scispace - formally typeset
Search or ask a question

Showing papers on "Frequency drift published in 1999"


Journal ArticleDOI
TL;DR: In this article, the active frequency drift method (AFD), also called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the island to drift up or down.
Abstract: Islanding of photovoltaic (PV) systems can cause a variety of problems and must be prevented. However, if the real and reactive powers of the load and PV system are closely matched, islanding detection by passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift method (AFD), also called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper, AFD is studied analytically, using the describing function analysis technique, and by simulation, using MATLAB. It is shown that AFD has a nondetection zone (NDZ) in which it fails to detect islanding, and that this NDZ includes a range of unity-power-factor loads. Finally, the paper describes a novel method using positive feedback which significantly shrinks the size of the AFD NDZ.

353 citations


Journal ArticleDOI
TL;DR: In this article, a novel and highly sensitive static strain interrogation technique is demonstrated, where the sensing element is a fiber-Bragg grating (FBG) and the light source is a frequency-locked diode laser.
Abstract: Novel and highly sensitive static strain interrogation technique is demonstrated, where the sensing element is a fiber-Bragg grating (FBG) and the light source is a frequency-locked diode laser. Locking the laser frequency to the center of an absorption line (atomic line of potassium in our experiment) eliminates the slow frequency drift of the laser. The stabilized laser source is used to measure low frequency ("static") strain, with a sensitivity of 1.2 nanostrain//spl radic/Hz rms at 1.5 Hz.

101 citations


Journal ArticleDOI
TL;DR: An effective FFL was demonstrated in vivo with no significant increase of the short‐term variance of the water frequency, and the sampling rate of the reference frequency and the smoothing window for the Z0 correction were carefully optimized.
Abstract: The stability of the main magnetic field is critical for prolonged in vivo magnetic resonance spectroscopy (MRS) acquisitions, especially for difference spectroscopy. This study was focused on the implementation and optimization of a field-frequency lock (FFL) on a whole body spectrometer, to correct the main field drift during localized proton MRS of the human brain. The FFL was achieved through a negative feed-back applied in real time on the Z0 shim coil current, after calculation of the frequency shift from a reference signal. This signal was obtained from the whole head with a small flip angle acquisition interleaved with the PRESS acquisition of interest. To avoid propagation of the important short-term time-correlated fluctuations of the head water frequency (mainly due to respiratory motion) onto Z0 correction, the sampling rate of the reference frequency and the smoothing window for the Z0 correction were carefully optimized. Thus, an effective FFL was demonstrated in vivo with no significant increase of the short-term variance of the water frequency. Magn Reson Med 1999 42:636-642, 1999.

70 citations


Patent
04 Nov 1999
TL;DR: In this paper, a method and apparatus for tracking the length of a sleep period within a mobile station using a sleep clock to precisely calibrate portions of the sleep period is described.
Abstract: A method and apparatus is described for tracking the length of a sleep period within a mobile station using a sleep clock to precisely calibrate portions of the sleep period. The sleep period subdivided into a sequence of sub-periods each of known duration wherein the durations of the sub-periods are not necessarily integer multiples of cycles of the sleep clock. Elapsed time is tracked within each individual sub-period of the sleep period using an integer sleep counter which tracks whole cycles of the sleep clock. Then any remaining fractional portions of the cycles of the sleep mode clock not accounted for by the integer sleep counter are tracked using a fractional sleep counter. The fractional sleep counter accumulates remaining fractional portions of sleep mode cycles from one sub-period to the next. A method and apparatus is also described for estimating frequency drift with a sleep clock signal used during a slotted paging mode of operation of a wireless mobile station. An initial frequency of the sleep clock signal is determined following power-up of the mobile station. A fixed frequency drift compensation factor representative of a difference between the initial frequency of the sleep clock signal and a predetermined nominal frequency is then determined. A dynamic frequency error compensation factor representative of a difference between the initial frequency and a current frequency of the slow clock signal is estimated. Then, throughout the slotted mode of operation, new values for the dynamic frequency compensation factor are iteratively determined by using a loop filter.

