Showing papers in "International Journal of Electronics in 1992"

110 GHz gyrotron with a built-in high-efficiency converter

Abstract: A 110 GHz 1 MW pulse gyrotron has been elaborated. A built-in electrodynamic duct consisting of a new type quasi-optical converter and three matching mirrors transforms operating mode TE15,4 into a gaussian beam going through the output window. The efficiency of the duct (ratio of the gaussian beam power outside the gyrotron to the total microwave power at the output of the cavity) is about 95%. A system consisting of the gyrotron and an outer mirror transmission line is proved to have efficiency (ratio of the microwave power measured by calorimeter at the end of line to the power of the electron beam) more than 40%.

Switching in amorphous devices

Abstract: Electrical switching of a kind can be observed in a great variety of materials in many different forms and structures. Much the most reproducible switching is observed, however, in small and geometrically well-defined devices fabricated from thin films of certain amorphous semiconductors. This paper is concerned with such devices. The general features of electrical switching are first reviewed, followed by a more detailed account of recent work in the authors' own laboratories on digital and analogue switching in hydrogenated amorphous silicon.

Quantization effects in metal/a-Si:H/metal devices

Abstract: We present experimental results showing that metal/p+/metal amorphous silicon (a-Si: H) memory structures exhibit room temperature quantized electron transport associated with quantized resistance. The quantization of resistance is observed at values of R = h/2ie2, where i is an integer or a half integer.

New current-mode biquad filter

Abstract: A new current conveyor-(CC-)based active biquadratic filter configuration is proposed. The proposed structure offers the following advantageous features in contrast to the previously known CC-based current mode filters: (i) the realization of all the five generic filter functions (namely, low-pass, band-pass, high-pass, notch and all-pass) from the same configuration without requiring critical matching conditions/cancellation constraints; (ii) use of only two grounded capacitors; (iii) availability of non-interacting tunability of the parameters of the realized filters through grounded resistors; (iv) employment of all grounded RC elements; (v) easy conversion into a voltage mode biquad; and (vi) suitability for IC implementation. The workability of the proposed structure has been demonstrated by the results of SPICE simulations based upon translinear CC implementations.

Multifrequency theory of high power gyrotron oscillators

Abstract: A multifrequency time dependent model for high power gyrotron oscillator operation is developed and presented. A computer code based on this model is then used to simulate recent experiments carried out at the Massachusetts Institute of Technology. The simulation code indicates that the probable cause for the degradation of efficiency observed in the experiment is mode competition.

Marginal stability design criterion for gyro-TWTs and comparison of fundamental with second harmonic operation

Abstract: Stability properties of both the fundamental and second harmonic gyrotron travelling wave amplifier (gyro-TWT) are examined with multi-mode particle simulations. The second harmonic cyclotron interaction with an axis-encircling electron beam is found to be more stable to oscillations and can yield significantly greater power than the fundamental harmonic gyro-TWT. A multiple stage interaction structure based on a marginal stability criterion is proposed and illustrated with examples of a 128kW fundamental gyro-TWT and a 532 kW second harmonic gyro-TWT, Stable amplification at much higher power levels is in principle possible.

Soft-switched matrix converter for high frequency direct AC-to-AC power conversion

Abstract: A soft-switched matrix converter is proposed using the zero voltage switching technique in some resonant pole inverters A high operating frequency with safe and efficient switching improves the dynamic and spectral performances and simplifies the protection logics and snubber networks Further, it can be implemented using simple analogue circuits, having similar transfer characteristics to those of the modern pulse width modulated matrix converters, such as maximum voltage transfer ratio and unity input displacement factor Analyses, design and simulation results are presented to verify the operating principle

Tutorial review Trends in current conveyor and current-mode amplifier design

Abstract: A current-mode approach, involving current conveyor and current-mode amplifiers, is playing an increasingly important role in the development of many new high-performance circuits for signal processing applications. This paper will review the recent trends that have emerged over the last two years in certain areas of current-mode design, with particular attention to current conveyors and amplifiers.

Theory of gyro-travelling-wave tubes at cyclotron harmonics

Abstract: The generalized theory of gyro-travelling-wave tubes operating at arbitrary cyclotron harmonics is developed taking into account the transverse drift of electron guiding centres. In the framework of small-signal theory, the dispersion equation is obtained and analysed and a problem of spurious counterpropagating waves excitation is discussed. The results of the large-signal theory are presented, which predict a high efficiency of operation at the first four cyclotron harmonics.

