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Express analysis of the dependence of the critical temperature of different superconducting films on its thickness was proposed, developed, and tested. The technique is based on a mathematical analysis of an integral equation that describes a one-time measurement of the electrical resistance temperature dependence of a sufficiently long superconductor film with variable thickness. The dependence of the film thickness and width along its longitudinal coordinate (film geometry) is set or measured using known methods. The express analysis has significant advantages over the more labor-consuming method of time-shared measurement of the critical temperature of film segments with different thicknesses.

We describe the first phase of experimental study of the superconducting bridge RFTES detector at temperatures 20-300 mK including the measurement of its thermal conductance, which fits the model of electron gas heating. We discuss the idea of the RFTES scheme, which is based on the probing of microwave loss near superconducting transition of the bridge. The heat applied to the bridge is generated by the probing signal at the frequency of the high-Q resonator. Since the real part is dominating in the nonlinear impedance of the bridge, the applied heat provides merely amplitude modulation of Q suggesting the suppression of phase jitter of the resonator. The bridge was made from a 50-nm-thick hafnium film (T C ≈ 380 mK) sized to 2.5 μm × 2.5 μm. The resonator and the rest of the circuit were made from 200-nm-thick film of niobium (T C ≈ 9 K) demonstrating the loaded Q-factor up to and above 10 000 at 1.5 GHz. A cryogenic semiconductor amplifier was used in the readout circuit. The thermal conductance was measured using the steady Q regime of the resonator and found to follow T 5 down to and below G ≈ 1×10 -13 W/K. The NEP below 10 -18 W/√Hz is estimated for the electron temperature of the bridge about 300 mK.

A high-quality superconducting resonator with a microbridge of hafnium film for use in a circuit for readout a terahertz-band imaging array with frequency division multiplexing is demonstrated experimentally. The variability of the impedance of the bridge at a frequency of 1.5 GHz, which is a key factor in the control of the quality of the resonator, is studied. The bridge, having a thickness of about 50 nm, a critical temperature TC ≈ 380 mK, and a plan size of 2.5 × 2.5 μm, was connected as a load of a resonator made of niobium film with a thickness of about 100 nm (TC ~ 9 K). It is shown that the bridge smoothly changes its impedance proportionally to the bias power in the entire temperature range. The effective thermal insulation of the bridge was measured in a dilution cryostat at temperatures of 50–300 mK. Thermal conductivity G of the bridge was calculated and found to be ~4 × 10–13 W/K, which gives an estimate of the sensitivity of the structure in the bolometric mode NEP ≈ 8 × 10–19 W/Hz1/2 at a temperature of 150 mK.

Our new detector and readout concept brings together TES (Transition Edge Sensor) and MKID (Microwave Kinetic Inductance Detector) technologies and exploits the idea of a microwave-induced superconducting transition in a small thin-film microbridge. The superconducting transition of the bridge manifests itself as variation in the Q -factor of niobium resonators at 5–8 GHz, somewhat similar to MKID operation. We present data showing the potential for developing this concept into multipixel detector arrays. Single-pixel sensitivity was measured at 4.5 K for an input band of 600–700 GHz using a prototype 10-nm-thick Nb bridge of size 1 μm × 500 nm. Radiation from human skin was detected with a resolution better than 1 K/rtHz, which is encouraging for terahertz imaging applications. To further improve device sensitivity, we are also developing Hf-based devices that operate near 0.35 K. Details about the physics and stability of these devices are discussed.

Aeroelastic instability of skin panels, known as panel flutter, can occur in the form of coupled-mode or single-mode flutter. While the first type of flutter usually occurs in one eigenmode (composed of the first and the second natural modes in vacuum) and yields well-studied nonlinear limit cycle oscillations, the single mode flutter can occur in several simultaneously growing eigenmodes, leading to complex nonlinear panel dynamics, including different co-existing limit cycles, periodic and non-periodic higher-mode oscillations. Structural nonlinearity and linear aeroelastic growth mechanism play the major role in this dynamic. While the linear panel flutter boundaries in the two-dimensional formulation have been studied in detail, there are only few investigations of the boundaries in the three-dimensional case. Since the linear growth mechanism plays an essential role in nonlinear oscillations, its comprehensive study is an important step toward understanding of complex dynamics of skin panels in the three-dimensional case. In this paper, we investigate the flutter boundaries of rectangular panels simply supported at all edges, and use potential flow theory to calculate the unsteady pressure. The problem is considered in two formulations: a series of rectangular plates, attached to each other, and a single rectangular plate. Flutter boundaries of the first four modes are calculated, and their transformations with the change of the spanwise plate width are studied in detail.