63 citations


Patent
29 Sep 1999
TL;DR: In this paper, a method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided, where the adaptive controller can either utilize look-up tables to achieve the desired output frequency or it can use a multi-step process in which it first determines the frequency requirements, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements.
Abstract: A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilize look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator. The reference oscillator output is used to control the frequency of the signal from the receiving transducers and/or to generate the desired frequency of the tone burst sent to the transmitting transducers. In another embodiment that is intended to compensate for both global and local frequency variations, the adaptive controller uses a digital signal processor. The digital signal processor, based on correction values contained in memory, defines a specific center frequency which preferably varies according to the signal delay, thus taking into account variations caused by localized variations in the acoustic wave reflective array. In yet another embodiment, a non-crystal local oscillator is used to provide the reference signal in the adaptive controller. The use of such an oscillator allows the controller to be miniaturized to a sufficient extent that it can be mounted directly to a touchscreen substrate. A feedback loop is used to compensate for oscillator drift. A discriminator circuit determines the degree of deviation from the desired frequency. The output from the discriminator is used to adjust the frequency of the local oscillator such that it tracks the frequency of the touchscreen.

57 citations


Patent
10 Mar 1999
TL;DR: An oscillator circuit residing internally to a semiconductor device for generating a clock signal for use by digital circuits is described in this article, where the frequency of the clock out signal remains substantially constant despite temperature, process and supply voltage variations in the semiconductor circuit.
Abstract: An oscillator circuit residing internally to a semiconductor device for generating a clock signal for use by digital circuits. The oscillator circuit includes a voltage regulator circuit responsive to frequency selection signals for selecting a predetermined frequency and a supply voltage. The voltage regulator circuit is operative to generate a voltage reference signal having a voltage level being adjusted to compensate for variations due to temperature, process and supply voltage variations. The oscillator circuit further includes a ring oscillator circuit responsive to the voltage reference signal for generating a clock out signal having a particular frequency based upon the voltage level of the voltage reference signal. Wherein the frequency of the clock out signal remains substantially constant despite temperature, process and supply voltage variations in the semiconductor circuit.

54 citations


Patent
04 Nov 1999
TL;DR: In this paper, the authors proposed a technique for activating an active-mode high frequency clock following a sleep period for use within a mobile station wherein selected components of the mobile station operate using a low power, low frequency sleep-mode clock during the sleep period and the faster high frequency active frequency clock during non-sleep periods.
Abstract: A technique for activating an active-mode high frequency clock following a sleep period for use within a mobile station wherein selected components of the mobile station operate using a low power, low frequency sleep-mode clock during the sleep period and the faster high frequency active-mode clock during non-sleep periods. In one embodiment, the technique is implemented by a device having a wake-up estimation unit for estimating a wake up time using the sleep-mode clock and a frequency drift compensation unit for compensating for any error in the estimated wake up time caused by frequency drift in the sleep-mode clock. An off-set time compensation unit is also provided for compensating for a lack of precision in the low frequency sleep-mode clock resulting in a possible error in the estimated wake up time. The lack of precision can result in an initial timing off-set error at the beginning of the sleep period and an final timing off-set error at the end of the sleep period. Both the frequency drift compensation unit and the off-set time compensation unit employ a high frequency transition-mode clock signal for use in calculating the time required to adjust the wake-up time. The transition-mode clock, which may have the same frequency as the active-mode clock, is employed only at the beginning and end of the sleep period and is deactivated throughout most of the sleep period to reduce power consumption.

52 citations


Proceedings ArticleDOI
23 Aug 1999
TL;DR: In this paper, an on-chip oscillator with small frequency variation in a digital 0.6 /spl mu/m CMOS technology is described, which utilizes a bias technique to compensate for the influences on the oscillation frequency caused by both temperature and process variations.
Abstract: An on-chip oscillator with small frequency variation in a digital 0.6 /spl mu/m CMOS technology is described. The oscillator utilizes a bias technique to compensate for the influences on the oscillation frequency caused by both temperature and process variations. No external components are needed in the oscillator. Simulation results show that the frequency of the proposed oscillator has a peak variation of /spl plusmn/6.8% for all process corners and a temperature range of 120/spl deg/C. The oscillator is measured to operate at a center frequency of 680 kHz and have a peak variation of /spl plusmn/4.7% over 29 sample chips in two different lots and a temperature range of 35/spl deg/C to 115/spl deg/C. As a comparison, a conventional inverter chain oscillator is made on the same chip. The frequency variation of the conventional inverter chain is /spl plusmn/14.6%.

