Showing papers in "International Journal of Electronics in 1989"

Ternary Reed-Muller switching functions with fixed and mixed polarities

Abstract: The representation of ternary switching functions by means of Reed-Muller algebraic expansions described over the Galois field GF(3) is considered. An investigation of the structure of the various fixed polarity transforms leads to an evaluation of the computational cost of performing these manipulations. The existence of a large number of consistent mixed polarity canonical forms is demonstrated and their basis vectors and transforms are isolated.

Ion-sensitive field-effect transistor with silicon nitride gate for pH sensing

Abstract: An ion-sensitive field-effect transistor (ISFET) has been fabricated with silicon nitride as the gate to provide a pH-sensing membrane. Measurements of pH sensitivity, selectivity, hysteresis effect and long-term stability have been made. The pH sensitivity is 46 mV per pH. The chemical response to the K+ ion is higher than that for the Na+ ion for this device. The long-term drift is about 1 mV per hour after a ten-hour immersion. Results for an oxide gate ISFET are also shown for comparison.

Non-linear analysis of the gyro-BWO in three dimensions

Abstract: The non-linear evolution of the gyrotron backward wave oscillator (gyro-BWO) is investigated numerically in the presence of a weakly non-uniform axial guide magnetic field. The set of coupled non-linear differential equations which govern the self-consistent evolution of the TE modes and the trajectories of an ensemble of electrons in a gyrotron are solved subject to boundary conditions for both the usual BWO (power extracted at the input end) and the reflection-type BWO (power extracted in the forward direction) configurations. Space charge effects are neglected in the analysis. Numerical simulations are carried out to model gyro-BWOs operating in the Ka -band with rectangular TE10 modes and near 104GHz with TE11 cylindrical modes. For a cold beam, calculations show that the efficiency of the device has a modest value of 10–15% in a uniform magnetic field but can be significantly enhanced to 25–30% by tapering the magnetic field. The frequency of the oscillator can be magnetically tuned over a 15% bandwi...

Method for determining the breakdown voltage in gas-filled tubes

Abstract: Average values of the dynamic breakdown voltage [Ubar]p as a function of the rate of increase of the applied voltage k for a nitrogen-filled tube with bulk copper electrodes one of which is gold plated are presented in this paper Extrapolating the resulting curve up to the intercept with the Up-axis allows the value of the static breakdown voltage to be found It is shown that the value of static breakdown voltage depends on the cathode material regardless of whether the tube has been irradiated with 60Co The distribution densities of 250 values of the dynamic breakdown voltage for values of the rate of increase of the applied voltage of 01 Vs−1 and 1Vs−1 are given It is shown that the agreement between the experimental values and the theory are better for a rate of 01 Vs−1

Recursive equations for hardwired binary adders

Abstract: A sum equation for the implementation of parallel hardwired binary adders is introduced. It is suggested that the proposed sum equation, when compared with Ling's high-speed sum, will result in some advantages, and that it can be used in the design of high-speed parallel adders using generally available technologies. It is shown that a 32-bit adder can be designed in three stages using 3 × 8 AND-ORs, 3 × 4 AND-OR-INVERTs and 2 × 4 OR-ANDs CMOS gates, and that a bipolar adder can be designed in four stages, with three-way NANDs and eight-way AND-dotting. In addition, it is suggested that a three-stage 32-bit adder using NANDs and AND-dotting is most likely unrealistic. The paper also describes the design of a number of adders, and discusses the speed, feasibility and complexity of their design.

Brief communication Simulation of lossless floating inductance using two current conveyors and an operational transconductance amplifier

Abstract: A method for the simulation of lossless floating inductance using two current conveyors and an operational transconductance amplifier as active elements is proposed. The circuit does not require component matching, and the simulated inductance value can be tuned electronically.

High performance current processing allpass filters

Abstract: A general configuration for a first order current processing allpass filter is described. It requires an active element having unity current gain in conjunction with two passive components only (i.e., one resistance and one capacitance). Two implementations using the following translinear circuits as active elements: (a) a negative impedance converter with current inversion (I-NIC) and (b) a current controlled current source (CCCS) have been inspected and experimentally compared. Because of the high performances obtained, they appear to be suitable for wideband applications.

