Crystal Oscillator Research Articles

Predicting frequency deviation of a crystal oscillator based on long short-term memory network and transfer learning technique

AbstractCrystal oscillators are fundamental to an extensive range of electronic systems, spanning computers, mobile phones, and automotive electronics. Their significance is accentuated in high-precision applications such as global positioning systems (GPS) and aerospace systems where the frequency-temperature characteristics and thermal hysteresis phenomena are of paramount importance. This study introduces a groundbreaking approach for predicting frequency deviations arising from thermal hysteresis using Long Short-Term Memory (LSTM) networks. Contrary to prior research which predominantly utilized cubic functions to model frequency-temperature characteristics and frequently overlooked thermal hysteresis, this investigation distinguishes itself by leveraging LSTM. The proposed methodology is aptly designed to model both time-dependent and temperature-dependent variations, consequently offering a heightened precision in predicting frequency deviations. By integrating transfer learning techniques, the model's adaptability to diverse databases is augmented, broadening its utility. Experimental evaluations with real-world data underscore the preeminence of the introduced method, registering a root mean square error (RMSE) of less than 0.05 ppm, more favorable than that by the traditional cubic functions and all the prior arts.

Erratum for the Report "SCFFbxl3 controls the oscillation of the circadian clock by directing the degradation of cryptochrome proteins" by L. Busino et al.

Erratum for the Report "SCFFbxl3 controls the oscillation of the circadian clock by directing the degradation of cryptochrome proteins" by L. Busino et al.

Simulation study of compressed ultrafast 3D imaging based on interferometry

Observing the 3D (three-dimensional) surface vibration in 100 MHz is challenging due to low speed of CCD/CMOS camera. In order to obtain the ultrafast dynamic 3D shape information, a compressed ultrafast 3D imaging framework based on interferometry is proposed in this paper. Based on this imaging framework, an reconstruction method combining plug and play-fast flexible denoising network is developed to recover high resolution interference fringe patterns and the corresponding 3D information. The simulation results show that the proposed method can observe the dynamic processes of the anti-phase vibration and the in-phase vibration of the crystal oscillator, therefore the dynamic 3D model is established. The proposed method outperforms other reconstruction methods in terms of average peak signal to noise ratio and structural similarity in recovery the ultrafast dynamic 3D surface.

Ultra-low power, high-data rate, fully on-chip radio frequency on-off keying receiver for internet-of-things applications

Despite the enormous potential of energy-efficient receivers for wireless sensor networks, the large power consumption or limited data rate support impedes its extensive applications. Here, we present an energy-efficient, ultra-low power, higher data rate supporting, completely on-chip radio-frequency receiver frontend for on-off keying modulated signals in the 2.4 GHz industrial, scientific, and medical band. This compact-sized receiver is achieved by implementing temperature-resilient oscillator, pseudo-differential mixer, and a wideband detector while avoiding bulky external components such as bulk-acoustic wave resonators, crystal oscillators. Measurement results demonstrate that the proposed on-off keying receiver can decode low power level radio-frequency signals up to 5 Mbps data rate while consuming only 178 µW power. This work also demonstrates support for lower data rates at reduced power. Since the proposed receiver operates in different power modes, it can be integrated in diverse applications including internet-of-things devices and continuously monitoring biomedical/wearable implants.

Disordered clock protein interactions and charge blocks turn an hourglass into a persistent circadian oscillator

Organismal physiology is widely regulated by the molecular circadian clock, a feedback loop composed of protein complexes whose members are enriched in intrinsically disordered regions. These regions can mediate protein-protein interactions via SLiMs, but the contribution of these disordered regions to clock protein interactions had not been elucidated. To determine the functionality of these disordered regions, we applied a synthetic peptide microarray approach to the disordered clock protein FRQ in Neurospora crassa. We identified residues required for FRQ’s interaction with its partner protein FRH, the mutation of which demonstrated FRH is necessary for persistent clock oscillations but not repression of transcriptional activity. Additionally, the microarray demonstrated an enrichment of FRH binding to FRQ peptides with a net positive charge. We found that positively charged residues occurred in significant “blocks” within the amino acid sequence of FRQ and that ablation of one of these blocks affected both core clock timing and physiological clock output. Finally, we found positive charge clusters were a commonly shared molecular feature in repressive circadian clock proteins. Overall, our study suggests a mechanistic purpose for positive charge blocks and yielded insights into repressive arm protein roles in clock function.

