Showing papers on "Frequency drift published in 2009"

Temperature-Insensitive Composite Micromechanical Resonators

Abstract: Utilizing silicon and silicon dioxide's opposing temperature coefficients of Young's modulus, composite resonators with zero linear temperature coefficient of frequency are fabricated and characterized. The resulting resonators have a quadratic temperature coefficient of frequency of approximately -20 ppb/degC2 and a tunable turnover temperature in the -55degC to 125degC range. Reduction of the temperature dependence of frequency is shown in flexural-mode resonators (700 kHz-1.3 MHz) and extensional-mode ring resonators (20 MHz). The linear temperature coefficient of Young's modulus of silicon dioxide is extracted from measurements to be +179 ppm/degC. The composite resonators are fabricated and packaged in a CMOS-compatible wafer-scale hermetic encapsulation process. The long-term stability of the resonators is monitored for longer than six months. Although most devices exhibit less than 2 ppm frequency drift, there is evidence of dielectric charging in the silicon dioxide.

A Low-Noise Multi-GHz CMOS Multiloop Ring Oscillator With Coarse and Fine Frequency Tuning

Abstract: A 7-GHz CMOS voltage controlled ring oscillator that employs multiloop technique for frequency boosting is presented in this paper. The circuit permits lower tuning gain through the use of coarse/fine frequency control. The lower tuning gain also translates into a lower sensitivity to the voltage at the control lines. Fabricated in a standard 0.13-mum CMOS process, the proposed voltage-controlled ring oscillator exhibits a low phase noise of -103.4 dBc/Hz at 1 MHz offset from the center frequency of 7.64 GHz, while consuming a current of 40 mA excluding the buffer.

A Two-Stage Ring Oscillator in 0.13- $\mu{\hbox{m}}$ CMOS for UWB Impulse Radio

Abstract: We present a two-stage digitally controlled ring oscillator designed mainly for impulse-radio ultra-wideband (UWB) applications. Each basic stage utilizes a local positive feedback, allowing to achieve steady oscillation at low current consumption levels, and to extend the frequency tuning over an ultra-wide range. The frequency tuning is achieved via the control of the tail resistor in each stage. The circuit is fabricated in a 0.13-mum CMOS technology. It features full UWB coverage at slightly higher than 1.3-V supply voltage, -121.7-dBc/Hz phase noise at a 5.6-GHz carrier, and 10-MHz offset, and less than 5-mW power consumption for the digitally controlled oscillator core alone at 10.18-GHz maximum frequency under 1.3-V supply voltage.

A 95nW ring oscillator-based temperature sensor for RFID tags in 0.13µm CMOS

Abstract: In this paper, a ring oscillator-based CMOS temperature sensor with nano-watt power consumption is presented for RFID applications. Unlike conventional temperature sensors based on bandgap reference and ADC that consume large amount of power, the proposed sensor exploits the temperature dependence of the threshold voltage and carrier mobility of MOS transistors that affect the frequency of a ring oscillator. In order to maximize the temperature sensitivity and dynamic range, a supply voltage of 0.3V is used, which allows the oscillator to operate in subthreshold, near-threshold and above threshold region under different temperature conditions. In order to handle process variation, the frequency of the oscillator can be digitally trimmed by both a capacitor bank and stacked transistors. Measured data from 0.13-µm CMOS test chips indicate that the proposed temperature sensor has a resolution of 0.4°C/LSB with a 10-bit digital output code over a temperature range of 8°C to 85°C. At 10Hz of sampling frequency, the proposed sensor consumes 95nW and occupies 0.04mm2.

Synchronization Performance of the Precision Time Protocol in Industrial Automation Networks

Abstract: This paper analyzes the factors that affect the synchronization performance in peer-to-peer precision time protocol (PTP). We first study the influence of frequency drift in the absence of jitter and compare the gravity of the master drift with that of the slave drift. Then, we study the influence of jitter under the assumption of constant frequencies and the effect of averaging. The analytic formulas provide a theoretical ground for understanding the simulation results, some of which are presented, as well as the guidelines for choosing both system and control parameters.

