Frequency Shift Of Oscillator Research Articles

Dephasing and relaxational polarized sub-Ohmic baths acting on a two-level system.

We study a quantum two-level system under the influence of two independent baths, i.e., a sub-Ohmic pure dephasing bath and an Ohmic or sub-Ohmic relaxational bath. We show that cooling such a system invariably polarizes one of the two baths. A polarized relaxational bath creates an effective asymmetry. This asymmetry can be suppressed by additional dephasing noise. This being less effective, the more dominant low frequencies are in the dephasing noise. A polarized dephasing bath generates a large shift in the coherent oscillation frequency of the two-level system. This frequency shift is little affected by additional relaxational noise nor by the frequency distribution of the dephasing noise itself. As our model reflects a typical situation for superconducting phase qubits, our findings can help optimize cooling protocols for future quantum electronic devices.

Study of the Doubly Clamped Beam Yarn Tension Sensor Based on the Surface Acoustic Wave

In this paper, a design method for the yarn tension sensor based on a surface acoustic wave is presented. When the yarn tension is applied to the sensor's doubly clamped beam (i.e., piezoelectric substrate), it is linearly related to the output frequency shift, which achieves the purpose of measuring the yarn tension. This paper deduces the functional relationship between the oscillation frequency shift of the sensor and the yarn tension. We put forward the choice of a piezoelectric substrate material, the choice of the piezoelectric die size, and the placement of interdigital transducers (IDTs) as the three key issues to be determined. By using the ANSYS software, we determined that the optimal piezoelectric substrate is quartz, and determined the optimal size of the die and the maximum strain area of the die. When IDTs are placed in the maximum strain area of the piezoelectric substrate, the sensor has the best sensitivity. We have designed and produced the sensor and also have tested the sensor. Experimental results: the range is 0–2 N, the linearity is 1.0112%, the hysteresis is 0.6153%, the repeatability is 1.1067%, the accuracy is 1.6205%, the maximum overload capacity is 200% (i.e., 4 N), and the fracture strength of the substrate is 5 N.

Mass sensing by quantum criticality.

Mass sensing connects mass variation to a frequency shift of a mechanical oscillator, whose limitation is determined by its mechanical frequency resolution. Here we propose a method to enlarge a minute mechanical frequency shift, which is smaller than the linewidth of the mechanical oscillator, into a huge frequency shift of the normal mode. Explicitly, a frequency shift of about 20Hz of the mechanical oscillator would be magnified to be a 1MHz frequency shift in the normal mode, which increases it by 5 orders of magnitude. This enhancement relies on the sensitivity appearing near the quantum critical point of the electromechanical system. We show that a mechanical frequency shift of 1Hz could be resolved with a mechanical resonance frequency ωb=11×2π MHz. Namely, an ultrasensitive mechanical mass sensor of the resolution Δm/m∼2Δωb/ωb∼10-8 could be achieved. Our method has potential application in mass sensing and other techniques based on the frequency shift of a mechanical oscillator.

High-sensitivity measurement of angular velocity based on an optoelectronic oscillator with an intra-loop Sagnac interferometer

A novel scheme for angular velocity measurement is proposed and demonstrated by using an optoelectronic oscillator (OEO) incorporating a Sagnac interferometer. In the OEO resonant cavity, the optical carrier (OC) and the first-order sidebands propagate in opposite directions in the Sagnac loop. Thus, the rotation-induced Sagnac phase difference between the OC and first-order sidebands will produce an oscillating frequency shift of the OEO which is proportional to the rotation angular velocity. Then a high-sensitivity angular velocity measurement is realized by monitoring the oscillating microwave frequency. The system is free from the lock-in problem, and the sensitivity scale is measured to be 51.8kHz/(rad/s) which is equivalent to a minimally detectable angular velocity of 3.98°/h with a frequency shift of 1Hz.

