X-band varactor tuned monolithic GaAs FET oscillators†

The design, fabrication and performance of X-band varactor-tuned monolithic GaAs FET oscillators is described. The design is based on small and large signal device characteristics. A manufacturable process is used in order to realize the oscillators. The experimental performance agrees with the theoretical expectations within 0·2% for the oscillation frequency and 4% for the tuning bandwidth. Best tuning bandwidth and output power values exceeded 2 GHz and 28 mW. Wafer dispersion depends on oscillator characteristics and varies between ±1% and ±7·7% for oscillators with a varactor in the FET source. The rf wafer yield is 65%. Finally, noise and temperature characteristics are given.     

Nanowatt operation of monolithic operational amplifiers†

A study was made of two micropowered operational amplifiers to determine degradation of unity gain frequency response, open-loop gain, and slow rate in amplifier circuits and maximum frequency of oscillation in Colpitts and Wein bridge oscillators as programmed. Quiescent current was reduced below specified operating levels into the nanoampere region.     

Non-isothermal effects in bulk GaAs transit-time-mode oscillators†

A small-signal, non-isothermal, space-charge-wave analysis of transit-time-mode oscillations in bulk GaAs EQUATION BENDING when demonstrates significant differences from an isothermal and instantaneous device analysis as the operating frequency is increased significantly above 10 GHZ. It is shown that at a given value of device negative resistance, the device reactance is virtually the same at the fundamental and second-harmonic frequencies. The agreement between the non-isothermal theory and experiment is quite good.     

Noise at large RF amplitudes in IMPATT oscillators †

The non-stationary noise generator of a large-signal IMPATT oscillator is studied. It is shown that only the zeroth-order term of the series expansion of the autocorrelation for the noise voltage is of importance for the oscillator noise spectrum. The zeroth-order term is determined by an integral of the square of the Green's function for the total voltage from a generation of a pair of carriers weighted by the mean generation rate

A PIN diode model with a fixed rectangular voltage is studied numerically. The short-circuit noise current is shown to be inversely proportional to the reverse saturation current,J_s. The possibility of improving the noise properties by increasing J_s is discussed.     

Chaotic Spread- Spectrum Communication using Discrete-Time Synchronization

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On the calculation of harmonic oscillators utilizing negative resistance†

When harmonic oscillators utilizing elements with N-type and S-type voltage/current characteristics (elements with negative conductance or negative resistance) are calculated, usually only the non-linearity of the voltage/current characteristic is taken into account. However, the impedance of these elements is of a complex character, and the non-linearity of the reactive component influences the different modes of operation. This influence may be considerable and in some cases even dominating. If, however, it is taken into account, then the calculation of such systems becomes very difficult. The method used in this paper (Samoylo 1964, 1968) enables these problems to be treated correctly and at the same time considerably simplifies the mathematical calculations.

The results given in the paper may be used when harmonic oscillators utilizing tunnel diodes, Gunn diodes, avalanche diodes, avalanche transistors, unijunction transistors, p-n-p-n-type elements, etc.. are studied.

The calculations are made considering the non-linearity of the active and reactive components of the impedance of these elements. The experimental results agree well with the theoretical results.     

Distributed mosfet amplifier using microstrip†

Viewing the input capacitance of a mosfet amplifier stage as an integral part of a microstrip transmission line, leads to a distributed amplifier of simple design. With today's mosfets, a bandwidth in excess of 500 MHz can be achieved ; it will be possible to extend this bandwidth substantially in the future by the use of mosfets with lower input capacitance. In addition, some data are given on transmission lines employing substrates of high dielectric permittivity.     

Scattering matrix synthesis using multiport cavities†

The necessary and sufficient conditions arc established on the scattering matrix for an n-port to be realizable as a cascade of multiport cavities having proportional ports coupled through circulators. Design equations, yielding cavity dimensions, are given including the incorporation of cavity loss : S₂₁ synthesis is presented. Although the theory can be used wherever the equivalent circuit is valid, the results are seen to be practically most useful for 2-port narrow-band microwave comb filters to which the theory is applied.     