A 10MHz 80μW 67 ppm/°C CMOS reference clock oscillator with a temperature compensated feedback loop in 0.18μm CMOS

Abstract: A 10MHz, 80μW CMOS reference clock oscillator is presented in 0.18μm CMOS. The proposed oscillator employs a supply-regulated ring-oscillator in a temperature compensated feedback loop, which minimizes the frequency sensitivity to supply and temperature variations. The clock oscillator achieves frequency variation of less than ±0.05% against supply variation of 1.2V ~ 3V and ±0.4% against temperature variation of −20°C ~ 120°C. In addition, low power consumption is achieved by using sub-threshold bias circuits.

A narrow linewidth and frequency-stable probe laser source for the 88Sr+ single ion optical frequency standard

Abstract: In this paper, we describe in detail a narrow linewidth and frequency-stable laser source used to probe the 5s2S1/2–4d2D5/2 clock transition of the 88Sr+ optical frequency standard. The performance of the laser system is investigated with studies of its frequency drift rates and with high resolution spectra of the 88Sr+ clock transition. The observed short-term drift rates are typically in the range of 10 to 23 mHz/s, and the current long-term drift rate is 13.9(3) mHz/s. The laser stability, after subtraction of linear drifts, reaches 5×10−16 at an averaging time of 3000 s. This high level of stability is attributed for the most part to stabilization of the reference cavity at the temperature where the coefficient of linear thermal expansion crosses zero. An upper bound for the laser linewidth is given by the observation of a Fourier-transform limited resonance of 4.3 Hz (Δν/ν=1×10−14) on the 88Sr+ clock transition. The effective averaging time during the linewidth measurements was about 100 s.

A 25-MHz Self-Referenced Solid-State Frequency Source Suitable for XO-Replacement

Abstract: Recent trends in the development of integrated silicon frequency sources are discussed. Within that context, a 25-MHz self-referenced solid-state frequency source is presented and demonstrated where measured performance makes it suitable for replacement of crystal oscillators (XOs) in data interface applications. The frequency source is referenced to a frequency-trimmed and temperature-compensated 800-MHz free-running LC oscillator (LCO) that is implemented in a standard logic CMOS process and with no specialized analog process options. Mechanisms giving rise to frequency drift in integrated LCOs are discussed and supported by analytical expressions. Design objectives and a compensation technique are presented where several implementation challenges are uncovered. Fabricated in a 0.25-mum 1P5M CMOS process, and with no external components, the prototype frequency source dissipates 59.4 mW while maintaining plusmn152 ppm frequency inaccuracy over process, plusmn 10% variation in the power supply voltage, and from - 10degC to 80degC. Variation against other environmental factors is also presented. Nominal period jitter and power-on start-up latency are 2.75 psrms and 268 mus, respectively. These performance metrics are compared with an XO at the same frequency.

Current Status of a Pulsed CPT Cs Cell Clock

Abstract: A Raman-Ramsey Cs cell atomic clock is presented. The relaxation times of the population and the hyperfine coherences in the cell are measured. The effect on the central Ramsey fringe amplitude of the critical experimental parameters such as laser intensity, magnetic field, temperature, and Ramsey time is investigated. The existence and impact of the additional Deltam = 2 transitions involved in the pumping scheme are pointed out. Narrow resonance linewidths as low as 33 Hz with reasonable signal-to-noise ratios have been recorded. By removing a frequency drift attributed to the cell, the achieved frequency stability is 7 times 10-13 tau-1/2. The main noise contributions that limit the short-term frequency stability are reviewed and estimated.