46 citations


Patent
29 Sep 1999
TL;DR: In this article, a method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided, where the adaptive controller can either utilize look-up tables to achieve the desired output frequency or it can use a multi-step process in which it first determines the frequency requirements, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements.
Abstract: A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilize look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator. The reference oscillator output is used to control the frequency of the signal from the receiving transducers and/or to generate the desired frequency of the tone burst sent to the transmitting transducers. In another embodiment that is intended to compensate for both global and local frequency variations, the adaptive controller uses a digital signal processor. The digital signal processor, based on correction values contained in memory, defines a specific center frequency which preferably varies according to the signal delay, thus taking into account variations caused by localized variations in the acoustic wave reflective array. In yet another embodiment, a non-crystal local oscillator is used to provide the reference signal in the adaptive controller. The use of such an oscillator allows the controller to be miniaturized to a sufficient extent that it can be mounted directly to a touchscreen substrate. A feedback loop is used to compensate for oscillator drift. A discriminator circuit determines the degree of deviation from the desired frequency. The output from the discriminator is used to adjust the frequency of the local oscillator such that it tracks the frequency of the touchscreen.

45 citations


Patent
23 Sep 1999
TL;DR: In this article, a method and a system for providing automatic frequency tuning for an RF electrode accelerating system in a cyclotron device for production of PET isotopes is presented, whereby the frequency of the RF power signal is continuously optimised for a maximum transfer of high voltage driving to the RF electrode acceleration system of the cyclotRON.
Abstract: A method and a system are disclosed for providing automatic frequency tuning for an RF electrode accelerating system in a cyclotron device (3) for production of PET isotopes. A controlled frequency oscillator (5) generates an RF signal of a predetermined frequency for the acceleration of an ion beam in the cyclotron, and a matched power transmission line (2) connects to and feeds the RF electrode system (10). A load phase sensor (8) connected between the RF signal generator and the matched power transmission line (2) feeds a detected load phase to a feedback amplifier (9), which produces an error signal connected to the controlled frequency oscillator (5) for a fine tuning of the frequency of the controlled frequency oscillator, whereby the frequency of the RF power signal is continuously optimised for a maximum transfer of high voltage driving to the RF electrode accelerating system of the cyclotron.

44 citations


Patent
09 Mar 1999
TL;DR: In this paper, a method and apparatus for stabilizing the wavelength of a laser is described, which uses a microcontroller to normalize the frequency path with respect to the optical power path, process the signals via software code and generate a signal which provides feedback to the laser for stabilization.
Abstract: A method and apparatus for stabilizing the wavelength of a laser are disclosed. The invention provides a way to stabilize a laser for applications in dense wavelength division multiplexing (DWDM) systems where frequency spacing is crucial. The invention accomplishes laser stabilization by generating an optical path which is passed through a filter to obtain a signal which is a function of frequency. A second optical path which does not contain a filter is generated to obtain a signal which is a function of power. The signals are then converted from optical to electrical and from analog to digital, and a microcontroller is used to normalize the frequency path with respect to the optical power path, process the signals via software code, and generate a signal which provides feedback to the laser for stabilization. By using a microcontroller; elements that lead to wavelength or frequency drift, or manufacturing component variations can be taken into account and the input signal to the laser can be adjusted accordingly.

Proceedings ArticleDOI
01 Jan 1999
TL;DR: A quadrature output ring oscillator based on three-stage sub-feedback loops is designed and fabricated in a 0.5 /spl mu/m CMOS process for a 1.25 GHz clock recovery application.
Abstract: This paper presents a general ring oscillator circuit topology for high speed operation, multiphase output and wide range tuning. The topology uses sub-feedback inverters to construct a fast loop for long chain ring oscillator to achieve high speed. The operating frequency of the ring oscillator is directly proportional to the transconductance (G/sub m/) of sub-feedback inverters which can be controlled with an external voltage. Both single-ended and differential controlled voltage and inverter stages can be used. A quadrature output ring oscillator based on three-stage sub-feedback loops is designed and fabricated in a 0.5 /spl mu/m CMOS process for a 1.25 GHz clock recovery application. The circuit operates from 400 MHz up to 2 GHz, and consumes 3 mW at 1.25 GHz with 3.3 V power supply.

