Showing papers on "Frequency drift published in 2012"

A review of MEMS oscillators for frequency reference and timing applications

Abstract: MEMS-based oscillators are an emerging class of highly miniaturized, batch manufacturable timing devices that can rival the electrical performance of well-established quartz-based oscillators. In this review, a description is given of the key properties of a MEMS resonator that determine the overall performance of a MEMS oscillator. Piezoelectric, capacitive and active resonator transduction methods are compared and their impact on oscillator noise and power dissipation is explained. An overview is given of the performance of MEMS resonators and MEMS-based oscillators that have been demonstrated to date. Mechanisms that affect the frequency stability of the resonator, such as temperature-induced frequency drift, are explained and an overview is given of methods that have been demonstrated to improve the frequency stability. The aforementioned performance indicators of MEMS-based oscillators are benchmarked against established quartz and CMOS technologies.

Metrological characterization of the pulsed Rb clock with optical detection

Abstract: We report on the implementation and metrological characterization of a vapour-cell Rb frequency standard working in a pulsed regime. The three main parts of the clock, physics package, optics and electronics, are described in detail in this paper. The prototype is designed and optimized to detect the clock transition in the optical domain. Specifically, the reference atomic transition, excited with a Ramsey scheme, is detected by observing the interference pattern on a laser absorption signal. The metrological analysis includes the observation and characterization of the clock signal and the measurement of frequency stability and drift. In terms of Allan deviation, the measured frequency stability is as low as 1.7 × 10−13τ−1/2, τ being the averaging time, and reaches the value of a few units of 10−15 for τ = 104 s, an unprecedented result for a vapour-cell clock. We discuss the physical effects leading to this result in this paper with particular care to laser and microwave noises transferred to the clock signal. The frequency drift, probably related to temperature, stays below 10−14 per day, and no evidence of flicker floor is observed. We also mention some possible improvements that in principle would lead to a clock stability below the 10−13 level at 1 s and to a drift of a few units of 10−15 per day.

Ultra-low-phase-noise cryocooled microwave dielectric-sapphire-resonator oscillators

Abstract: Two nominally identical ultra-stable microwave oscillators are compared. Each incorporates a sapphire resonator cooled to near 6 K in an ultra-low vibration cryostat using a pulse-tube cryocooler. The phase noise for a single oscillator is measured at −105 dBc/Hz at 1 Hz offset on the 11.2 GHz carrier. The oscillator fractional frequency stability, after subtracting a linear frequency drift of 3.5×10-14/day, is characterized by 5.3×10-16τ-1/2+9×10-17 for integration times 0.1s<τ<1000s and is limited by a flicker frequency noise floor near 1×10-16.

Design of Low Phase-Noise Microwave Oscillator and Wideband VCO Based on Microstrip Combline Bandpass Filters

Abstract: This paper presents a new low phase-noise microwave oscillator and wideband voltage-controlled oscillator (VCO) based on microstrip combline bandpass filters. For this type of oscillator, the passband filter is embedded into the feedback loop to treat as a frequency stabilization element. Instead of designing the oscillator at the group-delay-peak frequency of the filter to achieve a good phase-noise performance, in this paper, the peak frequency of the complex quality factor Qsc is adopted for oscillator design. To demonstrate the effectiveness of using Qsc-peak frequency, two filter-based oscillators are implemented at the Qsc-peak and group-delay-peak frequencies, respectively. The oscillator designed at the Qsc-peak frequency improves the phase-noise about 10 dB as compared with that realized at the group-delay-peak frequency. The developed oscillator with the three-pole combline filter is experimentally demonstrated at 2.05 GHz with -148.3-dBc/Hz phase noise at 1-MHz offset frequency. Moreover, by attaching a varactor on each resonator of the combline filter, the oscillator can be extended to a wideband VCO. The developed VCO has a frequency tuning range from 1.3 to 2.2813 GHz with a 54.8% bandwidth. Over this frequency range, all the phase noises measured at 1-MHz offset frequency are better than -117.19 dBc/Hz.

