Oscillator Loop Research Articles

CMOS Cross-Coupled Oscillator Operating Close to the Transistor’s $f_{\max }$

A design methodology of CMOS cross-coupled oscillator operating close to the transistor's maximum oscillation frequency (f max ) is proposed by utilizing the loop impedance matching and phase shift control technique to maximize the oscillator's loop gain. A fundamental oscillator following the proposed design methodology has been implemented in 65-nm CMOS. The measured results show that the oscillator achieves 192.3-GHz oscillation frequency, which is 71.1% of the transistor's f max . The spectrum output power is -10.4 dBm with the phase noise of -100 dBc/Hz at 10 MHz offset. The oscillator draws only 14-mA current from a 1.2-V power supply.

MEMS Gyroscopes Based on Piezoresistive NEMS Detection of Drive and Sense Motion

This paper presents yaw and pitch micro-electromechanical system gyroscopes embedding four active nanoelectromechanical (NEMS) piezoresistive gauges each, two of which are used for differential sensing of the Coriolis motion, and two of which are innovatively used to sense the drive motion and thus to close the drive oscillation loop. After presenting the devices design, this paper discusses the advantages of this particular implementation in terms of operating voltages, electrical equivalent model, and temperature behavior of the scale factor. In operation with voltages lower than 1.8 V without voltage boosting, the devices show sub mdps/ $\surd {\rm Hz}$ noise density within areas of about 1 mm2 per device at 0.2-mbar package pressure. Under temperature sweeps, a 3.7-fold better immunity of the scale factor stability is obtained, compared with a similar gyroscope embedding combs (and not NEMS) for drive detection. [2017-0050]

Enhanced Quality Factor Label-free Biosensing with Micro-Cantilevers Integrated into Microfluidic Systems.

Microelectromechanical systems (MEMS) have enabled the development of a new generation of sensor platforms. Acoustic sensor operation in liquid, the native environment of biomolecules, causes, however, significant degradation of sensing performance due to viscous drag and relies on the availability of capture molecules to bind analytes of interest to the sensor surface. Here, we describe a strategy to interface MEMS sensors with microfluidic platforms through an aerosol spray. Our sensing platform comprises a microfluidic spray nozzle and a microcantilever array operated in dynamic mode within a closed loop oscillator. A solution containing the analyte is sprayed uniformly through picoliter droplets onto the microcantilever surface; the micrometer-scale drops evaporate rapidly and leave the solutes behind, adding to the mass of the cantilever. This sensing scheme results in a 50-fold increase in the quality factor compared to operation in liquid, yet allows the analytes to be introduced into the sensing system from a solution phase. It achieves a 370 femtogram limit of detection, and we demonstrate quantitative label-free analysis of inorganic salts and model proteins. These results demonstrate that the standard resolution limits of cantilever sensing in dynamic mode can be overcome with the integration of spray microfluidics with MEMS.

A Broadband, Rectangular, and Self-Sustained Optical Frequency Comb Generation Employing Recirculation Frequency Shifter

To generate a self-sustained rectangular optical frequency comb (OFC) with tunable spacing and bandwidth, we propose and experimentally demonstrate a novel scheme by using an optoelectronic oscillator employing recirculation frequency shifter (RFS) loop. In this scheme, the oscillating signal is separated to drive the Mach–Zehnder modulator (MZM) in the oscillation loop and the inphase/quadrature modulator in the RFS loop separately. Then more than 50-tone OFCs, which have a rectangular spectral profile and the flatness better than 6 dB, are obtained with 8-GHz spacing and 10-GHz spacing by tuning the center frequency of the microwave filter respectively. Besides, the phase noise of the driving signals are both lower than $-$ 110 dBc/Hz at 10 kHz offset frequency.

Triple band frequency generator based on an optoelectronic oscillator with low phase noise.

A triple band frequency generator based on the optoelectronic oscillator (OEO) with low phase noise has been proposed and experimentally demonstrated. In this novel scheme, the phase-coherent triple band frequency in C, Ku and K bands can be achieved simultaneously by biasing the first modulator in the oscillation loop at the minimum transmission point (MITP) and the second modulator near the MITP with a small deviation. In the proof-of-concept experiment, the triple band frequency signals at 5.36, 16.08 and 21.44 GHz are generated with the phase noise of -123.32, -113.68 and -111.19 dBc/Hz at 10 kHz offset frequency, respectively. The proposed scheme provides a novel strategy for phase-coherent multi-band frequency and low phase noise signals generation, which can be potentially used in the multi-function and multi-band frequency electrical systems.