Journal ArticleDOI
TL;DR: In this paper, a design method for an optimized high-efficiency harmonic loaded oscillator is presented, which predicts the performance of oscillators including output power, dc-RF conversion efficiency and dc-bias current shift during start-up transition.
Abstract: We present a design method for an optimized high-efficiency harmonic loaded oscillator. The proposed approach predicts the performance of oscillators including output power, dc-RF conversion efficiency, and dc-bias current shift during start-up transition. In this method, the performance of the oscillator can he optimized based on the performance analysis of the active device under the assumed operation conditions. The effects of fundamental and harmonic loading on output power and efficiency are investigated by the proposed approach. Two kinds of stability conditions are addressed for an oscillator initially biased at a low gate voltage. Using the proposed approach, we design an oscillator that has a high efficiency of 61% at 1.86 GHz with a very low bias voltage of 2.0 V.

Journal ArticleDOI
TL;DR: In this paper, the authors extended the emitter model to include drift and frequency hopping, and the estimation methods were reanalyzed in a parametric Cramer-Rao (CR) analysis, which is confirmed by Monte Carlo simulations taking maximum likelihood (ML) as estimation procedure.
Abstract: It is well known that the position of a stationary radar can be estimated by a single moving observer from angle and/or frequency measurements taken passively at different points in its trajectory. Depending on the measurement set different localization methods result: the bearing method (BM), the frequency method (FM), and the combined method (CM). Previous studies analyze the three methods on the basis of constant emitter frequencies. However, radars with constant emitter frequencies are not realistic. Frequency drift and frequency hopping have to be taken into account. Therefore, to include radars the emitter model has been extended by drift and frequency hopping in this study, and the estimation methods have been reanalyzed. The effects of the model extensions become transparent in a parametric Cramer-Rao (CR) analysis. The results obtained in this way are confirmed by Monte Carlo simulations taking maximum likelihood (ML) as estimation procedure.

Proceedings ArticleDOI
13 Apr 1999
TL;DR: In this article, the performance of a post-processed clock ensemble dominated by active, cavity-tuned, hydrogen masers has been evaluated and the ensemble has an average frequency drift of less than /spl plusmn/3/spl times/10/sup -15/ per year.
Abstract: The performance of a post-processed clock ensemble dominated by active, cavity-tuned, hydrogen masers has been evaluated. The ensemble has an average frequency drift of less than /spl plusmn/3/spl times/10/sup -15/ per year, and an Allan deviation less than 1/spl times/10/sup -15/ for /spl tau/ between 4 hours and 100 days. This ensemble has been used to help characterize the frequency stability of a number of commercially available, high performance frequency standards.

Patent
02 Feb 1999
TL;DR: In this paper, a phase-locked loop frequency synthesizer circuit is presented, which synthesizes a carrier frequency through the use of an electronically controlled oscillator, which has a certain loop bandwidth, including a reference frequency source and a bypassed correcting integrator.
Abstract: The present invention relates to a frequency modulated system, and a method for operating same, including a phase locked loop frequency synthesizer circuit which synthesizes a carrier frequency through the use of an electronically controlled oscillator. The circuit, which has a certain loop bandwidth, includes a reference frequency source and a bypassed correcting integrator. A modulating signal simultaneously modulates the oscillator, the reference frequency source and the bypassed correcting integrator such that the carrier frequency is frequency modulated with a certain frequency deviation. The magnitude of the modulation of the oscillator, the reference frequency source and the correcting integrator are controlled over a frequency range by frequency blending the reference frequency source and the bypassed correcting integrator such that low distortion modulation over a wide frequency range is achieved.

