Abstract: A tunable local oscillator (10) with a tunable circuit (12) that includes a resonator (16) and a transistor (14) as an active element for oscillation. Tuning of the circuit (12) is achieved with an externally applied dc bias (22, 24) across coupled lines (20) on the resonator (16). Preferably, the resonator (16) is a high temperature superconductor microstrip ring resonator with integral coupled lines (20) formed over a thin film ferroelectric material. A directional coupler (38) samples the output of the oscillator (14) which is fed into a diplexer (40) for determining whether the oscillator (14) is performing at a desired frequency. The high-pass and low-pass outputs (42, 44) of the diplexer (40) are connected to diodes (48, 46) respectively for inputting the sampled signals into a differential operational amplifier (50). Amplifier (50) compares the sampled signals and emits an output signal if there is a difference between the resonant and crossover frequencies.

Abstract: X-band signals are generated from the output of a Josephson junction array which is excited by a first RF frequency waveform digitally implemented in a data stream generated by a digital waveform generator gated by a stabilized local oscillator operating at a second frequency (X-band). The Josephson junction array outputs a digital data stream having pulses of quantum mechanically accurate uniform amplitude and picosecond pulsewidth. These pulses are fed to a bandpass filter which operates to extract a low phase-noise RF signal at X-band and consisting of the sum of the first and second frequencies and which can thereafter be used to generate transmit signals in a radar system and more particularly a cryogenic radar system.

Abstract: An effective high frequency oscillator is made of a plurality of Josephson devices. A high frequency converter as a high frequency circuit is made of the high frequency oscillator, nonlinear superconductor devices, and transmission line. Josephson devices are connected in parallel to make a superconductor module. Then superconductive modules are connected in series for high frequency via a phase locking circuit such as a thin film type capacitor to make the high frequency oscillator. Consequently, the high frequency oscillator is used as a local oscillator for a frequency converter. The high frequency system comprises a high frequency package housing a high frequency circuit, a cooling unit including a low temperature stage in thermal contact with the high frequency package, and a shielding case for housing the high frequency circuit and the low temperature stage. The high frequency system of the present invention provides a small-sized and power-saving high frequency circuit having operational stability.

Abstract: A Gaussian-beam oscillator for microwave and millimeter wave comprising a negative resistance amplifier circuit which produces and amplifies a high-frequency signal, a resonator consisting of a pair of reflecting mirrors, which consist of a spherical mirror and a planar mirror or two spherical mirrors, and a wave path which transmits the high-frequency signal between said resonator and said negative resistance amplifier circuit, one reflecting mirror of said resonator having an electromagnetic wave coupling region constituted as a circular partially transparent mirror surface region having its center on the optical axis, the other reflecting mirror having a strip element provided at the center of the optical axis and on the rear surface of said strip element having a coupling region for coupling with said wave path, said one reflecting mirror constituting said resonator and having the electromagnetic wave coupling region having a higher reflectance than the reflectance of the other reflecting mirror.

Abstract: The present invention relates to a superconductive electromagnetic wave mixer comprising a local-oscillator section and a receiving section, said receiving section serving as a section at which an electromagnetic wave from the local-oscillator section and an externally originating electromagnetic wave are combined. The local-oscillator section and said receiving section are each formed by at least one Josephson junction employing at least one oxide superconductor.

Abstract: A remote temperature sensor includes a microwave oscillator which generates n output signal having a frequency which is proportional to the temperature of the environment in which it is located. The oscillator includes a relatively high transition temperature superconducting (HTSC) ring coupled to a transistor in a plurality of microstrip line oscillator configurations including those of a reaction oscillator, a transmission oscillator, a reflection oscillator and a parallel feedback oscillator. The superconducting ring operates below its transition temperature and in so doing, acts as a high Q resonator whose resonant frequency is proportional to temperature.

Abstract: A push-push microwave oscillator has two branch oscillators fabricated of a transistor and transmission line elements extending from terminals of the transistor, and a resonator which is fabricated of an annulus of superconductor material and serves to phase lock oscillations of the two branch oscillators. The superconductor material is a composite of a rare earth element and copper oxide such as yttrium-barium-copper oxide. A first transmission line in each of the branch oscillators extends past the resonator with a spacing to provide for electromagnetic coupling between the branch oscillator and the resonator. A second transmission line in each of the branch oscillators has a length equal to approximately one-quarter wavelength of the oscillation frequency to tune the branch oscillator to a common oscillation frequency.

Abstract: A conducting plane resonator (10) is used to stabilize an oscillating means (12) typically operating at microwave frequencies. The conducting plane resonator (10) is in proximity to the oscillating means (12) and is magnetically coupled thereto. In a first implementation, the conducting plane resonator (10) is magnetically coupled to an input conductor (16) of the oscillating means (12). In a second implementation, the conducting plane resonator (10) is magnetically coupled to an output conductor (18), which is coupled to the oscillating means (12). In a third implementation, the conducting plane resonator (10) is magnetically coupled to both the input conductor (16) and the output conductor (18). The conducting plane resonator (10) preferably comprises a thin, substantially planar conducting plane and is dimensioned such that it is resonant at the desired operating frequency. The conducting plane resonator (10) is preferably fabricated of a superconductor material to achieve high-Q performance.