Poultry farming in the Russian Federation is a dynamically and successfully evolving branch of agricultural production at the present stage of national economic development. The question of effective and efficient feeding in aviculture has always been a very acute problem. In the struc-ture of the final cost of products formation feeding stuffs reach 75% according to various es-timations. The most expensive in the production of feed mixtures are suchprotein components of the food ration as fish meal and bone tankage, soy and sunflower meal, protein additives and concentrates. However, as the study shows, the possibilities of such high-protein cultures, as soybean are not fully in use for feed production. Along with soybean and its processed prod-ucts, it is also possible to use food waste products from the meat and fish industry, in respect that the waste processing of poultry is more than 30% of the bird’s carcase weight. These com-ponents of the feedstuff are also quite valuable, because they are rich in high-grade protein and able to meet the daily demand of poultry in amino acids. Until now, it has not been paid enough attention to applied researches, related to obtaining binary soy-meat and bone meal, soy-fishbone meal, soy-herb and soy-luminaria feed mixtures. In such combinations, the mois-ture contained in the raw material is average and, therefore, it is possible, at least twice, to re-duce the energy costs for its removal during drying. At the same time, as a result of the analyti-cal review, it was revealed a contradiction between the desire and endeavor of producers to improve the efficiency of poultry production by finding rational methods of preparation, appli-cation of modern technologies and improved technical means in the preparation of feed pellets based on binary compositions on the one hand and a known level of scientific knowledge about the laws of obtaining meat-bone, fish-bone or vegetable-grass pastes, the processes of averaging of moisture in the binary compositions and mechanisms of formation of the final product, namely, seals, molding pellets with a low crumbling and their subsequent drying on the other hand. In this connection, studies aimed at improving lines for production of feed products in the form of protein-mineral and protein-vitamin compositions using soy component are relevant and have important economic significance. The presence of this problem is also due to the lack, at modern stage of development, of special equipment and technologies, as well as scientifical-ly-based data for the design and construction. The paper proposes the design of a promising device ¬- a press granulator designed for the preparation of granulated feed for poultry on the basis of soy-meat and bone compositions and the results of experimental studies.

We present a superconducting noise bolometer for terahertz radiation, which is suitable for large-format arrays. It is based on an antenna-coupled superconducting micro-bridge embedded in a high-quality factor superconducting resonator for a microwave bias and readout with frequency-division multiplexing in the GHz range. The micro-bridge is kept below its critical temperature and biased with a microwave current of slightly lower amplitude than the critical current of the micro-bridge. The response of the detector is the rate of superconducting fluctuations, which depends exponentially on the concentration of quasiparticles in the micro-bridge. Excess quasiparticles are generated by an incident THz signal. Since the quasiparticle lifetime increases exponentially at lower operation temperature, the noise equivalent power rapidly decreases. This approach allows for large arrays of noise bolometers operating above 1 K with sensitivity, limited by 300-K background noise. Moreover, the response of the bolometer always dominates the noise of the readout due to relatively large amplitude of the bias current. We performed a feasibility study on a proof-of-concept device with a ${1.0\times 0.5 \rm \mu m^{2}}$ micro-bridge from a 9-nm thin Nb film on a sapphire substrate. Having a critical temperature of 5.8 K, it operates at 4.2 K and is biased at the frequency 5.6 GHz. For the quasioptical input at 0.65 THz, we measured the noise equivalent power ${\approx 3\times 10^{-12}\rm W/\sqrt Hz}$ , which is close to expectations for this particular device in the noise-response regime.

We demonstrated and analyzed the smooth microwave-driven transition of a superconducting bridge made from Hf into its normal state at bath temperatures below the critical temperature of Hf (Tc ≈ 380 mK). The bridge is integrated on a silicon chip with both the 600-700 GHz double-slot antenna and the 1.5-GHz CPW quarter-wave resonator (Q-factor ~10⁴) made from 100-nm Nb film. The experimental bridge was sized 2.5 um by 2.5 um by 50 nm and tested at temperatures down to 50 mK. Similar to the technique of MKID, we measured the dependence of transmission S21 on microwave power at the bottom of the resonance curve. It was found that the microwave power absorbed in the bridge fits to the model of hot electron gas, P~Te⁶-Tph⁶. The internal NEP down to≈10¯¹⁸ W/√Hz is estimated due to thermal noise at the optimum electron gas temperature, Te ≈ 320 mK. The NEP can be scaled down below ≈10¯¹⁹ W/√Hz via reasonable reduction of the bridge volume. The new detector circuit is suitable for integration within a large imaging array exploiting the FDMreadout.

The results of pioneering experiments on using a new method of microwave recording the bolometric response from a metal film near its superconducting transition edge are analyzed. Experiments are carried out at 4.5 K using a thin-film niobium absorber with a critical temperature of 6.7 K. The validity of the adopted electrodynamic model is confirmed. The chip contains a miniature antenna tuned to approximately 600 GHz and integrated into a planar resonator with a frequency of 6 GHz, which is weakly coupled with a pump line. Based on the experimental and model data, the presence of electrothermal feedback is shown, stability criteria are found, and I–V characteristics at microwaves are obtained. Bulk experimental samples with an absorber measuring 5 μm × 2.5 μm × 15 nm are fabricated with optical photolithography. At an amplifier channel noise of 3 K, the optical sensitivity of a prototype receiver can be expected at a level of 10−15 W/Hz1/2.

We describe in detail the principles of designing a tunable mixer with suppression of the mirror channel for the frequency band 86–115 GHz and a mixer for the band 787–950 GHz with twochannel reception and absence of the mechanical-tuning components. The mixers are based on superconductor–insulator–superconductor tunnel superconducting junctions with normal metal (aluminum) in the tuning circuit. The two developed mixers are optimized for the one-side chip connection to the full-height rectangular waveguide, which is required for creating a submillimeterwave single-chamber balanced waveguide mixer with a wide intermediate frequency bandwidth. The input-signal reflection coefficient is below −15 dB and the loss of the signal transmission to the mixer is below 3 dB in the frequency band 787–950 GHz.