Surface electron-phonon energy exchange in small metallic particles

Abstract: In small metallic particles of certain dimensions, the well known ‘bulk’ electron-phonon energy exchange may become ineffective and, as a result, the governing effect proves to be that of interaction between electrons and surface modes. The paper presents a microscopic theory of such electron-surface energy exchange based upon a quantum-kinetic treatment.

Tunable OTA-based multiphase sinusoidal oscillators

Abstract: Using a simple scheme, realisation of some novel multiphase sinusoidal oscillators (MPSOs) employing operational transconductance amplifiers (OTAs) as the active device are considered. These oscillators can provide n signals (n being odd) equal in amplitude as well as equally spaced in phase. Two practical OTA: RC three-phase oscillators have been realised and studied in detail. Their corresponding OTA-C realisations have also been obtained. Both the circuits enjoy low component count, low sensitivity performance and wide range electronic tunability. The OTA-C oscillators are highly suitable for monolithic implementation in MOS-form.

Numerical simulation and experimental study of magnetron-injection guns for powerful short-wave gyrotrons

Abstract: The results of a numerical simulation and experimental study of magnetron-injection guns forming intense helical electron beams for powerful gyrotrons are compared. Beams of three types—laminar beams, beams with regularly intersecting trajectories and beams with irregularly intersecting (mixed) trajectories are studied. The numerical simulation is performed taking into account the influence of the space charge field. The experimental beam characteristics are measured by the retarding field method. The experimental data agree satisfactorily with the results of the theory if the temperature deformation of the electrode systems is taken into account. It is shown that the best velocity distribution characteristics are realized for guns forming laminar beams and boundary beams (intermediate topology between beams with regularly intersecting trajectories and laminar beams).

A simple realisation scheme for OTA-C universal biquadratic filter

Abstract: A simple scheme for realising four standard second-order voltage transfer functions, viz., low-pass, highpass, bandpass, and band-elimination is presented. It is implemented by using only operational transconductance amplifiers and capacitors to realise two universal biquadratic filters (UBFs), i.e. UBF-I and UBF-II. The UBF-I can also be converted into a sinusoidal oscillator by simply grounding a suitable node. The circuits have the attractive features of wide-range electronic tunability of its pole frequency, bandwidth and pole Q; these can also be programmed digitally. In addition, the filters enjoy excellent sensitivity performance and are suitable for monolithic MOS or Bi-MOS implementation. The effects of non-ideal buffer on the performance of the circuits are studied.

Mode competition using TE03 gyrotron cavities

Abstract: The gyrotron is a powerful source of millimetre wave radiation. Fusion applications require more power per tube than is currently available This in turn means that the resonator must be highly overmoded, with a dense mode spectrum, which leads to mode competition. The influence of external parameters, such as the applied magnetic field, electron beam, and resonator geometry, on mode competition in tubes designed to operate at 150 and 140 GHz in the TE03 mode is investigated theoretically and experimentally. It can be shown that even when the mode spectrum is fairly dense, single mode operation of a gyrotron is possible. The influence of startup conditions on output power is investigated in the 150 GHz experiment. In some cases, modes with an axial index of 2 were excited.

Direct current conductivity and thermally stimulated current of β-nickel phthalocyanine films using gold and aluminium electrodes

Abstract: Current density-voltage characteristics and thermally stimulated currents have been obtained from thin films of β-nickel phthalocyanine particles dispersed in a polymer binder, when sandwiched between ohmic gold and blocking aluminium electrodes. At low voltages, the current in the forward direction varies exponentially with voltage. At higher voltages, two separate regions of space-charge limited current conduction under forward bias were observed. Under reverse bias, the conduction process at low voltages is determined by Schottky emission over a potential barrier of approximate height, 0·89 eV and thickness 65 nm. At higher voltages, the Poole-Frenkel effect was observed. The activation energy of the hole trapping level determined from the thermally stimulated current measurements has an electric field dependence. The results are interpreted in terms of the Poole-Frenkel effect.

Real-time image template matching based on systolic array processor

Abstract: An architecture based on a systolic array for real-time image template matching is presented. The architecture consists mainly of four elements: a digitizer, a two-dimensional systolic array combined with variable-length shift register arrays, an adder tree, and a comparator. All the elements form a four-stage pipeline. The image data enter the pipe sequentially in the same order as the TV raster scan. The matching computation is, however, performed in a parallel manner. The analyses on time complexity and hardware complexity have shown that real-time performance is achieved. The analyses have also shown that the processing speed is higher and the hardware is simpler when compared to the architecture presented by Chou and Chen.

