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.

Ultra-Low Vibration Pulse-Tube Cryocooler Stabilized Cryogenic Sapphire Oscillator With ${\hbox{10}}^{-16}$ Fractional Frequency Stability

Abstract: A low maintenance long-term operational cryogenic sapphire oscillator has been implemented at 11.2 GHz using an ultra-low-vibration cryostat and pulse-tube cryocooler. It is currently the world's most stable microwave oscillator employing a cryocooler. Its performance is explained in terms of temperature and frequency stability. The phase noise and the Allan deviation of frequency fluctuations have been evaluated by comparing it to an ultra-stable liquid-helium cooled cryogenic sapphire oscillator in the same laboratory. Assuming both contribute equally, the Allan deviation evaluated for the cryocooled oscillator is σy ≈ 1 × 10-15τ-1/2 for integration times 1 <; τ <; 10 s with a minimum σy = 3.9 × 10-16 at τ = 20 s. The long term frequency drift is less than 5×10-14/day. From the measured power spectral density of phase fluctuations, the single-sideband phase noise can be represented by Lφ(f) = 10-14.0/f4+10-11.6/f3+10-10.0/f2+10-10.2/f+ 10-11.0 rad2/Hz for Fourier frequencies 10-3 <; f <; 103 Hz in the single oscillator. As a result, Lφ ≈ -97.5 dBc/Hz at 1-Hz offset from the carrier.

Sub-kilohertz excitation lasers for quantum information processing with Rydberg atoms

Abstract: Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high-fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry–Perot cavity made of ultra-low expansion glass, with a tunable offset-lock frequency. One laser operates at 852 nm, while the two locked lasers at 1018 nm are frequency doubled to 509 nm for excitation of Cs133 atoms to Rydberg states. The optical beat note at 509 nm is measured to be 260(5) Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days, yielding a linear frequency drift of ∼1 Hz/s.

A Robust Anti-islanding Method for Grid-Connected Photovoltaic Inverter

Abstract: In a modern power system, photovoltaic as distributed generated source is growing larger and it can cause a variety of problem. Most issued problem is an islanding phenomenon. In order to prevent islanding phenomenon, three kinds of active islanding detection methods have been studied. These are respectively to change magnitude, frequency, and the start phase of inverter output current. Among them, both frequency and start phase variation anti-methods make the islanding frequency drift away from the trip window of the frequency relay if an islanding is occurred. This paper presents a robust anti-islanding method, which are consisted of a frequency variation method as AFD (active frequency drift) method and a start phase variation method as SMS (slip mode frequency shift) method. Clearly, the proposed anti-islanding method shows the satisfied islanding detection ability to IEEE 1547 Standard. To validate the performance of the proposed method, simulation and experiment are performed. Possible islanding conditions are followed by the IEEE Standard 1547. The methodology presented in the paper can be extended to the other active anti-islanding methods

Apparatus for measuring frequency modulation noise signals and for calibrating same

Abstract: Apparatus is provided for the measurement of frequency modulation noise on the carrier signal output of a low-noise, low-power, high-frequency diode oscillator under test. An auxiliary injection phase-locked oscillator, driven by the oscillator under test, is used to provide a signal of sufficient level for operation of a high-frequency discriminator used for noise measurement. The auxiliary oscillator may additionally be used for calibration of the discriminator preliminary to taking noise measurements.