Temperature‐dependent characteristics of a RTD‐based microwave push‐push oscillator

AbstractIn this letter, the temperature dependence of a microwave push–push oscillator based on a resonant tunneling diode (RTD) has been investigated from 30°C to 80°C. An output power characteristic curve of the second‐harmonic RTD oscillator has been shifted to the higher bias voltages as temperature increases. An oscillation frequency shift of ΔfOSC has been obtained to be –9.8 MHz/K which is equivalent to the ΔfOSC of –4.9 MHz/K at the fundamental oscillation frequency of 14.45 GHz. To authors’ knowledge, this is the first report on the temperature dependent characteristics of the second‐harmonic push–push RTD oscillator.

Grating-patterned FeCo coated surface acoustic wave device for sensing magnetic field

This study addresses the theoretical and experimental investigations of grating-patterned magnetostrictive FeCo coated surface acoustic wave (SAW) device for sensing magnetic field. The proposed sensor is composed of a configuration of differential dual-delay-line oscillators, and a magnetostrictive FeCo grating array deposited along the SAW propagation path of the sensing device, which suppresses effectively the hysteresis effect by releasing the internal binding force in FeCo. The magnetostrictive strain and ΔE effect from the FeCo coating modulates the SAW propagation characteristic, and the corresponding shift in differential oscillation frequency was utilized to evaluate the measurant. A theoretical model is performed to investigate the wave propagation in layered structure of FeCo/LiNbO3 in the effect of magnetostrictive, and allowing determining the optimal structure. The experimental results indicate that higher sensitivity, excellent linearity, and lower hysteresis error over the typical FeCo thin-film coated sensor were achieved from the grating-patterned FeCo coated sensor successfully.

A mechanism for detecting on-chip radio frequency interference of field-programmable gate array

One-chip measurements without modifying the physical structure of packaged integrated circuits such as field-programmable gate arrays (FPGA) is challenging. This paper proposes a sensor for detecting the radio frequency interference (RFI) on the supply inside the FPGA chip. The core of the sensor is a ring oscillator built with FPGA look-up tables. The paper proposes a model to predict the response of the ring oscillator to power supply RFI, and shows that the normalized frequency shift of the ring oscillator resulting from the interference is determined by the amplitude of the interference. This relationship is independent of the interference frequency and the size of the ring oscillator. To verify the model, simulations on transistor-level look-up tables of 130-nm and 40-nm technologies were performed. The simulation results matched well with the model. In addition to simulation, an FPGA test board was fabricated. Measurements of FPGA RFI response were performed and the results were consistent with the theoretical model. The effect of the interference on the ring oscillator provided a mechanism to detect the amplitude of the supply interference on the FPGA chip. The frequency of the ring oscillator was monitored through the supply pin by measuring the spectrum of the supply noise. The properties of the sensor, such as constant response in a wide frequency range, insensitiveness to the oscillator size, ease of implementation, and minimal modification requirement of the physical structure, made it suitable for performing on-chip FPGA measurements.

Micromagnetic simulation for detection of magnetic nanobeads by spin torque oscillator

Micromagnetic simulation for detecting magnetic nanobeads is performed by using spin torque oscillation as the detector. The non-uniform stray field generated by magnetic beads can induce a detectable frequency shift of a spin torque oscillator. Simulations indicate that an 80-nm-diameter magnetic bead can be detected with a frequency shift of 1.2GHz and a maximum linewidth of 28MHz. Due to the non-uniform stray field, the frequency shift and linewidth vary with the bead position. For multiple beads detection, the oscillation frequency is linear with the number of 40-nm-diameter beads, namely 0.16GHz/bead on average.

Two-Element Mixture of Bose and Fermi Superfluids.

