Topic
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.
Papers published on a yearly basis
Papers
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30 Aug 1978TL;DR: In this article, a phase corrected raster scanned light modulator is proposed, where information modulated on a carrier is used to form a grating whose spatial frequency along the scanning line varies in accordance with the signal modulation frequency.
Abstract: The present invention relates to a phase corrected raster scanned light modulator in which information modulated on a carrier is used to form a grating whose spatial frequency along the scanning line varies in accordance with the signal modulation frequency. Thickness variation in the medium on which the grating is formed causes an undesired phase modulation of the light which may be corrected by altering the carrier frequency. A novel oscillator is described which may be stepped discontinuously in frequency while the waveform and its slope remain continuous, which is of sufficient accuracy and agility to provide a real time region by region phase correction of the raster in the light modulator. The variable frequency oscillator is of high stability and can step from one value to another for intervals as short as one microsecond.
46 citations
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03 Jun 2002TL;DR: In this paper, a first frequency divider divides the frequency of the local oscillator signal by a first division factor to produce a conversion signal, where the conversion means responsive to the conversion signal converts between said communication signal and base-band signal.
Abstract: Local oscillator apparatus comprising communication signal terminals for a communication signal, especially in a receiver or a transmitter, and a controlled frequency oscillator for producing a local oscillator signal. The local oscillator also includes a reference frequency generator and a feedback loop for selecting and adjusting the frequency of the local oscillator signal relative to the frequency of said reference frequency signal. A first frequency divider divides the frequency of the local oscillator signal by a first division factor to produce a conversion signal, where the frequency of said conversion signal is at least approximately equal to the frequency of the communication signal, and conversion means responsive to the conversion signal converts between said communication signal and base-band signal. A second frequency divider divides the frequency of the local oscillator signal by a second division factor and is connected in the feedback loop, where the division factor is different to the second division factor and the ratios between said first and second division factors are fractional.
45 citations
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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
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08 Mar 1993
TL;DR: In this article, a simplified frame/slot synchronization is followed by a symbol synchronization of higher accuracy, which is passed to a frequency offset unit which determines the amount of frequency drift between the transmitter and receiver and compensates for the frequency drift.
Abstract: A Time Division Multiple Access (TDMA) radio system achieves synchronization by performing a two-step synchronization. A simplified frame/slot synchronization is followed by a symbol synchronization of higher accuracy. This symbol timing is passed to a frequency offset unit which determines the amount of frequency drift between the transmitter and receiver and compensates for the frequency drift. This results in improved receiver performance for the TDMA digital radio system.
45 citations
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28 Apr 1995TL;DR: A new type of electronically tunable oscillator using a cascade of two capacitorless first order log- domain all-pass filters as the frequency and the gain controlling element is proposed, where it is shown that the log-domain circuit technique is ideally suited for implementation of electronically Tunable oscillators.
Abstract: A new type of electronically tunable oscillator using a cascade of two capacitorless first order log-domain all-pass filters as the frequency and the gain controlling element is proposed, where it is shown that the log-domain circuit technique is ideally suited for implementation of electronically tunable oscillators, The resulting oscillator enjoys several attractive properties, namely, low supply voltage, high oscillation frequencies, wide tuning range and relatively large oscillation levels can be obtained without excessive distortions, as oppose to previously reported forward-biased diode based electronically tunable oscillators.
45 citations