Abstract: There is disclosed a superconducting microwave component including a first substrate having a conductor line formed of an oxide superconductor on the surface thereof, a second substrate having a grounding conductor formed of an oxide superconductor on the surface thereof, and a package of a conducting material housing the first and the second substrates so that they are substantially parallel with each other. At least one portion of the grounding conductor is in contact with the inside of the package, through surface contact.

Abstract: A filter for an electromagnetic signal is formed of a set of planar resonators, preferably of superconductor material, interspersed among a set of electrically conductive sheets, outermost ones of the sheets serving as ground planes, and the inner ones of the sheets having irises for coupling electromagnetic power between the resonators. The resonators and the sheets have a planar shape, are parallel to each other, and are stacked one upon the other. Dielectric material insulates and serves to support the resonators and the sheets in their respective locations. There are at least two resonators in the set of resonators, and at least one inner sheet of the set of sheets. A first coupling element serves to couple an electromagnetic signal to a first resonator of filter to excite in the first resonator a first mode of electromagnetic vibration in a plane defined by the axis and a point of coupling of the first coupling element.

Abstract: An apparatus and method are described for gyromagnetic interaction between the electromagnetic field generated by an electromagnetic signal conducted by a superconductor and the magnetization contained in a magnetic structure. A ferrite magnetic structure is disposed in close proximity to a superconductor conducting the electromagnetic signal. A magnetization is induced in the magnetic structure with a geometry such that the magnetic flux is confined within the magnetic structure or eliminated from the magnetic structure so as not to produce an external magnetic field to interfere with the superconducting properties of the superconductor. The electromagnetic field of the signal conducted by the superconductor interacts gyromagnetically with the magnetization of the magnetic structure, inducing a phase shift in the electromagnetic signal traversing the superconductor. Thus, the invention induces a phase shift in the signal with minimum insertion loss due to electrical resistance.

Abstract: The disclosure relates to ferroelectric and superconducting thin films used in combination to produce low-loss passive microwave and millimeter wave devices which are frequency tuneable. Various metal oxide superconducting and ferroelectric thin films can be deposited in numerous multilayer geometries via a variety of deposition techniques to produce devices which can manipulate microwave and millimeter wave signals through the application of voltage bias signals across the ferroelectric films. Numerous superconducting microwave and millimeter wave devices, including delay lines, phase shifters, resonators, oscillators, filters, electrically-small antennas, half-loop antennas, directional couplers, patch antennas, and various radiative gratings, are made frequency-tuneable by utilizing voltage-tuneable capacitor structures fabricated from voltage-biased ferroelectric thin films.

Abstract: A cylindrical cavity is loaded with a ferroelectric rod and is resonant at the dominant mode. The loaded cylidrical cavity is a band pass filter. As a bias voltage is applied across the ferroelectric rod, its permittivity changes resulting in a new resonant frequency for the loaded cylindrical cavity. The ferroelectric rod is operated at a temperature slightly above its Curie temperature. The loaded cylindrical cavity is kept at a constant designed temperature. The cylindrical cavity is made of conductors, a single crystal high Tc superconductor including YBCO and a single crystal dielectric, including sapphire and lanthanum aluminate, the interior conducting surfaces of which are deposited with a film of a single crystal high Tc superconductor. Embodiments also include waveguide single and multiple cavity type tunable filters. Embodiments also include tunable band reject filters.

Abstract: A dielectric resonator apparatus for measuring the parameters of high temperature superconducting thin film is disclosed having improved means for positioning the dielectric and substrates, holding the resonator components in place during use, suppressing undesirable modes, adjusting the magnetic dipole coupling, and coupling to an electrical circuit.

Abstract: A planar SQUID magnetometer for detection and measurement of an applied magnetic flux is disclosed wherein a planar microwave-resonant element overlaps a Josephson device incorporated in a high-T.sub.c superconducting, thin-film SQUID device, thereby providing inductive coupling between the planar microwave-resonant element and the SQUID device. When the microwave-resonant element is excited by incident high-frequency microwave radiation, the intensity of reflected microwave radiation varies in response to a magnetic flux applied to the SQUID device in accordance with non-linear oscillatory behavior of the microwave-resonant element due to inductive loading by the SQUID device. The microwave-resonant element and the SQUID device are preferably fabricated photolithographically on a single substrate.