A 32.4 ppm/°C 3.2-1.6V self-chopped relaxation oscillator with adaptive supply generation

Abstract: A self-chopped relaxation oscillator with adaptive supply generation provides the stable output clock against variations in temperature and supply voltages. The frequency drift is less than ±0.1% for the supply voltage changing from 1.6 to 3.2 V and ±0.1% for a temperature range from −20 to 100°C, which is reduced by 83% with the self-chopped technique. This relaxation oscillator is implemented in a 60-nm CMOS technology with its active area equals to 0.048 mm2. It consumes 2.8 uA from a 1.6-V supply.

A Low-Energy Crystal-Less Double-FSK Sensor Node Transceiver for Wireless Body-Area Network

Abstract: An energy-efficient crystal-less double-FSK transceiver for wireless body-area-network (WBAN) sensor nodes is implemented in 0.18-μm CMOS technology with a 1-V supply. The injection-locking digitally controlled oscillator (IL-DCO) replaces the crystal oscillator (XO), which leads to significantly reduce the energy consumption and system cost. With the proposed calibration method using an injection-locking detector (IL-detector), the frequency drift of DCO can be calibrated within 100-kHz accuracy over 100° temperature variation. For the full satisfaction to the WBAN requirements, such as wide range of quality of service in terms of data rate, bit error rate, and network coexistence, we adopt a scalable double-FSK modulation scheme with divider-based transmitter by a power-efficient switching modulator. As a result, the fabricated crystal-less double-FSK WBAN compatible sensor node transceiver consumes 1 and 2 mW in calibrating and transmitting modes, respectively, at a data rate of up to 10 Mb/s, providing an 80 MHz reference source with 100-kHz accuracy by auto-calibrated DCO.

A 27 MHz temperature compensated MEMS oscillator with sub-ppm instability

Abstract: This paper reports on the design, implementation and characterization of a low phase-noise 27 MHz MEMS oscillator with sub-ppm temperature instability based on a high-Q composite bulk acoustic wave (BAW) resonator. An array of silicon dioxide (SiO 2 ) pillars has been uniformly embedded in the body of a piezoelectrically transduced silicon resonator to compensate its negative temperature coefficient of frequency (TCF). Using this technique, an overall frequency drift of 83 ppm is achieved for the resonator over the temperature range of −20°C to 100°C while resonator Q remains greater than 7,500 in atmospheric pressure. An electronically compensated oscillator using this resonator exhibits sub-ppm temperature instability with a consistent phase noise (PN) behavior over the entire temperature range and a value of −101dBc/Hz at 1 kHz offset-frequency. Long-term stability measurement has been carried out for both temperature-compensated resonator and oscillator in an environmental chamber to study their stability over time.

Radio fiber bursts and fast magnetoacoustic wave trains

Abstract: We present a model for dm-fiber bursts that is based on assuming fast sausage magnetoacoustic wave trains that propagate along a dense vertical filament or current sheet. Eight groups of dm-fiber bursts that were observed during solar flares were selected and analyzed by the wavelet analysis method. To model these fiber bursts we built a semi-empirical model. We also did magnetohydrodynamic simulations of a propagation of the magnetoacoustic wave train in a vertical and gravitationally stratified current sheet. In the wavelet spectra of the fiber bursts computed at different radio frequencies we found the wavelet tadpoles, whose head maxima have the same frequency drift as the drift of fiber bursts. It indicates that the drift of these fiber bursts can be explained by the propagating fast sausage magnetoacoustic wave train. Using new semi-empirical and magnetohydrodynamic models with a simple radio emission model we generated the artificial radio spectra of the fiber bursts, which are similar to the observed ones.

