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Proceedings of the IEE - Part B: Radio and Electronic Engineering

Issue 7 • Date 1957

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Displaying Results 1 - 25 of 32
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  • The influence of chemistry on B/H loop shape, coercivity and flux-reversal time in ferrites

    Page(s): 400 - 411
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1769 KB)  

    The factors which influence the shape of the B/H loop, the coercivity, the permeability and the flux-reversal time in ferrimagnetic spinels are considered on two levels; a macroscopic and an atomic level. To minimize consideration of shape-dependent properties, the ferrite components are assumed to be toroids. With the assumption that domain walls are present in the material, coercivity, permeability, flux reversal and the influence of grain-boundary magnetic poles on B/H loop shape are determined in terms of measurable physical parameters of the material. From these relationships it is possible for the design engineer to determine the optimum parameters for a given application. The spinel-like magnetic oxides may, to the first approximation, be considered as ionic lattices. In order to obtain some insight into the control of the macroscopically measurable physical parameters by chemical composition and preparation procedures, as a second approximation the directional character of the ionic orbitals is emphasized to describe the influence of covalent effects on magnetic moment, magnetic exchange, and crystalline anisotropy. These effects are applied theoretically to the cations of particular interest in ferrites. Finally, some properties of several ferrites are displayed graphically to illustrate the importance of processing and chemistry on the magnetic character of ferrospinels. View full abstract»

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  • Ordering in cobalt-ferrous ferrites

    Page(s): 412 - 417
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (654 KB)  

    Various cobalt-ferrous ferrites show a constricted hysteresis loop. After magnetic annealing of the samples the loop becomes rectangular. It appears that the magnetic annealing creates in each crystal a uniaxial anisotropy in a direction which is not necessarily the direction of the applied magnetic field but a crystallographic direction nearest to it. It is suggested that directional ordering is the most probable origin of the anisotropy found. View full abstract»

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  • Pulse-response properties of rectangular-loop ferrites

    Page(s): 422 - 427
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    An analysis of the voltage pulses obtained across a secondary winding of a ferrite core on reversing the magnetization shows that in the reversal two stages should be distinguished, namely a fast response, related to a magnetization by rotations, and a slower response due to the displacements of domain walls. The viscous movement of the domain walls determines the switching time of the core. It appears that the switching times of rectangular-loop ferrites with widely varying chemical compositions are always of the order of magnitude of one microsecond when the coercive force is of the order of magnitude of one oersted. Higher values of the coercive force mostly go hand in hand with an increased switching time. In order to obtain some information about the origin of the damping of domain-wall displacements, switching times have been measured as a function of temperature and as a function of a uniaxial pressure applied to the core. In the temperature range ¿115 to +250°C the switching time of an arbitrarily chosen rectangular-loop ferrite did not decrease more than by a factor of about three. A uniaxial pressure applied to a ferrite also increases both its coercive force and its switching time. It appears that the switching time is greater when the anisotropies in the ferrite are greater. This can at least partly be explained by the increased distance between the walls in the case of higher magnetic anisotropies. An earlier paper on this subject has been given elsewhere. View full abstract»

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  • Ferrites with constricted loops and thermal magnetic treatment

    Page(s): 428 - 432
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (747 KB)  

    After comparing the different types of magnetic hysteresis loop of metallic ferromagnets and non-metallic ferrites, the existence of constricted loops in ferrites containing cobalt oxide is pointed out. The necessary prerequisites in achieving loops of this type are presented, and their field and temperature dependence are demonstrated. In full analogy with metallic ferromagnets of the Perminvar type, these ferrites are susceptible to heat treatment in a magnetic field. The influence of the field strength as well as the temperature dependence of the treating process is shown. View full abstract»

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  • A magnetic-core matrix store with direct selection using a magnetic-core switch matrix

    Page(s): 436 - 444
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (966 KB)  

    The paper describes the magnetic-core matrix store developed for a large high-speed digital computer, Edsac II. The store has a direct selection system for reading, and the access switch using a matrix of switch cores is described. The results of measurements to find the optimum operating conditions for the storage cores used are given, and circuit details of the storage unit are included. Design criteria are established for the size and winding details of the switch cores. The proposed permanent store for frequently used subroutines and constants is also described. View full abstract»

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  • The magnetic cell: a new circuit-element

    Page(s): 445 - 456
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1342 KB)  

    The paper describes the properties of the circuit element formed by a wire passing through a hole in a block of rectangular-hysteresis-loop ferrite. This element is considered in relation to a small core of the same material, first as a storage element and secondly as a gating element. View full abstract»

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  • A matrix store for data rate conversion

    Page(s): 457 - 463
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (982 KB)  

    A description is given of a parallel-access ferrite-core store which forms part of a data-handling system. The storage capacity is 13750 binary digits. In any 10sec period, up to 625 words of 22 digits each can be written into the store at a random rate, and over the same period, the information in the 625 storage positions is read out sequentially and destructively at a fixed rate. Thus, conversion of a random to a regular flow of information is achieved by means of the store. Some of the circuits incorporated in the store and the construction of the core matrix are described. View full abstract»