New single-ended resonant inverter circuit and system for induction-heating cooking apparatus

Abstract: A novel type of single-ended resonant inverter using a new bipolar Darlington transistor that operates efficiently in the frequency range from 20 kHz to about 50 kHz is considered. The inverter implementation for an induction-heating cooker includes a unique power control strategy. The analysis and performance evaluations for the circuit design are also carried out.

Time-averaging equivalent circuit analysis of a resonant switching converter

Abstract: The sophisticated resonant switching converter is investigated by use of a new time-averaging equivalent circuit analysis method presented recently by the authors. The parameters of the time-averaging equivalent circuit model can easily be determined by the new approach without a prior knowledge of the d.c. solution for the converter. The d.c. analysis and a.c, small-signal analysis can then be performed based on the time-averaging equivalent circuit model. Design formulae for the buck resonant converter together with a numerical approximation example are also given.

Effectiveness of multiple compressions of multiple signatures

Abstract: The feasibility of combining multiple signature and multiple compression techniques to achieve a further reduction in the frequency of aliasing is studied. A critical study of the impact of primitive polynomials on the effectiveness of the scheme has been made. The observations are demonstrated through simulation results.

Two new integrable active-C OTA-based linear voltage (current)-controlled oscillations

Abstract: Two new integrable active-C oscillators using operational transconductance amplifiers (OTAs) are presented. In both circuits, the frequency of oscillation can be linearly controlled by adjusting the biasing voltage (current) of the OTAs. Experimental results are included.

Brief communication Condition code predictor for fixed-point arithmetic units

Abstract: This paper presents a method for determining the ‘results equals zero’ condition code and, by extension, all other related condition codes for arithmetic operations. The ‘result equals zero’ condition is predicted for all arithmetic operations computed by a typical hardwired adder, and can be implemented in hardware in parallel with such an adder without implicit or explicit use of the carries.

Suitability of GaAs Schottky metallizations for continuous device operation at elevated temperatures up to 300°C: a comparative study

Abstract: A comparative study of the thermal stability of Ti-Pt-Au, Ti, W-Au and WSi2-Ti-Pt-Au Schottky contacts on GaAs is presented. Various reliability tests at temperatures up to 400°C have been performed on these contacts leading to the conclusion that Schottky contacts containing refractory metal silicide diffusion barriers such as WSi2-Ti-Pt-Au remain stable even after long term reliability tests at 400°C. Contacts containing only refractory metal diffusion barriers (Ti-Pt-Au, Ti-W-Au) show severe degradations if operated at temperatures around or above 300°C.

Brief communication. Logic fault model for crosstalk interferences in digital circuits

Abstract: A logic fault model for crosstalk interferences is proposed. This model allows the incorporation of crosstalk effect faults in a general environment of logic fault simulation in VLSI digital circuits.

Shift register modification for multipurpose use in combinational circuit testing

Abstract: By modifying the shift registers of the commonly used built-in self-test (BIST) scheme, an effective multipurpose testing tool has been realized. The tool is capable of providing maximum enhancement in fault-cover, as well as significant improvement in error coverage.

Lattice predictive modelling of 3-D random fields with application to interframe predictive coding of picture sequences

Abstract: This paper further develops the recently proposed two-dimensional quarter-plane autoregressive (AR) lattice parameter modelling of two-dimensional (2-D) fields to three-dimensional (3-D) case with cubic-space support. Starting from the original 3-D random field, eight prediction error fields are generated at each lattice stage. The relationships between the prediction errors of successive lattice stage is defined by seven reflection coefficients. Besides the basic theory, an algorithm for determining the 3-D cubic-space recursive transfer function from the reflection coefficients is presented. A synthesis model for regenerating the original random field from a white noise field and the sufficient lattice parameter stability conditions are also included. In order to verify the theory, two numerical examples on modelling of random fields are given. Finally, an interframe predictive coding system based on the 3-D lattice model is presented to demonstrate the usefulness of the formulation. Results indicate th...

Switched-capacitor DFT and IDFT circuit

Abstract: The switched-capacitor realization of the discrete Fourier transform (DFT) is treated in this paper as well as the inverse discrete Fourier transform (1DFT). The output of the DFT has a sinusoidal waveform including the amplitude and phase information of the required spectra. These spectra are given simultaneously and almost in real time. The output of the 1DFT is given merely by adding DFT outputs. Furthermore, the circuit configuration of this system-from input to DFT, from DFT to 1DFT, and from 1DFT to output-is a very simple configuration constructed by a non-recursive filter circuit.