On the low-power design, stability improvement and frequency estimation of the CMOS ring oscillator

Abstract: In this paper, a simple method allowing optimization of the CMOS ring oscillator frequency dispersion and power consumption is discussed. It is shown, that for range of tens of MHz and less, the power consumption and variation of the frequency can be considerably reduced by using 3-stage, resistively coupled ring oscillator, with minimum channel width W and large channel length L MOS transistors. In addition, a simple analysis allowing to estimate the oscillator frequency from the process and transistor parameter values is provided.

CMOS THz Generator With Frequency Selective Negative Resistance Tank

Abstract: This paper reports a CMOS terahertz oscillator with a novel frequency selective negative resistance (FSNR) tank to boost its operating frequency. The demonstrated oscillator can operate at a fundamental frequency of about 0.22 THz, exceeding the CMOS device cutoff frequency of fT. The proposed architecture suppresses undesired 2nd and odd harmonics and boosts the fourth-order harmonic (0.87 THz), which radiates through an on-chip patch antenna. The THz oscillator's output spectrum is profiled by using a Michelson interferometer. The oscillator circuit consumes 12 mA from a 1.4 V supply and occupies a 0.045 mm2 die area in a 65 nm CMOS technology.

Microwave quasi-periodic pulsation with millisecond bursts in a solar flare on 2011 august 9

Abstract: A peculiar microwave quasi-periodic pulsation (QPP) accompanying a hard X-ray (HXR) QPP of about 20 s duration occurred just before the maximum of an X6.9 solar flare on 2011 August 9. The most interesting aspect is that the microwave QPP consists of millisecond timescale superfine structures. Each microwave QPP pulse is made up of clusters of millisecond spike bursts or narrowband type III bursts. There are three different frequency drift rates: the global frequency drift rate of the microwave QPP pulse group, the frequency drift rate of the microwave QPP pulse, and the frequency drift rate of individual millisecond spikes or type III bursts. The physical analysis indicates that the energetic electrons accelerating from a large-scale highly dynamic magnetic reconnecting current sheet above the flaring loop propagate downward, impact the flaring plasma loop, and produce HXR bursts. The tearing-mode (TM) oscillations in the current sheet modulate HXR emission and generate HXR QPP; the energetic electrons propagating downward produce Langmuir turbulence and plasma waves, resulting in plasma emission. The modulation of TM oscillation on the plasma emission in the current-carrying plasma loop may generate microwave QPP. The TM instability produces magnetic islands in the loop. Each X-point will be a small reconnection site and will accelerate the ambient electrons. These accelerated electrons impact the ambient plasma and trigger the millisecond spike clusters or the group of type III bursts. Possibly, each millisecond spike burst or type III burst is one of the elementary bursts (EBs). A large number of such EB clusters form an intense flaring microwave burst.

An Improved Performance Ring Oscillator Design

Abstract: This paper presents a new technique to improve frequency performance of CMOS ring oscillator. It is based on the addition of MOS transistor to boost switching speed of the oscillator delay cell. The method can be used for simple and differential oscillator and offers a simple way to implement frequency tuning without introduction of any additional phase noise. Using 0.35 µm CMOS technology, simulation results show that applying the technique to the simple ring oscillator allows a frequency oscillation improvement of 80%. Also, simulations show that frequency improvement can reach 300 % if the technique is associated to a positive feedback.

Electronic Temperature Compensation of Lateral Bulk Acoustic Resonator Reference Oscillators Using Enhanced Series Tuning Technique

