摘要:

The electrical length of long coaxial cables can be difficult to measure accurately, because of the weakness of the reflected signal and the presence of stray reflections from discontinuities in the cable. A method has been devised which makes use of a modulated reflector, a tuned hybrid network and a phase-sensitive detector to determine the phase of the reflected signal to within 0.5°, even when this is as much as 60 dB weaker than the transmitted signal.

DOI:10.1049/piee.1972.0020

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The investigation of acoustic-field distributions on free surfaces is important in several different classes of application. Measurements of the phase of acoustic surface waves using optical probes allow direct measurement of their velocity. A number of different optical-probe types are compared on the basis of sensitivity and stability. The operation and design of an optical heterodyne probe, capable of high-precision phase and group-velocity measurement, is described.

DOI:10.1049/piee.1972.0021

出版商:IEE    

年代:1972

数据来源: IET

DOI:10.1049/piee.1972.0022

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A new method of solving the problem of interference rejection in high-speed analogue-digital (a.d.) convertors is given. The measurement speed obtained in such a way in multichannel data-acquisition systems is much higher (up to two orders of magnitude) than that obtained with filters and integrating a.d. convertors which have the same rejection of line frequency. Different solutions of interference rejection, based on the same method, are presented. A time interval of only 20 ms is required to achieve line-frequency suppression higher than 50 dB, so that the fast a.d. convertors could replace the integrating ones. The method proposed is especially suitable for application in online computer systems.

DOI:10.1049/piee.1972.0023

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A 7-step algorithm for the design of sequential circuits is described. Its use enables engineering constraints such as gate-speed tolerances and fan-in restrictions to be met systematically, and it has been found helpful in meeting system modifications effectively at the design stage. The algorithm is developed with particular reference to NOR circuits; NAND circuits and relay circuits are treated briefly in Appendixes.

DOI:10.1049/piee.1972.0024

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The limited information transmitted between integrators in binary and ternary systems has led to consideration of multibit methods. However, conventionally implemented, these are expensive, because each integrator requires not only a more complex interconnection matrix, but also a full multiplier. The use of 2nd-order differences leads, in many instances, to a cheaper system, because, in a fast machine, the integral increments will not change significantly between solution steps.

DOI:10.1049/piee.1972.0025

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Analysis previously developed for the prediction of distortion outputs in broadband switching-diode mixers and modulators handling multifrequency inputs is modified to include the effects produced by tuning both source and load terminations. The compensation theorem is invoked to replace the sideband tuned circuits by equivalent generators. An important consequence of tuning the modulator terminations is shown to be the appearance of distortion products absent from the output spectra of the broadband-terminated circuits. Good agreement is demonstrated between theoretical predictions and the measured outputs from typical series and shunt modulators operating at high frequency.

DOI:10.1049/piee.1972.0026

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A bridge of four solid-state switches with a capacitor in one diagonal is connected in series between the supply and the load. The switches (thyristors) periodically reverse the current-flow direction through the capacitor. The load power is controlled by varying the switching frequency. The device may be used for the control of direct current and alternating current.

DOI:10.1049/piee.1972.0027

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Simple necessary and sufficient conditions are presented under which a 2-variable admittance function may be realised as a cascade of commensurate lossless transmission lines with several lumped shunt capacitors located at specified positions at the junctions of adjacent lines and terminated in a positive resistance. Two types of networks are considered. The first consists of equal-delay transmission lines, the second contains not necessarily equal-delay but commensurate-delay transmission lines. The main results are obtained on the basis of Trudi's theory of bigradient arrays.

DOI:10.1049/piee.1972.0028

出版商:IEE    

年代:1972

数据来源: IET

DOI:10.1049/piee.1972.0029

出版商:IEE    

年代:1972

数据来源: IET