the forward Hadamard-Walsh transform of completely and incompletely specified boolean functions that makes use of the properties of the disjoint cubes array representation of boolean functions.
Abstract: A new algorithm is described for calculation of the forward Hadamard-Walsh transform of completely and incompletely specified boolean functions. It makes use of the properties of the disjoint cubes array representation of boolean functions.
TL;DR: In this paper, different types of MI-M and M-I systems investigated in the past and at present and used as sources of electrons for vacuum electronic and solid-state devices are compared and their main properties are compared.
Abstract: Different types of M-I-M and M-I systems investigated in the past and at present and used as sources of electrons for vacuum electronic and solid-state devices are quoted and their main properties are compared. The problem of establishing the surface potential in M-I systems is emphasized. Physical processes determining electron emission are discussed. Three groups of system have to be distinguished, differentiated mainly by the thickness of the insulating layer. The importance of the inhomogeneous field distribution in this layer is pointed out. An idea is proposed explaining the conditions under which a transition can be effected from a cathode with 'normal’ characteristics to a formed system exhibiting 'anomalous’ characteristics. In such a way, it is possible to understand the emission phenomena of all the mentioned groups from the same point of view.
TL;DR: A simple operational transconductance amplifier (OTA)-based circuit implementing first-order all-pass function is presented in this paper, which employs a grounded capacitor and as many as four resistors.
Abstract: A simple operational transconductance amplifier (OTA)-based circuit implementing first-order all-pass function is presented. Besides using a single OTA, the circuit employs a grounded capacitor and as many as four resistors. The gain of the circuit is electronically-tunable through transconductance gain of OTA and a grounded resistor, which can be be made voltage dependent. The circuit provides non-interactive tuning of phase and gain without disturbing the realizability condition. The circuit is capable of providing a substantial amount of gain, as the scale factor is a function of two gain-controlling parameters. The circuit is highly stable against temperature variations, since the realizability condition is a function of the resistor ratio.
TL;DR: In this paper, it has been shown that in thin films showing space-charge-limited conductivity controlled by an exponential trap distribution, the mobility can be unambiguously determined by measuring current density as a function of inverse temperature at constant applied voltage.
Abstract: It has previously been shown that in thin films showing space-charge-limited conductivity controlled by an exponential trap distribution, the mobility may be unambiguously determined by measuring current density as a function of inverse temperature at constant applied voltage. Moreover, parameters of the trap distribution may be derived independently of the J–V characteristics. It was found that mobilities varied in the range (4–8) × 10-2m2V-1s-1 and that other parameters were consistent with those derived from J–V measurements.
TL;DR: In this article, an analogue frequency-to-voltage converter suitable for low and variable-frequency applications is presented, which includes zero output ripple, fast dynamic response, good accuracy and linearity in a wide frequency range.
Abstract: An analogue frequency-to-voltage converter, suitable for low and variable-frequency applications is presented. Circuit advantages include nominally zero output ripple, fast dynamic response, good accuracy and linearity in a wide frequency range.
TL;DR: In this paper, a new determination of the distortion power in linear and non-linear systems with non-sinusoidal voltage and/or current is proposed, and the existence of the active and reactive components of distortion power for linear and NLL systems is shown.
Abstract: A new determination of the distortion power in linear and non-linear systems with non-sinusoidal voltage and/or current is proposed. Existence of the active and reactive components of distortion power for linear and non-linear systems is shown. The distortion power components may exist even in pure resistive or pure reactive systems. Formulae for the direct calculation of any component are obtained. The Fourier and in-quadrature approaches in use today are compared with the proposed theory and observed differences are discussed. Calculation of the power components in two converter circuits is presented.
TL;DR: Performance evaluation made by computer simulation for a band-limited RC-shaped gaussian input signal, simulating speech, reveals a considerable improvement in signal-to-noise ratio when compared with constant factor delta modulation and linear delta modulation systems operating at the same output bit rate.
Abstract: A new algorithm for instantaneous step-size adaptation in a two-digit delta modulation system incorporating both memory and look-ahead step estimation is presented. The associated modulator generates output code words which consist of a binary and a ternary digit. Besides the wide range of step changes that it produces in the feedback waveform, it offers reduced overshoots and fast response to signal variations. Performance evaluation made by computer simulation for a band-limited RC-shaped gaussian input signal, simulating speech, reveals a considerable improvement in signal-to-noise ratio when compared with constant factor delta modulation (CFDM) and linear delta modulation (LDM) systems operating at the same output bit rate.
TL;DR: In this article, the applicability or various morphological methods (radial distribution functions, contact distribution function, distribution of nearest neighbours in two modifcations, quadratic counts, covariance and chord length distribution) for the analysis of metal island films, are tested by computer experiment.
Abstract: The applicability or various morphological methods (radial distribution function, contact distribution function, distribution of nearest neighbours in two modifcations, quadratic counts, covariance and chord length distribution) for the analysis of metal island films, is tested by computer experiment. All these methods are also applied to experimental data on In and Ag films.
TL;DR: In this paper, anodized aluminium is introduced as a possible substrate for hybrid microelectronic circuits and primary experimental results on the electrical and mechanical properties of routinely prepared anodic films are presented.
