The realization of high-pass equal-valued capacitor filters †

The paper presents design tables for high-pass RC active filters having capacitors of equal value. The functions realized are of the third-order Butterworth and Chebyshev variety. Account is taken of the resistor spread, total resistor stun and of the summed network sensitivity.     

Electronic realization of non-energic linear and non-linear network elements†

It has been stated as a conjecture (Duinker 1962) that every passive electrical system is equivalent to some network, exclusively containing elements of the set formed by the linear one-port and two-port elements (resistance, inductance, capacitance, transformer and gyrator), supplemented with the conjunetor (Duinker 1962) and the traditor (Duinker 1959).

In this paper it is shown that, with a well-designed voltage-controlled current source, the electronic realization of the non-energic elements is feasible. The circuits are presented and some aspects of their performance are mentioned.     

The Growth of Pre-breakdown Current in Helium†

The growth of pre-breakdown current across a uniform electric field discharge gap of finite dimensions has been calculated for helium. The current has been assumed to be amplified by electron ionization and by the production of secondary electrons at the cathode by positive ions, metastables and non-resonance radiation, with allowance made for the loss of secondary currant out of the discharge gap.

It has been shown that experimental measurements of the pre-breakdown current obtained for the range 3 ?1 torr^?1 cannot be analysed to give the electron ionization coefficient (α) without the help of subsidiary experiments to measure the relative abundance and secondary coefficients for the processes producing the secondary electrons. The analysis of these currents by the currents by the Townsend equations (1915) has been shown to give incorrect values of α, especially at the low E/p values where αT may be several times larger than α.     

Breakdown Voltages of Step Junctions in Silicon†

A synchronized frequency multiplication scheme based around frequency-dependent delays is outlined. Since these delays are produced by suitable control of standard TTL circuits, the circuit is easy to implement and its output frequency may be extended to over 1 MHz. A useful by-product of this multiplication scheme is a wide-band constant duty cycle generator.     

Temperature dependence of the ionization rate in silicon†

The problem of interpreting the temperature dependence of the breakdown voltage of silicon voltage reference diodes in terms of the physical processes that characterize the avalanche mechanism has been solved with the assistance of the model proposed by Shockloy in 1961. The associated theory allows the mean ionization rate to be expressed as a function of the electric field by an equation involving two factors, a and b. These, in turn, are related to the total energy lost to optical phonons between each ionizing event and the mean free path for optical phonon collisions respectively. An analysis is presented that leads to the expression

$

with the usual notation. Knowledge of either a or b allows the other to be evaluated from this equation and the experimental results. Since values for the optical phonon energy have been published by previous authors, b was chosen as the dependent variable. This yielded values for the electron phonon mean free path as a function of lattice temperature which are in close agreement with theoretical predictions over the temperature range 180 to 300°K. The analysis has not been extended below 180°K because significant departures from theory become apparent. It is expected that these are a consequence either of other processes affecting the experimental values of the breakdown voltage, or a different temperature relationship of the phonon energy from that appearing in the published literature.     

Dynamics of Current Sheets in a Coaxial Accelerator†

The theory of electromagnetically driven shocks is applied to coaxial accelerators. By assigning different values of γ, the ratio of specific heats, the three models of snow.plow, free particle and shook can be reconciled. This theory is compared with the experimental measurement of the current sheet velocity in a coaxial accelerator with an aspect ratio two, and uniform gas distribution. Only at early times does the snow-plow model give an adequate explanation of the current sheet velocity. At times later than 2 μsec, the sheet moves with a greater speed than the values calculated from a snowplow model.     

A study of the growth of current in non-linear inductive circuits†

The paper describes a method for the numerical study of the growth of current in circuits which comprise a non-linear inductor. The non-linear magnetization curve is supposed to be composed of a number of linear chords and an analytical expression for current is developed for each chord. Computation of current over any chord at equally spaced points along the time axis is carried out until the difference of the magnitude of this current and that at the end of the chord is the minimum. The method of solution has been explained taking the numerical illustration of the field circuit of a generator where the impressed potential difference is constant, the solution being obtained with the help of a digital computer. The graph showing the nature of the build-up of current is in perfect agreement with experimental data. The method has also been extended to circuits where the impressed voltage is alternating as in the case of an iron core transformer.     

The application of silicon nitride in the MIS system†

Results are presented which show that silicon nitride deposited directly onto silicon is of limited value for use in MIS devices, mid that most of these limitations can be removed by using the nitride in sandwich structures with thermally grown oxides. Tn such structures the higher dielectric constant and passivating qualities of the nitride are of value, and the electrical properties of the silicon/silicon dioxide interface can be controlled by existing technology.

     

On Some First-order Statistics of Fading Signals in Noise†

A series of results are derived for some first-order statistics of stationary fading signals when the signal envelope has a Pearson distribution. In particular, expressions are found for the distribution of the instantaneous value of the signal, both in the absence and presence of additive gaussian noise, and for the noisy envelope distribution of the received waveform. These results are useful in the evaluation of the performance of receivers operating in on incoherent fashion on fading signals corrupted by gaussian noise.     

