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.

Physical origin of the frequency shifts in cesium beam frequency standards-related environmental sensitivity

Abstract: When observed in a cesium beam frequency standard, the hyperfine transition frequency of the atoms differs slightly from the invariant transition frequency of the unperturbed atoms at rest. The various physical and technical origins of the frequency offsets are stated. They relate to fundamental physical effects, to the method of probing the atomic resonance and to the frequency control of the slaved oscillator. The variation of the frequency offsets under a change of the value of the internal operating characteristics is considered. The sensitivity to a change of the magnetic induction, the microwave power and the temperature is given. A comparison is made of the sensitivity of cesium beam frequency standards of the commercially available type, making use of magnetic state selection, and of devices under study in which the state preparation and detection is accomplished optically. The pathways between the external stimuli and the physical origin of the frequency offsets are specified. >

Micro-grid islanding detection method

Abstract: A micro-grid islanding detection method includes the steps: installing a device node for implanting an improved active frequency drift method at a common connection point of a micro-grid and a main grid; setting threshold values of voltage and frequency, injecting disturbing current with the disturbance factor of K0 into a system in real time, detecting the voltage UPCC and the frequency f of the common connection point, and judging that islanding happens when the voltage UPCC or the frequency f exceeds the threshold values; performing next discrimination if the voltage UPCC or the frequency f does not exceed the threshold values, comparing the current frequency fin of the injected grid with grid voltage frequency fgrid under a normal condition by a comparison circuit, and determining load characteristics; calculating a disturbance factor K in positive feedback application according to the load characteristics to generate final disturbing signals; transmitting the disturbing signals to an inverter of a distributed power generation system by a PWM (pulse width modulation) driving module, disconnecting a grid-connected circuit breaker when the frequency and the voltage of the common connection point are changed to trigger over/under frequency and over/under voltage detection due to islanding, and stopping power supply for a load by the inverter until the grids return to normal

11E-3 A Thermally Stable CMOS Oscillator Using Temperature Compensated FBAR

Abstract: This paper presents a passively temperature compensated CMOS oscillator utilizing Film Bulk Acoustic Resonator (FBAR). The resonator exhibiting f-Q product of 2~3times1012 sec-1 is comprised of molybdenum (Mo), aluminum nitride (AlN), and a compensation material that has positive temperature coefficient of Young's modulus. The 600 MHz oscillator consumes 6.6 mW from a 3.3 V supply and achieves an excellent phase noise performance of -102 dBc/Hz, -132 dBc/Hz, and -151 dBc/Hz at 1 kHz, 10 kHz, and 100 kHz carrier offset, respectively. The oscillator's temperature-dependent frequency drift is less than 80 parts per million (ppm) over a temperature range of -35 to +85degC.

Detecting method suitable for optical fiber distributed temperature and stress sensing device

Abstract: The invention discloses a detection method suitable for a sensing device of optical fiber distribution type temperature and stress. The sensing device of the optical fiber distribution type temperature and stress mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The detection method of the invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring the relative frequency of a outgoing laser beam to the frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, and outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of frequency discrimination is not sensitive to the frequency drift of the light source and the fluctuation of signal intensity.

Direct Measurements of the Inherent Frequency Stability of Quartz Crystal Resonators

Abstract: A technique is presented that allows one to measure directly the fluctuations of the natural resonant frequency of quartz crystal resonators in a passive circuit. This technique greatly aids in modeling the noise in both crystal resonators and crystal controlled oscillator circuits. Definite changes of slope in the spectral density of the frequency fluctuations,as a function of frequency offset from the natural resonant frequen of the crystals indicate that several mezanisms are contributing to the frequency instabilities in crystals. Our measurements also indicate that the electronics in the oscillators seriously degrade the frequency stability for sample times less than 100 S. The effects are especially dramatic for times less than 1 S.