摘要:

The use of a lossy variable termination becomes an undesirable necessity in certain measurement situations, while in others its deliberate use facilitates the measurement of low-loss structures. In both of these cases, the present approach permits the analysis of the data to proceed in a manner identical to that employed when lossless short-circuits are used, i.e. with already familiar procedures. It results in a composite 4-terminal network from which the desired parameters are separated using particularly simple relations.Applications are made to a variety of measurements, including those of dissipative, lossless and symmetric 4-terminal networks, attenuation and attenuation constants.

DOI:10.1049/pi-c.1956.0052

出版商:IEE    

年代:1956

数据来源: IET

摘要:

A method is presented for deducing someRCnetwork theorems, chiefly concerning the transfer function of an unbalanced structure from the properties of pure resistance networks. This is possible mainly since:(a) Zero of the transfer function (voltage ratio) of a 3-terminalRnetwork has a clear topological interpretation, namely in the case of a zero transfer the network disintegrates in two parts (at least), which may have only the reference node in common, and the input and output terminals belong to different parts.(b) The expansion of theRCnetwork transfer function about the values of all its susceptances is a quotient of two polynomials in all these susceptances. The coefficients in this expansion are composed exclusively of cofactors of purely real matrices. These matrices correspond to the original network with some capacitors short-circuited and others open-circuited.(c) Vanishing of some coefficients in the numerator of the expansion of the transfer function of a 3-terminalRCnetwork implies a zero of the transfer function for some of theRnetworks derived in this way. This fact according to (a) imposes definite conditions upon the topology of the originalRCnetworkThese limitations show that the only possible form of a degeneration of the transfer function in its non-reduced form is through the disappearance of some left or right consecutive terms of the numerator. For a generalized ladder realization of such degenerated transfer function the discussion offers the limits of the maximum gain.

DOI:10.1049/pi-c.1956.0053

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The behaviour of a basic remote-position-control system with velocity-feedback stabilization and integral-of-error control is investigated, taking torque limitation of the servo motor into account. It is shown that the transient response deteriorates as the magnitude of the input signal is increased and becomes unstable above a critical value. Both phase-plane analysis and describing-function techniques are employed. The experimental behaviour to random input signals is observed.The effect of other non-linear elements added to eliminate the possibility of amplitude-dependent instability is discussed.

DOI:10.1049/pi-c.1956.0054

出版商:IEE    

年代:1956

数据来源: IET

摘要:

Crystal resonators suitable for use in telephone system channel filters have been made from ethylene diamine tartrate (e.d.t.). Methods used in the fabrication and mounting of these units are described. The circuits used in the determination of the electrical parameters are given, and the results of a large number of measurements are outlined. Freedom from unwanted resonances over the desired frequency bands combined with the required characteristics has been achieved by suitably dimensioning the plates, and by applying electrodes to a part of the crystal surface only. Increased activity for crystals mounted in air can be obtained by the use of suitably placed reflectors.

DOI:10.1049/pi-c.1956.0055

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The first 21 Laguerre functions have been tabulated to four decimal places (or two significant figures when this is more accurate) for values of the argument 0(0-l)l(0-2)3(0-5)6(l)14(2)40(5)100. The practical applications of these functions are briefly considered. The zeros of these Laguerre functions are also tabulated to 5 places, the last of which is not reliable except in the case of the smallest zero for orders above 6. Differentiation and integration of Laguerre functions, orthonormal properties and addition formulae are briefly discussed. Finite or infinite series of Laguerre functions whose sums are well-known functions such as products of polynomials and circular or exponential functions, step and delta functions, Bessel and Kelvin functions, and gamma and error functions are stated. The general methods used for deriving some of these results are indicated in Section 13.

DOI:10.1049/pi-c.1956.0056

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The hypothesis that the magnetic energy of a current circuit is the kinetic energy of the effective conduction electrons, developed in a previous Monograph,1is applied to the case of a conducting sphere without resistivity in a uniform magnetic field. A surface current is induced which prevents the growth of a magnetic field within the sphere, and expressions are found for the number and velocity of effective conduction electrons which carry the current. It is found that these electrons are in stable radial equilibrium, moving in circular orbits under the action of magnetic forces.The well-known Meissner effect in pure superconductors is shown to be an expected rather than an unexpected phenomenon, since its absence would require, under certain conditions, a supercurrent lacking equilibrium.The theory is shown to lead, by means of a simple assumption, to the basic equations of the London theory of superconductivity, but with a different interpretation of the velocity parameter. Finally, the inertial supercurrent and magnetic field which should be produced by the steady rotation of a superconducting sphere, as deduced by the new theory, are shown to be exactly the same as those forecast by the London theory.

DOI:10.1049/pi-c.1956.0057

出版商:IEE    

年代:1956

数据来源: IET

摘要:

A study of some additional evidence has been made to determine the polarization of radio waves reflected from the ionosphere at 16kc/s over a transmission path 540 km long. The ratio between the amplitudes of the vertical and horizontal electric fields is found to be appreciably greater than unity, the mean value of the determinations made here being 5.

DOI:10.1049/pi-c.1956.0058

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The field distribution near the focus of a microwave lens is studied both theoretically and experimentally.The relation between vector-field diffraction theory and scalarfield diffraction theory is discussed for this particular problem, and it is shown that in the case in question the principal component of the electric field vector can be evaluated with sufficient accuracy from the scalar theory.Measurements of the transverse component of the electric field have been made by a perturbation method using a spinning dipole. The experimental results are in good agreement with the theory.The often-discussed phase-shift of 180° in the passage of a wave through the focal plane is considered in some detail and the related change in wavelength near the focus is verified experimentally.

DOI:10.1049/pi-c.1956.0059

出版商:IEE    

年代:1956

数据来源: IET