Mode competition in a high harmonic gyrotron

Abstract: Non-linear theory is used to examine the limits on the maximum power that might be obtained from a high harmonic gyrotron. In particular, special attention is paid to the situation where the power is limited by mode competition from a nearby fundamental resonance. We find good qualitative agreement between theory and some observations made on a high harmonic gyrotron at Fukui University.

On the effective electron mass in strained layer superlattices of non-parabolic semiconductors under strong magnetic quantization

Abstract: An attempt is made to study the effective electron mass in strained layer superlattices of non-parabolic semiconductors with graded structures under sirong magnetic quantization and to compare the same with the bulk specimens of the constituent materials, by formulating the appropriate magneto-dispersion laws. It is found, taking InAs/GaSb superlattice as an example, that the effective electron mass oscillates with the inverse quantizing magnetic field due to the Shubnikov-de Hass effect. The dependence of the effective mass on the magnetic quantum number in addition to Fermi energy is an intrinsic property of such semiconductor heterostructures. The stress makes the mass quantum number dependent in bulk specimens and even in the presence of broadening, the effective masses in superlattices exhibit significant oscillations with enhanced numerical values from that of the constituent semiconductors. Besides the effective electron masses also increase in an oscillatory way with increasing electron c...

On the possibility of high power gyrotrons for super range resolution radar and atmospheric sensing

Abstract: High power gyrotrons have been developed recently; this makes a number of high power millimeter wave oscillators available. Currently their main application is the heating of fusion plasmas. This examines other potential applications for these RF sources. If used in multipulse radar mode, the pulses may be somewhat different from each other and this must be considered. A variant of coherent-on-receive data processing can be used. With this, the entire pulse, not only the phase, is renormalized to a reference pulse. The data are analysed off line. Possible applications of the quasi-optical gyrotron in a radar mode include exploiting its wide tuning range to achieve super range resolution and also remotely sensing the distribution of the size of ice crystals in cirrus clouds. Possible applications of a fixed frequency (94 GHz) gyrotron in the radar mode include studying the structure of clouds. In a forward scatter mode, these high power sources could provide the capability to remotely sense the st...

Integrable CMOS sinusoidal frequency doubler and full-wave rectifier

Abstract: A CMOS integrable circuit technique for the realization of both a sinusoidal frequency doubler and a full-wave rectifier is described in this paper. The realization method makes use of the characteristic of a simple CMOS class AB amplifier configuration. Simulation and experimental results demonstrating the circuit performance are also included.

Routing and path length algorithm for a cost-effective four-tree multistage interconnection network

Abstract: The characteristics of a new class of irregular fault-tolerant multi-stage interconnection network (MIN) called the four-tree (FT) network are analysed. A FT network can provide ‘full access’ capability even in the presence of multiple faults and is also cost-effective in comparison to other fault tolerant MINs. Rerouting in the presence of faults can be accomplished dynamically without resorting to backtracking. Further, for a non-uniform reference model, the network gives a larger throughput than any regular type of MIN due to smaller path lengths between a processor and its favourite memory modules. Algorithms for computing the path lengths and routing tags are developed for the proposed networks.

Experiments on highly efficient operation of the auto-resonant peniotron oscillator

Abstract: The auto-resonant peniotron has been theoretically expected to have a very high conversion efficiency (nearly 100%) for an ideal electron beam with an appropriate value for the velocity ratio interacting in a suitable circuit with an electromagnetic wave whose phase velocity is equal to the velocity of light in free space. This paper presents experimental results showing more than 70% electronic efficiency obtained from an auto-resonant peniotron oscillator with a magnetron type cavity.

Non-linear theory of a large-orbit gyrotron

Abstract: It is shown that the approach used in the theory of conventional, small-orbit gyrotrons can also be used in the theory of large-orbit gyrotrons. Such a conclusion permits one to apply readily the results of the well-studied non-linear theory of small-orbit gyrotrons to large-orbit gyrotrons in order to estimate their achievable efficiency and mode selectivity. A comparison of the efficiencies of gyroklystrons, and free running and phase-locked gyro-oscillators is given for devices operated at the first five harmonics of the electron cyclotron frequency.

