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.

System and method for improving the regulation of a supply voltage for a controllable oscillator using feed forward control techniques

Abstract: A system and method for regulating the voltage at an input node of a varying current demand circuit is provided. The input node may be a power supply node and the varying current demand circuit may be a controllable oscillator. In addition, a frequency synthesizer may be formed from a phase locked loop which includes the controllable oscillator and a voltage control circuit. The voltage control circuit may receive an input control signal that varies as the current demand of the controllable oscillator varies. In response to the input control signal, the voltage control circuit may provide a more stable voltage supply to the controllable oscillator even as the current demands of the oscillator vary widely. The input control signal may be generated by generating a signal from the loop path of the phase locked loop. The frequency synthesizer may be utilized in a data storage system data detection circuit, such as for example, a data detection circuit used for recovering data from an optical disk.

Wavelet-Based Characterization of Small-Scale Solar Emission Features at Low Radio Frequencies

Abstract: Low radio frequency solar observations using the Murchison Widefield Array have recently revealed the presence of numerous weak, short-lived and narrow-band emission features, even during moderately quiet solar conditions. These non-thermal features occur at rates of many thousands per hour in the 30.72 MHz observing bandwidth, and hence, necessarily require an automated approach for their detection and characterization. Here, we employ continuous wavelet transform using a mother Ricker wavelet for feature detection from the dynamic spectrum. We establish the efficacy of this approach and present the first statistically robust characterization of the properties of these features. In particular, we examine distributions of their peak flux densities, spectral spans, temporal spans and peak frequencies. We can reliably detect features weaker than 1 SFU, making them, to the best of our knowledge, the weakest bursts reported in literature. The distribution of their peak flux densities follows a power law with an index of -2.23 in the 12-155 SFU range, implying that they can provide an energetically significant contribution to coronal and chromospheric heating. These features typically last for 1-2 seconds and possess bandwidths of about 4-5 MHz. Their occurrence rate remains fairly flat in the 140-210 MHz frequency range. At the time resolution of the data, they appear as stationary bursts, exhibiting no perceptible frequency drift. These features also appear to ride on a broadband background continuum, hinting at the likelihood of them being weak type-I bursts.

Observations of Powerful Type III Bursts in the Frequency Range 10 – 30 MHz

Abstract: The properties of powerful (flux >10−19 W m−2 Hz−1) type III bursts observed in July – August 2002 by the radio telescope UTR-2 at frequencies 10 – 30 MHz are analyzed. Most bursts have been registered when the active regions associated to these bursts were located near the central meridian or at 40° – 60° to the East or West from it. All powerful type III bursts drift from high to low frequencies with frequency drift rates 1 – 2.5 MHz s−1. It is important to emphasize that according to our observations the drift rate is linearly increasing with frequency. The duration of the bursts changes mainly from 6 s at frequency 30 MHz up to 12 s at 10 MHz. The instantaneous frequency bandwidth does not depend on the day of observations, i.e. on the disk location of the source active region, and is increasing with frequency.

Parametric Noise Reduction in a High-Order Nonlinear MEMS Resonator Utilizing Its Bifurcation Points

Abstract: An electrostatically actuated non-linear microelectromechanical systems (MEMS) resonator can describe double hysteresis behavior in the measured frequency response due to the interplay between electrical and mechanical non-linearities in the system. This paper provides the first experimental mapping of the stable and unstable branches of the frequency response of a MEMS resonator describing a double hysteretic frequency response using a closed-loop phase feedback oscillator. Furthermore, the frequency stability of the oscillator is compared for varying amplitude and phase feedback conditions, and it is experimentally demonstrated that parametric noise up-conversion can be suppressed in such a system by suitably biasing the resonator at one of the four bifurcation points in such a system. This result is qualitatively consistent with theoretical prediction and demonstrates that improved frequency stability in a non-linear MEMS oscillator is possible by suitably biasing the resonator using simultaneous amplitude and phase feedback.

Multicycle synchronous digital phase measurement used to further improve phase-shift laser range finding

Abstract: Multicycle synchronous digital phase measurement is proposed in this paper to further improve the phase measurement in phase-shift laser range finding. In the method, heterodyne processing is employed to convert the phase measurement of a high frequency signal into that of a low frequency signal, and by keeping phase measurement independent of the signal frequency to be measured and the gate signal synchronous with the measurement signal during multicycle phase measurement, errors caused by the frequency drift of a local oscillator during conventional auto-digital phase measurement are totally eliminated, and the time required to complete range measurement is shortened. Experimental results show that an uncertainty better than ?1.5 mm can be achieved at a data rate up to 20 Hz (t = 0.05 s) for a laser range finder using the method proposed with fe = 10.000 MHz.