Abstract: A tetrahedral junction waveguide switch having a first length of hollow rangular waveguide and a second length of hollow rectangular waveguide adjacent each other with a ferrite rod longitudinally disposed therebetween. A magnetic field is created by a superconducting switching coil placed around the junction of the two lengths of waveguide. The normally magnetically biased ferrite rod permits electromagnetic wave energy to be transmitted through the first and second lengths of waveguide. An open circuit control means selectively and controllably interrupts the current flowing around the superconducting switching coil causing the longitudinal magnetic field to be removed from the normally magnetically biased ferrite rod. The waveguide switch is thereby placed in a cut off, nontransmission, or reflective mode preventing transmission of electromagnetic wave energy.

Abstract: To reduce the losses, high Tc superconductive waveguide filters are disclosed. There are two approaches to make the filters. In the first approach, all waveguide sections, irises, flanges are made of a single crystal high Tc superconductor. The single crystal is machined to the desired shape and size, the pieces are brazed and connected with flanges. In the second approach all waveguide sections, irises and flanges are made of a single crystal dielectric material the conducting surfaces of which are deposited with a film of a single crystal high Tc superconductor. The waveguide sections, irises and flanges are connected together by brazing or by a similar method. There are two basic types, (1) band pass and (2) band reject, of filters. In the band pass type, a series of resonators are placed one after another with a separation, typically, of three quarters of a wavelength between the centers of adjacent resonators. In the band reject filters, the resonators are in branch lines, i.e.

Abstract: To reduce losses of commercial room temperature couplers, high Tc superconducting waveguides and waveguide flanges are used for couplers. There are two approaches for making these high Tc superconducting waveguide structures. One is to use a single crystal such as YBaCuO (YBCO), cut and machine the crystal to the desired shape, and use high Tc superconducting flanges. In the second method, a good quality dielectric, such as sapphire is used and cut and machined to the desired shape. The conducting surfaces are coated with a single crystal high Tc superconducting material such as YBCO. The waveguides are brazed together. Low loss is important particularly for high power couplers. Significant amount of RF power is lost even with a low loss coupler. The high Tc superconducting couplers will provide a significant benefit in high power RF systems handling power levels such as 0.5 megawatts.

Abstract: A microwave resonator includes a superconducting signal conductor formed on a first dielectric substrate, and a superconducting ground conductor formed on a second dielectric substrate. The first dielectric substrate is stacked on the superconducting ground conductor of the second dielectric substrate. A temperature adjustable heater is mounted near to the second dielectric substrate, so that the resonating frequency .function..sub.o of the microwave resonator can be easily adjusted by controlling the temperature of the superconducting conductors by the adjustable heater.

Abstract: A microwave resonator includes a superconducting signal conductor formed on a first dielectric substrate, and a superconducting ground conductor formed on a second dielectric substrate. The first dielectric substrate is stacked on the superconducting ground conductor of the second dielectric substrate. A rod is adjustably provided to be able to penetrate into an electromagnetic field created by a microwave propagation through the superconducting signal conductor, so that the resonating frequency .function..sub.0 of the microwave resonator can be easily adjusted by controlling the position of a tip end of the rod.

Abstract: Novel articles are provided of thin super-conductive thallium-based copper oxide layers on inorganic, usually crystalline substrates. Novel methods are provided for ease of producing such articles, particularly involving sol-gel techniques and laser ablation. The articles have a highly oriented superconductive thallium-based copper oxide film, particularly epitaxial, with high superconductive transition temperatures and desirable electrical properties. The subject articles find use in a wide variety of electronic applications, particularly in microwave and millimeter wave devices.

Abstract: A superconducting accelerating tube which is constructed by welding and connecting a plurality of half cells (11) formed of superconductor material in a dish form having a substantially constant wall thickness of the material, and having a small-diameter portion (11a) and a large-diameter portion (11b) and in which the shell diameter periodically varies. The half cells (11) are welded together via ring-shaped connecting members (12) formed of superconducting material and disposed between the small-diameter portions (11a), and the half cell (11) and connecting member (12) are formed of Nb.

Abstract: Active superconductive devices are formed having a variable conductive element in electromagnetic contact with a superconductor. In one embodiment, a variable ohmic conductive device, such as a photoconductor, is placed adjacent a superconductor. By varying the optical radiation on the photoconductor, the electromagnetic environment adjacent the superconductor is changed, resulting in changed electrical properties. The superconductor may be patterned as a reject filter, with a photoconductor forming a microwave switch. Alternatively, a delay line plus variable ohmic element forms a phase shifter.