Numerical Study of Strong Interplay Between Cavity and Store During Launching

AbstractNumerical investigation of the strong interplay between a cavity and a store under supersonic inflow condition is conducted by using Improved Delayed Detach-Eddy Simulation (IDDES). Pressure fluctuations in the cavity are analyzed with smooth pseudo Winger-Vile distribution method and the time-frequency features are obtained. The effects of fluctuating flow inside the cavity on the aerodynamic loads of the store are also studied. It was shown that when the store is falling through the shear layer, the self-sustained oscillation loop is destroyed and the cavity tone vanishes. Vortex structures concentrate in the back of the cavity, as a result the noise levels at the rear of the cavity increase. After the store falls out of the cavity, the oblique shock wave formed at store's head interferences with the shear layer, which changes the cavity tone frequencies. The forces and moments acting on the store fluctuate strongly influenced by highly unsteady flow-field. Affected by oblique shock and the impact of shear layer, the store's pitch up angle keeps rising up and reaches to 24° at its maximum.

Systems Biology-Derived Discoveries of Intrinsic Clocks.

A systems approach to studying biology uses a variety of mathematical, computational, and engineering tools to holistically understand and model properties of cells, tissues, and organisms. Building from early biochemical, genetic, and physiological studies, systems biology became established through the development of genome-wide methods, high-throughput procedures, modern computational processing power, and bioinformatics. Here, we highlight a variety of systems approaches to the study of biological rhythms that occur with a 24-h period—circadian rhythms. We review how systems methods have helped to elucidate complex behaviors of the circadian clock including temperature compensation, rhythmicity, and robustness. Finally, we explain the contribution of systems biology to the transcription–translation feedback loop and posttranslational oscillator models of circadian rhythms and describe new technologies and “–omics” approaches to understand circadian timekeeping and neurophysiology.

Self-Oscillating Triangular Pulse Generator Based on 90° Photonic-Assisted Phase Shifter

In this letter, we proposed and experimentally demonstrated a novel self-oscillating triangular pulse generator based on a 90° photonic-assisted phase shifter. The fundamental harmonic is produced by the optoelectronic oscillation loop for generating triangular pulses. Meanwhile, the even-order harmonic suppression and the phase matching between odd-order harmonics are simultaneously realized by carrier phase-shifted double sideband modulation using a dual-parallel Mach-Zehnder modulator. Furthermore, the nine times amplitude ratio between the fundamental and third-order harmonics can be achieved by properly tuning the gain of the open oscillation loop. In the proof-of-concept experiment, self-oscillating triangular pulses with the repetition rates of 4 and 5.7 GHz are successfully generated with the phase noises of about -114 and -122 dBc/Hz at 10-kHz offset frequency. The corresponding root-mean-square errors between the generated and the ideal triangular waveforms are 5.9777e-4 and 6.0002e-4, respectively.

A 110 nW Resistive Frequency Locked On-Chip Oscillator with 34.3 ppm/°C Temperature Stability for System-on-Chip Designs

This work presents a sub- $\mu \text {W}$ on-chip oscillator for fully integrated system-on-chip designs. The proposed oscillator introduces a resistive frequency locked loop topology for accurate clock generation. In this topology, a switched-capacitor circuit is controlled by an internal voltage-controlled oscillator (VCO), and the equivalent resistance of this switched-capacitor is matched to a temperature-compensated on-chip resistor using an ultra-low power amplifier. This design yields a temperature-compensated frequency from the internal VCO. The approach eliminates the traditional comparator from the oscillation loop; this comparator typically consumes a significant portion of the total oscillator power and limits temperature stability in conventional RC relaxation oscillators due to its temperature-dependent delay. A test chip is fabricated in $0.18~\mu \text {m}$ CMOS that exhibits a temperature coefficient of 34.3 ppm/°C with long-term stability of less than 7 ppm (12 second integration time) while consuming 110 nW at 70.4 kHz. A radio transmitter circuit that uses the proposed oscillator as a baseband timing source is also presented to demonstrate a system-on-chip design using this oscillator.

The Circadian Timing System and Environmental Circadian Disruption: From Follicles to Fertility.

The internal or circadian timing system is deeply integrated in female reproductive physiology. Considerable details of rheostatic timing function in the neuroendocrine control of pituitary hormone secretion, adenohypophyseal hormone gene expression and secretion, gonadal steroid hormone biosynthesis and secretion, ovulation, implantation, and parturition have been reported. The molecular clock, an autonomous feedback loop oscillator of interacting transcriptional regulators, dictates the timing and amplitude of gene expression in each tissue of the female hypothalamic-pituitary-gonadal (HPG) axis. Although multiple targets of the molecular clock have been identified, many associated with critical physiological functions in the HPG axis, the full extent of clock-driven gene expression and physiology in this critical system remains unknown. Environmental circadian disruption (ECD), the disturbance of temporal relationships within and between internal clocks (brain and periphery), and external timing cues (eg, light, nutrients, social cues) due to rotating/night shift work or transmeridian travel have been linked to reproductive dysfunction and subfertility. Moreover, ECD resulting from exposure to endocrine disrupting chemicals, environmental toxins, and/or irregular hormone levels during sexual development can also reduce fertility. Thus, perturbations that disturb clock function at the molecular, cellular or systemic level correlate with significant declines in female reproductive function. Here we briefly review the evidence for molecular clock function in each tissue of the female HPG axis (GnRH neuron, pituitary, uterus, oviduct, and ovary), describe the human epidemiological and animal data supporting the negative effects of ECD on fertility, and explore the potential for novel chronotherapeutics in women's health and fertility.