In order to improve the frequency-division multiplexing (FDM) in transition edge sensor (TES) imaging arrays, it is suggested to replace commonly used SQUID amplifiers with a semiconductor high-frequency cooled amplifier. This would result in a single 10-GHz bandwidth amplifier serving the array of more than 1000 detectors. The basic idea is to implement an antenna-coupled TES as a load for a high-Q resonator, weakly coupled to a microwave transmission line. This high-frequency scheme substitutes the traditional wire connections to the TES. The NEP as low as 2×10-19 W/Hz0.5 is estimated at ambient temperature of 300 mK for submicron-size TES absorber made of Ti; the NEP is limited by 3 K noise temperature of the amplifier. To verify the new concept, prototype TES devices made of Nb are developed and tested above 4 K. The NEP of about 1.5×10-15 W/Hz0.5 is estimated for the experimental micron-size prototype devices made of Nb at 4.5 K. The IV -curves of the TES at different temperatures are recovered using the RF and heat balance models along with the experimental R(T) data; presence of the negative electrothermal feedback is verified.

The inherent noise of a prototype panel of the millimeter-wave telescope main reflector is measured at room temperature. A modulation radiometer based on a heterodyne detector with an input superconducting mixer and a balanced antenna switch is used. The noise temperature of the detector in the double-sideband mode equals 570 K at a local oscillator frequency of 842 GHz. The absorption factor of the aluminum panel calculated from the thermal radiation intensity is 0.31 ± 0.07%. This value is checked on samples made of phosphor bronze and stainless steel. The respective absorption factors are 0.41 ± 0.07 and 1.30 ± 0.07%, which are close to those obtained earlier for these materials using radiometers with direct-reading detectors. The wide dynamic range of the heterodyne detector simplifies calibration of the radiometer: there is no need to cool down the sensitive element below liquid helium temperature. A balanced switch of a new design makes it possible to radically suppress the influence of the background and take precision room-temperature measurements.

A comparative review of research works and development of ultrasensitive superconducting sensor nanobolometers for the imaging array radiometers of the terahertz frequency range is presented. Various absorbers and several methods for the radiation input are considered, and the necessary conditions for the production technology are analyzed. The optimal structures of the nanobolometers are determined for various applications.

We develop a high-sensitivity matrix radiometer which will be used on the large altazimuth telescope BTA of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (Fig. 1) for performing astronomical observations in atmospheric transparency windows in the poorly explored frequency range from 0.13 to 0.38 THz (wavelengths from 2.3 to 0.8 mm). Mounting of the radiometer at the focal point of the 6-m BTA telescope will enhance the capability of the SAO in the transparency windows of the Earth’s atmosphere from the UV range (wavelengths about 3000 A) up to the ultimate wavelength of the RATAN-600 telescope (about 0.5 m). This will make it possible to perform unique comprehensive multifrequency studies in one observatory. The radiometer is presumed to be used with other radio and optical telescopes, both in the above-mentioned and higher-frequency intervals of the terahertz range.

TELIS (Terahertz and submm Limb Sounder) is a cooperative European project to develop a three-channel heterodyne balloon-based spectrometer for measuring a variety of atmospheric constituents within the lower stratosphere. The 600-650GHz channel is based on a phase-locked Superconducting Integrated Receiver (SIR). SIR is the on-chip combination of a low-noise SIS mixer with quasioptical antenna, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and an SIS harmonic mixer (HM) for FFO phase locking. A number of new solutions was implemented in the new generation of SIR chips. To achieve the wide-band performance of the spectrometer, a side-feed twin-SIS mixer with 0.8 /spl mu/m/sup 2/ junctions integrated with a double-dipole (or double-slot) antenna is used. A Fourier transform spectrometer (FTS) test demonstrated a possibility to obtain the required instantaneous bandwidth for the SIS mixer. To ensure the autonomous operation of the phase-locked SIR on the balloon a number of approaches for the PLL SIR automatic control have been developed.

A low-noise rf amplifier based on a dc SQUID (SQA) is developed and tested within frequency range 3.0-4.5 GHz. The 4-channel chips are designed using proven balanced output configuration; they employ special damping filters. Each channel is tested separately demonstrating the following parameters at 3.95 GHz central frequency: gain (9.5 /spl plusmn/ 1.0) dB, 3-dB bandwidth 300 MHz and noise temperature (1.0 /spl plusmn/ 0.5) K. The 1-dB gain compression estimate is 50 K*GHz for bias voltage 80 /spl mu/V and characteristic voltage 285 /spl mu/V.