Variable-Frequency Fluidic Oscillator Driven by a Piezoelectric Bender

Abstract: §This paper describes a new actuator for flow control applications ‐ the piezo-fluidic oscillator. The actuator is a fluidic device based on wall-attachment of a fluid jet, and modulated by piezoelectric devices. The piezo-fluidic oscillator successfully decouples the operating frequency from the flow characteristics of the device. The frequency is specified by an input electrical signal that is independent of pressure, making this actuator ideal for closed-loop control applications. The oscillator exhibits high bandwidth (up to 1.2 kHz), modulation rates up to 100%, and a velocity range reaching sonic conditions. Furthermore, the bi-stable actuator may be operated in a steady state, with momentum flux in one of two desired directions. The piezo-fluidic oscillator may be used in flow control applications where synthetic jets cannot provide enough momentum for control authority. The actuator can also be used as an alternative to traditional aircraft control surfaces while operating in the steady bi-directional mode. This paper details the design and characterization of the piezo-fluidic oscillator. The dynamic response characteristics are evaluated with flow visualization and hot film probe measurements on the output. **

Simulations of coronal type III solar radio bursts: 3. Effects of beam and coronal parameters

Abstract: [1] A recently developed simulation model is used to investigate the effects of varying the coronal and electron heating conditions on the dynamic spectra of coronal type III bursts (70–370 MHz) observed at Earth. The flux of 2fp emission is significantly higher than that of fp emission, which is unlikely to be observable except under very favorable propagation conditions. Moreover, the 2fp emission is unlikely to continue into the solar wind, although some bursts are very strong and will extend into the upper corona with lower frequencies than simulated, consistent qualitatively with observations. The flux and brightness temperature of 2fp emission are affected significantly by variations in the parameters, while the frequency drift rate and half-power duration are affected only weakly. Further, the simulations confirm the standard interpretation of the drift rate of 2fp emission in terms of the plasma density profile and a characteristic beam speed that agrees quantitatively with the simulated beam dynamics for wide ranges of coronal and heating conditions. For weak heating events or events with high coronal electron temperature, the remote radiation shows characteristics that agree quantitatively with microbursts. When the heating is even weaker and/or the electron temperature is even higher, the heating events are radio quiet, consistent qualitatively with hard X-ray observations. For similar heating originating in similar frequency ranges, different density models yield quantitatively similar results except for the drift rate. Variations of the levels of a given density profile, corresponding to background corona or coronal streamers, can also cause significant changes in spectral characteristics.

A tunable flipflop-based frequency divider up to 113 GHz and a fully differential 77GHz push-push VCO in SiGe BiCMOS technology

Abstract: We present a tunable flipflop-based frequency divider and a fully differential push-push VCO designed in a 200GHz f T SiGe BiCMOS technology. A new technique for tuning the sensitivity of the divider in the frequency range of interest is presented. The chip works from 60GHz up to 113GHz. The VCO is based on a new topology which allows generating differential push-push outputs. The VCO shows a tuning range larger than 7GHz. The phase noise is 75dBc/Hz at 100kHz offset. The chip shows a frequency drift of 12.3MHz/C. The fundamental signal suppression is larger than 50dB. The output power is 2×5dBm. At a 3.3V supply, the circuits consume 35mA and 65mA, respectively.

“Drifting tadpoles” in wavelet spectra of decimetric radio emission of fiber bursts

Abstract: Aims. The solar decimetric radio emission of fiber bursts was investigated searching for the “drifting tadpole” structures proposed by theoretical studies. Methods. Characteristic periods with the tadpole pattern were searched for in the radio flux time series by wavelet analysis methods. Results. For the first time, we have found drifting tadpoles in the wavelet spectra of the decimetric radio emission associated with the fiber bursts observed in July 11, 2005. These tadpoles were detected at all radio frequencies in the 1602-1780 MHz frequency range. The characteristic period of the wavelet tadpole patterns was found to be 81.4 s and the frequency drift of the tadpole heads is -6.8 MHz s -1 . These tadpoles are interpreted as a signature of the magnetoacoustic wave train moving along a dense flare waveguide and their frequency drift as a motion of the wave train modulating the radio emission produced by the plasma emission mechanism. Using the Aschwanden density model of the solar atmosphere, only low values of the Alfven speed and the magnetic field strength in the loop guiding this wave train were derived which indicates a neutral current sheet as the guiding structure. The present analysis supports the model of fiber bursts based on whistler waves.