Abstract: An electronic clock has a single Josephson junction connected in parallel to a resonant circuit, which is a delay line with a matching resistance at the input end to provide series termination. The opposite end of the delay line is an open end to reflect pulses, and the pulse transit time on the line determines the clock rate. A zero crossing detector is provided to initiate the clock operation when an input signal rises above a given threshold, and a reset circuit is included to turn off the clock when the input signal falls below this threshold. A flip-flop circuit allows the clock to be turned on by alternate initiating signal pulses. A modification includes a pulse rejuvenating circuit at the end of the delay line to offset pulse degradation. All of the circuits are fabricated with Josephson junction elements, and the zero crossing detector, reset circuit, flip-flop circuit and pulse rejuvenator circuits include dc-SQUID's.

Abstract: A low-noise cryogenic oscillator has a resonant circuit formed of superconducting material for generating a signal at a desired frequency. A linear amplifier and a limiter are electrically connected to the resonant circuit at first, second and third locations. A buffer amplifier is electrically connected to the resonant circuit at a fourth location and applies the signal generated by the resonant circuit to a load. The first, second, third and fourth locations are selected to minimize the impedance from those locations to ground at 1/f frequencies. The resonant circuit, the linear amplifier, the limiter and the buffer amplifier are all maintained at a temperature below the critical temperature of the superconducting material.

Abstract: A two-dimensional array of Josephson junctions is used as a high-frequency oscillator capable of emitting coherent power of predetermined frequencies since the geometry of the two-dimensional array allows the individual Josephson junctions to phase lock at predetermined frequencies. The array is controlled at a given voltage and excited by the application of DC current through the array, in effect providing a rapidly tunable DC-to-AC converter at GHz and THz frequencies. The oscillator operates without the application of external high frequency signals or a connection to a cavity resonator. Load matching and other adjustments can be made by selecting the appropriate number of Josephson junctions in the array, selecting a damping factor which determines non-hysteretic operation, adding resistive shunts or a superconducting ground plane.

Abstract: A low-noise oscillator includes a resonator constituted by a coil, a capacitor and a sustaining coil which are made of superconductivity material and maintained at a low temperature below the critical temperature; a linear amplifier which always operates in its linear zone; and a load.The amplitude of oscillation is stabilized when it has attained a threshold value such that the superconducting material constituting the coil of the resonator becomes progressively resistive under the action of the magnetic field produced by this coil. The coil then dissipates part of the energy injected into the resonator. Since the high-frequency noise of the oscillator is essentially determined by the low-frequency noise of its nonlinear element, the use of superconducting material at low temperature in order to constitute the nonlinear element makes it possible to obtain an oscillator having very low noise.

Abstract: Disclosed is a novel switching device. In its currently preferred embodiment the device comprises a conductive path that comprises a superconductive section, with the remainder of the path being non-superconductive, means for applying a voltage across the path such that a current flows, and means for changing the current in the path from a first value to a second value, where one of the two values is below, and the other is above, a critical current associated with the superconductive section of the path. Depending on the choice of applied voltage and path parameters changing the current from the first to the second state results in switching of the current, either oscillating between two levels of current, or to a steady value. Exemplarily, the current is changed by changing the applied voltage or by changing the resistance of the non-superconductive portion of the conductive path. The device can be used as, for instance, a microwave oscillator or a (binary) photodetector.

Abstract: An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

Abstract: A coherent array of Josephson oscillators is provided. Individual hysteresis-free Josephson junctions are longitudinally arranged in a line and have such a spacing as to substantially eliminate quasiparticle interactions. To provide a common frequency of operation, equal and opposite dc voltages are produced in adjacent pairs of the Josephson junctions by an arrangement of interlocking dc SQUID's (Superconductive Quantum Interference Device) connected to transversely extending biasing leads. Phase coherence for the array is provided by a rf current circulating in an inductive feedback path that loops between the ends of the array.

Abstract: A coherent array of Josephson oscillators is provided. Individual hysteresis-free Josephson junctions are longitudinally arranged in a gap of a central conductor in a line and have such a spacing as to substantially eliminate quasiparticle interactions. To provide a common frequency of operation, equal and opposite dc voltages are produced in adjacent pairs of the Josephson junctions by an arrangement of interlocking dc SQUID's (Superconductive Quantum Interference Device) connected to the longitudinal central conductor using microwave bias tees. Phase coherence for the array is provided by a rf current circulating in an inductive feedback path that loops between the ends of the array.