RC active network synthesis using an amplifier†

A new RC active network synthesis procedure for realizing a given open-circuit voltage transfer function is presented. The interconnection of an ideal voltage amplifier of gain greater than unity and two RC sub-networks in a grounded 2-port configuration is considered for this purpose. It is shown that a general rational transfer function of any order can be realized by such a configuration, provided the transfer function does not have zeros on the positive real axis of the s plane. The method compares favourably with other active RC synthesis procedures using a single finite-gain amplifier.     

The Thermal Oxidation of Silicon using Wet Oxygen†

Experiments on the oxidation of silicon in a stream of wet oxygen are carried out at various temperatures and for different values of saturation water vapour pressure. The results are consistent with the simple oxidation kinetics derived for oxidation in dry oxygen and for steam giving equations for layer thickness x, of the form: x² = Cp^mt exp (1·18/kT), where C and m are constants and p and t are pressure and time respectively     

Synthesis of stable driving point functions using gyrators†

It is shown that a stable, driving point admittance function is synthesizable as an active two-port lossless non-reciprocal network, with a termination of 1 ohm resistance. The active two-port structure consists of two gyrators dud a lossless -π structure. In most of the cases augmentation is not required. The cases when augmentation is required are investigated.     

A new type of depressed collector using a magnetic field†

A new form of depressed collector for microwave tubes has been investigated. It is shown that the use of a suitably selected transverse magnetic field in the collector leads to a smoothing of the power dissipation curve on the collector walls and to a fifty-fold reduction in the returning secondary-electron current.     

The eigenvalue solution of asymmetric-ridge waveguides using the mode-matching method †

The guide wavelengths of an asymmetric-ridge waveguide as applied to the T-septum guide have been numerically computer using the mode-matching method. The theoretical results thus obtained are compared with Elliott's experimental results. Good agreement between the two sets demonstrates the mode-matching method to be quite simple and useful.     

Potential gradient measurements in argon-nitrogen mixtures using a wall-stabilized arc†

The potential gradient in wall-stabilized atmospheric pressure arcs in argon, nitrogen and argon-nitrogen mixtures has been measured over the current range 5 to 40 A.

The potential gradient was measured by four methods which were found to agree to within 3%. The values obtained were found to be a function of the state of the surface of the discs forming the arc channel and independent of the gas flow rate in the range l·-9·0 1/min.

The results demonstrate that the effect of a small trace of nitrogen in argon is much greater than that of a small trace of argon in nitrogen. For example, at 26 A 5% nitrogen in argon increases the potential gradient by ～30%, while 5% argon in nitrogen reduces it by ～ 3% from the pure argon and pure nitrogen values, respectively.

A simple two zone arc model is used to explain the results. This model indicates that the arc in argon entirely fills the channel for currents greater than 5 A. However, when nitrogen is added a central core is formed whose diameter decreases as the nitrogen concentration is increased, the current being kept constant.     

New generalized-immittance converter circuits obtained by using the current conveyor†

The realization of special types of the generalized-immittance converters will be given here using the second-generation current conveyor. Of particular interest in this paper is the new realization of the voltage generalized-immittance converter having conversion immittance function proportional to 8² . It will be seen that two realizations exist for each converter.     

Very low Q-factor impedance measurements using a lock-in amplifier technique†

A technique for very low Q-factor impedance measurements, based on a lock-in amplifier as a vector voltmeter, is presented. Some practical details are discussed. The accuracy of the measurements has been studied by comparison, using a bridge method. As an application, the forward bias impedance of a variety of p-n junction is presented.     

Realization of two-dimensional recursive digital filters using the mixed Cauer form†

The application of the mixed cauer continued fraction expansion to synthesis of two-dimensional recursive digital filters is presented. Examples are provided to show how to perform a mixed cauer expansion on two-dimensional transfer functions and eventually obtain canonic digital ladder filter structures. Furthermore, a test for two-dimensional mixed-cauer continued fraction expansion which at the same time determines the expansion coefficients is included.