The Autonomous Cryocooled Sapphire Oscillator: A Reference for Frequency Stability and Phase Noise Measurements

The Cryogenic Sapphire Oscillator (CSO) is the microwave oscillator which feature the highest short-term stability. Our best units exhibit Allan deviation σy(τ) of 4.5x10-16 at 1s, ≈ 1.5x10-16 at 100 s ≤ t ≤ 5,000 s (floor), and ≤ 5x10-15 at one day. The use of a Pulse-Tube cryocooler enables full two year operation with virtually no maintenance.Starting with a short history of the CSO in our lab, we go through the architecture and we provide more details about the resonator, the cryostat, the oscillator loop, and the servo electronics.We implemented three similar oscillators, which enable the evaluation of each with the three- cornered hat method, and provide the potential for Allan deviation measurements at parts of 10-17 level. One of our CSOs (ULISS) is transportable, and goes with a small customized truck. The unique feature of ULISS is that its σy (τ) can be validated at destination by measuring before and after the roundtrip. To this extent, ULISS can be regarded as a traveling standard of frequency stability.The CSOs are a part of the Oscillator IMP project, a platform dedicated to the measurement of noise and short-term stability of oscillators and devices in the whole radio spectrum (from MHz to THz), including microwave photonics. The scope spans from routine measurements to the research on new oscillators, components, and measurement methods.

Design of Oscillation Control Loop With Coarse-Precision Mode Transition for Solid-State Resonant Gyroscope

This paper presents a dual mode oscillation control loop design for a solid-state hemispherical resonator gyroscope (HRG) which uses the hemispherical vibrating shell for detecting the Coriolis force. A desirable control loop needs to be robust, fast, and also to have small driving and frequency noises which may cause significant errors, such as angular random walk. To design a fast and robust oscillation loop for precision gyroscope, a novel approach using a sequential resonance control mode transition is proposed in this paper. The coarse resonance control mode principally consists of phase shifter and limiter, which provides fast startup and tolerant tracking performances. The precision mode uses phase-locked loop for the sake of precision tracking performance. In addition, a theoretical analysis on the designed control loop considering mode transition is presented. In this paper, the tracking performances of the proposed loop are demonstrated via both simulation and experiments. The experimental results using a fabricated HRG verified the effectiveness of the proposed method.

Oscillator PM Noise Reduction From Correlated AM Noise.

We demonstrate a novel technique for reducing the phase modulation (PM) noise of an oscillator in a steady-state condition as well as under vibration. It utilizes correlation between PM noise and amplitude modulation (AM) noise that can originate from the oscillator's loop components. A control voltage proportional to the correlated AM noise is generated and utilized in a feedforward architecture to correct for the steady state as well as the vibration-induced PM noise. An improvement of almost 10-15 dB in PM noise is observed over one decade of offset frequencies for a 635-MHz quartz-MEMS oscillator. This corresponds to more than a factor of five reductions in vibration sensitivity.

Conditional Deletion of Bmal1 in Ovarian Theca Cells Disrupts Ovulation in Female Mice.

Rhythmic events in female reproductive physiology, including ovulation, are tightly controlled by the circadian timing system. The molecular clock, a feedback loop oscillator of clock gene transcription factors, dictates rhythms of gene expression in the hypothalamo-pituitary-ovarian axis. Circadian disruption due to environmental factors (eg, shift work) or genetic manipulation of the clock has negative impacts on fertility. Although the central pacemaker in the suprachiasmatic nucleus classically regulates the timing of ovulation, we have shown that this rhythm also depends on phasic sensitivity to LH. We hypothesized that this rhythm relies on clock function in a specific cellular compartment of the ovarian follicle. To test this hypothesis we generated mice with deletion of the Bmal1 locus in ovarian granulosa cells (GCs) (Granulosa Cell Bmal1 KO; GCKO) or theca cells (TCs) (Theca Cell Bmal1 KO; TCKO). Reproductive cycles, preovulatory LH secretion, ovarian morphology and behavior were not grossly altered in GCKO or TCKO mice. We detected phasic sensitivity to LH in wild-type littermate control (LC) and GCKO mice but not TCKO mice. This decline in sensitivity to LH is coincident with impaired fertility and altered patterns of LH receptor (Lhcgr) mRNA abundance in the ovary of TCKO mice. These data suggest that the TC is a pacemaker that contributes to the timing and amplitude of ovulation by modulating phasic sensitivity to LH. The TC clock may play a critical role in circadian disruption-mediated reproductive pathology and could be a target for chronobiotic management of infertility due to environmental circadian disruption and/or hormone-dependent reprogramming in women.