For the optimum design of integrated receivers operating above the gap frequency of Nb, we have designed, fabricated and tested NbN-based quasi-optical superconductor/insulator/superconductor (SIS) mixers. The mixer chip incorporates a resonant half-wavelength epitaxial NbN/AlN/NbN junction, a twin-slot antenna and their coupling circuits. We adopted two kinds of coupling circuit between the antenna and the SIS junction: one is an in-phase feed with a length of 95 µm and the other is an anti-phase feed of 30 µm length. It was found that the anti-phase mixer reveals a 3 dB bandwidth of 43% of the centre frequency; the uncorrected double-sideband receiver noise temperature TRX = 691 K at 0.91 THz and TRX = 844 K at 0.80 THz, while 17% and TRX = 1250 K at 0.79 THz for the in-phase version. Possible reasons for this difference are discussed, which could be transmission loss and its robustness with respect to the variation of junction parameters. These experimental results suggest the NbN-based distributed mixer with the anti-phase feed is a better candidate for wide-band integrated receivers operating above 0.7 THz.

We overview recent achievements in the field of cryogenic submillimeter-wave receivers based on superconductor–insulator–superconductor (SIS) tunnel junctions. The main attention is paid to the novel superconducting integrated receivers (SIRs) with an on-chip superconducting local oscillator. The single-chip microcircuit of the receiver, which integrates a quantum mixer based on the nonlinearity of a quasi-particle current in the SIS junction, a planar superconducting receiving antenna, and a cryogenic local oscillator, is described. Being dc-powered only by batteries, such a microcircuit operates as a submillimeter-wave superheterodyne receiver without any additional microwave equipment. Such receivers are very attractive for radioastronomical research, space communication systems, and monitoring of the environment from satellites, balloons, and special aircraft.

A submillimeter heterodyne spectrometer employing a superconducting local oscillator is demonstrated for the first time. The sensor chip comprises a quasioptical double-dipole lens-antenna SIS mixer (T/sub RX/=250 K at 380 GHz), a Josephson flux-flow oscillator and a SIS harmonic mixer. Room temperature PLL electronics is used with a reference source at 10 GHz. The PLL bandwidth of 10 MHz and the hold range of 3 GHz are estimated for locking at 32-th harmonic of the reference source. The spectral resolution better than 1 MHz and broadening effect of a spectral line of SO/sub 2/ gas at 326867 MHz are measured with a laboratory gas cell at 300 K at pressure 0.03 - 0.3 mbar using acousto-optical spectrometer.

To develop an efficient local oscillator (LO) integrated with a SIS mixer operating above the gap frequency of Nb, we have investigated the radiation power P of NbN-based flux-flow-type Josephson oscillators (FFO's). The designed and fabricated chip incorporates FFO's, SIS power detectors (DET's), and their coupling circuits. Both FFO's and DET's consist of epitaxial NbN/AlN/NbN junctions with high critical current density J/sub C/ (15 200 nW, enough for the optimum pumping of a SIS mixer with rf-resistance of 50 /spl Omega/, is coupled to DET's for 0.5-0.9 THz. The coupling bandwidth is larger than 20% of its central frequency. In the band, the radiation frequency is tuned by the control current through the FFO of 10-100 mA. The maximum coupling frequency of the present experiment is quantitatively agreed with the theoretical one. The peak power of 1.3 /spl mu/W is detected at 0.76 THz. The dissipated power in a FFO is smaller than 500 /spl mu/W, which is 10/sup -4/ times less than that of semiconductor sources. These results indicate the feasibility of NbN-based FFO's for a practical on-chip LO.

A Josephson flux flow oscillator (FFO) is the most developed superconducting local oscillator for integration with an SIS mixer in a single-chip submm-wave receiver. Recently, using a new FFO design, a free-running linewidth /spl les/10 MHz has been measured in the frequency range up to 712 GHz, limited only by the gap frequency of Nb. This enabled us to phase lock the FFO in the frequency range 500-712 GHz where continuous frequency tuning is possible; resulting in an absolute FFO phase noise as low as -80 dBc at 707 GHz. Comprehensive measurements of the FFO radiation linewidth have been performed using an integrated SIS harmonic mixer. The influence of FFO parameters on radiation linewidth, particularly the effect of the differential resistances associated both with the bias current and the applied magnetic field has been studied in order to further optimize the FFO design. A new approach with a self-shielded FFO has been developed and experimentally tested.

A number of new fabrication techniques are developed and optimized in order to fit the requirements of contemporary superconducting electronics. To achieve ultimate performance of integrated submm receivers with operational frequency of 1 THz, tunnel junctions with AlN tunnel barrier having a R/sub n/S value as low as 1 /spl Omega//spl mu/m/sup 2/ have been developed. High quality characteristics of Nb/AlN/Nb tunnel junctions with R/sub j//R/sub n/=16 and R/sub n/S=10 /spl Omega//spl mu/m/sup 2/ have been demonstrated. Electron Beam Lithography (EBL) in combination with Chemical Mechanical Polishing (CMP) has been incorporated to produce Nb/AlN/Nb junctions with 0.03 /spl mu/m/sup 2/ area. A new approach to obtain overdamped Nb/AlO/sub x//Nb tunnel junctions has been proposed and realized. The dependencies of the main parameters of novel junctions on the current density and circuit geometry have been studied. These junctions may have a good potential in Josephson junction arrays and Single-Flux-Quantum applications (RSFQ).

