Showing papers on "Equivalent series resistance published in 1968"

A large signal analysis of IMPATT diodes

Abstract: This paper presents results on RF power output and efficiency of IMPATT oscillators obtained from a large-signal model of these devices. The results are obtained from a closed-form solution of the nonlinear equations describing a Read-type IMPATT diode. The closed-form solution is obtained by assuming a short transit time through the drift region compared to the RF period. The solution is used to obtain the large-signal diode impedance. The analysis shows that the power output of an IMPATT diode depends strongly on the series load resistance presented to the active part of the diode and that the change in diode reactance with increasing bias current also depends on the series resistance. Plots of power output as a function of frequency, bias current, and load resistance are presented. Frequency tuning of the oscillator through current variation is also discussed. Experimental results are presented and compared with the theoretical ones wherever possible. The results lead to an improved understanding of such oscillators and are extremely useful in optimizing their performance and determining their limitations.

Reverse‐Biased Gallium Phosphide Diodes as High‐Frequency Light Modulators

Abstract: Reverse‐biased gallium phosphide diodes have been successfully operated as high‐frequency intensity and phase modulators of light at room temperature. The high‐frequency modulation is fundamentally limited by the series resistance and the capacitance of the diodes. Cutoff frequencies as high as 7 GHz have been measured. Diode capacitance, typically less than 7 pF at the operating point, and driver impedance determine the broad‐band characteristic. Intensity modulation measurements have been performed up to 500 MHz. The power consumption per MHz bandwidth for 40% intensity modulation was 2.7 mW for a diode only 0.7 mm long. A diode of 1.5 mm length used as a phase modulator needed only 1.5 mW of power per MHz bandwidth for a modulation index of 1 rad at a wavelength of 0.633 μ. This latter value corresponds to an intensity modulation depth of over 80%.

Precision microwave measurement of the internal parasitics of tunnel-diodes

Abstract: This paper reports the results of precision microwave standing-wave measurements using a superheterodyne technique from 4 to 11 GHz on the internal parasitics of tunnel-diodes terminating a coaxial-line. Because of past conflicting conjectures as to the frequency dependence of the series resistance, particular attention has been paid to its accurate evaluation. Errors due to transmission-line attenuation and mount discontinuities have been explicitly eliminated from the measured results. The frequency invariance of the series inductance and junction capacitance is verified; but a new variation of series resistance with frequency is proposed of the form r=T_{dc}+(af)^{2} , in accordance with the experimental results. The effect of this variation on the resistive cutoff frequency is discussed and a comparison is made With the relevant results of other researchers.

The effect of series resistance on avalanche diode (IMPATT) oscillator efficiency

Abstract: Theoretical results are derived for the transmission efficiency in an IMPATT diode oscillator. The transmission efficiency is a measure of the RF losses in the passive diode resistance and the circuit which couples the diode to the load.

Resistance limited currents in solids with blocking contacts

Abstract: The existing theory of electric conduction in solids fitted with blocking contacts has been modified to include the effect of a series resistance. Experimental current‐voltage curves for trigonal Se with indium electrodes are reported which show the essential features predicted by our theoretical analysis.

Double layer relaxation in liquid electrolytes. Part 1.—Theory of the space charge polarization

Abstract: The linearized transport theory of space charge polarization in alternating fields is applied to relaxation of the diffuse double layer in melts and solutions of the salt Mµ+aXν–µa/ν The method reveals factors which limit the validity of empirical ac network analogues of the layer In the approximation to which the calculation is taken, there is a single relaxation time which depends on the cell length and the permittivity and transport coefficients of the electrolyte Formation of the layer causes dc polarization in conductivity cells Its relaxation with frequency is illustrated by the dispersion curves for conductance and capacitance in a parallel network The series capacitance, to which the parallel capacitance reduces at low frequencies, depends on the ratios of the transport coefficients and contains separate contributions from each ion It is converted to the low-potential limit of the Gouy capacitance by substitution of the Nernst-Einstein relations The relaxation time is numerically equal to the product of the series resistance and the series capacitance and does not resolve into separate ionic contributions The origin and significance of these results is discussed

Bridge circuit for differentially measuring capacitance

Abstract: An AC bridge includes two variable capacitors and two complementary conductivity transistors. The two transistors conduct during opposite one-half cycles of the AC bridge excitation voltage to alternately couple the two capacitors in circuit with a load resistor. When either one of the capacitors is not coupled to the load, it is clamped to a source of reference potential by a diode. The output across the load is proportional to the difference in value between the two capacitors.

