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We designed a digital double relaxation oscillation SQUID (DROS) with an SFQ up/down counter. The DROS is connected to a feedback SQUID loop and a signal magnetic flux is input to the feedback SQUID loop. The DROS generates two kinds of voltage pulses corresponding to the total magnetic flux in the feedback SQUID loop. Two kind of voltage pulses are converted to SFQ and anti-SFQ pulses and input to the feedback SQUID loop to keep the magnetic flux in the SQUID loop constant. The number of the generated SFQ pulses is counted using the SFQ up/down counter. Thus, the count corresponds to the input magnetic flux. Because the SFQ up/down counter is operated in the pulse driven mode, the digital DROS needs only dc bias current for operation. We designed and fabricated a digital DROS with a relaxation oscillation frequency of 3 GHz and an 8-bit SFQ up/down counter. Numerical simulation suggested the designed digital DROS has a dynamic range exceeding \pm100\ \Phi0 and magnetic flux slew rate of 3\times10^9\ \Phi0/s. [ABSTRACT FROM AUTHOR]

Compact and low-cost SQUID electronics to operate double relaxation oscillation SQUIDs (DROSs) has been constructed for detecting magnetocardiogram (MCG) fields. SQUID electronics consists of low-noise preamplifier with a white noise of 0.6 nV/√Hz, flux-locked loop (FLL) circuit with auto-reset, and interface circuit to control FLL using 3 digital lines from a computer. The automatic control software adjusts SQUID parameters to the optimum operating condition within 15 seconds for 62 channels. Outputs of FLL circuits are passed through the hardware filter box to the 64-channel data acquisition board. Each SQUID electronics for FLL and digital control is built together on a printed circuit board of 45 mm × 95 mm. When SQUID electronics is connected to DROS gradiometer with typical flux-to-voltage transfers of 1 mV / Φ0, the noise contribution of FLL circuit is about 0.6 μΦ0/√Hz or 0.6 fT/√Hz at 100 Hz, low enough to measure MCG fields. [ABSTRACT FROM AUTHOR]

A double relaxation oscillation SQUID with a reference junction (RJ-DROS) already has a fixed reference current, so that it holds a fixed flux-to-voltage characteristics when fabricated. When an additional current flows through the reference junction but not through the signal junction in the RJ-DROS, we have obtained the variation of its characteristics. The additional reference current has an effect on reducing the fixed reference current, which results in changing averaged relaxation voltage and transfer coefficient. In particular, while the critical current of the signal SQUID exceeds the reference current, the averaged relaxation voltage at the reference junction is enlarged by the added bias current combined with an additional current and an initial bias current. Therefore the additional reference current can provide the RJ-DROS with variable modulation depth and width within the operating range. Although the characteristics of RJ-DROSs are fixed differently each to each when they are fabricated, the additional current can adjust their characteristics to the same one, which is useful for controlling DROSs in a multichannel DROS system. However, an input-bias current in the preamplifier detecting the outputs at the reference junction, acts as an additional current, and then makes the reference current shift from the optimum current or deviate from the operating range, the input-bias current needs to be regulated within the operating range. [ABSTRACT FROM AUTHOR]

This paper describes the development, along with detailed phase-noise analysis, of V-band monolithic-microwave integrated-circuit (MMIC) dielectric-resonator oscillators (DROs) achieving state-of-the-art performances. A TE[sub 01δ]-mode Ba(Mg,Ta)O[sub 3] cylindrical dielectric resonator (DR) is directly placed on a MMIC GaAs substrate to avoid the loss and uncertainty of bonding wires. A 0.15-µm AlGaAs-InGaAs heterojunction field-effect transistor with optimized structure is developed as an active device. A design procedure proposed by the authors is employed, which allows us to analyze and optimize circuits in consideration for the output power, phase noise, and temperature stability. A developed DRO co-integrated with a buffer amplifier exhibits a low phase noise of -90 dBc/Hz at 100-kHz offset, a high output power of 10.0 dBm, and an excellent frequency stability of 1.6 ppm/° C at an oscillation frequency of 59.6 GHz, all of which are state-of-the-art performances reported for MMIC DROs above V-band. An experimental and theoretical analysis for the phase.noise-reduction effect of a DR is also addressed. [ABSTRACT FROM AUTHOR]

Describes a systematic approach to the design and analysis for dielectric resonator oscillators (DRO). Temperature and structural-parameters-dependent dielectric resonator (DR) model; Temperature-dependent heterojunction FET large-signal model; Structural-parameters dependence DRO characteristics.