Energy distribution of emitted electrons from electroformed MIM structures: the carbon island model

Abstract: The electrons emitted from an electroformed metal island metal (MIM) device have a broad energy distribution with an FWHM of more than 2eV. The emission is thermionic from potentials somewhere between the electrodes. Islands, as detected by potentiography in an STM, are assumed to be the emitting spots. This model is able to describe all features of electron and photon emission, as well as electrical properties of electroformed MIM devices. It involves hot electrons in the lattice of small carbon islands embedded between carbon electrodes.

Study of combined transmission line for high power wave generated by a gyrotron in the millimetre wavelength range

Abstract: A powerful millimetre-wave line transmitting energy from a gyrotron to a tokamak is studied. The line is open and combines mirrors and sections of an irregular oversized circular waveguide. The construction of the transmission line units is improved to provide selectivity for the operating TE01 mode. Particularly, the open quasioptical elbow operating at the long-wave region of the millimetre range and rotating the line by an angle of 90° is experimentally investigated. The operating TE01 mode insertion losses are 0.2-0.3 dB with a 4% bandwidth.

Prospects for metal/non-metal microsystems: sensors, sources and switches

Abstract: For many purposes the requirements of device miniaturization present a great challenge. Here, the fields of microsensors, microsources of electrons and photons, and non-conventional microelectronic devices, e.g. switches, memory elements and molecular electronics, will be traced and discussed by a few examples.

Novel technique for immittance simulation—realisation of some all-active simulators

Abstract: Two novel and generalised schemes are given for the realisation of grounded and floating immittance simulators. The use of operational transconductance amplifiers (OTAs) lends wide range electronic tunability to the schemes. The first scheme is particularly used in the realisation of new all active device ideal grounded inductance and super inductance simulators. These circuits employ only an OTA along with an operational amplifier (OA) modelled in its first pole roll-off characterisation. Similarly, the second scheme is used in realising novel ideal floating inductance and super inductance simulators. The all active device floating simulators only require a simple matching constraint to be satisfied in its realisation. Both the circuits use only active devices and have wide range linear electronic tunability and reliable high frequency performance. The effects of non-ideality of the OAs on the circuit performance is also examined. The simulators are highly suitable for monolithic implementation in either...

Self-consistent theory of mode competition for gyrotrons

Abstract: The equations for a fully self-consistent theory of mode competition in gyrotrons are derived and some possible methods of solution are discussed. The importance of including interaction in the resonator output taper is discussed in connection with the validity of linearizing the equations in the amplitude of the parasitic mode.

A long-pulse, CARM oscillator experiment

Abstract: Results of a long-pulse, cyclotron autoresonance maser (CARM) oscillator experiment are reported. A Stanford accelerator (SLAC 5045) klystron gun produced a 1 pis electron beam at 250-300 kV and 10-25 A at a repetition rate of up to 4 Hz. A beam α≡β⊥/β1, variable from 0 to 1, was produced on this electron beam with a wiggler magnetic field near guide field resonance. The experiments were carried out with two different Bragg reflection resonators designed for the TE11 mode. Using the first resonator, many harmonic gyrotron modes were observed in the 28-40GHz frequency range in the TE21 and TE01 modes and, for the first time, a second harmonic upshifted (CARM) TE11 mode at 74-5 GHz. Using the second resonator, fundamental CARM operation was observed for many parameter settings, and for frequencies ranging from 29 to 32 GHz. Output powers ranged from ∼01 kW to l00kW, resulting in efficiencies of 01% to 2%. Identification of CARM and gyrotron modes is made by comparison of measured frequencies with d...

Observations of Schottky and Poole-Frenkel emission in lead phthalocyanine thin films using aluminium injecting electrodes

Abstract: DC current density-voltage measurements have been performed on vacuum evaporated aluminium-lead phthalocyanine-gold sandwich structures for both electrical polarities. The electrical characteristics differed markedly depending on whether the positive hole-injecting electrode was gold (forward-bias) or aluminium (reverse-bias). An extensive study of such characteristics revealed two distinct regions in the forward-bias characteristics. In the first of these a power-law dependence of current density (J) on voltage {V) was observed with exponent n∼4, and this was identified with space-charge-limited conductivity (SCLC) controlled by an exponential distribution of trap levels of approximate concentration 1025 m−3 in agreement with the authors’ earlier work. In the second region a square-law dependence of J on V was observed, which was identified with SCLC controlled by traps of approximate concentration 1026m−3 and situated at a discrete energy level. Under reverse-bias, current density was considerably lower...