Abstract: An inductor uses high temperature superconductors in order to obtain high Q for high frequency operation. The superconductors are applied as thin films to substrates. In some embodiments, superconductor thin films are applied to opposite sides of the same substrate. Superconductive thin films are applied outside the magnetic field establishing superconductive thin films in order to shield against leakage of the magnetic field beyond the inductor. The inductor is connected to a capacitor to realize a resonant circuit used in a power conversion system.

Abstract: The invention is directed to a superconducting microwave resonator, to holding devices for those resonators, and to their methods of manufacture. The superconducting microwave resonator employs at least two superconducting films on substrates positioned on a dielectric. The holding devices include a variety of configurations, such as, a spring loaded device. The superconducting microwave resonators have Q values of as high as microwave resonators formed of Nb, but operate at much higher temperature.

Abstract: An electronically controlled ferroelectric RF switch is an active medium formed from a ferroelectric material the permittivity, and as such the refractive index, of which may be varied by varying the strength of an electric field in which it is immersed. The ferroelectric RF switch includes the ferroelectric material having electrodes or conductors mounted thereon that are connected to an adjustable d.c. or a.c. voltage source. The switch may be placed in an RF transmission line that includes appropriate input and output impedance matching devices such as quarterwave transformers. The active medium of the RF switch is constructed of two prismatic structures of a ferroelectric material. When the two prisms are at the same zero bias voltage, then the RF energy passing through the switch is not deflected and the switch is in the OFF condition. Application of a bias voltage reduces the permittivity and the refractive index of the outer prismatic structure.

Abstract: Electronic circuit node structures which minimize parasitic capacitance in linear path and angular circuit topographies for high frequency circuits are described. The electronic circuit comprises at least two signal conductor elements and an active or passive circuit element on a substrate. The conductor elements are arranged to define a gap between their ends. The circuit element bridges the gap. In one embodiment, the longitudinal axes of the conductor elements are laterally offset and generally parallel. The conductors are arranged to form the gap between adjacent edges on the ends of the conductors. The circuit element is arranged to bridge the gap. The other conductor edges near the gap are arranged at angles which increase the distance between them. In another embodiment, the conductor elements form an angle with the gap at the apex. The circuit element bridges the gap between the conductor edges nearest the apex.

Abstract: A superconducting non-linear device comprising a superconducting conductor, a current source associated with the conductor for applying to the conductor a bias current, and a control device associated with the current source for selectably controlling the magnitude of the bias current. The non-linear device according to the invention may be used in a number of circuit configurations, including current limiting, switching, mixing and detecting circuits.

Abstract: A superconducting microwave selective filter system having a superconducting filter connected to receive RF signals and perform filtering before the RF signals are applied to nonlinear circuitry such as receiver protectors and low noise amplifiers. A single pole n throw point switch selects a desired one of the filters to provide a receiver with a desired frequency, such as an active radar frequency. The low loss and high dynamic range of a superconducting filter permits these filters to be employed in the front end of the system before system nonlinear circuitry.

Abstract: A microwave resonator includes a ground conductor formed on an under surface of a dielectric layer and a signal conductor formed on an upper surface of the dielectric layer separately so that the signal and ground conductors cooperate to form a microstrip line. The signal conductor has a launching pad portion for receiving a signal, and a resonating conductor portion forming an inductor. The resonating conductor portion is formed separated from the launching pad portion so that a gap between the launching pad portion and the resonating conductor portion forms a capacitor. Thus, the inductor formed by the resonating conductor portion of the signal conductor and the capacitor formed by the gap between the launching pad portion and the resonating conductor portion form a resonator circuit.

Abstract: A structure having a surface exposed to electromagnetic radiation in the microwave or millimeter-wave spectrum wherein discrete elements including a high-temperature superconducting film formed on a substrate are disposed on the surface.

Abstract: A variable superconducting delay line system and method having a high temperature superconducting trace and ground plane characterized by a variable inductance L per unit length and capacitance C per unit length, wherein the system and method permit users to select a delay time for an incoming signal propagating through a the transmission line. The system is adapted to keep the ratio of L/C constant, while independently changing L and C to achieve the desired delay time, which corresponds to the product of L times C.