A low-noise RF amplifier based on a dc SQUID (SQA) has been tested in the frequency range 3.0-4.6 GHz in the open-loop configuration. The following parameters have been measured for the single-stage balanced type SQA at 4.0 GHz: gain (12/spl plusmn/1) dB, 3 dB bandwidth of 500 MHz and noise temperature (1.0/spl plusmn/0.25) K. For the nonbalanced type SQA at 4.0 GHz gain was (15/spl plusmn/1) dB, 3 dB bandwidth 200 MHz and noise temperature (0.5/spl plusmn/0.25) K. The improved performance is obtained due to the increased characteristic voltage (/spl ap/420 /spl mu/V) of the small-area (down to 0.7-0.9 /spl mu/m/sup 2/) high-quality Nb-AlO/sub x/-Nb SIS junctions. The saturation power (normalized to 1 GHz) referred to the input at 1 dB gain compression is estimated as /spl ap/55 K*GHz at a bias voltage of 60 /spl mu/V. The reasons for saturation of the SQA are discussed.

We present an X-band amplifier concept based on a HTS grain boundary dc SQUID, which allow for extended dynamic range for use with SIS mixers, e.g., as a buffer amplifier in front of an RSFQ ADC, or possibly for satellite and cellular phone communications. The proposed RF design is based on a combination of single-layer slot and coplanar lines forming novel input and output circuits. The following parameters (per stage) are obtained via simulation for central frequency 11 GHz: bandwidth 0.5-1 GHz, power gain 11-12 dB, noise temperature 5-10 K. A saturation product as high as 500-1000 K/spl middot/GHz is estimated for a characteristic voltage of 1-2 mV. The realization of these parameters makes HTS SQA competitive with existing coolable HEMT-amplifiers for radio astronomy and satellite communication.

A quasi-optical mixer containing two Nb/Al/AlOx/Nb superconducting tunnel junctions integrated into a NbTiN/SiO2/Al microstrip line is studied experimentally in the 800–1000 GHz frequency range. The mixer is developed as an optional front end of the heterodyne receiver operating in frequency band 3 or 4 and incorporated into the HIFI module of the Herschel space-borne telescope. The double-dipole antenna of the mixer is made of NbTiN and Al films; the quarter-wavelength reflector, of a Nb film. The mixer is optimized for the IF band of 4–8 GHz. The double-sideband noise temperature TRX measured at 935 GHz is 250 K at a mixer temperature of 2 K and an IF of 1.5 GHz. Within 850–1000 GHz, TRX remains below 350 K. The antenna pattern is symmetrical with a sidelobe level below −16 dB.

A quasi-optical mixer employing a Nb/Al/AlOx/Nb twin-SIS junction with a NbTiN/SiO2/Al microstrip coupling circuit is tested at 800–1000 GHz. The receiver noise temperature TRX=250 K (DSB) is measured at 935 GHz for the bath temperature 2 K at IF=1.5 GHz; TRX remains below 350 K within the frequency range 850–1000 GHz. The integrated lens-antenna demonstrated good beam symmetry with sidelobes below −16 dB.

We present a concept of a broadband IF amplifier based on experimental results obtained with a dc SQUID rf amplifier (SQA). The frequency range is broadened by using several SQAs, each one tuned to its own central frequency at both input and output; the numerical simulations are presented. A possibility of fine adjustment of the input impedance is numerically demonstrated in the range of 1–1000 Ω . The following parameters are expected for a three-channel SQA: central frequency ≈4 GHz, bandwidth 1 GHz, noise temperature ≈2 K, input saturation ≈300 K GHz.

We present a concept of a rf amplifier based on a directly coupled dc SQUID with bicrystal junctions, which have high saturation power and can be used with SIS mixers or possibly for satellite and cellular phone communications. A novel input resonant circuit is proposed using single layer of HTS. Estimated parameters are (per stage): central frequency ≈11 GHz, bandwidth≈400 MHz, noise temperature≈10 K, gain≈10 dB and input saturation≈1000 K GHz.

Presently a Josephson flux flow oscillator (FFO) appears to be the most developed superconducting on-chip local oscillator for integrated submillimeter-wave SIS receivers. The feasibility of phase locking the FFO to an external reference oscillator at all frequencies of interest has to be proven for practical FFO implementation in radio astronomy and other spectral applications. A linewidth of a phase-locked FFO as low as 1 Hz has been measured relative to an external reference oscillator in the frequency range 270–440 GHz on steep Fiske steps in the low damping regime. The increase of the intrinsic linewidth at higher voltages due to an abrupt increase of the internal damping considerably complicates phase locking of the FFO. Comprehensive measurements of the FFO radiation linewidth have been performed using an integrated harmonic SIS mixer. Results on FFO linewidth and spectral line profile have been compared to theory in order to optimize the FFO design. The influence of FFO parameters on radiation linewidth, particularly the effect of the differential resistances associated both with the bias current and the applied magnetic field, has been studied. Two integrated receiver concepts with phase-lock loop have been developed and experimentally tested. 2002 Published by Elsevier Science B.V.