Patent
26 Mar 1999
TL;DR: In this article, an arrangement for the precise measuring of the filling level of a liquid in a tank, by means of FMCW radar, provides that the output frequency of a frequency-variable oscillator is linked in a phase-lacked loop to a reference signal and that the reference signal in thin case is obtained digitally based on the principle of the digital direct synthesis DDS, from a stabilized fixed-frequency oscillator signal.
Abstract: An arrangement for the precise measuring of the distance, in particular the filling level of a liquid in a tank, by means of FMCW radar, provides that the output frequency of a frequency-variable oscillator is linked in a phase-lacked loop to a reference signal and that the reference signal in thin case is obtained digitally, preferably based on the principle of the digital direct synthesis DDS, from a stabilized fixed-frequency oscillator signal. The arrangement according to the invention makes it possible to measure distances in the range of, for example, 50 m with an accuracy of one or several millimeters. Standard components, which are generally used for generating and stabilizing the oscillator signal, can be used for this arrangement, thereby ensuring a low-cost setup of the arrangement.

Patent
Horng-Der Chang1
14 Jun 1999
TL;DR: In this article, a phase-locked loop with a multi-phase voltage controlled oscillator and a switching unit was presented. But the switching time of the switching unit is controlled by the clock counter to achieve the effect of frequency expansion.
Abstract: The present invention provides a phase-locked loop having a multi-phase voltage controlled oscillator. The phase-locked loop comprises a divided-by-N counter, a divided-by-M counter, a phase frequency detector, a charge pump, a loop filter, a multi-phase voltage controlled oscillator, a switching unit, and a clock counter. It utilizes a multi-phase voltage controlled oscillator instead of a conventional voltage controlled oscillator and a switching unit is used to select the output signal from the multi-phase voltage controlled oscillator. The switching time of the switching unit is controlled by the clock counter to achieve the effect of frequency expansion.

Patent
29 May 1999
TL;DR: A high frequency anharmonic oscillator provides a broad band chaotic oscillation with a noise-like spectra as discussed by the authors, which is suitable for modulation by data providing for improved secure communication.
Abstract: A high frequency anharmonic oscillator provides a broad band chaotic oscillation with a noise-like spectra. The oscillator output signal is suitable for modulation by data providing for improved secure communication. The chaotic oscillator is based upon a forced second order Duffing equation that is tolerant of delay in the feedback path for high frequency operation.

Journal ArticleDOI
TL;DR: In this paper, a survey of magnetic line radiation (MLR) events at Halley station, Antarctica (75°30′S, 26°54′W, L ≈ 4.3) in part of June 1995 is presented.
Abstract: Magnetospheric line Radiation (MLR) events are relatively narrowband VLF signals that sometimes drift in frequency, and have been observed in both ground based and satellite data sets. Line radiation has been attributed by some authors to be power line harmonic radiation (PLHR), generated from harmonics of the power transmission frequency (50 or 60 Hz) and radiated into the ionosphere and magnetosphere by long power lines. We present the result of a survey undertaken on the basis of measurements made of MLR events observed at Halley station, Antarctica (75°30′S, 26°54′W, L ≈ 4.3) in part of June 1995. Particular attention is given to the frequency spacing, drift rates, and amplitude of the MLR lines. MLR is present in 7.0% of the minute-long VLF recordings made at Halley. The MLR lines rise in frequency as often as they fall. However, these lines do not necessarily rise or fall monotonically and can oscillate while drifting. The Halley MLR has a wide range of line spacings and does not preferentially show spacings near harmonics of electrical transmission frequencies, either 50 Hz or 60 Hz. There is no correlation between the frequency drifts of the local 50 Hz Halley electrical supply and those of the observed MLR lines. The distribution of MLR line spacings observed in the Halley data has a roughly exponential form, suggesting a different mechanism for MLR than for PLHR.

Patent
28 May 1999
TL;DR: In this paper, a digital voltage controlled oscillator is described, which includes an input for receiving input signals representative of a desired frequency and a logic circuit for developing an oscillating signal having a predefined waveform and desired frequency by controlling the energy contained in the pulses output by the pulse generator.
Abstract: A digital voltage controlled oscillator is disclosed. The digital voltage controlled oscillator includes an input for receiving input signals representative of a desired frequency. It also includes a pulse generator and a logic circuit. The logic circuit develops an oscillating signal having a predefined waveform and the desired frequency by controlling the energy contained in the pulses output by the pulse generator. The disclosed digital voltage controlled oscillator also includes a capacitor which is charged by the pulses to a voltage that generally varies in accordance with the predefined waveform and the desired frequency.