Abstract: A waveguide cavity filter having a conductive housing, a plurality of high dielectric constant ceramic resonators disposed within the conductive housing and at least a portion of a sheet of superconductive material which is constrained to be at an ambient temperature below the critical temperature of the superconductor and disposed in contact with at least one of the side walls of the conductive housing and with an opposing surface of each of the resonators, such that the resonators are in close superconductive contact with the side walls of the conductive housing. In particularly, the superconductive sheet is a layer of high temperature superconductor. In a first embodiment of the invention, the resonators in the shape of cylindrical plugs are disposed with a flat surface juxtaposed to the side wall.

Abstract: Planar dual mode filters (30) are formed by a conductive resonator (20) having circular symmetry and two pairs of symmetrically oriented planar conductive leads (22, 26 and 24, 28). The conductive leads (22, 26 and 24, 28) are aligned colinearly with two orthogonal diameters (32, 34, respectively) of the circular conductive resonator (20) and are electrically isolated from said resonator (20). A perturbation (38) located on an axis (36) oriented symmetrically with respect to the two pairs of conductive lead (22, 26 and 24, 28) couples electromagnetic modes which are injected into the resonator (20) by the planar conductive leads (22, 26 and 24, 28). Higher order filter circuits can be realized by combining multiple filters (30) of the present invention. The filters (30) are amenable to printed circuit (microstrip to stripline) fabrication using superconductors for the conductive elements.

Abstract: A stripline filter with suppressed electro-magnetic leakage. A filter topology suppresses generation of spurious waveguide modes by structuring microstrip launchers to operate as a waveguide way beyond cutoff of the waveguide modes, and by damping out remaining waveguide mode energy with lossy stripes in the filter package.

Abstract: A superconducting variable phase shifter providing improved performance in the microwave and millimeter wave frequency ranges. The superconducting variable phase shifter includes a transmission line and an array of superconducting quantum interference devices (SQUID's) connected in parallel with and distributed along the length of the transmission line. A DC control current I.sub.DC varies the inductance of the individual SQUID's and thereby the distributed inductance of the transmission line, thus controlling the propagation speed, or phase shift, of signals carried by the transmission line. The superconducting variable phase shifter provides a continuously variable time delay or phase shift over a wide signal bandwidth and over a wide range of frequencies, with an insertion loss of less than 1 dB. The phase shifter requires less than a milliwatt of power and, if one or more of the Josephson junctions fails, the whole device remains operational, since the SQUID's are connected in parallel.

Abstract: A magnetometer is prepared by depositing three thin-film SQUID magnetic field detectors upon a substrate. Two of the detectors incorporate stripline SQUID detectors deposited at right angles to each other, to measure the orthogonal components of a magnetic field that lie in the plane of the substrate. The third detector uses a planar loop SQUID detector that measures the component of the magnetic field that is perpendicular to the substrate. The stripline SQUID detectors have thin-film base and counter electrodes separated by an insulating layer which is at least about 1 micrometer thick, and a pair of Josephson junctions extending between the electrodes through the insulating layer.

Abstract: A transmission line using superconductors instead of conventional conductors substantially reduces ohmic losses compared to conventional conductors. The superconductors are cooled by refrigerant flowing through a hollow superconducting inner conductor. The refrigerant is transported to the inner conductor using a novel connector.

Abstract: Systems for transmitting and/or receiving electromagnetic signal radiation are disclosed. The inventive systems are distinguished from previous such systems in that each includes at least one resonant cavity comprising a housing containing a body, e.g., a cylindrical or helical body, of relatively high T.sub.c superconducting material. Significantly, this body is fabricated using a new, unconventional procedure. As a result, the body exhibits substantially lower surface resistances than either previous such bodies of relatively high T.sub.c superconducting material, fabricated using conventional procedures, or bodies of copper, at 77 Kelvins and at frequencies ranging from about 10 MHz to about 2000 MHz. Moreover, as a consequence, the resonant cavity containing the unconventionally fabricated body exhibits much higher quality factors, Q, at the above temperature and frequencies, than previous such cavities containing either conventionally fabricated bodies of relatively high T.sub.