We report on the production of a stable mixture of bosonic and fermionic superfluids composed of the elements ^{174}Yb and ^{6}Li which feature a strong mismatch in mass and distinct electronic properties. We demonstrate elastic coupling between the superfluids by observing the shift in dipole oscillation frequency of the bosonic component due to the presence of the fermions. The measured magnitude of the shift is consistent with a mean-field model and its direction determines the previously unknown sign of the interspecies scattering length to be positive. We also observe the exchange of angular momentum between the superfluids from the excitation of a scissors mode in the bosonic component through interspecies interactions. We explain this observation using an analytical model based on superfluid hydrodynamics.

Enhanced sensitivity of temperature-compensated SAW-based current sensor using the magnetostrictive effect

A temperature-compensated surface acoustic wave (SAW)-based current sensor was proposed in this contribution, composed of a sensor chip made by SAW delay line patterns on a SiO2/128° YX LiNbO3 piezoelectric substrate, a magnetostrictive FeCo film deposited on the SAW propagation path, and a corresponding differential oscillation configuration. The FeCo coating produced magnetostrictive strain under the magnetic field generated by the applied current, leading to linearity changes in the SAW propagation in the form of velocity change. The corresponding differential oscillation frequency shift was used to evaluate the tested current. By solving the coupled electromechanical field equation in a layered structure while considering the magnetostrictive effect, the optimal FeCo film thickness, and sensor operation frequency yielding high current sensitivity, were determined, and then confirmed experimentally by evaluating the developed SAW current sensor system utilizing a Helmholtz coil. A high sensitivity of 16.6 KHz A−1 (8.3 KHz m−1 T−1), excellent linearity, and lower detection limit (∼0.2 mA) were achieved with our 300 MHz SAW sensor with a 500 nm FeCo coating and aspect ratio of 2:1.

The investigation of hydrogen gas sensing properties of SAW gas sensor based on palladium surface modified SnO2 thin film

The sol-gel method and the magnetron sputtering method were used to deposit the SnO2 thin films on 128° YX LiNbO3 piezoelectric substrate for fabricating different kinds of delay-line surface acoustic wave (SAW) hydrogen gas sensors. To improve hydrogen gas sensing performance of SnO2 sensing films, the bi-layer structure sensitive films was used, which was composed of one pure SnO2 layer and one highly dispersed palladium nanoparticle layer. This bi-layer structure evidently enhanced the hydrogen gas sensing properties of SnO2 thin films. The microstructure, surface morphology and composition of as-prepared SnO2 sensitive films were analyzed by XRD, FESEM and XPS. The oscillator circuit with SAW sensor as resonate was designed to transduce the response of sensitive film into the frequency shift of oscillator. One precise temperature control system was used to ensure the temperature stability of SAW device. The Pd-surfaced-modified SnO2 thin film deposited by magnetron sputtering method has the highest frequency shift of 115.9kHz to 2000ppm hydrogen gas at 175°C. The influence of thickness on the morphology of Pd nanoparticles and hydrogen gas sensing performance was studied. The size of Pd nanoparticle increases with thickness of Pd films and too thick Pd layer will reduce the hydrogen gas sensing performance of SnO2 films.

Temperature compensation of the SAW yarn tension sensor

The objective of this research was to investigate the possibility of the temperature compensation for the surface acoustic wave (SAW) yarn tension sensor. The motivation for this work was prompted by the oscillation frequency of the SAW yarn tension sensor varying with the temperature.In this paper, we deduce the functional relationship between the temperature variation and the oscillation frequency shift caused by the temperature. This functional relationship and the temperature sensor are used to get the oscillation frequency shift caused by the temperature, so that we can use the oscillation frequency shift caused by the temperature to implement the temperature compensation of the SAW yarn tension sensor. In this paper, we also get the relative error of the temperature compensation. The theoretical and experimental results confirm that this temperature compensation method can implement the temperature compensation of the SAW yarn tension sensor.