Journal ArticleDOI
TL;DR: In this paper, the root mean square deviation (RMSD) is used as a single-parameter function of the fundamental frequency of the oscillator, so it makes the fitting process optimize the period fit at the expense of a lesser evaluation of the other parameters such as the amplitude and the phase.
Abstract: A period fitting method, which is a variant of the classical least-square fitting method, is proposed to determine the fundamental frequency of a physical oscillator. The root mean square deviation used as the criterion in this method is a single-parameter function of the fundamental frequency of the oscillator, so it makes the fitting process optimize the period fit at the expense of a lesser evaluation of the other parameters such as the amplitude and the phase. Theoretical analysis shows that this method is intrinsically independent of the disturbances of the high order harmonic frequencies oscillation, and the computer simulation experiments show that it is effective to overcome the disturbances of the finite quality factor and the monotonic drift of an oscillator system, as well as the white noise, and this method can determine the fundamental frequency or period of a physical oscillator with a relative precision of 10−7 orders.

PatentDOI
TL;DR: In this paper, a method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided, where the adaptive controller can either utilize look-up tables to achieve the desired output frequency or it can use a multi-step process in which it first determines the frequency requirements, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements.
Abstract: A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilize look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator. The reference oscillator output is used to control the frequency of the signal from the receiving transducers and/or to generate the desired frequency of the tone burst sent to the transmitting transducers. In another embodiment that is intended to compensate for both global and local frequency variations, the adaptive controller uses a digital signal processor. The digital signal processor, based on correction values contained in memory, defines a specific center frequency which preferably varies according to the signal delay, thus taking into account variations caused by localized variations in the acoustic wave reflective array. In yet another embodiment, a non-crystal local oscillator is used to provide the reference signal in the adaptive controller. The use of such an oscillator allows the controller to be miniaturized to a sufficient extent that it can be mounted directly to a touchscreen substrate. A feedback loop is used to compensate for oscillator drift. A discriminator circuit determines the degree of deviation from the desired frequency. The output from the discriminator is used to adjust the frequency of the local oscillator such that it tracks the frequency of the touchscreen.

Patent
28 May 1999
TL;DR: An adjustable frequency oscillator with a wide tuning range which can be voltage or current controlled is presented in this article, where a maximum tuning per feedback current is obtained by phase shifting a feedback signal by approximately 90 degrees with respect to the oscillating output signal, which is internally generated by the adjustable frequency Oscillator.
Abstract: An adjustable frequency oscillator with a wide tuning range which can be voltage or current controlled. A maximum tuning per feedback current is obtained by phase shifting a feedback signal by approximately 90 degrees with respect to the oscillating output signal, which is internally generated by the adjustable frequency oscillator. Over the frequency range of operation, the oscillation frequency of the oscillating output signal is linearly controllable. The adjustable frequency oscillator is also implemented as a ring oscillator and/or an oscillator with ranging.

Proceedings ArticleDOI
30 May 1999
TL;DR: A high frequency, fully integrated frequency-locked loop (FLL) design based on a new architecture of a CMOS frequency-to-voltage converter that is very fast, operates over a wide frequency range and occupies a small integrated area compared to an equivalent PLL.
Abstract: In this paper, we propose a high frequency, fully integrated frequency-locked loop (FLL) design based on a new architecture of a CMOS frequency-to-voltage converter. The design is similar to a phase-locked loop (PLL) in the way that it generates an output signal that tracks an input reference signal, however, in this case the two signals are synchronized in frequency and not in phase. The frequency of the FLL output could be also controlled by an input voltage, therefore, it could be also used as an integrated high-precision voltage-controlled oscillator. The proposed FLL is very fast, operates over a wide frequency range and occupies a small integrated area compared to an equivalent PLL.

Patent
Jr. Robert O. Conn1
07 Oct 1999
TL;DR: In this paper, a method for measuring localized operating temperatures and voltages on an integrated circuit is described, where an oscillator circuit with a frequency that varies with temperature and/or applied voltage is used to establish a known relationship between oscillation frequency and temperature.
Abstract: A method is described for measuring localized operating temperatures and voltages on an integrated circuit. The integrated circuit includes an oscillator circuit with a frequency that varies with temperature and/or applied voltage. The frequency of the oscillator is then determined, using a constant voltage, for a number of temperatures to establish a known relationship between oscillation frequency and temperature. Once the relationship is known, a similar oscillator is included within or adjacent a second circuit of the integrated circuit. The operating temperature or operating voltage of the second circuit may then be determined by monitoring the frequency of the oscillator while the second circuit is operational.

