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.

Tunable low-drift spurious-free optoelectronic oscillator based on injection locking and time delay compensation

Abstract: A finely tunable low-drift spurious-free single-loop optoelectronic oscillator (OEO) incorporating injection locking and time delay compensation is proposed and experimentally demonstrated. In the proposed OEO, one mode of a single-loop OEO is injection locked by a tunable electronic oscillator resulting in single-mode oscillation. A time delay compensation system is used to compensate the OEO’s loop length change caused by environmental changes, such as temperature and strain. Tuning of the oscillation frequency is realized by controlling the injection frequency and absolute loop length of the single-loop OEO. In the experiments, when the ambient temperature varies between 22°C and 31°C within 1000 s, an output signal at the frequency of 10.664 GHz with a frequency drift better than −0.1 ppb and side-mode suppression ratio greater than 78 dB has been realized. Also, the OEO can be tuned with a precise frequency step of 10 Hz.

Temperature compensation for a variable frequency oscillator without reducing pull range

Abstract: A variable frequency oscillator having multiple, independent frequency control inputs, each coupled to a respective tuning sub-circuit. The tuning sub-circuits are connected in parallel with each other and with a resonator module, which may be a quartz crystal, inductor, or other reactance component. Each tuning sub-circuit consists of two varactors with their respective cathodes coupled to each other and to their corresponding frequency control input. By having the tuning sub-circuits connected in parallel to the resonator, the overall frequency pull range of each frequency control input remains unaffected by the activation of any other frequency control input. Preferably, at least one frequency control input is a temperature compensation control input that can maintain the variable oscillator insensitive to temperature variations while the remaining frequency control inputs provide functional frequency control.

Dc offset compensation for zero if quadrature demodulator

Abstract: The present invention provides dc offset compensation circuit (800) for a zero IF FM quadrature demodulator in an AMPS cellular mobile telephone system. A frequency offset is introduced to remove modulation inherent dc components from supervisory audio tones and Manchester codes from a modulated signal. The local oscillator (608) is operated at a frequency that is slightly different, e.g. 5 kHz from a frequency which would mix down the intermediate frequency signal to zero. A dc offset is produced with a control loop to eliminate fixed dc components caused by leakage from a local oscillator (608). After a given time, the control loop may be frozen and the frequency offset of the local oscillator (608) can be removed.

Silicon resonator of the tuning-fork type

Abstract: The invention relates to a silicon resonator (10) of the tuning-fork type in which the linear frequency drift depending on the temperature is compensated. The resonator comprises a silicon base (14), a plurality of parallel arms (11, 12, 13) capable of vibrating and actuation means (18, 21, 22), wherein said arms include a silicon layer provided between two layers of silicon oxide having a thickness, relative to that of the silicon layer, such that it ensures the first-order compensation of the resonator thermal drift.

Identical servo frequency modulated passive ring laser gyroscope

Abstract: A phase locked passive ring resonator gyroscope comprising a fixed frequency reference signal generator (Fm); a single piece body having laser and passive resonator cavities; a laser means using the laser resonator cavity responsive to a laser control signal from a laser servo for providing a single frequency light source (F0) for frequency modulating the single frequency light source to form a light source (F0) and having respective upper and lower side bands at frequencies F0+Fm and at F0-Fm; first and second voltage controlled oscillator means responsive to respective first and second control signal for frequency shifting the first and second frequency modulated ray center frequencies by a first and second variable offset frequencies to form a propagating and counterpropagating light sources; the second resonator cavity being a passive high Q evacuated cavity; a detector means for detecting a first offset frequency error signal and for detecting a second offset frequency error signal; cavity servo means responsive to the first and second offset frequency error signals from the detector means for providing, a first control signal to the first voltage controlled oscillator means for frequency shifting the first frequency modulated ray by a first variable offset frequency to maintain the propagating light beam in the second resonator at peak resonance and to provide a second control signal to the second voltage controlled oscillator means for frequency shifting the second frequency modulated ray by a second variable offset frequency (F2) to control and maintain the counterpropagating light beam (FCCW) at peak resonance; means for constantly adjusting the passive cavity path length servo signal to keep the passive cavity at peak resonance at a frequency substantially mid-range between the propagating and the counterpropagating beams; output counter means for measuring and outputting the frequency difference between the first variable offset frequency (F1) and the second variable offset frequency (F2), the measured frequency difference representing the difference in frequency due to an input gyro body rate about the gyro sensitive axis.