A study of the effect of spacing of probes in two-element directional couplers†

An analysis of the interaction between the two coupling elements of a waveguide directional coupler is made. The observed fact that the required separation of the elements is less than one-quarter wavelength is theoretically explained.     

Electron Attachment in Oxygen†

Processes of electron detachment in Townsend discharges in oxygen ore discussed and, it is suggested, are negligible for pressures greater than very approximately 1OO—200 mm Hg in the range of values of the parameter E/P(≯E/P～50 v/cm/mm Hg) used in the experiments. At lower pressures, in agreement with Frommhold's recent work, detachment becomes important particularly at higher values of E/p.     

Study of two types of turnstile aerial immersed in a warm plasma †

The radiation properties of two types of turnstile aerial in a warm plasma are studied. One aerial type has crossed dipoles fed with currents in quadrature ; the other has currents in the four elements, such that the current in any one element is ±π/2 out of phase with the current in adjacent elements. The field patterns of both the electromagnetic and plasma waves are investigated, and it is shown that the field strength of the electromagnetic waves is reduced by the presence of the plasma. The radiation resistances of the electromagnetic and plasma waves of the two aerial types are evaluated for specific aerial parameters.     

Stability of negative resistances†

Three assumptions are introduced that allow of the deduction of the stability properties of a negative-resistance device from the shape of its d.c. characteristic. Whether or not a device satisfies the three assumptions can only be ascertained by considering its physical. structure.     

Effect of junction heating on the magnetocurrent in semiconductor diodes†

The effect of junction heating on the temperature dependence of magnetocurrent in semiconductor diodes is explained by taking into account the temperature dependence of various diode parameters.     

The Effect of Temperature on the Ionization Coefficient in Silicon†

The avalanche breakdown of p-n junction diodes across their space charge regions is known to be analogous to the Townsend mechanism for gases. Electric charge carriers, which gain sufficient energy from the field, are able to produce secondary electron-hole pairs. Both the holes and the electrons can themselves have ionizing collisions and thus the process leads to an avalanche. An important factor, controlling the breakdown, is the ionization coefficient a, defined as the number of electron-hole pairs produced by a carrier moving unit distance in the direction of the field.

This paper presents the results of nn investigation into the effect of lattice temperature on the ionization coefficient. This has been achieved by observing the breakdown voltage of a range of silicon diodes with either step or linear graded junctions, and applying simple and well-known relationships between ionization coefficient and breakdown voltage.

Measurements have been made over the temperature range 77 to 400°K, and for field strengths from 4 to 9 × 10⁵ volts/cm. Results show the ionization to become more efficient with decrease in temperature over this range of field strength. Temperature is found to have a greater effect at the lower field strength. This is shown to be consistent with modern theory.     

Analysis of a centre-driven antiphase dipole in a warm plasma†

The radiation properties of a thin dipole in a warm plasma, fed with currents in opposite phase, have been theoretically investigated using linearized hydrodynamic theory. Expressions for the far-zone electromagnetic and electroacoustie fields are derived in terms of general propagation constant β. The values of fields and of the radiation resistance are computed using β = β_e and compared with those of a standard dipole. It is found that tho eradiation of the electromagnetic mode is partially suppressed, whereas that of plasma mode remains almost unaltered, suggesting that the antenna could be used for launching electroacoustic waves.     

The different manifestations of the calor-electric effect in flame plasmas†

The calor-electric effect emerges as a broad phenomenon which shows various manifestations under different experimental conditions. A proposed scheme classifies the full range of this phenomenon into three categories which are referred to as the normal, anomalous and the enhanced calor-electric effect. The experimental conditions are defined for the appearance of each of these three manifestations. The anomalous calor-electric effect is discussed in slightly more detail by elaborating on the possible mechanisms responsible for the massive formation of heavy negative particles near a water-cooled electrode. A re-evaluation of earlier results leads to an improved value of 2·2 volts for the maximum calculated value of the anomalous calor-electric voltage. This compares very favourably with the maximum experimentally observed value of 1·9 volts for an atmospheric CH₄-O₂ stoichiometric flame.     

Hardware realization of the robust time–frequency distributions

A hardware realization of the L-estimate forms of robust time–frequency distributions is proposed. This hardware realization can be used for instantaneous frequency estimation for signals corrupted by a mixture of impulse and Gaussian noise. The most complex part in the hardware implementation is the block that performs sorting operation. In addition to the continuous realization, a recursive realization of the Bitonic sort network is proposed as well. The recursive approach also provides a fast sorting operation with a significantly reduced number of components. In order to verify the results, the FPGA implementations of the proposed systems were designed.     

Electrical Transport in nGe-pGaAs Heterojunctions†

A multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodiodes. Two different, but quite similar models are used to qualitatively describe the observed forward and reverse characteristics. Quantitative agreement with the experimental characteristics of the many devices presented is obtained by an empirical modification of the resulting equations. The lack of minority carrier injection in these devices is in agreement with the proposed model.