Patent
16 Dec 1999
TL;DR: In this article, an ultra-stable microwave output with less jitter than a prior art atomic oscillator was obtained and an ultra-short optical pulse train was generated with a normalized repetition frequency stabilized at the same level as a time-consuming standard.
Abstract: An ultra-stable microwave output with less jitter than a prior art atomic oscillator is obtained and an ultra-short optical pulse train is generated with a repetition frequency stabilized at the same level as a time standard. The repetition frequency of a regeneratively mode-locked laser pulse oscillator with a superior low-jitter characteristic is locked directly to a resonance frequency of various atoms. The oscillator provides the means (27) for detecting the frequency difference between the clock signal frequency and a predetermined atomic resonance frequency and outputting it as an error signal, a cavity length tuning device for varying the length of a laser cavity so that the clock signal frequency and the predetermined resonance frequency coincide, and a device (16) for negatively feeding back the error signal output from the frequency difference detection device (27) to the cavity length tuning device (18). This allows the generation of an optical pulse train (optical output) and a clock signal (microwave output) of a repetition frequency stabilized to the predetermined atomic resonance frequency.

Patent
19 Aug 1999
TL;DR: In this article, the steering voltage applied to a crystal oscillator over time, and compensating for spurious frequency jumps in determining the drift rate, was used to estimate oscillator stability by comparing a projected steering voltage against an actual voltage after simulated holdover period, or analyzing a steering voltage recorded over a period of time and evaluating rates of change.
Abstract: The invention includes analyzing the steering voltage applied to a crystal oscillator over time, and compensating for spurious frequency jumps in determining the drift rate of a crystal oscillator. The steering voltage may be used to estimate oscillator stability by comparing a projected steering voltage against an actual voltage after a simulated holdover period, or analyzing a steering voltage recorded over a period of time and evaluating rates of change. Spurious frequency jumps may be removed from data collected while not in an actual holdover, making the data more accurately represent the frequency drift rate of the oscillator. Also, the rate of occurrence of spurious frequency jumps while not in holdover may be monitored to provide information regarding the physical condition of the crystal.

Patent
20 Mar 1999
TL;DR: In this article, a method was proposed to derive a frequency of a pulse signal from a line frequency using a measured frequency derived from an oscillator frequency, which is used to determine if the period of the line frequency pulse signal is within a predetermined tolerance limit.
Abstract: A method derives a frequency of a pulse signal from a line frequency. The method includes measuring a period of a line frequency pulse signal having the line frequency using a measured frequency derived from an oscillator frequency. The method further includes determining if the period of the line frequency pulse signal is within a predetermined tolerance limit. The line frequency is used to derive the frequency of the pulse signal when the period is determined to be within the predetermined tolerance limit, and the oscillator frequency is used to derive the frequency of the pulse signal when the period is determined to be outside the predetermined tolerance limit.

Patent
Hongmo Wang1
04 Oct 1999
TL;DR: In this paper, a variable frequency oscillator (VFO) circuit with an increased frequency tuning range is presented, where a switchable capacitor is included for selectively providing a predetermined step-wise decrease of the oscillating frequency to a frequency value below the set frequency of the circuit.
Abstract: A variable frequency oscillator (VFO) circuit having an increased frequency tuning range to selectively obtain operating frequencies above and below a set frequency. The circuit includes a tank inductor connected in parallel with a tank capacitor for primarily defining the set oscillating frequency of the VFO circuit. A switchable capacitor is included for selectively providing a predetermined step-wise decrease of the oscillating frequency to a frequency value below the set frequency of the circuit, and a varactor is included for accommodating selective tuning of the oscillating frequency within a range of frequency values below the set frequency. The inventive circuit selectively includes a switchable inductance element which is selectively electromagnetically coupled to the tank inductor to decrease the overall inductance value of the VFO circuit and, thereby, selectively increase the oscillating frequency above the set frequency value.