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  • A ferrite-core switch-matrix for magnetic-recording-head selection

    Page(s): 464 - 469
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (651 KB)  

    The simple circuit of a rectangular-hysteresis-loop core driving an inductance is discussed. Cores may be used as saturable transformers, the power transfer being inhibited by the application of a steady bias. Methods of pulse modulation requiring current in a recording head of either direction require two cores associated with each head if this property is used for selection. The operation of the two-core circuit is discussed. The introduction of a non-linear resistor enables the same head to be used for recording and reading. Details are given of the construction of a switch matrix for head selection in the main store of an electronic digital computer. View full abstract»

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  • A 1000-channel neutron-velocity spectrometer using ferrite data storage

    Page(s): 470 - 480
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1483 KB)  

    The paper describes the electronic sorting and counting equipment for a spectrometer using `time of flight¿ techniques in the energy range 1¿1000eV, the neutron source being a nuclear reactor in conjunction with a mechanical shutter. This provides bursts of neutrons at about 0·25microsec duration and 1000pulses/sec repetition rate. After passing through the test specimen, the neutrons are sorted into 1000 energy channels and the number of neutrons counted in each channel during the experiment is scaled and recorded. Thus 1000 numbers must be stored. Each number store takes the form of ten 2mm ferrite toroidal cores, and the 1000 channel store is arranged as a matrix of 1000×10 cores, controlled from a common 10-stage transistor binary scaler. Selection of each channel requires the use of an address matrix of a thousand 8mm cores arranged in a 10×10×10 matrix. At the end of the experiment the contents of the store may be taken out on to a punched-tape machine. View full abstract»

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  • A digital computer based on magnetic circuits

    Page(s): 485 - 490
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (828 KB)  

    The paper discusses in some detail that part of a digital computer, Decca Cl, which has been built with `square¿ hysteresis-loop ferrite cores. This part of the computer comprises the arithmetic and controlling circuits and the storage registers. The development of three basic logical circuits is indicated, and there is some discussion of the behaviour of these circuits. Designs of the basic circuits are given, and, using these, the logical designs of parts of the computer are indicated. One section of the paper is a brief description of those parts of the computer in which magnetic circuits combine with familiar electronic circuits. In conclusion, two possible lines of fruitful development are indicated which would increase the efficiency of computers. One particular barrier at present is the absence of any satisfactory cheap low-resistance rectifier. View full abstract»

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  • Some applications of square-loop ferrite cores in telecommunication switching circuits

    Page(s): 491 - 501
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1416 KB)  

    After an introductory discussion of the importance of electronic switching for certain functions in telephone and telegraph exchanges, the paper sets out the principles of switching with square-loop ferrite cores and the advantage of their use in combination with transistors. Various examples are given of the use of square-loop ferrite cores in telecommunication switching circuits. They refer particularly to electronically controlled telephone exchanges (register, impulse generators, counting circuits, code convertors), a multi-metering system for telephone exchanges, a memory circuit for the storage of telegraph characters and finally an automatic reservation system for airline companies. View full abstract»

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  • The application of square-loop ferrite material in data-processing systems

    Page(s): 502 - 511
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1572 KB)  

    Digital computing systems using very small ferrite cores have been developed because of the rapidity with which data can be inserted or withdrawn. The paper describes other applications of ferrite material in data-processing systems, either as toroidal cores or as blocks which are subdivided into a number of independent cells by drilling holes through which the controlling circuit connections are threaded. One application takes the form of buffers for modifying the speed or mode of presentation of data; a second concerns counters, distributors and scalers, and, as an example of such requirements, an incoming line terminal for a telegraph exchange is quoted. Attention is directed to the possibility of using a ferrite selector and a ferrite store for electronic telephone-exchange systems employing time division. In both these applications speed is of importance. In the case of dial registers, it is explained that substantial economy can be derived from rapid processing of the data. The application to telephone-message accounting is also described. It is shown that magnetic material can be used to replace electromagnetic switches, meters and relays and electronic triggers, counters and gates. View full abstract»

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  • A core-transistor logical element

    Page(s): 512 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1352 KB)  

    The paper describes a square-loop magnetic-core/junction-transistor circuit-element which is suitable for operation in complex logical systems at medium digit rates. Temporary storage between logical operations is obtained by virtue of the remanent property of the core. Use is made of the constant-current pulse from each stage and the field threshold of the material to provide a number of the elementary logical operations by the method of analogue summation of field inputs. Regenerative connection of each stage enables the power requirements of the master pulse trains to be considerably reduced. For flexible operation the input to each stage is strobed, so that the input/output characteristic is improved and output-pulse-length variation is overcome. Some examples of the applications of the element are given, and the limitation on its use is explained. A modified form of the basic circuit is described which enables shift-register circuits based on the single-core-per-bit principle to be constructed. Generalized design data are given, and the results are evaluated for components currently available. View full abstract»

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  • Some current and future applications for ferrite components in radio and television receivers

    Page(s): 526 - 533
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    Freely Available from IEEE
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