The investigation of real-time LEO timing via GPS PPP with different RT products

Low Earth Orbit (LEO) satellites mostly utilize crystal oscillators instead of high-performance atomic clocks mounted on medium to high-orbit satellites. Therefore, keeping high-precision time synchronization between LEO and GNSS satellites is the premise of realizing the high-precision application of LEO satellites. In this contribution, GPS precise point positioning (PPP) technology was employed to release precise timing for LEO satellites with different Real-time (RT) products. GRACE-FO C and GRACE-FO D satellites and five precise RT products from different analysis centers, which are CNES, GFZ, GMV, WHU, and CAS were chosen to achieve precise timing. The results indicated that the overall trend of clock difference fluctuations presented with all real-time products is generally consistent, fluctuating within the range of ± 4 ns. Furthermore, real-time precise products from GMV and GFZ exhibit significant fluctuations during the daily initial time period. Additionally, real-time products from WHU outperform other products and demonstrate greater stability. In terms of frequency stability, the clock stability of various analysis centers is generally consistent, with short-term stability (1280 s) reaching approximately 10−13 and long-term stability (10240 s) reaching around 10−14. WHU's timing stability is notably superior to other real-time products. In the time synchronization experiment, real-time products fluctuate within the range of ± 2 ns, while IGS final products fluctuate within ± 1 ns. In terms of time synchronization stability comparison, short-term stability (1280 s) still fluctuates around 10−13, and long-term stability (10240 s) fluctuates around 10−14. WHU exhibits relatively good overall stability, while GFZ shows comparatively lower overall stability.

An adaptive MAC-agnostic ranging scheme for underwater acoustic mobile networks

In the last ten years several simulation studies on Autonomous Underwater Vehicle (AUV) swarm fleet formation have been performed, and some preliminary sea demonstrations of proof-of-concept prototypes were carried out. However, their actual realization is hindered by the challenges imposed by the underwater acoustic channel and the difficulties of keeping track of the vehicles’ positions due to the long latency required by traditional Two-Way Travel-Time (TWTT) ranging measurements, that require a specific signaling, hence limiting the throughput of the underwater network. Although One-Way Travel-Time (OWTT) halves the latency, it requires a high precision oscillator, such as an atomic clock or an oven controlled crystal oscillator (OCXO), to be installed in each modem processing unit: while atomic clocks are still very expensive, OCXO are very power demanding, making their application to underwater acoustic networks not always possible, especially in the case of low cost vehicle swarms.In this paper we present a network protocol stack able to perform ranging and localization within the communication task in underwater acoustic networks, limiting the network overhead. Specifically, new layers have been added to the preexisting DESERT Underwater protocol stack to perform the ranging tasks without compromising the correct operation of the communication network. A ranging layer is placed on top of the Medium Access Control (MAC) scheme, allowing the latter to be changed according to the network topology and requirements. This MAC-agnostic ranging layer is further optimized by adapting the amount of data transmitted according to the channel state, and the ranging entries inserted in the data packets according to the least recent information transmitted, hence minimizing the Age of Information. Simulation results obtained with the DESERT Underwater Framework show how this layer allows all AUVs in the swarm to know their distance from every other node in the network, thus limiting the probability of vehicle collisions and allowing better mission coordination.

Integration of piezoelectric and electrothermal actuators for high-resolution Atomic Force Microscopy

The development of ultrasensitive silicon-based microcantilevers has significantly improved the imaging resolution of the Atomic Force Microscope (AFM). However, most of these microcantilevers require one or more external actuators and sensors for imaging, thus increasing the footprint and operational complexity of the instrument. Here we propose a novel active microcantilever that does not require any external actuator apart from the sample positioner to perform high-resolution AFM imaging. The proposed microcantilever is equipped with two different on-chip actuators: a piezoelectric actuator for oscillating the probe at a high frequency and an electrothermal actuator for providing large-range Z-motion. An on-chip differential piezoelectric sensor measures probe oscillation during imaging. To demonstrate the proof of concept, the microcantilever was microfabricated and integrated with an in-house developed AFM setup comprising of sample positioner and drive electronics. Finally, 3 different calibration gratings were imaged with a closed-loop bandwidth of 150Hz.

The effect of crystal phase noise on the proton precession magnetometer magnetic field measurement accuracy

The proton precession magnetometer is a crucial piece of equipment for measuring magnetic fields because it can determine the value of the magnetic field by measuring the frequency of the Free Induction Decay (FID) signal. The frequency source, one of the crucial parts of the frequency measurement system, has a direct impact on how well the system works as a whole. The communication quality and detection accuracy of the frequency measuring system are directly influenced by phase noise, which is a crucial indicator of frequency stability. By acquiring various output frequencies of crystal oscillators using the Phase Locked Loop (PLL) frequency doubling technique, this study investigates the extent to which crystal phase noise impacts the accuracy of magnetometer frequency measurement.

