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 for achieving highly reproducible acceleration insensitive quartz crystal oscillators

Abstract: An oscillator and a method for producing an improved oscillator that will generate an accurate frequency when encountering a vibration. The oscillator and method uses a crystal with minimal cross-axis coupling. Further, a first accelerometer produced using MEMS technology is used. The first accelerometer is positioned inside of the oscillator so that the accelerometer accurately measures any vibration encountered by the oscillator. The first accelerometer and the crystal are maintained at constant temperature to minimize phase shifts and gain variations.

Method and apparatus for frequency control of multiple oscillators using a single frequency-locked-loop

Abstract: Frequency control of multiple oscillators using a single frequency locked loop is accomplished by a single frequency-control device that is time-shared with a plurality of voltage-controlled oscillators and selectively establishes a "desired" frequency for each oscillator. The output of each oscillator is, in turn, selectively routed to a frequency counter which measures the "actual" frequency of the oscillator. A comparison between the desired frequency and the actual measured frequency for each oscillator is made, and an error voltage developed. This error voltage is routed to the appropriate capacitor, which stores the voltage required to keep the selected oscillator on frequency until the next time it is measured.

Radio communication apparatus free from interference between local signal and transmission signal

Abstract: A radio communication apparatus capable of carrying out transmission and reception of signals at a time has a frequency synthesizer and a frequency modulator both in novel structures for removing interference between a local signal and a transmission signal. The frequency synthesizer has a local oscillator controlled by a first phase comparator for phase-comparing a frequency divided output of the local oscillator and a reference frequency signal to provide a local signal. The frequency division of the output of the local oscillator is effectd by a first frequency divider for dividing the frequency of the output of the local oscillator and a variable division ratio frequency divider for dividing the frequency of the output of the first frequency divider. The frequency modulator has a transmission oscillator controlled by a second phase comparator for phase-comparing the output of the first frequency divider and a frequency divided output of the transmission oscillator to provide a transmission signal. The frequency division of the output of the transmission oscillator is effected by a second frequency divider.

An Yb Optical Lattice Clock: Current Status at KRISS

Abstract: The current status of an Yb optical lattice clock at the Korea Research Institute of Standards and Science (KRISS) is reported. The systematic uncertainty of the Yb clock in the first accuracy evaluation was 1.5 × 10−14 [Park et al., Metrologia 50, 119 (2013)]. The uncertainty was dominated by the large uncertainties in the lattice ac Stark shift and the collisional shift, which were mainly limited by the large linewidth and jitter of the clock laser. Recently, a highly stable clock laser at 578 nm was developed with a short-term linewidth of 3.5 Hz and a frequency jitter of about 25 Hz at 1 s and 10 s measurement times, respectively. The long-term frequency drift showed only a linear dependence on time, confirming that the temperature of the super-cavity was maintained a zero coefficient of thermal expansion. The frequency of the lattice laser at 759 nm was phase locked to the optical frequency comb and could be stabilized at the “absolute” frequency of the “magic wavelength”, to within a 1-MHz uncertainty. This improvement greatly reduced the fractional uncertainty due to the lattice ac Stark shift down to 2 × 10−16. The systematic uncertainty of the clock is currently 5.3 × 10−15 and is dominated by the collisional frequency shift.

Method and apparatus for supplying synchronization signals serving as clock signals with defined phase relationships

Abstract: The present invention relates to a method and apparatus for recovering the time base of signals which change at periodic intervals The apparatus comprises gated voltage controlled oscillators (GVOC) that are alternated or exchanged, to reduce phase and frequency deviations in the recovered time base signal, such as the deviations induced by inherent GVCO differences Each GVCO is stabilized by a respective phase locked loop The respective GVCOs are gated only in response to a chosen polarity transition in the input signal, to make the circuit more tolerant of waveform distortions More than two GVCOs may be used to provide improved frequency drift resistance The circuit uses resynchronization control signals, such as the time slot signal in synchronous switching systems, to indicate resynchronization or reassignment the GVCOs in gaps in the data transmission Automatic reassignment is insured when there are periods of non-transitioning data that last longer then the stability of the GVCOs to prevent frequency drift in the recovered clock