Abstract: Josephson devices are distributed in series in a transmission line structure in which electromagnetic waves are used to synchronize the dynamics of the Josephson devices in order to achieve coherence between the devices. Electromagnetic waves, such as oscillatory traveling waves, standing waves, and solitary waves along the transmission line couple the Josephson devices in a manner such that coherence is achieved for the entire array. The Josephson devices can be tunnel junctions, point contacts, micro bridges, and weak links, and more generally include any such superconductive device which obeys the Josephson equations of voltage and current. The transmission line is any line which controllably supports electromagnetic waves, and can include strip lines located over a ground plane, coaxial lines, etc. A DC bias is supplied to the transmission line, and the ends are terminated in accordance with the type of wave to be propagated along the line.

Abstract: A DC powered, self-resetting Josephson junction logic circuit relying on relaxation oscillations is described. A pair of Josephson junction gates are connected in series, a first shunt is connected in parallel with one of the gates, and a second shunt is connected in parallel with the series combination of gates. The resistance of the shunts and the DC bias current bias the gates so that they are capable of undergoing relaxation oscillations. The first shunt forms an output line whereas the second shunt forms a control loop. The bias current is applied to the gates so that, in the quiescent state, the gate in parallel with the second shunt is at V=O, and the other gate is undergoing relaxation oscillations. By controlling the state of the first gate with the current in the output loop of another identical circuit, the invert function is performed.

Abstract: The fluxon oscillators for producing electromagnetic radiation having a wavelength shorter than the shortest radio waves, but longer than the longest infrared radiation, may comprise two closely spaced superconductive ring-shaped members having a ring-shaped Josephson junction barrier therebetween capable of supporting the tunnelling of superconductive electrons across such barrier, a source of magnetic flux for initially producing at least one fluxon in the barrier, a power supply for producing an electrical biasing current between the superconductive members and across the barrier for causing movement of the fluxon along and around the ring-shaped barrier in a closed path, and a plurality of centers to produce enhanced superconductive electron current across the barrier, such centers being spaced around the ring-shaped barrier for causing cyclical variations in the velocity of the fluxon and thereby causing the radiation of electromagnetic energy at a frequency corresponding to the frequency of such cyclica

Abstract: A picosecond pulse generator for producing pulses having widths in the or of 10.sup.-12 seconds utilizes a Josephson junction that has an external load resistor connected in shunt therewith by a balanced transmission line. The Josephson junction is driven by a high frequency oscillator, and the AC current, I.sub.1, flowing through it is adapted to have its amplitude varied with respect to I.sub.c, the critical current of the junction. As the value of I.sub.1 /I.sub.c exceeds one and increases, first a single and then an increasing number of picosecond pulses are produced during each half cycle of the high frequency oscillator.

Abstract: Josephson interferometers contain inductive, capacitive and resistive components, and, as a result, such devices are subject to the presence of relatively high amplitude resonances similar to those found in in-line gases. Interferometer structures exhibit the same resonant behavior as long tunnel junctions, except that there exist only as many discrete resonance voltages as meshes in the interferometer device. Hence, a two-junction interferometer has one resonance as compared to two resonances in a three-junction device. In the I-V characteristic of a Josephson tunneling device such as an interferometer, such resonances appear as current steps which must be taken into account in the design of Josephson switching circuits primarily to avoid the situation where the load line of an external load intersects a resonance peak. Where the load line and the resonance peak intersect, because such an intersection is stable, the device is prevented from switching to the full voltage desired.

Abstract: A method for preparing superconductive Nb.sub.3 Sn layers on niobium surfaces for high frequency applications in which a defined reaction zone which contains a tin source and the niobium surface is formed in an open reaction chamber and sealed off to the extent that, while interfering gases are being drawn off from the reaction zone during the evacuation, the vapor pressure of the tin remains higher within the reaction zone, when heated, than in the rest of the chamber. While pumping continuously, the reaction zone is then heated to a temperature between 930.degree. and 1400.degree. C and held at this temperature until an Nb.sub.3 Sn layer 0.5 to 5 .mu.m thick is formed on the niobium surface.

Abstract: A quantum interference Josephson junction logic device is disclosed which comprises three or more junctions connected in parallel which are capable of carrying Josephson current and includes means integral with at least one of the junctions for carrying a larger maximum Josephson current than the remaining junctions. This integral means includes means for carrying a maximum Josephson current which is twice as large as the maximum Josephson current in the remaining junctions. While the spacing between the lobes of the threshold curve (I.sub.m vs. I.sub.c) is increased over that of a two junction interferometer by adding another junction resulting in an increased operating region in which logic circuits switch to the voltage state, good current gains with large lobe separation could not be achieved by the mere addition of junctions. Current gain with large lobe separation is obtained if the two outer junctions having a zero field threshold current, I.sub.

Abstract: Various injection locking arrangements employing Josephson oscillators are disclosed for achieving signal amplification, frequency conversion and the detection of extremely low level signals at high frequency ranges.