摘要:

Asynchronous sequential logic using NOR/NAND integrated circuits is extensively used in fast digital systems. The standard design procedure results in a set of excitation equations for the secondary variables, which must be examined (and corrected) for static logical hazards prior to implementation.A modified design technique is postulated which allows sequential circuits to be implemented directly in terms of d.c. set/reset bistables (i.e. cross-coupled NOR/NAND elements). It is shown that the use of d.c. bistables in this manner prevents the occurrence of static hazards, thus obviating hazard correction. Additional advantages are that the-circuits evolved use fewer modules than conventionally designed logic, and exhibit a simpler logical structure.Detailed designs (both methods are used for comparison) for an asynchronous Gray-code counter, employing TTL logic, are described.

DOI:10.1049/ree.1968.0114

出版商:IERE    

年代:1968

数据来源: IET

摘要:

This paper describes convenient laboratory methods of measuring the hybrid π parameters as a function of collector current. Typical results are given, and the variation of the transition frequency with collector current is discussed.

DOI:10.1049/ree.1968.0115

出版商:IERE    

年代:1968

数据来源: IET

摘要:

Experiments which use coherent waves at frequencies near 1010Hz are possible in suitable materials at low enough temperatures. The techniques which are used are determined by the very short acoustic wavelength (̃ 5000 Å) and by the availability of transducers and detectors. An interesting area of research is into their use for spectroscopic purposes in crystals, a technique which is complementary to electron spin resonance (e.s.r.). As the selection rules and the quantities which govern the intensities are quite different, it is possible to detect impurities which e.s.r. misses. By obtaining information on the strength of the impurity-lattice vibration coupling a good deal of light is thrown on the problem of spin-lattice relaxation. The propagation of pulses in the vicinity of absorption lines gives some striking demonstrations of anomalous propagation. A related technique is that in which the waves, are generated incoherently from a black body source. This extends the range of frequencies which can be used, though at the expense of increased difficulty in the interpretation of the results. Nevertheless, some remarkable changes in the thermal conductivity of crystals at low temperatures can be obtained in a magnetic field. The general field is one of considerable promise and some possible directions in which developments may occur are outlined.

DOI:10.1049/ree.1968.0116

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The paper describes three approaches to the problem of manufacture of capacitors by methods compatible with thick film technology. In the first, the capacitor is regarded entirely as a discrete component and is manufactured or purchased independently. The problems of integration become those of surface bonding and of the protection of devices with irregular outlines.The second approach is to produce the resistor network on a high permittivity ceramic substrate, and manufacture capacitorsin situby the printing of appropriate electrode regions. This technique has the advantage of simple processing and produces co-planar components, but it necessitates a compromise on thermal and mechanical properties of the substrate material.The third and probably the best approach is to produce the capacitor by printing and firing of a suitable dielectric glaze. This introduces no compromise on substrate, no design allowances for strays, the component is co-planar and is produced by identical processes to the resistors. Multi-layer techniques offer the prospect of significantly wider range of values, and adjustable capacitors may eventually permit close tolerances to be achieved. This approach involves complexity of the process sequence for active R-C networks, possibly with multi-layer capacitors.

DOI:10.1049/ree.1968.0119

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The digital multiplication of two numbers of any sign by the successive addition of partial products is critically examined for the purpose of reducing the time of computation. The theory of Booth's method is reviewed and extended to show its validity for use with numbers of any radix. Multiple digit multiplication algorithms can then be derived and the quaternary algorithm for the multiplication of binary numbers two digits at a time is presented. Using this algorithm, computed results for numbers of varying size confirm that the carry propagation time, averaged over the whole multiplication, is very nearly one-half that obtained by either Booth's or Robertson's method.A further significant decrease in computing time can be achieved by using asynchronously-operated circuits and a three-bit multiplier, using Booth's algorithm, was constructed, using R-T micrologic elements, to check stability; a maximum multiplication time of 650 ns was achieved together with wide stability margins.A design for a multiplier using the faster quaternary algorithm is presented and it is envisaged that by using high-speed logical elements in its implementation a multiplication time of less than 1 fis should be achieved for 16-bit numbers.

DOI:10.1049/ree.1968.0121

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The paper describes a multi-layer interconnection system suitable for 50–100 unencapsulated integrated circuit elements of the type used in high-speed computers. The power and earth planes with their associate dielectrics are made using the thick film technique. Methods of producing the conductor and dielectric films are discussed. Two additional conductor planes, forming the signal matrix in which the logic connections are made, are deposited by the thin film technique.

DOI:10.1049/ree.1968.0123

出版商:IERE    

年代:1968

数据来源: IET

摘要:

A system for general classification of non-uniform transmission lines—by transforming the independent variablex(representing distance) of the telegraphists' second-order linear differential equation to another independent variablew=F(x)which is some function ofxand then by constraining the transformed telegraphists' equation to simulate a standard second-order linear differential equation (the solution of which is wellknown) expressed in terms of the same independent variable,w—is introduced. On the basis of this classification, two sets of generalized expressions for non-uniformity corresponding to each of the classes of the non-uniform lines have been derived. One set is in terms of the new independent variablewwhich may be any arbitrary function ofxand the other set is in terms of another arbitrary functionf(x)[org(x)] ofxwheref(x)[org(x)] characterizes the series impedanceZ(x)[or shunt admittanceY(x)] per unit length of the line in the formZ(x) = Zof(x)[orY(x) = Yog(x)] withZo[orYo] being a constant of impedance [or admittance]. Corresponding to each set of generalized pattern of non-uniformity, one general solution for voltage for each class of line has been worked out. It is shown that the two sets of non-uniformity, derived for each class, are the most general ones and they require no further generalization.3 Most of the non-uniform transmission lines, for which solutions are hitherto available, are found to be the members of the general classes introduced here. In addition, the generalized patterns of non-uniformity of certain new classes of non-uniform lines are derived and the applicability of this basic principle of classification for obtaining a number of transformable sub-classes is illustrated.

DOI:10.1049/ree.1968.0124

出版商:IERE    

年代:1968

数据来源: IET

摘要:

For low-value capacitors (tens of picofarads) glass dielectrics have been chosen, whereas for higher values it has been necessary to use a mixture of a high-permittivity ceramic and a binder material. Existing thick-film conductor compositions have been used for electrodes. In the work on the low-value systems, a large number of combinations of different dielectric and electrode materials and their processing conditions have been assessed, and several usable systems have been determined. The reasons for the poor performance of other systems have been studied and are described.The need to use multi-phase dielectrics for higher values, and the behaviour to be expected from such systems are discussed. Dielectrics have been made from mixtures of high-permittivity ceramics based on barium titanate and various glasses or bismuth oxide, and the various materials and processing parameters have been varied to attain the optimum performance. Data on the performance of high- and low-value capacitor systems are included.

DOI:10.1049/ree.1968.0126

出版商:IERE    

年代:1968

数据来源: IET