Diode Oscillator Research Articles

Performance of a magnetic susceptometer for thin films and surfaces

The design and performance of a magnetic susceptometer for thin films and surfaces is described. The device uses a 14-MHz resonant circuit driven by a tunnel diode oscillator with a superconducting meander line as the inductive element. Magnetic properties of thin films deposited near the line in ultrahigh vacuum at low temperature affect the inductance of the meander line and thus the frequency. The device can detect a susceptibility change equal to that of a change in Fe thickness of 0.03 atomic layers. The minimum detectable change in the diamagnetism of superconducting Pb corresponds to a thickness difference of 10−3 Å. The effect of 10−6 atomic layers of Fe can be detected by its depairing effect on a superconducting Pb film. The oscillator circuit including the film being studied is analyzed and the oscillation frequency calculated so that the effect of the various circuit elements can be determined. Suggestions for extending this technique are given.

A study of the phase transition of a ferromagnetic material

The Curie temperature is determined from a resistivity measurement of a nickel sample, and the result is compared to that obtained from a method previously described in this Journal. In addition, the Curie temperature is determined for nickel and Monel 400 using a tunnel diode oscillator. Data analysis includes a method to calculate a critical point exponent.

Subharmonic Entrainment of Avalanche Oscillations Through Optical Terminals

In optical subharmonic entrainment, the locking signal, having a frequency close to a subharmonic of the free running oscillator frequency, takes the form of an amplitude modulation of an optical carrier which is coupled to the avalanche diode. Based on the field theoretic approach, the paper presents a numerical analysis of optical subharmonic injection locking of an avalanche diode oscillator. It brings out some important features of optical subharmonic entrainment such as optimum locking conditions, dependence of locking range on the laser modulation depth, locking asymmetry etc.

Current-to-frequency isolation converter

A simple radiation-resistant current-to-frequency converter has been developed for the remote measurement of small currents (0.1-30 mu A) in lines at up to 4 kV above ground potential. the 6.5-9 MHz output frequency is a quasi-logarithmic function of the input current. The converter operates on the principle of a tunnel diode oscillator tuned by a varactor diode.

Flicker fluctuations in impatt diode oscillations

Flicker fluctuations in impatt diode oscillations

Proportional temperature controller using a solid-state heat pump (for Gunn diode oscillator)

An electronic temperature controller using a single solid-state heat pump as a heating and cooling element has been developed. It is capable of maintaining an insulated metal block of thermal mass approximately 650 J K-1 and 10 W internal heat sources at 58 degrees C (331K) for ambient temperatures of -10 degrees C (263K) to +70 degrees C(343K) with steady state regulation of better than +or-0.25K at 70 degrees C (343K) and +or-0.1K at -10 degrees C (263K). The time to reach demand temperature from -10 degrees C (263K) is approximately 23 min. Emphasis has been placed on minimising the levels of electromagnetic interference (EMI) normally associated with phase controlled air switched mode controllers. Component count has been minimised by the use of single chip microcomputer with zero crossing proportional control implemented in software.

Mutual phase locking of a coupled laser diode-Gunn diode pair

Mutual phase locking has been achieved through series connection of a semiconductor laser and a Gunn diode oscillator. Experimental results obtained demonstrate a mutual interaction between the two oscillators which results in a short term Gunn diode oscillator stability and improved spectral purity of its output. We also observe a narrowing of laser pulses and an improvement in regularity.

Indium phosphide millimeter-wave devices and components

The ability to grow high purity indium phosphide material as required for Gunn effect devices and the increased understanding of the operation of both Gunn amplifier and oscillator diodes has lead to some significant improvements in the performance of these devices. For oscillator operation the most important development has been the design and application of temperature stable current limiting cathode contacts. With current limiting contacts CW efficiencies improve significantly and the thermal impedance for a given input power is equally reduced.

Magnetic susceptibility measurement method for thin films and surfaces

A new method is described for the measurement of the susceptibility of thin films of magnetic materials. This method uses the inductance change of a superconducting meander line as sensed by a tunnel diode oscillator and is specially suitable for measurements during deposition of the films on a cryogenically cooled substrate. The sensitivity of initial tests agree with design calculations and can detect 1% or less of the signal from a monolayer of Fe.

Integrated Tunable Cavity Gunn Oscillator for 60-GHz Operation in Image Line Waveguide

The design, construction, and experimental test results of a mechanically tunable Gunn oscillator using a recessed diode metal coaxial cavity coupled to an image line waveguide is described. The oscillator frequency was changed by about 10-percent by varying the bias post length into the coaxial structure. The oscillator is designed so that both the Gunn diode and resonant cavity can be quickly replaced to provide extended frequency coverage and efficiency. This Gunn diode oscillator has provided up to 15-mW CW power at 60 GHz with 10-percent tuning range.