Simulation investigation of multiple domain observed in In0.23Ga0.77As planar Gunn diode

A numerical study for an AlGaAs/InGaAs-based quantum well structure planar Gunn diodes was performed by initially proposing imperfect metallic contacts that can introduce multiple anode–cathode spacings caused by etching process during the fabrication. Through Fast Fourier transform (FFT) algorithm, the result reveals that, at moderate bias voltage above the threshold, multi-channel planar Gunn diode exhibits multiple oscillations which were consistent with experimental observation due to non-uniformity of contact terminal. A downwards shift of oscillation frequency by varying the applied voltage across terminal was observed due to Gunn effect. The finding may be utilized not only to generate multiple millimeter wave or even terahertz signal sources on single chip, but also to achieve frequency tunability through tuning the applied bias voltage.

Influence of Amplitude Fluctuations on the Noise-Induced Frequency Shift of Noisy Oscillators

We discuss the effect of the estimation of the amplitude variations on the noise-induced frequency shift in nonlinear oscillators. The analysis is based on a general reduction approach to a phase macromodel making use of the Ito interpretation of the stochastic differential equations representing noisy autonomous systems. We show that a significant improvement of the accuracy can be obtained by using the average value of the amplitude component determined from a linearization of the amplitude equation.

Activation of D2 autoreceptors alters cocaine-induced locomotion and slows down local field oscillations in the rat ventral tegmental area

Psychoactive substances affecting the dopaminergic system induce locomotor activation and, in high doses, stereotypies. Network mechanisms underlying the shift from an active goal-directed behavior to a “seemingly purposeless” stereotypic locomotion remain unclear. In the present study we sought to determine the relationships between the behavioral effects of dopaminergic drugs and their effects on local field potentials (LFPs), which were telemetrically recorded within the ventral tegmental area (VTA) of freely moving rats. We used the D2/D3 agonist quinpirole in a low, autoreceptor-selective (0.1 mg/kg, i.p.) and in a high (0.5 mg/kg, i.p.) dose, and a moderate dose of cocaine (10 mg/kg, i.p.). In the control group, power spectrum analysis revealed a prominent peak of LFP power in the theta frequency range during active exploration. Cocaine alone stimulated locomotion, but had no significant effect on the peak of the LFP power. In contrast, co-administration of low dose quinpirole with cocaine markedly altered the pattern of locomotion, from goal-directed exploratory behavior to recurrent motion resembling locomotor stereotypy. This behavioral effect was accompanied by a shift of the dominant theta power toward a significantly lower (by ∼15%) frequency. High dose quinpirole also provoked an increased locomotor activity with signs of behavioral stereotypies, and also induced a shift of the dominant oscillation frequency toward the lower range. These results demonstrate a correlation between the LFP oscillation frequency within the VTA and a qualitative aspect of locomotor behavior, perhaps due to a variable level of coherence of this region with its input or output areas.

High-SNR Capacitive Multi-Touch Sensing Technique for AMOLED Display Panels

A mutual-capacitive multi-touch sensing technique is presented, especially for ultra-thin active-matrix organic light-emitting diode (OLED) display panels. The proposed scheme recognizes touch positions by detecting LC oscillation frequency shift. The signal feedback to the common cathode electrode of OLEDs cancels out the effects of parasitic coupling capacitances. In addition, the ground-floating-based scanning method enables a multi-touch function. The proposed touch sensor was implemented in a 0.35-μm CMOS process. Simulations were performed in model of 3.97-in on-cell-type TSP with various noise signals gathered by actual measurements. The proposed sensing technique achieves 68.9- and 61.6-dB signal-to-noise ratios with 6- and 2-mm diameter metal pillars, respectively.