Steady-State Performance and Analysis of the Series Resistance--Capacitance Circuit with Control by Adjustable Thyristor Triggering

Abstract: A pair of thyristors connected inverse parallel, with symmetrical triggering, are found to give smooth, stepless control of the current and load voltage in a series resistance-capacitance circuit. Large current pulses of adjustable amplitude are produced that appear to be suitable for electric welding. The application to power factor compensation of inductive loads is limited in usefulness due to poor waveform and high dissipation in the resistance-capacitance branch.

Delay lines with added shunt conductance

Abstract: A delay line in which resistors or resistive films are connected between conducting strips so to shunt-load the line that L/R is substantially equal to C/G, where for a predetermined unit length of line L is the series inductance, R is the series resistance, C is the shunt capacitance and G is the shunt conductance.

A high Q temperature insensitive inductive transistor circuit

Abstract: The inductive transistor circuit of ‘reactance diode’ type is generalized to the form in which the base resistance is replaced by a series combination of a resistance and another reactance diode, and the frequency and temperature dependences of the equivalent impedance of the circuit are studied. The equivalent impedance shows a strong frequency dependence. The equivalent resistance passes through a minimum at a frequency nearly equal to the geometrical mean of the two cut-off frequencies of the transistors. The sign of this minimum resistance can be adjusted to be either positive or negative. The series equivalent inductance increases monotonically as a function of frequency below the higher cut-off frequency of the two transistors. The increase in both the equivalent resistance and the series inductance results from the increase in the value of the resistances which were connected in series with the second reactance diode. The temperature dependence of these quantities can be explained by assuming a reasonable temperature dependence for cut-off frequencies of the transistors. Compensation of these temperature effects is possible by giving appropriate negative temperature coefficients to the external base resistances. The magnitudes of these temperature coefficients fall well within the range realizable by the use of semiconductor resistances. On the basis of these features of this circuit a design procedure having a temperature-insensitive high Q inductance is proposed.

Improvements in apparatus for, and methods of determining temperature at remote or inaccessible locations

Abstract: 1,108,478. Thermal simulation circuits. GRAVINER (COLNBROOK) Ltd. 6 Dec., 1965 [12 Dec., 1964], No. 50676/64. Heading G4G. An aircraft brake assembly comprises a circular plate 10 (Fig. 1) at whose centre heat is developed by a friction pad and at whose periphery the consequent elevated temperature is measurable. The plate is divisible into n annuli 11 of radius x, width dx, temperature #; each having thermal capacity represented by analogue capacitance dC and thermal resistance represented by analogue resistance dR; while radiation and convection losses are represented by analogue resistance L (x, #). The unknown centre temperature is represented by analogue voltage V S and the peripherally measured temperature by analogue voltage V o , and V s is given by an n order differential equation simulated by a ladder network (Fig. 2, not shown) of sections each comprising a series resistance dR, a shunt capacitance dC, and a shunt resistance L (x, #) which is reducible to an approximation (Fig. 3, not shown) comprising a series resistance R, shunt capacitance C, and shunt resistance L. Alternatively, the network is reducible to an approximation (Fig. 6) comprising two series resistances R and two shunt capacitances C such that in which V o represents the peripheral temperature arid V s the central temperature. In Fig. 8, voltage V 0 is applied to one input of operational amplifier 13 energizing the approximation circuit of Fig. 3 (not shown) and output terminal 14, while the output of the circuit is returned to a second input of the amplifier, which is self-adjusting to equality of inputs so that the amplifier output V s represents the central temperature. The approximation circuit of Fig. 6 is simulated by a circuit (Fig. 9), wherein voltage V o excites buffer amplifier 15 and series differentiating amplifiers 17, 19; the output of 15 being connected to the input of summing amplifier 16 over variable resistance VR 1 ; the output of 17 being connected thereto over inverter 18 with variable feedback resistance VR 2 ; and the output of 19 being connected thereto over variable resistance VR 3 . Output voltage V s representing central ternperature is given by wherein A, B, C are constants set in by resistances VR 1 , VR 2 , VR 3 .

Skin effect in microwave semiconductor diodes

Abstract: It is commonly assumed that the skin effect is the cause of an increase in the series resistance of a semiconductor diode at microwave frequencies. This letter presents some simple theoretical calculations which show that the validity of such an assumption is highly doubtful.

A theoretical analysis of the ideal step-recovery diode in the series-mode of operation

Abstract: An analysis is given of frequency multiplication with the ideal step-recovery diode in the series-mode of operation. Only one conduction angle per period of the fundamental frequency is allowed. The series resistance of the diode is assumed to be different from zero. General and explicit formulae are given for the input impedance, the output power and the power efficiency. The validity of the approximations is discussed throughout. It is shown that the efficiency, -q, of the power conversion is proportional to 1/n2, and that the maximum value for 17 is about 15% for a times 10 multiplier in this series-mode of operation.