The mechanism of loss in the impedance spectrum of longitudinal piezoelectric oscillator

The mechanism of loss in the impedance spectrum of longitudinal piezoelectric oscillator

The aggregation of micro-particles based on hydraulic vortices

The large-scale and nondestructive aggregation of micro-particles in the solvent has a crucial role on cell detection and the preparation of micro-nano drugs. To achieve directional aggregation of micro-particles, a piezoelectric cantilever probe structure can be utilized to generate a vortex region by driving the liquid with low-frequency oscillation. By adjusting the driving voltage and frequency of the piezoelectric oscillator, polystyrene microspheres in the liquid can be effectively aggregated and manipulated. Experimental results using fixed concentration polystyrene solvent demonstrated that micro-particle aggregation occurred within the frequency range of 20–70 Hz and voltage range of 20–80 V. The particles were stably concentrated in front of the probe, with a maximum aggregation area of 0.71 mm2 and a maximum number of aggregated particles reaching 2495, when the driving voltage was 60 V and the driving frequency was 60 Hz. Furthermore, the flow field particle image velocimetry experiment revealed that when four main vortices with opposite rotation directions were present, the micro-particle aggregation exhibited a regular Arc and Witch-shaped pattern. Conversely, in the presence of an indefinite number of large main vortices in the flow field, the micro-particle aggregation displayed an irregular Small symmetry and Large symmetry-shaped pattern. This method of micro-particle aggregation manipulation using hydraulic vortices has the potential to meet the demands of biomedical and fine chemical fields for precise micro-particle manipulation.

The Interaction between Anesthetic Isoflurane and Model-Biomembrane Monolayer Using Simultaneous Quartz Crystal Microbalance (QCM) and Quartz Crystal Impedance (QCI) Methods.

The interaction between anesthetic Isoflurane (Iso) and model-biomembrane on the water surface has been investigated using quartz crystal microbalance (QCM) and quartz crystal impedance (QCI) methods. The model-biomembranes used were dipalmitoyl phosphatidyl choline (DPPC), DPPC-palmitic acid (PA) mixture (DPPC:PA = 8:2), DPPC-Alamethicin (Al) mixture (DPPC:Al = 39:1), and DPPC-β-Lactoglobulin (βLG) mixture (DPPC:βLG = 139:1) monolayers, respectively. The quartz crystal oscillator (QCO) was attached horizontally to each monolayer, and QCM and QCI measurements were performed simultaneously. It was found that Iso hydrate physisorbed on each monolayer/water interface from QCM and changed those interfacial viscosities from QCI. With an increase in Iso concentration, pure DPPC, DPPC-PA mixed, and DPPC-Al mixed monolayers showed a two-step process of Iso hydrate on both physisorption and viscosity, whereas it was a one-step for the DPPC-βLG mixed monolayer. The viscosity change in the DPPC-βLG mixed monolayer with the physisorption of Iso hydrate was much larger than that of other monolayers, in spite of the one-step process. From these results, the action mechanism of anesthetics and their relevance to the expression of anesthesia were discussed, based on the "release of interfacial hydrated water" hypothesis on the membrane/water interface.

Study of oscillation characteristics for quartz crystal oscillators based on equivalent multi‐physics model

AbstractIn recent years, high‐performance quartz‐crystal oscillators (XOs) for integrated circuits have been receiving considerable attention due to their featuring low voltage and high‐frequency stability. However, recent studies tend to focus solely on the impact of temperature as a single factor on crystal oscillator circuits, overlooking the circuit structure of the crystal oscillator itself. In this paper, a novel four‐parameter crystal model of XOs is detailed demonstrated, and analyzed to interpret typical XO oscillation characteristics at room temperature. The relationship between the RLC circuit and the oscillation was investigated. Meanwhile, the study delves into the various factors that influence oscillation behavior, paving the way for a comprehensive understanding of XOs' performance characteristics. temperature sweep simulations were induced to verify the theory and found that the parameter drift and thermal perturbation are close to the theory we proposed, which can be applied in temperature‐compatible XOs. The significance of this study lies not only in its contribution to the design and implementation of compact footprint XOs in the oscillator circuit platform but also in its provision of experimental evidence for fabricating wide temperature range compensated XO devices. The results show that the capacitance in the equivalent model of a crystal oscillator plays a dominant role in shaping the output waveform and exhibits relatively good temperature stability characteristics and serve as a valuable resource for engineers and researchers working on improving the performance and reliability of XOs, ultimately enabling the development of more advanced and efficient integrated circuits.