Gunn source for electron-spin-resonance spectroscopy

A Gunn diode oscillator stabilized by a transmission cavity is described; it has a center frequency of 9.4 GHz and a tuning range of about 1.2 GHz. The cavity provides a stabilizing factor of the order of 600 relative to the unstabilized oscillator. It was tested as the microwave source in an ESR spectrometer and gives the same performances as a commercially available klystron.

Modulation Schemes in Low-Cost Microwave Field Sensors

The use of modulation schemes in short-range microwave field sensors are discussed and in particular the ideas are applied to low-cost self-detecting doppler sensors based on a two-terminal negative resistance diode oscillator which acts as a load variation detector. FM-CW and pulse modulation techniques are described which can lead to improved performance in these sensors, and experimental results of bias modulation, varactor modulation, and pulsed operation of transferred-electron oscillators are presented. Modulation techniques can be applied in order to eliminate false alarms due to unwanted targets by enabling the doppler sensor to measure or discriminate target range, and the potential merits of different schemes based on frequency modulation with linear and sinusoidal modulation patterns are explored. A novel environmental profiling technique is proposed which exploits the response of frequency-modulated sensors to multiple stationary targets for use in a versatile short-range surveillance system employing digital processing techniques. The mechanism of pulsed operation in self-detecting sensors is described, and the effects of temperature variations in the active device, which result in frequency chirp, are considered. The technique of extracting the doppler signal from the pulsed bias current using a pulse cancellation circuit is demonstrated, and the effects of bias current changes during the pulse (due to temperature variations) on the use of this type of circuit are discussed.

Effect of oscillation amplitude on noise in gallium arsenide impatt diode oscillators with uniform doping profile

Effect of oscillation amplitude on noise in gallium arsenide impatt diode oscillators with uniform doping profile

Effect of Package Parasitics in Injection Locked Diode Oscillators

Effect of Package Parasitics in Injection Locked Diode Oscillators

8 GHz Tunable Gunn Oscillator in WR-137 Waveguide

The conventional technique of realising waveguide resonators for Gunn diode oscillators to operate at the band edge of the waveguide fails owing to the excitation of a coaxial mode resonance formed by the post and the side walls of the waveguide. One of the solutions to the problem is to mount the diode in a ridged waveguide resonator. This has been demonstrated by constructing an 8 GHz Gunn oscillator using a single ridge in WR-137 waveguide.The steps in designing the oscillator system are also presented.

Wide-band varactor-tuned oscillators

Ancillary to RF oscillation conditions, a more fundamental limitation of bandwidth has been established for single and multiple varactor diode oscillators due to the combined capacitance swing of the active device dominant capacitance and the varactor(s). Second, modification of the varactor characteristics is investigated to achieve linear tuning.

Power Combiner with Gunn Diode Oscillators

Combiners were developed using two Gunn diodes in dielectric waveguide (image line) oscillator circuits. The optimum configuration consisted of each Gunn diode being imbedded in a separate dielectric cavity as a primary source of oscillation. The dielectric resonators were then radiatively coupled to a common dielectric resonator from which the combined power could be obtained. It was found that the combined power was greater than the sum of the power obtainable from separate isolated oscillators. The proposed combiner appears attractive from the point of view of simplicity of construction and low cost and should be applicable to the millimeter-wave region, where the difficulties of precision machined metal-walled cavities are very great.

A cryogenic RE oscillator, the heart of a new NMR dispersion spectrometer

Describes a new CW-NMR dispersion spectrometer based on the detection of the frequency shift of a cryogenic tunnel diode oscillator, in which the inductance of the coil is influenced by the magnetic resonance phenomenon. Besides the design, the details of the construction and the operation of the oscillator, an outline of the performances and the major advantages and disadvantages of this spectrometer are given. The performances are compared with those of conventional NMR absorption (and dispersion) spectrometers.

Use of superconducting cavities in the stabilization of tunnel diode oscillators

We describe the design criteria of tunnel diode oscillators stabilized by superconducting RF cavities and how these are applied to the construction of a cryogenic oscillator operating at 600MHz for gravitational wave research.

Modeling of tunnel diode oscillators

The detailed behavior of tunnel diode LC oscillators is calculated by three different methods and compared with experiment. We present both analytic formulas and numerical methods which give corrections to the oscillator frequency calculated using the expression 1/(LC)1/2 and show that these corrections are often not negligible. The calculations also yield rf amplitude, bias current dependence, and other details necessary for the full realization of the performance of LC oscillators as transducers of pressure, temperature, and other physical quantities.