摘要:

The paper evaluates and compares the flip-chip and beam-lead methods of making microcircuit assemblies, paying particular attention to thermal and mechanical considerations. The thermal studies indicate that the beam-lead and flip-chip approaches are similar for chips with many mounting points, and that the use of heat spreaders offers a considerable advantage. The use of a glazed ceramic substrate material is not recommended for glaze thicknesses greater than 10−3in. The mechanical studies show that considerable forces can be set up when beam-lead and flip-chip assemblies are temperature-cycled. These forces can almost reach the ultimate shear or tensile strengths of gold with typical temperature changes.

DOI:10.1049/piee.1969.0293

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The paper discusses the limitations on the high-frequency performance of superconducting tunnel diodes. The noise performance should be comparable to the best low-noise amplifiers available, and, with the present technology, a maximum operating frequency in the microwave region is predicted.

DOI:10.1049/piee.1969.0294

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Three practical constraints on the choice of a deterministic routing doctrine for a connected network are defined, leading to a class of doctrines for which a weighted graph of the network exists so that the specified routes are given uniquely by minimum-cost routes through the graph. A technique for finding such a weighted graph is given. An adaptive routing doctrine is defined, which considers the current delays along links of the network. The implementation of such a doctrine is discussed, and a ‘distributed’ solution described which is efficient, decentralised, and resilient under fault conditions. More general adaptive routing doctrines are defined, considering two parameters associated with each link, where the routing of a message may depend on its history as well as its present position and destination. A device called a dynamic route selector is described, which takes routing decisions according to the most general doctrine discussed. It is faster than a digital computer. Finally a method for first introducing deterministic, and then adaptive, routing on a computer-based network is outlined.

DOI:10.1049/piee.1969.0295

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Generation formulas from which the sets of trees and cotrees of a graph are expressed as the ring sums or the unions of the Cartesian products of the sets of subgraphs of the component graphs which are obtained from the original graph by decomposition are presented. If the subgraphs of the component graphs are given, the procedure will not generate any duplications, redundancies or cancellations of terms. Methods of generating certain types of desired subgraphs of the component graphs, and illustrative examples, are also given.

DOI:10.1049/piee.1969.0296

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Formulas are derived for the computation of distortion-noise power in frequency-dependent nonlinear networks represented by a Volterra series. The integrals for the distortion-power spectrum contain higher-dimensional Laplace transforms of the corresponding kernels of the Volterra series. An analysis of the frequency-dependent nonlinearity is carried out for transistor feedback amplifiers and f.m. radio-relay amplifiers used in frequency-division-multiplex transmission systems. The nonlinearity of a given order for transistor feedback amplifiers is characterised by a distortion term, and its frequency characteristic, which can be computed or determined from certain intermodulation measurements. A linear f.m. amplifier is completely characterised by its transfer immittanceW12(jω).

DOI:10.1049/piee.1969.0297

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The voltage-current matrix parameters for a network may always be expressed in terms of its six characteristic functions, which were originally introduced by Matthaei and subsequently used by Chirlian. This paper outlines a simple procedure by which the derivation of the [Z] parameters alone, for the common 2-port configuration of a nonuniform transmission line, is shown to be sufficient for the evaluation of all the characteristic functions for three 2-port configurations of the line. It is shown that each of the characteristic functions can be expressed in terms of the two linearly independent functions of the distance variablexwhich constitute the general solution of the telegrapher's equation governing the line. The characteristic functions for the three different configurations of a nonuniform line are derived and tabulated. The characteristic functions for the common 2-port configuration of three classes of generalised nonuniform lines, with their voltage solutions in closed forms, are tabulated, and their usefulness is shown by examples. The potential field of application for these functions is in the evaluation of the responses of integrated circuits which have the forms of the tabulated classes of nonuniform line. Since it has been shown by Bolinder that all types of wave parameter, e.g. scatting matrix, may be expressed in terms of voltage-current matrix parameters, the concept of characteristic functions of nonuniform lines may be employed to obtain these wave parameters for any device which employs TEM wave propagation in an isotropic medium.

DOI:10.1049/piee.1969.0298

出版商:IEE    

年代:1969

数据来源: IET

摘要:

From results obtained, both in the UK and the USA, it is shown that the measured intensities of layer-type radar echoes, observed at vertical and oblique incidence at centimetric wavelengths, agree with values calculated from measurements of the spectral density of refractivity variations in the pulse volume. The radar soundings sometimes show as many as five or six horizontal layers in the first 5 km above the ground. Some layer-type echoes could be explained at decimetric wavelengths in terms of reflection from smooth ‘disc-type’ irregularities but this model is an inadequate explanation of other clear-air echoes.

DOI:10.1049/piee.1969.0299

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Finite-element equations are derived for wave propagation in inhomogeneous waveguides. A variational expression is used for the wavenumberk0. A discretised finite-element equation is found at a point surrounded by four dielectrics, and special cases deduced. The method is applied to the solution of the dominant LSM mode in a dielectric-slab-loaded waveguide.

DOI:10.1049/piee.1969.0300

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Loss reduction in coaxial cables brought about by dielectric linings has been experimentally observed, but various theoretical considerations fail to explain this feature. To clarify this situation, the paper gives consideration to the general conditions for obtaining lower losses by means of a thin concentric dielectric shell placed anywhere between the two conductors. The analytical criteria obtained agree well with numerical results derived directly from the exact Maxwellian field problem, but are much easier to apply and give a more unified insight into the significance of the various parameters concerned. The analytical method is particularly useful in the range of special interest, namely for thin linings. For electrically thick linings, the exact results may be understood from coupled-mode considerations. While not explaining the experimental observations, the present analytical theory admits to reduced attenuation in other, more favourable circumstances discussed in the paper. This is in accordance with exact numerical computations, but restricts the use of quasistatic transmission-line theories to frequencies lower than previously assumed.

DOI:10.1049/piee.1969.0301

出版商:IEE    

年代:1969

数据来源: IET

DOI:10.1049/piee.1969.0302

出版商:IEE    

年代:1969

数据来源: IET