Abstract: A superconductive array antenna system provides a substantial improvement of gain, in the range of from about 5 db to over 20 db, at frequencies in excess of 20 gigahertz, and preferably in the range from 40 to 100 gigahertz and beyond. The antenna system includes a phased antenna array, operating at superconductive cryogenic temperatures, with superconductive phasing and switching systems, to permit antenna beam steering and polarization independent of operating frequencies. The invention also permits the elimination of amplifiers and other such elements that have been needed to overcome system losses, and permits further miniaturization of such systems.

Abstract: A method of constructing ultra-low-loss miniaturized microstrip type microwave transmission lines, circuits, and resonators and their resulting structures are disclosed. The method includes etching a groove of the appropriate width and depth into the surface of a first substrate as determined by a preselected characteristic impedance. Appropriate thin film superconductors are then deposited on the surfaces of the first substrate and a second substrate. The thin film superconductors are then patterned after which the two substrates are sealed together by field-assisted thermal bonding such that a novel two-conductor electromagnetic transmission line results.

Abstract: A sensor for measuring magnetic flux has at least one hole or opening in a strip resonator of superconductive material defining a ring in which a Josephson element is integrated into the strip resonator and coupled thereto so that attenuation in the tank circuit formed by the ring when a standing wave is established in the strip resonator can be picked up capacitively by a further strip conductor.

Abstract: Connecting a superconductive material wiring layer to an electrode formed of normal metals (i.e. non-superconductive metals, such as aluminum), and connecting a part of a semiconductor region to the normal metal. The normal metal can contact the superconductive wiring layer via a barrier metal, such as TiN, at least at a side wall of the superconductive wiring layer which is essentially orthogonal to the layer wiring. Accordingly, even when the wiring layer is anisotropically superconductive mainly in a direction parallel to the plane of deposition, the superconductive property can be fully realized. The inventive structure prevents copper atoms in the superconductive material and silicon atoms in the semiconductor region of the IC from producing an undesirable alloy. This improves reliability of the IC operation, i.e. the semiconductor material as well as the superconductive material is not deteriorated.

Abstract: Apparatus for determining the electrical characteristics of a superconductive material in a range of microwave frequencies and in a range of cryogenic temperatures has the material incorporated within a resonant cavity mounted on a cold finger for maintaining the material at a predetermined temperature. A pair of test waveguides extend oppositely of the cavity and terminate in separable waveguide junctions for passage of microwave energy to measure the microwave characteristics of the cavity as affected by the superconductive material. The cavity and test waveguides are enclosed in a vacuum chamber from which the cold finger extends for connection to controlled temperature cryogenic cooling equipment. The chamber also contains a plurality of calibration waveguides which extend parallel to the test waveguides, each calibration waveguide terminating oppositely in separable junctions.

Abstract: A ferrite device has a closed superconductor which encircles a ferrite element. The closed superconductor continuously circulates a current to produce a magnetic field for biasing the ferrite element.

Abstract: The structures for confining or guiding high frequency electromagnetic radiation have surfaces facing the radiation constructed of high temperature superconducting materials, that is, materials having critical temperatures greater than approximately 35.degree.K. The use of high temperature superconductors removes the constraint of the relatively low energy gaps of conventional, low temperature superconductors which precluded their use at high frequencies. The high temperature superconductors also provide larger thermal margins and more effective cooling. Devices which will benefit from the structures of the invention include microwave cavities, millimeter-wave/far infrared cavities, gyrotron cavities, mode converters, accelerators and free electron lasers, and waveguides.

Abstract: A microwave switch comprises a transmission line section which separates into two arms, at least one of which can go from a normal state to a superconductive state at a critical temperature, a junction rejoining the two arms in a second microwave transmission line section, and means to control the normal or superconductive state of one arm or of the two arms. The difference in length between the two arms is chosen to be substantially equal to an odd of half wavelengths of operation of the switch in such a way that the switch is off or on when the two arms are respectively in the same state, namely normal or superconductive, or in a different state. The state of the arms can be controlled by a magnetic field which causes the critical temperature to vary.

Abstract: The quality of superconducting cavity resonators depends to a very great extent on the surface quality of the cavities. The invention relates to a process for the manufacture of superconducting cavity resonators with improved surface quality, whereby even complex shaped cavity resonators can be made with cavities coated with NbN.

Abstract: For reduction in occupation area, there is disclosed a microwave device fabricated on a semi-insulating substrate and comprising a passive component area where a plurality of passive component elements are formed and an active component area where at least one active element is formed, the passive component area having a film overlain by a dielectric film and a strip conductor extending on the dielectric film, wherein the film and the strip conductor are formed by a superconductive material, so that the dielectric material is decreased in thickness by virtue of the strip conductor of the superconductive material.