Frequency stability measurement of a transfer-cavity-stabilized diode laser by using an optical frequency comb

Abstract: We report results of frequency stability measurements of an extended cavity diode laser (ECDL) whose frequency is stabilized by a non-evacuated scanning transfer cavity. The transfer cavity is locked to a commercial frequency stabilized helium–neon laser. Frequency stability is measured by use of an optical frequency comb. The environmental perturbations (variations of temperature, air pressure, and humidity) are also simultaneously measured. The observed frequency drift of the ECDL is well explained by environmental perturbations. An atmospheric pressure variation, which is difficult to control with a non-evacuated cavity, is mainly affected to the frequency stability. Thus we put the cavity into a simple O-ring sealed (non-evacuated) tube. With this simple O-ring sealed tube, the frequency drift is reduced by a factor of 3, and the Allan variance reaches a value of 2.4×10−10, corresponds to the frequency stability of 83 kHz, at the average time of 3000 s. Since the actual frequency drift is well estimated by simultaneous measurement of the ambient temperature, pressure, and humidity, a feed-forward compensation of frequency drifts is also feasible in order to achieve a higher frequency stability with a simple non-evacuated transfer cavity.

Method and system for flexible FM tuning

Abstract: A system for processing signals is disclosed and may include a single chip having an integrated Bluetooth radio and an integrated FM radio. The single chip may include at least one processor that enables selecting from a range of FM channels, a particular frequency for one of the FM channels based on an intermediate frequency (IF). The particular frequency may be selected so that it is an integer multiple of a channel spacing between neighboring allocated FM channels within the range of FM channels, and may be offset by at most one-half the channel spacing. The at least one processor may enable determining a frequency error of the selected particular frequency for the one of the FM channels. The at least one processor may also enable determining, whether the particular frequency includes an on-frequency channel based on the determined frequency error.

Ring oscillator having wide frequency range

Abstract: Provided is a ring oscillator having an extended range of oscillation frequency by varactors coupled to delay cells even in a simple structure. The wide frequency range results from simply varying an oscillation frequency by control signals applied to the varactors. Since additional switches connected to the delay cells contribute to increase or decrease of the oscillation frequency range, the ring oscillator can conveniently be employed in various types of oscillation systems.

Anti-islanding protection for distributed generation systems based on reactive power drift

Abstract: This paper demonstrates that the close-loop control of distributed generation systems' output power has negative impacts on island detecting schemes using phase-shift techniques, such as Active Frequency Drift (AFD), Slide-Mode Frequency Shift (SMS), etc. On that basis, an anti-islanding protection scheme is proposed, which takes system frequency as feedback to adjust the reactive power output of grid-connected inverter. This control scheme can yield a quick frequency shift in an islanding situation and trigger the detection module. Comparing with AFD and SMS, this scheme produces no current waveform distortion, and has a better performance in real power control during transient state after islanding. Corresponding mathematical model is presented. Comparison results with AFD and SMS shows the advantages of proposed anti-islanding protection scheme. Finally, simulation results validate the proposed control scheme.

A very fast control based on hysteresis of the C out current with a frequency loop to operate at constant frequency

Abstract: The combination of non-linear control and linear control proposed in [1] provides very fast transient response (voltage step from 1 V to 1.5 V in 2 ?s). This non-linear control is based on hysteretic control of the C out current. This system is very sensitive to effects like aging, temperature, input and output voltage variation, etc., that modify the switching frequency. This paper proposes a frequency loop to avoid the frequency variation and to adjust the switching frequency to the nominal value by changing the hysteretic band. The design and analysis of the nonlinear loop, the voltage loop and frequency loop are presented in detail with a design example. A 5 MHz buck converter is developed and experimental results validate the loops design, obtaining the same fast transient response (from 1.5 V to 2.5 V in 2 ?s) but keeping constant the switching frequency in steady state.