Optoelectronic Oscillators (OEOs) to Sensing, Measurement, and Detection

Besides distinct features on RF/optical signal generation, optoelectronic oscillators (OEOs) have also been rapidly developed as emerging techniques towards sensing, measurement, and detection. In this paper, we start with the conceptual architecture and the analytical model of OEOs. Then, three operation principles behind sensing, measurement, and detection applications are categorized, including the variation on the time delay of loop, the passband reconfiguration of microwave photonic filter in loop, and the oscillation gain from injection locking, which clearly clarify the X-to-frequency mapping (X denotes target parameter or signal) for supporting practical solutions and approaches. Next, a comprehensive review to advances in OEO-based sensing, measurement, and detection applications is presented, including length change and distance measurement, refractive index estimation, load and strain sensing, temperature and acoustic sensing, optical clock recovery, and low-power RF signal detection. As a new application example, a novel approach for in-line position finding is proposed. When a long fiber Bragg grating inserted into OEO is locally heated to slightly broaden its reflection spectrum, the target position heated is mapped into the oscillating frequency shift, according to the first operation principle. A sensitivity of 254.66 kHz/cm is obtained for position finding in the experiment. Afterward, solutions for calibration and stabilization are briefly introduced, which enable us to improve the accuracy and reliability. Finally, features and future prospects on the sensing, measurement, and detection applications are discussed, such as compact and integrated OEOs.

Study of oscillation performance characteristics of unidirectional photorefractive ring resonators: Cavity detuning dependence

Single unidirectional photorefractive ring resonator (SUPRR) and coupled unidirectional photorefractive ring resonator (CUPRR) were considered with BaTiO3 and LiNbO3 crystals as inter-cavity photorefractive media. The relative oscillation intensity and oscillation frequency shift of two SUPRRs with BaTiO3 and LiNbO3 crystals in their cavities, and four CUPRRs with BaTiO3-BaTiO3, LiNbO3-LiNbO3, BaTiO3-LiNbO3 and LiNbO3-BaTiO3 combinations were analysed relative to cavity detuning parameters and compared the oscillation performance of SUPRR with that of CUPRR. In SUPRR, maximum value of relative oscillation intensity is found for BaTiO3 as compared to that of LiNbO3 for zero cavity detuning. In CUPRR, the oscillation intensity in secondary cavity increases with increasing cavities detuning whereas in primary cavity it decreases with increasing cavities detuning. Major finding of this study is that the BaTiO3-LiNbO3 combination of the coupled system provides the highest relative oscillation intensity.

Physiologically motivated multiplex Kuramoto model describes phase diagram of cortical activity.

We derive a two-layer multiplex Kuramoto model from Wilson-Cowan type physiological equations that describe neural activity on a network of interconnected cortical regions. This is mathematically possible due to the existence of a unique, stable limit cycle, weak coupling, and inhibitory synaptic time delays. We study the phase diagram of this model numerically as a function of the inter-regional connection strength that is related to cerebral blood flow, and a phase shift parameter that is associated with synaptic GABA concentrations. We find three macroscopic phases of cortical activity: background activity (unsynchronized oscillations), epileptiform activity (highly synchronized oscillations) and resting-state activity (synchronized clusters/chaotic behaviour). Previous network models could hitherto not explain the existence of all three phases. We further observe a shift of the average oscillation frequency towards lower values together with the appearance of coherent slow oscillations at the transition from resting-state to epileptiform activity. This observation is fully in line with experimental data and could explain the influence of GABAergic drugs both on gamma oscillations and epileptic states. Compared to previous models for gamma oscillations and resting-state activity, the multiplex Kuramoto model not only provides a unifying framework, but also has a direct connection to measurable physiological parameters.

Humidity responses of Love wave sensors based on [formula omitted] ZnO/R-sapphire bilayer structures

Love wave humidity sensors are fabricated by sputtering (1 1 2¯ 0) ZnO thin films on R-sapphire substrates and lithographing interdigital transducers on the surfaces of ZnO films. The response characters of the sensors to humidity are investigated experimentally and theoretically. The experimental data show nonlinear function relations between oscillation frequency shifts of the sensors and relative humidity variations. Meanwhile, the phenomena can be explained by combining Brunauer–Emmett–Teller model for physical adsorption isotherms and surface acoustic wave propagation theory in inhomogeneous media. The experimental and theoretical results are in good agreement with each other.