A new method of bolometer response readout is proposed, whereby a resistive temperature sensor with a miniature antenna for terahertz range is integrated into a planar terahertz-range resonator weakly coupled to a pumping line, in which the amplitude of a gigahertz signal depends on the sensor resistance that changes under the action of a terahertz radiation received by the antenna. The proposed method can be used to create detector arrays with the number of elements above 1000, which implement the frequency multiplexing method and require only one physical channel of amplification for the gigahertz range. Results of numerical simulations show that, using nanosized transition-edge sensors operating at 300 mK and an amplification channel with 3 K noise temperature, it is possible to achieve a record high sensitivity of 1.6 × 10−19 W/Hz1/2.

To improve both scalability and noise-filtering capability of a Transition-Edge Sensor (TES), a new concept of a thin-film detector is suggested, which is based on embedding a microbridge TES into a high-Q planar GHz range resonator weakly coupled to a 50 Ohm-readout transmission line. Such a TES element is designed as a hot-electron microbolometer coupled to a THz range antenna and as a load of the resonator at the same time. A weak THz signal coupled to the antenna heats the microbridge TES, thus reducing the quality factor of the resonator and leading to a power increment in the readout line. The power-to-power conversion gain, an essential figure of merit, is estimated to be above 10. To demonstrate the basic concept, we fabricated and tested a few submicron sized devices from Nb thin films for operation temperature about 5 K. The dc and rf characterization of the new device is made at a resonator frequency about 5.8 GHz. A low-noise HEMT amplifier is used in our TES experiments without the need for a SQUID readout. The optical sensitivity to blackbody radiation within the frequency band 600-700 GHz is measured as $\sim3\times 10^{-14} \textrm W/\sqrt{\textrm Hz}$ at Tc {\approx} 5 K at bath temperature ~ 1.5 K.

A data acquisition system for the Integrated Receiver Test and Control ("IRTECON") was developed and tested with the single-chip quasioptical receiver containing a planar double-dipole antenna SIS mixer and FFO as a local oscillator. The basic system includes a controlling computer with two acquisition cards, an analogue bias supply and GPIB linked peripheries. The system collects and analyzes I-V data of the FFO and SIS mixer, tunes their regimes over the receiver frequency range. The possibility to optimize automatically the receiver noise temperature is realized. This system can be adopted to control a wide range of SIS-based receiving system such as an imaging receiver on remote location.

A low-noise rf amplifier based on a dc SQUID (SQA) is tested in the frequency range 3.3-4.1 GHz. A new signal launching system for the SQA rf coupling has been developed and successfully implemented. The following parameters have been measured at 3.65 GHz using a band-pass filter at the input of a single-stage SQA: gain (11.0/spl plusmn/1.0) dB, 3 dB bandwidth of 300 MHz and noise temperature (4.0/spl plusmn/1.0)K. This figure corresponds to a flux noise S/sub /spl Phi///sup 1/2 /=0.6 /spl mu//spl Phi//sub 0//Hz/sup 1/2 / and an energy sensitivity /spl epsi//sub i//spl ap/75 h. The input saturation power, P/sub s/, (1 dB gain compression) is measured for different bandwidths of the input band-pass filter, A corresponding input signal saturation temperature (normalized for a 1 GHz bandwidth) T/sub SAT//sup 1GHZ/=P/sub SAT//k/sub B/ is estimated to be 11.5 K GHz at an SQA bias voltage 27 /spl mu/V (condition for minimum noise temperature). The dependencies of the SQA gain, noise temperature and saturation level on the operation point are studied. The reason for the SQA saturation is discussed.

A laboratory-purpose submillimeter wavelength receiver is developed and tested. The device can in situ detect the spectrum of an rf source working below 100 K within the frequency range 400-600 GHz. A sample is placed close to the receiver sensor; both are in vacuum inside the probe stick and cooled by liquid helium in the standard transport dewar. The quasioptical sensor design is based on the superconducting integrated receiver chip; its noise temperature below 300 K was measured at /spl ap/500 GHz with a variable-temperature black body. The output level of the tester is suitable for the direct readout by a spectrum analyzer. Details of the design and main test data are reported.

The Josephson Flux Flow Oscillator (FFO) has proven to be a perfect on-chip local oscillator for integrated submm receivers; a noise temperature (DSB) below 100 K has been achieved at 500 GHz. Recently a FFO linewidth as low as 1 Hz has been measured in the frequency range 270 - 440 GHz. A new technique for both linewidth measurements and phase locking of the FFO is developed; this method employs an offchip harmonic multiplier. By measuring the frequency of the FFO radiation emission, its IV-curve (IVC) can be reconstructed with an accuracy better than 1 nV. A superfine resonant structure with a voltage spacing of about 20 nV and extremely low differential resistance has been observed in the FFO IVCs. This resonant structure modifies the performance of the FFO compared to the one expected from the "averaged IVC". The influence of this resonant structure on phase locking is discussed. Also results of FFO phase noise measurements are presented.

Low temperature scanning laser microscopy (LTSLM) is demonstrated to be capable of imaging sub-THz electromagnetic fields in cryoelectronic integrated structures. This method allows one to evaluate the spatial distribution of time-averaged field amplitudes with a resolution of about one micrometer for samples with characteristic dimensions of order millimeters. Using LTSLM, cryoelectronic devices with both passive and active superconducting elements can be characterized. Local heating of superconducting structures by a laser beam introduces extra loss for the propagating and standing sub-millimeter waves. We present LTSLM images of two-dimensional 400 to 500 standing GHz wave patterns in integrated superconducting receiver chips.