A low power current reused quadrature VCO for biomedical applications

Abstract: This paper presents a low power current reusing quadrature voltage controlled oscillator for use in implantable electronics operating in the 402 MHz to 405 MHz Medical Implant Communication Service (MICS) frequency band. The oscillator was designed in IBM CMOS8RF 0.13 µm CMOS technology and simulated using Cadence IC5.141. The current reuse structure draws half the bias current as a conventional quadrature voltage controlled oscillator while exhibiting performance comparable to or exceeding that of previously published designs. Simulation results show that the oscillator phase noise is −127 dBc/Hz and consumes 1 mW of power from a 1 V supply. When the supply voltage is scaled to 0.65 V and biased for the same current consumption, the power consumption is reduced to 650 µW with phase noise of −111 dBc/Hz, which is almost 50% less power consumption when compared to oscillators in the same frequency band. The tuning range of the oscillator is 401.25 MHz to 407.5 MHz, enough to cover the MICS frequency band.

Micro-Electromechanical Devices Having Variable Capacitors Therein that Compensate for Temperature-Induced Frequency Drift in Acoustic Resonators

Abstract: Micro-electromechanical devices include a temperature-compensation capacitor and a thin-film bulk acoustic resonator having a first terminal electrically coupled to an electrode of the temperature-compensation capacitor. The temperature-compensation capacitor includes a bimorph beam having a first electrode thereon and a second electrode extending opposite the first electrode. This bimorph beam is configured to yield an increase in spacing between the first and second electrodes in response to an increase in temperature of the micro-electromechanical device. This increase in spacing between the first and second electrodes leads to a decrease in capacitance of the temperature-compensation capacitor. Advantageously, this decrease in capacitance can be used to counteract a negative temperature coefficient of frequency associated with the thin-film bulk acoustic resonator, and thereby render the resonant frequency of the micro-electromechanical device more stable in response to temperature fluctuations.

Method for carrier frequency recovery and optical intradyne coherent receiver

Abstract: A method for carrier frequency recovery in an optical coherent transmission system is provided in which at least one kind of equalization of a received signal is performed in frequency domain, the method comprising: performing a frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset; obtaining the signal with the frequency offset compensated. Further, an optical coherent receiver is provided comprising: an equalization unit, adapted to perform at least one kind of optical distortion compensation of a received signal in frequency domain; a frequency offset compensation unit, adapted to perform the frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset to obtain the signal with frequency offset compensated. The method and the receiver provided by the present invention in carrier frequency recovery need only a frequency shift of the signal spectrum, reducing the computation complexity dramatically thus the processing is speed up and the resources needed are very much saved.

Digital communications receiver and method of estimating residual carrier frequency offset in a received signal

Abstract: A carrier frequency offset can be present in a signal received by a communications receiver, when the receiver has a local frequency oscillator that generates a carrier frequency different from a carrier frequency generated by a local frequency oscillator at a transmitter that transmitted the signal. A residual carrier frequency offset can remain after most of the carrier frequency offset has been removed from the received signal using conventional techniques. The residual carrier frequency offset is estimated using first and second channel impulse responses derived from first and second portions of the received signal. An estimated phase difference between the first and second channel impulse responses is computed. An estimate of the residual carrier frequency offset is computed using the estimated phase difference.

Estimating frequency offset using a feedback loop

Abstract: According to particular embodiments, a signal communicated from a transmitter to a receiver is received A frequency offset estimate of the signal is determined The frequency offset estimate indicates a frequency difference between the transmitter and the receiver The frequency offset estimate is provided as feedback A next frequency offset is compensated for according to the feedback

Temperature compensated BAW resonator and its integrated thermistor for a 2.5GHz electrical thermally compensated oscillator

Abstract: This paper presents a miniaturized 2.5 GHz frequency source based on compensated BAW resonator with its integrated temperature molybdenum sensor assembled on the differential Colpitts oscillator. The presence of silicon dioxide layer having a positive temperature coefficient compared to other layers is used to reduce the resonator's drift. A demonstration oscillator achieves a frequency drift of 40 ppm over a temperature range from −35°C to +85°C. The oscillator's phase noise of −113 dBc/Hz at 10 kHz offset from the carrier is reported at 2.5 GHz.