Потенциальные возможности узкополосной радиолокации с пространственной модуляцией сигналов

The methods of radar with narrow-band radiation by switching the antenna pattern around the equi-signal zone or in orthogonal planes are considered, which significantly (by tens of dB) reduce the power of the transmitter by narrowing the receiver bandwidth. The range to the target is determined by calculating the phase difference of the received signal at the switching frequency of the reference signal of this frequency by a stabilized quartz oscillator. It is shown that it is possible to increase the accuracy of measuring the range by introducing two scales: coarse, determined by the switching frequency, the wavelength of which corresponds to a double range to the target, and accurate, with a higher switching frequency.Since the required radiation power of the transmitter in the narrowband case is determined by the noise immunity of phase measurements, then at a given range of the system, by increasing the power of the transmitter, it is possible to reduce the error of measuring the range. As is known, in the pulsed radar method, the accuracy of the range estimation is limited by the duration of the emitted pulse and practically does not depend on the power of the transmitter. For this reason, the radars used do not allow for the accuracy of estimating their coordinates better than tens of meters. A possible solution to such a problem is the use of continuous signals with partial modulation, but requiring a wide bandwidth of receivers determined by frequency deviation, which significantly reduces the noise immunity of the system. The disadvantage of the narrowband radar method described below with spatial signal modulation is the inability to distinguish targets located at the same azimuth. However, in a number of tasks, for example, when used in altimeters, over-the-horizon radar, high-precision radio geodesic measurements, etc., the radar options described in the article make it possible to increase the accuracy of measuring the range not achieved by other methods. The main advantage of the new method is: stealth; high noise immunity; minimum radiation power of the transmitter; the ability to quickly change the carrier frequency, independence from the speed of movement of the target, since the measurement of the signal phase is determined only by the switching frequency.

A novel multi-degree of freedom kinetic energy harvester for self-powered low-power applications in ships

The utilization of kinetic energy from the motion of small fishing boats to energize ship-borne wireless sensors offers a promising solution to address the power supply challenges of these sensors in the maritime environment. Nonetheless, the constrained scope of retrievable kinetic energy in the prevailing ship-borne kinetic energy harvester has evolved into a hindrance, curbing its progression. Hence, this paper proposed a novel multi-degree of freedom kinetic energy harvester for low-power applications in ships, where the harvester is harnessed by combining a ball rod, sliding bearing, and slider body. Relying on this mechanical device, the ship's kinetic energy in the surge, roll, sway, and pitch directions is transformed into the swinging motion of the mass ball, subsequently converted into the movement of the slider body. Under the influence of the magnetic force between the slider body and the piezoelectric beam, the piezoelectric beam experiences frequent oscillations, ultimately translating mechanical motion into electrical energy. The experimental results show that the harvester can charge capacitors with capacities of 220 μF, 470 μF, and 1000 μF to 1 V within time intervals of 15 s, 24 s, and 36 s. The prototype has been effectively deployed on a ship in an artificial lake, achieving an impressive maximum average power output of 173.10 μW. This study serves as compelling evidence that the harvesting of kinetic energy from ships presents a promising solution for self-powering low-energy applications onboard while also introducing a novel design concept for applying kinetic energy harvesters on fishing vessels.

Actuators linearization of a large volume environmental simulation chamber via pulse code modulation

Ultra-stable room-sized environmental chambers may involve significant power variations leading to hysteresis and nonlinearities of the stabilization system. This paper describes utilization of a pulse code modulation control which significantly reduces observed nonlinearity of the chamber actuation system. Stability of environmental conditions for temperature ΔT=±25 mK (15–35 °C dynamic range), relative humidity ΔRh=±0.1% (3%–95% dynamic range), and pressure ΔP=±12 Pa (±500 Pa dynamic range) was achieved within 27 m3 chamber volume, which is two orders of magnitude better than the corresponding stabilization achievable using a standard linear proportional–integral–derivative (PID) controller. Utilizing this chamber we have demonstrated two orders of magnitude improvement of the operational relative frequency stability of ultrastable quartz oscillators (USO), reaching 2×10−13 stability at 1-105 s averaging time.