A distributive D-algorithm for generating the test pattern for faulty combinational circuit

Abstract: In this paper we propose a method for generating test patterns very efficient for stuck-at faults, either in symmetric or unsymmetric circuits. The faulty symbol D or D is distributed like any binary variable, from the site of source to the primary output passing through all possible paths. The test pattern for the stuck-at fault is generated by only one backtrack and simultaneously determined whether the test pattern exists or not. There is therefore no need for tracing paths forwards and backwards several times as the conventional D-algorithm or the modified version of D-algorithm during the process of the test pattern generation.

Structural investigations and colour centres in MoO3 films deposited by vacuum evaporation

Abstract: Structural investigations concerning colour centres in MoO3 are described. The structure of MoO3 is studied by electron diffraction and by X-ray diffraction (powder technique). The films are coloured thermally, optically (UV), and electrically. During the crystallization process, the dangling bonds tend to connect the constituent atoms with neighbouring bonds. Heat is expected to be generated at the interface between the crystalline and amorphous regions during crystallization. The crystal grows by coalescence with neighbouring crystallites as a result of the heat treatment process. A blue colouration is caused by inter-electron transfer from an oxygen (2p) to a molybdenum (4d) orbital that creates an isolated Mo(V) oxidation state.

Effect of film thickness and substrate deposition temperature on the a.c. electrical properties of molybdenum trioxide

Abstract: The dielectric and electrical propoerties of vacuum-deposited MoO3 amorphous thin films have been studied in the thickness range 100 to 300 nm, in the substrate deposition temperature range 293 to 543 K and over the frequency range 200 Hz to 1 MHz at various temperatures in the range 193 to 393 K. The frequency dependence of conductivity was found to obey an equation of the form σ(ω) = Aω s , where s is a temperature-dependent quantity, whose value is close to unity. The capacitance was found to increase with decreasing frequency and increasing temperature. A decrease in capacitance was observed with the increasing thickness of the samples, indicating that the permittivity was constant for the samples. The value of dielectric constant remains unchanged at high frequencies irrespective of temperature change, whereas its value increases at high temperature with decreasing frequency. The dielectric loss tan δ showed a pronounced minimum with varying frequency and increased with the rise of temperatu...

Characterization of discontinuities in dielectric waveguides using Schelkunoff's method: application to tapers and transitions

Abstract: Transitions, tapers and abrupt discontinuities are frequently used between different types of dielectric waveguides. This work presents a theoretical method to analyse the former structures. A modal matching method together with the generalized telegraphists’ equations are used. By using the generalized scattering matrix of two discontinuities, we can find the generalized scattering matrix of the cascaded set. Theoretical results of reflection and transmission coefficients, both module and phase, as well as some measurements are compared with those published by other authors.

Calculation of steady-state oscillations in non-linear circuits

Abstract: An analytical approach for calculations of stationary (steady-state) oscillations in non-linear circuits is considered. The circuit block-diagram is simplified so that the variable at the input of the element with non-linear characteristic is considered. The obtained higher-order non-linear differential equation is expanded using a combination of the harmonic balance method and perturbation techniques into a system of differential equations. Then the forced solutions of all equations in the system are calculated and the solution of the initial equation is obtained as the sum of these forced solutions. Consideration is concentrated on techniques that permit fast and efficient solution of the first three equations of the system. The approach is especially suitable for circuits where steady-state oscillations have a dominant first harmonic.

Electron beam annealed Ge-WSi-Au and Ge-Ni-WSi-Au high temperature stable ohmic contacts on n-GaAs

Abstract: Detailed analysis of electron beam annealed Ge-WSi-Au and Ge-Ni-WSi-Au ohmic contacts is reported. Lower contact resistance values with better reproducibility and much lower standard deviation are achieved with Ni doped TLM devices. Ar+ ion X-ray photoelectron depth profiling was used to relate the distribution of Ge, Ni, W, Si, Au, Ga and O to the electrical properties of contacts. Ohmic behaviour was found probably to be dependent upon the Ge and Ni compound formation on the GaAs surface.