Abstract: This paper reports on the demonstration of series tuning for lateral micromechanical oscillators and its application for electronic temperature compensation of piezoelectric lateral bulk acoustic resonator (LBAR) micromechanical oscillators. Two aluminum nitride-on-silicon (AlN-on-Si) piezoelectric LBARs, one operating at 427 MHz (Rm ≈180 Ω, Qunloaded ≈ 1400) and the other operating at 541 MHz (Rm ≈ 55 Ω, Qunloaded ≈ 3000) are interfaced with a 13 mW three-stage tunable TIA implemented in 0.18 μm 1P6M CMOS process to sustain the oscillation. Recognizing the impact on the frequency tuning range due to the body capacitances appearing in parallel with the ports of the resonator, the TIA uses parasitic cancellation techniques to neutralize this effect and boost the tuning range of 427 MHz and 541 MHz oscillators, by as much as 12× to 810 ppm and 1,530 ppm, respectively, with negligible impact on the phase noise performance. The shunt parasitic capacitor is either resonated out with an active inductor or is cancelled out by using a single-terminal negative capacitor of equal value. However, the oscillator that uses negative capacitance parasitic cancellation yields larger tuning. This extended tuning range is used for temperature compensation. A 2 mW bandgap-based temperature compensation circuit which uses second-order parabolic approximation is fabricated on the same chip. Using this temperature compensation circuit has lowered the overall frequency drift of a 427 MHz tunable oscillator using negative capacitance cancellation from ±390 ppm to ±35 ppm in the -10°C to 70°C temperature range. The phase noise of this oscillator reaches -82 dBc/Hz at 1 kHz offset. The total phase noise variation for offset frequencies below 10 kHz is under 5 dB within the specified tuning range, and the best phase noise floor is under -147 dBc/Hz . Due to the higher Q and lower insertion loss of the resonating tank, the 541 MHz oscillator achieves -86 dBc/Hz at 1 kHz offset, and lower phase noise floor of -158 dBc/Hz.

A Temperature-Compensation Technique for Substrate Integrated Waveguide Cavities and Filters

Abstract: A new temperature compensation method is proposed and demonstrated in this paper for cavities and filters realized in substrate integrated waveguide (SIW). The SIW structures largely preserve the well-known advantages of conventional rectangular waveguide, namely, high Q and high power capacity, and have the advantages of microstrip lines, such as low profile, small volume, and light weight. In this paper, we demonstrate that by an adequate selection of substrate properties, SIW cavities can provide self-temperature drift compensation. The compensation is achieved by using an appropriate ratio between the coefficient of thermal expansion and the thermal coefficient of the permittivity. The theoretical prediction is confirmed by an experimental investigation using inductive post filters. Three commercially available substrates are used to design cavities at 10 GHz with the Roger TMM10 substrate providing a close fit to the required characteristics for temperature compensation. The results for the cavity show a stability of 2 ppm/°C in calculation and 8 ppm/°C in measurement. A SIW fourth-order Chebyshev filter, centered at 10 GHz with 1-GHz bandwidth, has also been designed. The measured frequency drift is 9.1 ppm/°C and the bandwidth variation is 0.13% over the temperature range of 40°C to 80°C.

Investigation and evaluation of active frequency drifting methods in multiple grid-connected inverters

Abstract: As the development of distributed generation goes on, more grid-connected inverters are being inevitably connected to the same local electrical power system and the perturbations exerted by each inverter for islanding detection might interfere with each other The islanding detection principle of commonly used active frequency drift (AFD), sandia frequency drift and slip-mode frequency shift are comprehensively investigated and improved algorithms are proposed as well for better detection performance Moreover, the interaction of these strategies applied in multiple-inverter systems especially with frequency measurement errors is systematically analysed The corresponding detection performance is summarised, which can also serve as an effective guideline for designing AFD methods in multi-inverter systems Finally, simulation and experimental results are provided to verify the islanding detection performance of these methods under multiple-inverter operation

2.32 THz quantum cascade laser frequency-locked to the harmonic of a microwave synthesizer source.

Abstract: Frequency stabilization of a THz quantum cascade laser (QCL) to the harmonic of a microwave source has been accomplished using a Schottky diode waveguide mixer designed for harmonic mixing. The 2.32 THz, 1.0 milliwatt CW QCL is coupled into the signal port of the mixer and a 110 GHz signal, derived from a harmonic of a microwave synthesizer, is coupled into the IF port. The difference frequency between the 21st harmonic of 110 GHz and the QCL is used in a discriminator to adjust the QCL bias current to stabilize the frequency. The short-term frequency jitter is reduced from 550 kHz to 4.5 kHz (FWHM) and the long-term frequency drift is eliminated. This performance is compared to that of several other THz QCL frequency stabilization techniques.