Fabrication procedure and yield analysis of superconducting integrated receivers is reported. These chip receivers, apart from the quasi-optical SIS mixers, contain internal local oscillators and associated rf and dc interfaces. Due to both complexity and design requirements of the integrated circuit, certain restrictions are applied to the standard Nb/Al/Al/sub x/O/sub y//Nb SNEAP process. To obtain accurate area for micron-size SIS junctions and thickness for multi-layer SiO/sub 2/ insulation, a few solutions and modifications were developed. The possibility of transferring this fabrication process worldwide has been proven experimentally.

The concept of a fully superconducting integrated receiver is developed and experimentally tested. This single-chip sub-mm wave receiver includes a planar antenna integrated with a SIS mixer and an internal superconducting Josephson-type local oscillator (flux-flow oscillator, FFO). The receiver is tested with a DSB noise temperature below 100 K around 500 GHz being pumped by its internal local oscillator (LO). The instantaneous bandwidth of 15-20% is estimated via FTS and heterodyne measurements that meet the requirements of most practical applications. The far field antenna beam is measured as ≈f/10 with sidelobes below -16 dB that is suitable for coupling to a real telescope antenna. A nine-pixel imaging array receiver with each pixel containing an internally pumped receiver chip is developed and tested. A linewidth of the phase locked FFO as low as 1 Hz is measured relative to a reference oscillator in the frequency range 270-440 GHz. An rf amplifier on the base of a dc SQUID is developed and tested showing a noise figure below 10 K at 4 GHz and a bandwidth of about 300 MHz. This amplifier can be included as a part of an integrated receiver that is valuable for array applications.

We report on measurements of the linewidth of the emitted radiation from Josephson Flux Row Oscillators (FFOs). Frequency and phase locking to an external 10 MHz reference oscillator an demonstrated experimentally in the frequency range 270-440 GHz. A linewidth as low as 1 Hz (as determined by the resolution bandwidth of the spectrum analyzer) has been measured. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The damping mechanisms are discussed and related to the self-excitation Of quasiparticles. Narrow linewidth, wide-band tunability and low noise are important for radio astronomy and air- and space-borne spectroscopy for atmospheric research and environmental monitoring. (C) 2000 Elsevier Science B.V. All rights reserved.

The combination of narrow linewidth and wide band tunability makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated sub-mm wave receivers for, e.g., spectral radio astronomy. The feasibility of phase locking the FFO to an external reference oscillator is demonstrated experimentally. A FFO linewidth as low as 1 Hz (determined by the resolution bandwidth of the spectrum analyzer) has been measured in the frequency range 270-440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The results of residual FFO phase noise measurements are also presented. Finally, we propose a single-chip fully superconductive receiver with two superconductor-insulator-superconductor mixers and an integrated phase-locked loop. (C) 2000 American Institute of Physics. [S0034-6748(00)01701-9].

We present experimental and theoretical results showing that the distributed electromagnetic environment of a Josephson junction array can cause the junctions in the array to synchronize. Based on our experimental results and our distributed array model, we find that an external load is not necessary for junction synchronization. Also, we show that the high-frequency performance of an array can be significantly better than the performance of a single isolated junction.

The Josephson Flux-Flow Oscillator (FFO) has been used as an on chip local oscillator at frequencies up to 650 GHz. The FFO linewidth of about 1 MHz was measured in the resonant regime at V

Experimental details of a unique superconducting imaging array receiver are discussed. Each pixel contains an internally pumped receiver chip mounted on the back of the elliptical microwave lens. Each chip comprises a quasi-optical SIS mixer integrated with a superconducting flux-flow oscillator (FFO) both fabricated from the same Nb/AlO/sub x//Nb trilayer on a silicon substrate. Properties of the integrated lens antenna were studied using an externally pumped reference SIS mixer which showed antenna sidelobes below /spl sim/17 dB and a receiver double side band noise temperature, T/sub RX/(DSB), below 100 K within the frequency range 460-500 GHz that is close to the quantum noise. For the imaging array T/sub RX/(DSB)=150 K has been measured at 500 GHz using the internal flux-flow oscillator as a local oscillator (LO). A balanced SIS mixer was tested showing T/sub RX/(DSB)

A 6 mm/spl times/6 mm chip comprising two identical DC SQUID based amplifiers (SQAs) has been designed, fabricated and tested as a two-stage RF amplifier in a frequency range 3.5-4.0 GHz. Each SQA consists of a double washer type DC SQUID with novel integrated input resonant circuit. The reflection coefficient of both input and output of the SQA has been measured in the two stage configuration. To avoid SQA saturation at the wide band noise tests a tunable 40 MHz bandpass YIG-filter has been used. The following parameters of the two-stage SQA have been measured at the 3.65 GHz: gain of (17.5/spl plusmn/1) dB, 3 dB bandwidth of about 250 MHz, and noise temperature (4.0/spl plusmn/0.5)K what corresponds to intrinsic flux noise S/spl phi//sup 1/2//spl ap/0.6 /spl mu//spl Phi//sub 0/Hz/sup -1/2/ and energy sensitivity /spl epsiv//sub i//spl ap/75 /spl planck/ (7.8/spl middot/10/sup -33/ J/Hz). If the measured RF mismatch between the input/output of SQA and source signal/post-amplifier is taken into account a gain of (20.5/spl plusmn/1.5) dB and noise temperature as low as (2.5/spl plusmn/1.0) K (intrinsic flux noise S/spl phi//sup 1/2//spl ap/0.4 /spl mu//spl Phi//sub 0/Hz/sup -1/2/, energy sensitivity /spl epsiv//sub i//spl ap/47 /spl planck/) can be estimated.