Effects of film thickness and substrate temperature on DC conduction in thin amorphous films of MoO3

Abstract: DC conduction in MIM sandwich structures based on substoichiometric amorphous dielectric films of MoO3, prepared by vacuum evaporation in the thickness range 100-500nm were studied. Some samples 400nm thick were studied in the substrate deposition temperature range 293-543 K. A 100 nm thick sample was studied as a function of temperature in the range 193-393 K. It was difficult to distinguish between the Poole-Frenkel and Schottky high-field conduction mechanisms. The increase in conductivity due to increasing thickness is attributed to the increasing number of oxygen vacancies present in the samples. Heating the substrates in vacuum at 473 K or above results in the formation of a defect band near the Fermi level which is associated with the coloration of the samples and in the formation of reduced state species. The greatly enhanced conductivity in the blue samples is due to the higher mobility of the electrons in the defect band and the conduction band.

Some sequential graph colouring algorithms

Abstract: We describe a heuristic algorithm to colour the vertices of a graph which relies upon the comparison of the degrees and structure of the graph. We have compared it with the maximum-degree-node-first and minimum-degree-node-last criteria based algorithms. The interchange of colours without bound normally amounts to an exhaustive search and hence is not taken into account. Additionally, this paper reviews a broad spectrum of sequential vertex colouring algorithms based on heuristics.

Experiments on the high efficiency operation of the modified peniotron oscillator

Abstract: The modified peniotron oscillator proposed by the authors has been experimentally studied, and a reasonable electronic efficiency of 50% has been obtained. This efficiency has been enhanced to 62% by using a potential-depressed collector. This paper describes the operation characteristics of the modified peniotron and points out that the alignment of the respective axes of the tube and the magnetic circuits is very important in a peniotron tube.

Resonant PWM inverter linked d.c.-d.c. power converter utilizing parasitic circuit constants of high-voltage transformer and cables

Abstract: A state-of-the-art resonant d.c.-d.c. converter using new power transistors has been incorporated into an X-ray generator applicable to multidiverse X-ray apparatus. This converter consists of a resonant inverter to convert the d.c. voltage to a high-frequency a.c. voltage. It incorporates a high-voltage transformer to boost the inverter output voltage corresponding to a set value, together with a high-voltage rectifier. In practice, the high-voltage transformer includes inherently parasitic impedances such as a magnetizing inductance and leakage inductances, together with stray capacitances which exist between the layers of the secondary windings. This paper is mainly concerned with a resonant high-frequency inverter linked d.c.-d.c. converter which is able to utilize effectively the transformer parasitic impedances as resonant circuit parameters as well as the input capacitance of high-voltage cables as a smoothing capacitor.

Incremental-cost approach for the synthesis of CCD 4-valued unary functions

Abstract: Several approaches have been developed for the synthesis of one-variable 4-valued functions using CCDs. In all these approaches an attempt has been made to reduce the cost of implementing a given function. In this paper, we propose a new approach for the synthesis of such functions. Starting at zero cost, a search is conducted for the possible functions that can be realized using basic CCD gate structures. These functions are recorded in a list. At a given cost C, each of the four possibilities of using addition, overflow, inhibit, and multiplication as an output gate is considered. For each possibility, the set of possible inputs to the gate are determined and used. Only those outputs which are not covered at lower costs are added to the list. The cost is then incremented by one and the search is repeated for new functions. The process terminates when all possible 256 functions are in the list. Using this approach, it is shown that in 195 functions (76% of the total) there is a cost improvement compared ...

Resolution of branching with prediction

Abstract: A scheme for the resolution of branch instruction outcome is described. The branch instructions considered perform an increment operation whose result is saved, and then a comparison is made between the increment result and a comparison operand. The result of the comparison reflects the outcome of the branch. The resolution of the branch outcome is made by prediction directly from the three operands presented by the instruction. No increment or comparison need be performed explicitly to determine the branch outcome. The outcome of the branching is determined in the same amount of time as it takes to perform the increment, which in essence, is performed with a two-to-one adder, and is required as a data result of the branch instructions.

Some electrical and differential scanning calorimetry studies of sodium tetraborate glasses containing iron oxide

Abstract: A series of glass samples has been prepared from mixtures of Na2B4O7, and Fe2O3. Measurements have been made of the d.c. conductivity as a function of temperature and composition. These results have been interpreted in terms of the activation energy, which increased with a small addition of Fe2O3 (0.5 mol.%) in Na2B4O7 glasses but decreased again with further addition of Fe2O3. D.c. conductivity measurements have revealed a mixed conduction phenomenon in which ionic as well as electronic conduction occur in the glass. Differential scanning calorimetry (DSC) as a function of Fe2O3 content is also measured.