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.

Multi-mode relaxation oscillator

Abstract: In a relaxation oscillator where the oscillation frequency is proportional to the charge rate of a capacitor, independent current sources are connected through separate switches to change the charge rate of the capacitor and thus the oscillation frequency. Each switch is controlled by signals from a separate detector of a condition which requires that the oscillation frequency be changed. An oscillation frequency increase between the standby and alarm modes of a smoke detector is accomplished in one disclosed embodiment and duty cycle means for controlling the operative period of the alarm indicator during each cycle of the increased oscillator frequency is disclosed in a more particular embodiment.

Method and apparatus for activating a high frequency clock following a sleep mode within a mobile station operating in a slotted paging mode

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.

Automatic frequency control

Abstract: An automatic frequency control tracks a television signal before and after a period of interruption. The automatic frequency control comprises a voltage controlled feedback loop including a voltage controlled local oscillator and a mixer for mixing the output of the oscillator with the TV signal. The output of the mixer is filtered to remove unwanted components of the mixed signal and to equalize sidebands of the television signal. The output of the filter is supplied to a detector which is tuned to a component of the television signal, and produces a voltage corresponding to the frequency of the component. The output of the detector is supplied to the voltage control input of the local oscillator to track the television signal component. Circuitry automatically senses the absence of the TV signal component from the mixer, and automatically applies a reference voltage to the voltage control input of the oscillator when the TV signal component is absent. The detector is operative to detect the television signal component following the application of reference voltage to the oscillator so that when the television signal returns, the detector is capable of tracking it.

Anti-islanding device and method for grid connected inverters using random noise injection

Abstract: A device and method for detecting islanding of a grid connected inverter makes use of an injected white noise as a perturbing force on the output voltage of the inverter. The white noise is injected at least once in every cycle and can be generated at different rates in implementation. On loss of the grid, a frequency drift of the output voltage is detected and a positive feedback is activated that accelerates the drift.

Battery saving frequency synthesizer arrangement

Abstract: The phase-locked loop section (10, 14) of the synthesizer is periodically disconnected from the battery supplied power by means of a switch (60). In order to prevent substantial drift of the phase-locked loop during such power interruption, means (22, 24) are provided for maintaining a control signal on the VCO (12) associated with the loop (10) that maintains the VCO frequency. By minimizing the frequency drift, the loop can be re-locked in a short period of time following each power interruption.