Frequency drift

About: Frequency drift is a research topic. Over the lifetime, 5054 publications have been published within this topic receiving 56191 citations. The topic is also known as: chirp rate.

Method of deriving a frequency of a pulse signal from alternate sources and method of calibrating same

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.

Variable frequency oscillator 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.

Phase-shift correlation method for accurate phase difference estimation in range finder

Abstract: High-precision phase-difference measurement is a key technology for a phase-shift laser range finder In order to improve the estimation accuracy of phase difference between two sinusoidal signals with identical frequency, the phase-shift correlation method is described Theoretical analysis shows that the conventional cross-correlation method will bring notable deviations when the true phase difference is close to 0° or 180° in the presence of noise For reducing the influence of noise, two step calculations--phase-shift autocorrelation and phase-shift cross correlation--are used in the phase-shift correlation method The estimation bias is eliminated by phase-shift autocorrelation in which the autocorrelation is calculated between the 2π phase-shifted signal and the original signal, and the periodic errors are eliminated by phase-shift cross correlation in which the phase difference is estimated when the true phase difference is near 90° or 270° The effect of frequency drift on the phase difference is also discussed The experiment results show that the maximum error of the conventional method is about 015°, while the estimation error of our proposed method is much less than 001° under the same conditions

Voltage and temperature compensated ring oscillator for a memory device

Abstract: A refresh circuit of a memory device includes a ring oscillator with a frequency stabilizing circuit. The frequency stabilizing circuit produces compensated voltage signals in response to changes in supply voltage and temperature to modify the conductances of field-effect transistors of the frequency stabilizing circuit to compensate the conductive path of the discharge current of a capacitor from the ring oscillator in order to stabilize the oscillation frequency.

Implantable medical device incorporating performance based adjustable power supply

Abstract: A method or apparatus for conserving power in an implantable medical device (IMD) of the type having at least one IC powered by a battery wherein, in each such IC, a voltage dependent oscillator for providing oscillator output signals at an oscillation frequency dependent upon applied supply voltage to the IC is incorporated into the IC. The voltage dependent oscillator oscillates at a frequency that is characteristic of the switching speed of all logic circuitry on the IC die that can be attained with the applied supply voltage. The applied supply voltage is regulated so that the oscillation frequency is maintained at no less than a target or desired oscillation frequency or within a desired oscillation frequency range. The power supply voltage that is applied to the IC is based directly on the performance of all logic circuitry of the IC. In order to provide the comparison function, the oscillator output signals are counted, and the oscillator output signal count accumulated over a predetermined number of system clock signals is compared to a target count that is correlated to the desired oscillation frequency. The counts are compared, and the supply voltage is adjusted upward or downward or is maintained the same dependent upon whether the oscillator output signal count falls below or rises above or is equal to the target count, respectively. The supply voltage adjustment is preferably achieved employing a digitally controlled power supply by calculating a digital voltage from the comparison of the oscillator output signal count to the target count, and storing the digital voltage in a register of the power supply.