Microwave Quasi-periodic Pulsation with Millisecond Bursts in A Solar Flare on 2011 August 9

Abstract: An peculiar microwave quasi-periodic pulsation (QPP) accompanying with a hard X-ray (HXR) QPP of about 20 s duration occurred just before the maximum of an X6.9 solar flare on 2011 August 9. The most interesting is that the microwave QPP is consisting of millisecond timescale superfine structures. Each microwave QPP pulse is made up of clusters of millisecond spike bursts or narrow band type III bursts. There are three different frequency drift rates: global frequency drift rate of microwave QPP pulse group, frequency drift rate of microwave QPP pulse, and frequency drift rate of individual millisecond spikes or type III bursts. The physical analysis indicates that the energetic electrons accelerating from a large-scale highly dynamic magnetic reconnecting current sheet above the flaring loop propagate downwards, impact on the flaring plasma loop, and produce HXR bursts. The tearing-mode (TM) oscillations in the current sheet modulate HXR emission and generate HXR QPP; the energetic electrons propagating downwards produce Langmuir turbulence and plasma waves, result in plasma emission. The modulation of TM oscillation on the plasma emission in the current-carrying plasma loop may generate microwave QPP. The TM instability produces magnetic islands in the loop. Each X-point will be a small reconnection site and accelerate the ambient electrons. These accelerated electrons impact on the ambient plasma and trigger the millisecond spike clusters or the group of type III bursts. Possibly each millisecond spike burst or type III burst is one of the elementary burst (EB). Large numbers of such EB clusters form an intense flaring microwave burst.

Piezoelectric actuator, robot hand, and robot

Abstract: A piezoelectric actuator includes a frequency controller that controls the frequency and power of the driving signal, wherein when the phase difference falls within a predetermined range, the control unit stores the value of the frequency of the driving signal as a first frequency memory value, sets a voltage to a upper limit voltage value, and performs control of adjusting the frequency of the driving signal so that the phase difference is maintained to be within a predetermined range, and when the frequency of the driving signal is changed from the first frequency memory value by an amount exceeding a first value determined in advance, the control unit stores the value of the frequency of the driving signal as a second frequency memory value and sets the voltage to a lower limit voltage value lower than the upper limit voltage value.

System for doppler positioning of seismic sensors and method

Abstract: Method and system for determining positions of underwater sensors. The method includes sending a Doppler variant signal from a moving source; recording the signal with the at least one seismic sensor; evaluating a frequency drift of the recorded signal; and determining a position of the at least one seismic sensor based on the evaluated frequency drift and a source movement relative to the at least one sensor.

A Low Voltage All-Digital On-Chip Oscillator Using Relative Reference Modeling

Abstract: This paper presents a low voltage on-chip oscillator which can compensate process, voltage, and temperature (PVT) variation in an all-digital manner. The relative reference modeling applies a pair of ring oscillators as relative references and estimates period of the internal ring oscillator. The period estimation is parameterized by a second-order polynomial. Accordingly, the oscillator compensates frequency variations in a frequency division fashion. A 1-20 MHz adjustable oscillator is implemented in a 90-nm CMOS technology with 0.04 mm area. The fabricated chips are robust to variations of supply voltage from 0.9 to 1.1 V and temperature range from 0°C to 75°C. The low supply voltage and the small area make it suitable for low-cost and low-power systems.