Enhanced dynamical response of derivative controlled third order phase locked loops

Dynamical responses of third order phase locked loops with resonant filters are examined by modifying the control signal applied to loop oscillator. Using signals obtained at some internal nodes of loop resonant filter, the control signal is modified. These signals are effectively single or double derivatives of normal control signal. Performances of modified loops are found to improve during transient and tracking modes of loop operation. This is established through analytical, numerical simulation and experimental studies. The dynamics of the loops in unstable self-oscillatory and aperiodic oscillating modes could also be controlled by these additional derivative control signals.

Detuned Grating Single-Mode Laser With High Immunity to External Optical Feedback

In this paper, we report a novel single-mode laser with high immunity to external optical feedback following the principle of active-filter-tuned oscillator. Within the conventional Fabry-Perot (FP) cavity, a high-Q bandpass filter formed by two tilted gratings with detuned Bragg wavelengths is embedded, and the resultant mode selection mechanism can purify the lasing spectrum by eliminating all but one of the FP cavity modes near the peak wavelength of the said filter. The proposed laser inherently bears the distinct feature of being robust against any small disturbances to oscillation loop. Simulation results from the large-signal dynamic model show that a stable single-mode operation has been achieved with a side-mode suppression ratio of as high as 50 dB. Further, compared with conventional index-coupled distributed feedback lasers, the proposed laser exhibits a much higher immunity to external optical feedback, even at a very high feedback level of −3 dB, and its single-mode yield is also less susceptible to variations of effective facet phases caused by cleaving in semiconductor laser fabrications.

Self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators.

An ultraflat self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators was proposed and experimentally demonstrated. By incorporating the optoelectronic oscillation loop with cascaded modulators into the optical frequency comb generator, 11 ultraflat comb lines would be generated, and the frequency spacing is equal to the oscillation frequency of the OEO. 10 and 12GHz optical frequency combs are demonstrated with the spectral power variation below 0.82dB and 0.93dB respectively. The corresponding spectral pure microwave source are also generated and evaluated. The corresponding single-sideband phase noise are as low as -122dBc/Hz and -115 dBc/Hz at 10 kHz offset frequency.

THE SYNTHESIS OF THE OPTIMAL STRUKTURE TRACK RECEIVER OF SIGNALS WITH AMPLITUDE MODULATION

The optimal structure of the receiver is a heterodyne receiver. Problem in practical implementation isto ensure strict phase and local oscillator voltage, so the auto lock systems with centralized deployment of equipment in use as a local oscillator signal from the carrier signal “his” track generator. With decentralized deployment of equipment necessary to use the phase locked loop oscillator signal.

A 180 GHz differential Colpitts VCO in 65 nm CMOS

A 180 GHz differential Colpitts VCO in 65 nm CMOS is presented. The choice and placement of the varactors are analyzed with the Y parameters looking into the oscillation loop. Based on this analysis, the varactors are placed close to the source terminal of the transistors to minimize their load effect on the oscillator. The VCO occupies 0.097 mm2 core die area and consumes 21.8 mW DC power from a 1.2 V power supply. The measured tuning range is from 174.9 to 178.9 GHz. The measured output power after calibrating out the measurement conversion loss is ?13.15 dBm and the measured phase noise at 10 MHz offset is ?94 dBc/Hz.

Fiber-optic temperature sensor interrogation technique based on an optoelectronic oscillator

We have proposed and experimentally demonstrated a fiber-optic temperature sensing system based on an optoelectronic oscillator (OEO). A part of the fiber in the oscillator loop is used as the sensing fiber. As the free spectrum range (FSR) of the OEO is determined by the length of the oscillator loop, when the temperature of the sensing fiber is changed, the refractive index of the fiber varies; thus, the optical path length changes as well as the FSR of the OEO. By tracking one peak of the OEO harmonics, the temperature variation can be monitored. Therefore, the temperature variation can be converted to the frequency shift of the radio frequency signals. In the experiment, we have measured the spectra of the OEO with different temperatures, which show good sensing linearity. We have also measured the relationship between the sensing responsivity and the tracked frequency (1.0, 1.5, 2.0, and 3.0 GHz) in the experiment, which shows that the harmonics at a higher frequency produce a higher sensing responsivity. The proposed temperature sensing system exhibits good tunability, stability, linearity tailorable sensing responsivity, and ease of implementation, thus it shows good application potential in remote fiber-optical temperature sensing and monitoring.