Abstract-In this paper, the effects of electromagnetic fields from the frequency band of digital wireless telephones on a superconducting quantum interference device (SQUID) were experimentally investigated. A first-order planar gradiometer based on the double relaxation oscillation SQUID (DROS) was operated without low-frequency magnetic shielding, and was exposed to radiated electromagnetic fields in the frequency range of 300 MHz-2 GHz. The experiments have been performed in a fully anechoic chamber to minimize reflected waves in the chamber. The flux-to-voltage transfer and the field sensitivity of the gradiometer have been observed under the irradiation of fields. Results show that the performance of the gradiometer was significantly affected at a typical power level of the digital wireless telephones for both horizontally and vertically polarized electromagnetic waves. The noise level of the DROS output voltage also increases as the strength of the external fields becomes higher. [ABSTRACT FROM AUTHOR]

Examines the design of fast digital double relaxation oscillation superconducting quantum interference devices or DROS. Relaxation oscillation frequency; Quantization units of the feedback flux; Advantages of DROS; Design optimization.

Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux /spl Phi/, whereas the output of a DROS is a dc voltage, with a typical flux-to-voltage transfer of /spl part/V//spl part//spl Phi//spl ap/1 mV//spl Phi//sub 0/. The flux-to-frequency response of several ROSs has been measured and compared with theory for frequencies up to 7 GHz. Various DROS designs-a multi-loop direct coupling DROS, a DROS with a washer type signal SQUID and a DROS with gradiometric signal SQUID-will be discussed in this paper. The integration of a DROS with a digital flux locked loop ("Smart DROS") will also be analyzed. [ABSTRACT FROM PUBLISHER]

Double relaxation oscillation SQUID (DROS) combined with an on-chip superconducting digital flux locked-loop (FLL) circuit has been proposed. In this study, we described superconducting digital FLL circuit which consists of an 8-bit up/down counter and an 8-bit R-2R ladder D/A converter. The circuit was designed using 4-Junction Logic (4JL)-gates which are driven by a two phase power supply. In the up/down counter, we employed binary carry lookahead (B CL) circuits for high-speed operation. Logic simulations for the BCL 8-bit up/down counter showed correct operation up to 4 GHz, assuming a 2.5 kA/cm² Nb/Al-AlOx/Nb junction technology. From simulation results high slew rate of 107 Φ0/s and dynamic range of 2.5 Φ0 can be expected. [ABSTRACT FROM AUTHOR]

Focuses on a one-megahertz low noise preamplifier based on double relaxation oscillation superconducting quantum interference device (DROS). DROS and flux locked loop parameters; Flux to voltage transfer curve; Cryogenic particle detectors.

This letter theoretically verifies that a second Dielectric Resonator (DR) placed at the drain port of a push-push FET Dielectric Resonator Oscillator (DRO) can provide compensation for some phase difference/error between the output signals and improve the output power level. The theoretical verification starts from understanding the relationship between output power and phase in a balanced push-push oscillation scheme. The phase compensation causing power improvement is analyzed with an conceptual configuration of the circuit. The effect is confirmed by Advanced Design System (ADS) simulation for the same circuit as that in an earlier experimental report. [ABSTRACT FROM PUBLISHER]

We have fabricated a single-stage superconducting quantum interference device (SQUID) current amplifier for detecting pulse outputs of a superconducting microcalorimeter. The current amplifier is made of a double relaxation oscillation SQUID (DROS) that provides a high flux-to-voltage transfer of about 1 mV/Φ[sub 0] and a large modulation depth of 80 µV. Due to the high flux-to-voltage transfer, the voltage output of the DROS is measured directly with a room-temperature dc preamplifier. The bandwidth of the current amplifier is measured to be 1.2 MHz. Typical noise of the DROS current amplifier is about 6 pA/ √Hz. [ABSTRACT FROM AUTHOR]

We constructed a multichannel superconducting quantum interference device (SQUID) magnetometer system for magnetoencephalogram measurements. The SQUID is based on the double relaxation oscillation SQUID (DROS), which consists of a hysteretic signal SQUID and a reference junction, and shunted by a relaxation circuit of a resistor and an inductor. With the high flux-to-voltage transfers, usually larger than 1 mV/Φ[sub 0], simple flux-locked loop circuits could be used for SQUID operation. The SQUID system consists of 37 integrated magnetometers, distributed on a hemispherical surface, and external feedback scheme was used to eliminate magnetic coupling with the adjacent channels. In addition to the 37 signal channels, 8 reference channels were installed to pickup background noise and to apply software gradiometer. The average noise level of the magnetometers is about 3 fT/ √Hz at 100 Hz, operated inside a magnetically shielded room. The magnetometer system was applied to measure auditory-evoked fields. [ABSTRACT FROM AUTHOR]

Focuses on smart superconducting quantum interference device (SQUID) based on relaxation oscillation SQUID. Numerical simulation results; Operation principles of smart SQUID; Chip layout.