A single LC tank self-compensated CMOS oscillator with frequency stability of ±100ppm from −40°C to 85°C

Abstract: This work presents a new all CMOS Self-Compensated Oscillator (SCO) that is highly stable across temperature and is utilized as a reference clock source. The new architecture utilizes an innovative phase shift technique that adjusts the phase of the tank at a specific Temperature Null (TNULL) phase where the frequency deviation across temperature is minimized. The single LC tank architecture used in the new oscillator reduces die area significantly compared to a previously reported dual LC tank architecture. The new oscillator achieves a total frequency stability of ±100ppm across temperature (−40–85°C), supply (3.0–3.6V) and load (0–15pF). CMOS output frequencies from 1–133MHz can be produced with a 2.8ps rms period jitter and 7mA current consumption at 25MHz output.

Frequency drift estimation for low cost outdoor unit frequency conversions and system diagnostics

Abstract: Systems and devices for controlling frequency drift in satellite broadcast systems. A receiver antenna system for a direct broadcast satellite signal communications system in accordance with one or more embodiments of the present invention comprises an oscillator, a mixer, coupled to the oscillator, for converting satellite signals at a first frequency to signals at an intermediate frequency, an analog-to-digital (A/D) converter, coupled to the mixer, for receiving the signals at the intermediate frequency and for converting the signals at the intermediate frequency at near-real-time to a digital data stream, a Digital Signal Processor (DSP), coupled to the A/D converter, for processing the digital data stream, and a drift estimator, coupled to the DSP, the drift estimator determining a frequency drift of the oscillator, wherein the receiver antenna system corrects the frequency drift of the oscillator using the determined frequency drift.

An inductorless CMOS quadrature oscillator continuously tuneable from 3.1 to 10.6 GHz

Abstract: Modern RF front-ends require wide tuning-range oscillators with quadrature outputs. In this paper we present a two-integrator quadrature oscillator, which covers the whole bandwidth of UWB applications. A circuit prototype in a 130 nm CMOS technology is continuously tuneable from 3.1 to 10.6 GHz. The circuit die area is less than 0.013mm2, leading to a figure-of-merit FOMA of −176.7dBc/Hz at the upper frequency. The supply voltage is 1.2 V, and the power consumption is 7 mW at the lower frequency and 13 mW at the upper frequency. Copyright © 2010 John Wiley & Sons, Ltd. (We present a two-integrator quadrature oscillator, which covers the whole bandwidth of UWB applications. A circuit prototype in a 130 nm CMOS technology is continuously tuneable from 3.1 to 10.6 GHz. The circuit die area is less than 0.013 mm2, leading to a figure-of-merit FOMA of −176.7 dBc/Hz at the upper frequency. The supply voltage is 1.2 V, and the power consumption is 7 mW at the lower frequency and 13 mW at the upper frequency.)

Temperature Compensation of Aluminum Nitride Lamb Wave Resonators Utilizing the Lowest-Order Symmetric Mode

Abstract: : Frequency references with a low phase noise and a low temperature-induced frequency drift are important components for navigation systems, wireless communication systems, and signal processing applications. As is well known, crystal oscillators (XOs) and temperature compensated crystal oscillators (TCXOs) based on AT-cut quartz dominate this market because AT-cut quartz has outstanding frequency-temperature performance and long-term stability. However, there are drawbacks and fabrication limitations for quartz-based resonators related to down-scaling for future applications. In addition, the material properties of quartz limit the integration of the frequency references and the complementary metal-oxide semiconductor (CMOS) circuits on a single chip. As a result, there has been a great interest in the realization of low-cost, CMOS-compatible, high quality factor (Q), and temperature-stable micro-electro-mechanical systems (MEMS) resonators.