The results of a detailed study of the microwave linewidth of Nb-AlO/sub x/-Nb flux flow oscillators (FFO) are presented. The dependence of the FFO linewidth on the junctions parameters has been measured by using an improved technique based on harmonic mixing in the frequency range 250-600 GHz. Experimental data are compared with theoretical estimates to evaluate the influence of the possible mechanisms responsible for the broadening of the FFO linewidth. The origins of the increased linewidth at the transition from the resonant to the "pure" flux-flow regime are discussed. The results of the linewidth measurements for the FFO locked to an external synthesizer via a wideband feedback loop are presented. The possibility of phase locking of the Josephson oscillator has been demonstrated experimentally. A FFO linewidth as low as 3.3 kHz (determined by the resolution bandwidth of the spectrum analyzer) has been measured at 310 GHz; it is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction.

We report measurements of mm-wavelength radiation from two-dimensional arrays of underdamped Josephson junctions. All of our samples emit coherently in a novel synchronized state, which is triggered by a resonance in the array structure. Measurements of the detected power as a function of the number $N$ of active junctions show a threshold, suggesting population inversion. Above threshold, the power scales with ${N}^{2}$ up to an array size bigger than the free-space radiation wavelength. The highest measured conversion efficiency from dc to ac power is about 17%. Our data are consistent with stimulated emission causing coherence and cannot be explained by existing classical coupling mechanisms.

A transition-edge sensor multi-layer film absorber (Mo/Cu, T c = 0.3 –0.4 K) is assumed to connect the leads of the antenna made from Nb. The RF current from antenna is the source of hot electrons within the absorber; the heat escape to the substrate is limited by the low electron–phonon interaction at low temperature. The Andreev electron-reflection effect can prevent the heat leak to the antenna terminals. To build an imaging array, the multiplexing procedure via method of projections allows for readout from columns or rows, not from individual pixels, so the number of leads can be reduced to N+M for N × M double-polarized array. The full-time signal accumulation is effective for all pixels employing a polarization separating cross-slot antenna. Microstrip and coplanar waveguides are used in the matching circuit of the 9-pixel array. Wide-band signal coupling is simulated for a 5- Ω absorber at 600 GHz.

The dc SQUID based RF amplifier (SQA) looks very attractive as an IF amplifier for integration with a SIS mixer and a flux-flow oscillator (FFO) in a fully superconducting submillimeter wave receiver suitable for space applications. Important advantages of the SQA are its low noise, extremely low power consumption, and complete compatibility with the fabrication process currently used for SIS mixers. Single stage amplifiers with a novel signal coupling circuit have been developed and tested in the frequency range 3.6-4.1 GHz. The 1 /spl mu/m/sup 2/ area Nb-AlO/sub x/-Nb junctions shunted by Ti resistors are grouped in a double washer dc SQUID. Two samples with slightly different designs showed the following gain, noise temperature and 3 dB bandwidth: 10.0/spl plusmn/1 dB, 5.0/spl plusmn/1.5 K, 3.86-3.90 GHz, and 6.8/spl plusmn/1 dB, 22/spl plusmn/7 K, 3.89-4.05 GHz, respectively.

Presently Flux Flow Oscillators (FFOs) are being developed for integration with superconductor-insulator-superconductor (SIS) mixers intended for submillimeter wave integrated receivers. Here we report on a detailed study of the dc and microwave properties of Nb-AlO/sub x/-Nb FFOs. A model based on the Josephson self-pumping effect is proposed for explanation of the experimentally measured dc I-V curves (IVC). Extensive measurements of the spectral linewidth of the radiation emitted from a FFO have been performed up to 600 GHz using a new reliable technique based on harmonic mixing. The results are compared to recent theoretical predictions.

We study microwave properties of a superconducting tunable coplanar waveguide (CPW). Pairs of Josephson junctions are forming superconducting quantum interference devices (SQUIDs), which shunt the central conductor of the CPW. The Josephson inductance of the SQUIDs is varied in the range of 0.08-0.5 nH by applying an external dc magnetic field. The central conductor of the CPW contains Josephson junctions connected in series that provide extra inductances; the magnetic field controlling the SQUIDs is weak enough not to influence the inductance of the chain of the single junctions. The circuit is designed to have left- and right-handed transmission properties separated by a variable rejection band; the band edges can be tuned by the magnetic field. We present transmission measurements on CPWs based on up to 120 Nb-AlOx-Nb Josephson junctions. At zero magnetic field, we observed no rejection band in the frequency range of 8-11 GHz. When applying the magnetic field, a rejection band between 7 GHz and 9 GHz appears. The experimental data are compared with numerical simulations., 8 pages, 8 figures