Under the low-damping limit, flux to voltage transfer function and classical intrinsic noise expressions for both thermal fluctuation and relaxation oscillation in double relaxation oscillation SQUID(DROS)s can be obtained with numerical calculation. The expressions show that the noise has T/sup 6/5/ temperature dependence and that at low relaxation oscillation frequencies, /spl omega//sub r/, the noise has a 1//spl omega//sub r/ behavior, and then turns up and gradually saturates at very high frequencies comparable with the plasma frequency. The upturn point, which gives the optimum energy resolution, might be near 10 GHz for typical DROS circuit parameters. [ABSTRACT FROM PUBLISHER]

In this paper, we fabricated a low-TC second-order superconducting quantum interference device gradiometer (SQUID) to measure magnetocardiography (MCG) in unshielded environment. The second-order gradiometer consists of the pickup coil and the SQUID. The pickup coil is formed with two single-turn coils and one double-turn coil. The three coils are connected in order of single-, double-, and single-turn coil. The coupling polarity of two single coils is opposite to the double-turn coil. The SQUID is based on double relaxation oscillation SQUID (DROS), which consists of a hysteretic signal SQUID, a reference junction, and shunted a relaxation circuit with a resistor and an inductor. The DROS has ten times larger flux-to-voltage transfer coefficient (~1 mV/Φo) than that of the conventional SQUID. Therefore, DROS could be operated with a simple flux-locked loop circuit. The pickup coil and the SQUID were fabricated on the independent wafers and connected superconductively using an Nb wire. The overall size of the second-order gradiometer is 94 × 12 mm2 with a baseline of 35 mm. The average field noise was about 8 fT/√Hz at 100Hz with the second-order gradiometer in shielded or unshielded environment. The noise level is low enough to measure MCG signals in the unshielded environment. Finally, we measure the MCG in shielded and unshielded environments by using the second-order gradiometer and compared the signal characteristics measured in both environments. [ABSTRACT FROM AUTHOR]

A 64-channel planar gradiometer system was developed to measure magnetocardiogram (MCG) signals. The planar gradiometers are second-order planar gradiometers with a baseline of 50 mm, fabricated from Nb thin films on Si wafers using thin film processes. The SQUIDs were fabricated from Nb/Al-oxide/Nb junctions, and a double relaxation oscillation SQUID (DROS) scheme was used to have a large flux-to-voltage transfer, typically about 1 mV/Φ0. The planar gradiometers were arranged to measure magnetic field components tangential to the chest surface, which has a field distribution peak just above the current dipole. The diameter of the sensor coverage area is 190 mm, which was proved to be large enough to provide MCG field distribution in a single measurement. Inside a thin-wall shield room, the white noise level of the planar gradiometer system is about 8 fT/√Hz. The 64-channel system was operated in a thin-wall shield room, and MCG signals were measured. [ABSTRACT FROM AUTHOR]

Presents a compact and reliable planar gradiometer for a multichannel system measuring tangential components of biomagnetic fields. The readout electronics was simplified by using a double relaxation oscillation SQUID (DROS) which provides very large flux-to-voltage transfer of typically 3 mV//spl Phi//sub 0/, enabling direct readout by a DC preamplifier with modest voltage noise. The DROS was made from hysteretic Nb/AlO/sub x//Nb junctions. To realize a compact and reliable gradiometer, the planar pickup coil is integrated on the same wafer with the SQUID. The planar pickup coil consists of two 10 mm/spl times/10 mm coils connected in series to form a first-order gradiometer and has a baseline of 30 mm. The field gradient noise is 9 fT/cm/spl radic/Hz at 1 Hz inside a magnetically shielded room. The gradiometers were arranged to measure simultaneously x and y components of biomagnetic fields. [ABSTRACT FROM PUBLISHER]