Resonator fiber optic gyroscope with digital serrodyne scheme using a digital controller

Abstract: To get rid of the complex analogue control loops that are traditionally used in resonator fiber optic gyroscope (R-FOG) and to meet the requirements of high accuracy as well as small-size and light-weight in Inertial Navigation Systems (INSs), a digital controller is developed and demonstrated experimentally to control the R-FOG with the digital serrodyne modulation. The digital controller is designed to implement the function of tracking the laser diode frequency drift and to compensate for the imperfect 2π modulation voltage of the phase modulator for the serrodyne modulation. To acquire the resonant frequency, the digital serrodyne modulation with symmetric frequency shift is adopted as a counter-measure for Rayleigh backscattering noise. The optimal serrodyne modulation generated frequency shift is decided to be in the range of 100~120 kHz according to the numerical calculation. The successful demonstration of the open loop operation with the digital controller is deemed as the basis for the digitalized closed-loop experiment in future.

Studies and possible improvements on EAL algorithm

Abstract: A new algorithm for the clock frequency prediction used to calculate EAL is presented. The mathematical model adopted in the new prediction algorithm takes in account the effect of the frequency drift of the H-masers. We demonstrate that there is an improvement in long term stability of EAL by using the new prediction algorithm.

Gated tunnel diode in oscillator applications with high frequency tuning

Abstract: A gated tunnel diode has been introduced into a wave-guide oscillator circuit and the gate is used to tune the oscillation frequency and to turn the oscillator on and off. Oscillators with oscillation frequencies in the range of 9-22 GHz with a typical oscillator output power about -20 dBm have been fabricated. We found that the output power remains essentially constant over a gate bias range (about -260 to 200 mV at V-c = 1.0 V in one oscillator), while it rapidly drops to the noise level over a gate bias range of less than 60 mV above or below the threshold, respectively. In the region with constant power, a total frequency tuning of about 30% is achieved. The maximum oscillation frequency. f(max) (osc), of the gated tunnel diode is set by the tunnel diode and the gate-collector capacitance, and does not depend on the gate-emitter capacitance. This oscillator implementation, in particular, eliminates the need for a separate switch in the realisation of oscillator-based ultra-wide band impulse radios. (C) 2009 Elsevier Ltd. All rights reserved.

Low KVCO phase-locked loop with large frequency drift handling capability

Abstract: A phase-locked loop that supports a large frequency drift capability, yet maintains a low Kvco, and does not introduce noise or discontinuities in the frequency of the generated phase-locked loop output signal. The phase-locked loop may include a VCO with an LC tank circuit, the capacitance of which may be adjusted in incremental units. By gradually adjusting a control signal applied to a selected VCO LC tank circuit frequency adjustment control line, e.g., in a continuous ramped function, or time-averaged ramped function, from LOW-to-HIGH or from HIGH-to-LOW, over a period of time that is greater than the response time of the phase-locked loop, a frequency range supported by the VCO may be shifted to either a higher frequency range or a lower frequency range, as needed, to accommodate environmentally induced frequency drift in the VCO, without introducing noise or discontinuities in the frequency of the generated phase-locked loop output signal.

A 1.5GHz CMOS/FBAR frequency reference with ±10ppm temperature stability

Abstract: A temperature compensated 15GHz FBAR-based frequency reference implemented in a 035µm CMOS process is presented The ultra-small form factor and low power dissipation of a temperature compensated FBAR oscillator presents a promising alternative for replacement of quartz crystal frequency references The measured frequency post-compensation drift over a 0-100°C temperature range is ≪20ppm The measured phase noise is -125dBc/Hz at 100 kHz offset from carrier The overall system power consumption is 960µW