A process-induced-frequency-drift resilient 32 kHz MEMS resonator

Abstract: This paper applies a frequency-drift resilient method for a 32 768 Hz lateral capacitive microelectromechanical system (MEMS) resonator design to make its resonant frequency insensitive to process-induced variation. The basic idea of the method is to synthesize the design of the supported springs and the releasing holes in the proof mass so that process-induced effective spring constant variation is approximately balanced by effective mass variation, and thus to keep their ratio and determined resonant frequency approximately unchanged. The 32 768 Hz MEMS resonator has been fabricated based on 30 µm silicon-on-insulator wafer for real-time clock application. The related testing results of more than 100 working devices from two different wafers show that the resonant frequencies are in the range of 32 102 ± 25 Hz and obey basically the normal distribution, and the drift from the designed value is less than 2.1%. The method is expected to significantly improve the reliability and fabrication yield of MEMS resonator, and can also be extended to other vibrating MEMS devices.

Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft

Abstract: [1] Magnetospheric line radiation (MLR) events are electromagnetic waves in the frequency range of about 1–8 kHz observed in the inner magnetosphere that, when presented in a form of frequency-time spectrograms, consist of several nearly parallel and almost equidistant intense lines. Although many observations of these events have been reported using ground-based instruments and a survey of a large data set based on low-altitude satellite data has been published recently, their origin remains unclear. We use low-altitude satellite observations of MLR events to study their detailed properties, namely, the frequency spacing of individual lines and their frequency drift. Since the satellite, unlike ground observatories, is moving, it allows us to analyze the properties of the events as a function of the position, especially L-shell. We show that neither the frequency spacing of the events nor their frequency drift varies significantly with the L-shell where the event is observed. Moreover, the frequency drift is generally positive. The individual lines forming the events cannot be explained as harmonics of the base frequency equal to the frequency spacing. We suggest that a possible generation mechanism might be an interaction between a wave of a carrier frequency and an additional wave with the frequency equal to the observed frequency spacing. We cannot exclude that it comes from human activity (power lines), but a magnetospheric origin is more likely. We suggest that the emissions might be guided by the plasmasphere inner boundary before they deviate to lower L-shells at altitudes of a few thousands of kilometers. Citation: Němec, F., M. Parrot, and O. Santolik (2012), Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft,

Laser system for secondary cooling of 87Sr atoms

Abstract: A laser system with a narrow generation line for secondary laser cooling of 87Sr atoms has been developed and investigated. It is planned to use ultracold 87Sr atoms loaded in an optical lattice in an optical frequency standard. To this end, a 689-nm semiconductor laser has been stabilised using an external reference ultrastable cavity with vibrational and temperature compensation near the critical point. The lasing spectral width was 80 Hz (averaging time 40 ms), and the frequency drift was at a level of 0.3 Hz s-1. Comparison of two independent laser systems yielded a minimum Allan deviation: 2 × 10-14 for 300-s averaging. It is shown that this system satisfies all requirements necessary for secondary cooling of 87Sr atoms using the spectrally narrow 1S0 — 3P1 transition (λ = 689 nm).

Temperature compensated oscillator with improved noise performance

Abstract: An oscillator system addresses power supply noise and temperature dependence. The system includes a multi-stage regulator circuit that receives a supply voltage and generates a lower voltage oscillator supply voltage that is less noisy than the supply voltage. A charge pump circuit receives the oscillator supply voltage and the oscillator output signal and supplies the regulator circuit with a boosted voltage. A reference generator circuit supplies a reference signal that is used to determine the oscillator supply voltage. The reference signal varies with temperature and is used to offset the temperature coefficient of the oscillator.

Design of Low-phase Noise, Low-power Ring Oscillator for OC-48 Application

Abstract: A low-power, low-phase noise, high tuning range, and fully integrated inductorless RC-VCO (voltage-controlled oscillator) for OC-48 application is designed and simulated in standard 0.18 µm CMOS technology. The proposed inductorless RC-VCO has a simulated phase noise of -141 dBc/Hz at 1 MHz offset from the carrier frequency of 2.4 GHz, with a bias current of 605 µA and voltage headroom of 1.8 V. It has 50% tuning range at 2.4 GHz of operating frequency and consumes 1.09 mW of power. This RC-VCO shows a figure of merit performance of -208.2 dBc/Hz at the desired frequency.