We present a 62-channel double relaxation oscillation SQUID (DROS) planar gradiometer system to measure magnetocardiogram (MCG) signals tangential to the chest surface. The DROSs were fabricated using Nb/Al-oxide/Nb junctions, and provided flux-to-voltage transfers of larger than 1 mV /Φ0 typically, which is large enough for direct readout by room-temperature flux- locked loop (FLL) circuits. The analog FLL circuits and digital control circuits are made in a single printed circuit board. The planar gradiometers are integrated, series-connected first-order pickup coils with a baseline of 4 cm. White noise level of the planar gradiometer is about 1.5 (fT/cm)/√HZ or 6 fT/ √Hz, operated inside a magnetically shielded room. The planar gradiometers were arranged to measure dBx / dz and dBy/dz simultaneously. The covering area of the 62 channel system is 162 mm × 162 mm, which is smaller than the sensor coverage area of vertical measurement systems, but large enough to measure the essential MCG field distribution in a single position measurement. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a low-noise integrated superconducting quantum interference devices (SQUID) gradiometer for biomagnetic sensor applications. Sensitivity of magnetometers based on direct current SQUID; Layout of the SQUID gradiometer; Characteristics of the sensors; Conclusion.

Transposed flicker noise reduction and removal is demonstrated in 7.6 GHz microwave oscillators for offsets greater than 10 kHz. This is achieved by using a GaAs-based feedforward power amplifier as the oscillation-sustaining stage and incorporating a limiter and resonator elsewhere in the loop. 20 dB noise suppression is demonstrated at 12.5 kHz offset when the error correcting amplifier is switched on. Three oscillator pairs have been built. A transmission line feedback oscillator with a Q0 of 180 and two sapphire-based, dielectric resonator oscillators (DROs) with a Q0 of 44,500. The difference between the two DROs is a change in the limiter threshold power level of 10 dB. The phase noise rolls-off at (1/f)² for offsets greater than 10 kHz for the transmission line oscillator and is set by the thermal noise to within 0-1 dB of the theoretical minimum. The noise performance of the DROs is within 6-12 dB of the theory. Possible reasons for this discrepancy are presented. [ABSTRACT FROM AUTHOR]

We designed a digital superconducting quantum interference device (SQUID) system that contains a double relaxation oscillation SQUID (DROS) as a magnetic flux comparator that is connected to an additional relaxation oscillation (RO) circuit with mutually coupled inductances. In the designed digital SQUID, the RO circuit works as a resonator and increases the relaxation oscillation frequency without decreasing the input current of dc/SFQ converters. Numerical simulation shows that the digital SQUID system can operate up to 7 GHz. A fabricated digital SQUID using a DROS comparator with an RO circuit provides correct digital SQUID operation. For a magnetometer using the digital SQUID system, we can realize a magnetic field noise less than 1 pT/ \sqrt\mathrmHz with a small signal bandwidth of more than 10 MHz. [ABSTRACT FROM AUTHOR]

The resource allocation in vehicle-to-everything (V2X) communications face a great challenge for satisfying the heterogeneous quality of service (QoS) requirements of the ultra-reliable safety-related services and the minimum throughput required entertainment services, due to the channel uncertainties caused by high mobility. In this paper, we first consider an optimistic scenario where the distribution of uncertain channel state information (CSI) can be deterministic and accurately known at the eNB. Then, a low-complexity resource allocation approach is developed, in which the probabilistic QoS constraint of V2V is transformed into a computable optimization constraint. To deal with the scenario with unknown uncertain CSI distribution, we develop a distributionally robust resource allocation approach for converting the intractable chance constraint of V2V into a deterministic semidefinite constraint based only on the first- and second-order moments of uncertain CSI. For alleviating the conservatism of above approach, a support-based distributionally robust resource allocation approach is developed to tighten the semidefinite constraint by utilizing the support information of uncertain CSI. Finally, we conduct simulations to show that the effectiveness of the proposed approaches outperforms other state-of-art approaches. [ABSTRACT FROM AUTHOR]

We demonstrate time and frequency transfer using a White Rabbit (WR) time transfer system over millimeter-wave (mm-wave) 71–76 GHz carriers. To validate the performance of our system, we present overlapping Allan deviation (ADEV), time deviation (TDEV), and phase statistics. Over mm-wave carriers, we report an ADEV of ${7.1}\times {10}^{-{12}}$ at 1 s and a TDEV of <10 ps at 10 000 s. Our results show that after 4 s of averaging, we have sufficient precision to transfer a cesium atomic frequency standard. We analyze the link budget and architecture of our mm-wave link and discuss possible sources of phase error and their potential impact on the WR frequency transfer. Our data show that WR can synchronize new network architectures, such as physically separated fiber-optic networks, and support new applications, such as the synchronization of intermittently connected platforms. We conclude with recommendations for future investigation, including cascaded hybrid wireline and wireless architectures. [ABSTRACT FROM AUTHOR]