Abstract: A superconducting cavity has a long time constant when the coupling factor of its output port is low so as to accumulate input microwave energy therein, and after a certain accumulation of the input microwave, an output microwave pulse with a large power is extracted from the cavity by suddenly increasing the coupling factor of its output port.

Abstract: A waveguide phase conjugate mirror for high power radiation at 10.6 .mu.m. The phase conjugate mirror comprises an optical waveguide of liquid nitrogen clad by gaseous nitrogen. The waveguide is maintained in a porous tube which allows the gaseous nitrogen to escape through the walls. The tube is also used to maintain a temperature gradient across the radius of the liquid nitrogen waveguide. Pressure in the waveguide, is maintained by a pressure drop across the porous walls of the containing tube. In maintaining the pressure, one or more additional porous tubes may be used around the containing tube with an additional pressure drop across the wall of each tube until a final volume is reached where the pressure may be maintained constant by the use of a small exhaust pump. An optical system such as a window or a lens or both is supplied at the input end for coupling the 10.6 .mu.m laser light into the waveguide mirror.

Abstract: The low temperature electronic package is a right angle connection utilizing an interposer rod between horizontal and vertical substrates. The interposer rod of insulating crystalline substrate material, has a superconducting metal ground plane on its surface, which ground plane is covered by an insulating film. Over the insulating film, the interposer has a number of arcuate conductors to which respective conductors of both the horizontal and vertical substrates are connected at controlled collapse pads for good electrical and mechanical connection. All circuits are effectively transmission lines because the underlying ground plane is continuous.The interposer rod provides a robust, low inductance connector mechanism with a strain minimizing configuration, which permits both horizontal and vertical substrates to interconnect with great connection versatility. It provides for convenient removal and has great resistance to failure related to repeated temperature cycling.

Abstract: A superconducting transversal filter circuit for processing signals in the 2-20 GHz range consisting of a miniature transmission line of niobium or similar material, a series of taps for coupling the input and output, and cryogenic refrigerator.

Abstract: This interface permits the testing of high speed semiconductor devices (room-temperature chips) by a Josephson junction sampling device (cryogenic chip) without intolerable loss of resolution. The interface comprises a quartz pass-through plug which includes a planar transmission line interconnecting a first chip station, where the cryogenic chip is mounted, and a second chip station, where the semiconductor chip to be tested is temporarily mounted. The pass-through plug has a cemented long half-cylindrical portion and short half-cylindrical portion. The long portion carries the planar transmission line, the ends of which form the first and second chip mounting stations. The short portion completes the cylinder with the long portion for part of its length, where a seal can be achieved, but does not extend over the chip mounting stations. Sealing is by epoxy cement. The pass-through plug is sealed in place in a flange mounted to the chamber wall.

Abstract: A transmission line having substantially reduced far-end forward wave crosstalk is characterized by a single layer of dielectric material having a thickness chosen to provide a forward wave coupling constant K.sub.F substantially equal to zero. The dielectric layer is located on a ground plane, and has a plurality of signal carrying conductors embedded in it. The thickness H of the dielectric underlayer below the signal carrying conductors is chosen to provide a transmission line having the selected values of impedance, etc. and substantially reduced forward wave crosstalk. The thickness t of the dielectric overlayer above the signal carrying conductors is chosen (for the selected value of thickness H of the dielectric underlayer) at the finite value critical thickness at which forward wave mutual capacitance and forward wave mutual inductance cancel to a null. The ground plane and the signal carrying conductors can be superconductors.

Abstract: An acoustic superlattice of alternating layers of different acoustic impedance is disclosed as a filter for high frequency phonons. Applications discussed include spectrometers, acoustic imaging apparatus, and cavity resonators.

Abstract: A device for cooling a superconductive resonator has a tube for containing liquid coolant and a diffusion weld connecting an outer face of the tube with the resonator wall in a heat-exchanging relationship therewith.

Abstract: A compact cryogenically coolable choked waveguide particularly for low-noise input coupling into a cryogenically cooled device, such as a maser or parametric amplifier, utilizes coaxial stainless steel support tubes surrounding the waveguide and connected in cascade to provide a folded low thermal conduction path. The edges of the tubes connected are welded.