Abstract: The requirements for substrates useful in hybrid microelectronics are changing. Substrates of high thermal conductivity are becoming very desirable mainly due to the trend and demand for electronic components and parts to be more dense and fine. Important properties of several alternative substrates are described and anodized aluminium is introduced as a possible novel substrate for hybrid microelectronic circuits. Primary experimental results on the electrical and mechanical properties of routinely prepared anodic films are presented.
TL;DR: In this paper, electron emission from island metal films (IMFs) composed of closely packed chains or islands is studied and the dependence or the emission current on the voltage applied to an IMF is linear in the coordinates In Ie versus 1/V. This indicates that both electron gas heating and lowering of the potential barriers caused by a strong electron field are important.
Abstract: Electron emission from island metal films (IMFs) composed of closely packed chains or islands is studied. The dependence or the emission current on the voltage applied to an IMF is linear in the coordinates In Ie versus 1/V. This indicates that both electron gas heating and lowering of the potential barriers in IMFs caused by a strong electron field are important. In addition to the stimulation of electron emission from chain-like IMFs by passing a current, an alternative way of feeding high density power into such films by laser irradiation is studied.
TL;DR: In this article, a short review is presented of various models used for computer simulation of the initial stages of the nucleation and growth of metals on dielectric substrates, with a focus on both the algorithms used and the results obtained.
Abstract: A short review is presented of various models used for computer simulation of the initial stages of the nucleation and growth of metals on dielectric substrates. Attention is devoted to both the algorithms used and the results obtained. In the second part of the paper, a simple atomistic model is proposed and some new possibilities for such kinds of model are shown.
TL;DR: In this paper, a new technique to compensate for the offset voltage and to improve the S/N ratio of high-gain MOSFET pre-amplifiers is proposed.
Abstract: We explain a new technique to be used with high-gain MOSFET pre-amplifiers, to compensate for the offset voltage and to improve the S/N ratio. This technique is based on the carrier-heating phenomenon associated with short-channel MOSFETs. Study and analysis of this technique indicates that the geometry (channel length L and width Z) has to be optimized for the best offset compensation and noise reduction. It also shows that it is compatible with the MOSFET scaling-down trends. The paper presents a study and characterization of the offset voltage and drift of the MOSFET IC operational amplifiers, It comprises an investigation and modelling of the noise sources of short-channel MOSFETs. This study helps to evaluate and predict the a.c. response and the noise performance of the high-gain MOSFET pre-amplifiers in video-frequency regions.
TL;DR: Algorithm simulations and experimental performance of integrated test sub-circuit prototypes indicate that this proposed new DCT/IDCT chip would be capable of the real-time proces...
Abstract: A unified discrete cosine transform and inverse discrete cosine transform (DCT/IDCT) architecture is used in the design of a proposed single-chip VLSI implementation of this function. An 8-point by 1 organization of the DCT/IDCT is chosen to allow easy implementation of the 8 × 8 format under consideration for recommendation by the International Consultative Committee for Telephone and Telegraph (CCJTT) for 384 K-bit CODECs. Fast DCT and IDCT algorithms are merged into a single hardware architecture that is programmable with a single DCT/IDCT selection switch. To accomplish real-time 10 MHz video data processing, the basic system clock brings data in and sends data out each 100 ns. Eight pixels are loaded for simultaneous processing every 800 ns and the module of each pipeline stage processes these eight elements simultaneously. Algorithm simulations and experimental performance of integrated test sub-circuit prototypes indicate that this proposed new DCT/IDCT chip would be capable of the real-time proces...
TL;DR: In this paper, 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.
Abstract: 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 frequenc...
TL;DR: In this article, the results of experimental investigations and the development of broadband amplifiers with transformer feedback were described and the theory of which has been given in Part 1. The amplifiers have a gain of 6 to 30dB, a noise figure of 1.5 to 2, a bandpass of 1 to 250 MHz and a dynamic range of 85 to 104dB, the consideration of cascading is presented, ensuring stability and other design features.
Abstract: The results are described of experimental investigations and the development of broadband amplifiers with transformer feedback, the theory of which has been given in Part 1. The amplifiers have a gain of 6 to 30 dB, a noise figure of 1.5 to 2, a bandpass of 1 to 250 MHz and a dynamic range of 85 to 104 dB, The consideration of cascading is presented, ensuring stability and other design features. Design principles are given for low-noise amplifiers with high gain and wide dynamic range.
TL;DR: In this article, matched broadband amplifiers that use lossless transformer feedback are studied and two basic circuits are studied in detail: one with transformer feedback and the other with autotransformer feedback, the latter has been shown to ensure higher linearity and a substantially broader bandpass.
Abstract: Circuits are studied of matched broadband amplifiers that use lossless transformer feedback. The latter ensures high stability, linearity, constancy of gain and an extremely low noise figure. Actual parameters of transistors and transformers are accounted for. First, two basic circuits are studied in detail: one with transformer feedback and the other with autotransformer feedback. The latter has been shown to ensure higher linearity and a substantially broader bandpass. Subsequently, lossless current amplification was introduced in both circuits. Two circuits with positive and negative feedback are briefly discussed.