Quasi-2D Fermi surface in the anomalous superconductor UTe2

The heavy fermion paramagnet UTe2 exhibits numerous characteristics of spin-triplet superconductivity. Efforts to understand the microscopic details of this exotic superconductivity have been impeded by uncertainty regarding the underlying electronic structure. Here we directly probe the Fermi surface of UTe2 by measuring magnetic quantum oscillations in pristine quality crystals. We find an angular profile of quantum oscillatory frequency and amplitude that is characteristic of a quasi-2D Fermi surface, which we find is well described by two cylindrical Fermi sheets of electron- and hole-type respectively. Additionally, we find that both cylindrical Fermi sheets possess considerable undulation but negligible small-scale corrugation, which may allow for their near-nesting and therefore promote magnetic fluctuations that enhance the triplet pairing mechanism. Importantly, we find no evidence for the presence of any 3D Fermi surface sections. Our results place strong constraints on the possible symmetry of the superconducting order parameter in UTe2.

Pterostilbene targets the molecular oscillator RORγ to restore circadian rhythm oscillation and protect against sleep restriction induced metabolic disorders

BackgroundConsiderable researches have directed toward metabolic disorders caused by sleep restriction (SR). SR-induced disruption of circadian metabolic rhythmicity is identified as an important pathophysiological mechanism. The flavonoid pterostilbene (PTE) is abundant in the traditional Chinese medicine dragon's blood with protective efficacy against obesity-related metabolic dysfunctions. Our previous study found that PTE ameliorates exercise intolerance and clock gene oscillation in the skeletal muscles subjected to SR. PurposeThis study aimed to explore whether PTE improves SR-induced metabolic disorders and delineate the relationship between PTE and the circadian clock. Study design and methodsTwo hundred male C57/B6J mice were kept awake for 20 h/d over five consecutive days and concurrently gavaged with 50, 100, or 200 mg/kg·bw/d PTE. Food consumption and body weight were monitored, and the metabolic status of the mice was evaluated by performing OGTT and ITT, measuring the serum lipid profiles and liver histopathology in response to SR. Daily behavior was analyzed by Clocklab™. The circadian rhythms of the liver clock genes and metabolic output genes were evaluated by cosine analysis. Binding between PTE and RORα/γ or NR1D1/2 was investigated by molecular docking. A luciferase reporter assay was used to determine the impact of PTE on Bmal1 transcription in SR-exposed mice co-transfected with Ad-BMAL1-LUC plus Ad-RORγ-mCherry or Ad-NR1D1-EGFP. ResultsPTE significantly ameliorated abnormal glucose and lipid metabolism (p < 0.05) in SR-exposed mice. PTE improved circadian behavior (p < 0.05) and rescued the circadian rhythm oscillation of the liver clock (p < 0.05) and metabolic output genes (p < 0.05) under SR condition. Molecular docking disclosed that PTE might interact with RORs, and PTE was found to increase Bmal1 promoter luciferase activity with RORE elements in the presence of Ad-RORγ-mCherry (p < 0.05). ConclusionsPTE may protect against SR-induced metabolic disorders by directly modulating RORγ to maintain circadian metabolic rhythm. The findings provide valuable insights into the potential use of PTE in the treatment of metabolic disorders associated with disruptions in the circadian rhythm.

Теоретическая оценка стабильности частоты сигнала цифрового термокомпенсированного кварцевого генератора с термодатчиком на основе двух вспомогательных кварцевых генераторов

The article provides a theoretical limit assessment of the stability of a digital thermocompensated quartz oscillator with a temperature sensor based on two auxiliary quartz oscillators. The results are 7,5 ppb (for a restless environment) and 0,75 ppb (for a calm environment). Technical solutions are considered for obtaining a linear one-to-one dependence of the difference frequency value on temperature and increasing the steepness of this dependence. The proposed solutions allow obtaining a temperature measurement resolution of up to 0,001 ºС.

A Low Phase Jitter MEMS Oscillator with Centrally-Anchored Piezoelectric Resonator for Wide Temperature Range Real Time Clock Applications.

This paper describes prototype temperature compensated piezoelectric MEMS oscillators operating in the wide temperature range of -40 °C to 85 °C for RTC applications. The AlN-on-Si resonator is centrally anchored at one point and designed for low power operation with a wide frequency tuning range of 5000 ppm. The oscillators exhibit a stable sinusoidal output at about 497 kHz frequency for time keeping applications with an integrated phase jitter being 10× better than the best commercially available MEMS RTC oscillators for supplementary use in portable devices for clocking audio circuits. The measured oscillator performance remains relatively unchanged when comparing the wafer level packaged capped MEMS resonator with the uncapped one, showing great potential for a high performance low-power RTC oscillator.