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.

Digital frequency and phase modulator for radio transmission

Abstract: For digital transitions from one binary logic level to another by frequency or phase shift of an electric carrier wave the modulation sidebands are reduced by performing each transition by means of several phase steps at small intervals. Equal phase steps at varying intervals are preferred over equal intervals between varying phase steps although both procedures can provide a low-bandwidth transition. This procedure is readily incorporated at low cost in frequency synthesizers. The use of a higher-frequency master oscillator (16) followed by a fixed-ratio frequency divider (17) ahead of a variable-ratio frequency divider (18) makes it easy to shift phase or frequency digitally by small quick steps. Another variable-ratio frequency divider (13) is desirable but not essential in the final PLL between a ultimately controlled oscillator (10) and a loop filter (12) connected to a phase discriminator (11). The discriminator (11) and the two variable-ratio frequency dividers (17, 13) require simultaneous or coordinated initialization (line 20). A binary digital signal produces GMSK modulation by means of a processor in which the divider ratios and their timings and sequence are stored. The steps are small enough for the loop filter to provide adequate bandwidth reduction. Steps each produced by a divisor one unit higher than the divisor which keeps the phase constant for the nominal frequency are produced by one cycle of the reference frequency, which corresponds to a number equal to the overall divisor of cycles of the master oscillator.

Dynamically Reconfigurable All Optical Frequency Measurement System

Abstract: A microwave photonic frequency measurement system is demonstrated practically. The system employs the four-wave mixing effect in a highly nonlinear fiber to produce a low-frequency output voltage, which is a function of input RF frequency. Using an algorithm that allows dynamic reconfiguration, the system is able to instantaneously monitor a broad frequency range for threat signals and to provide fast yet accurate frequency measurement. An operating frequency range of 0.04–40 GHz with at most 0.016% error is achieved.

Temperature compensation of a capacitive MEMS accelerometer by using a MEMS oscillator

Abstract: This study reports a temperature compensation method for a capacitive MEMS accelerometer by using a MEMS double-ended-tuning-fork (DETF) resonator integrated with the accelerometer structure on the same die. The proposed method utilizes the frequency information of the clamped-clamped DETF resonator which is oscillating in a closed-loop operation. In order to compensate the temperature dependence of the accelerometer output, frequency drift of the DETF resonator against changing temperature is used, i.e., the resonator frequency is used as the temperature data for compensation purposes. On-chip integration of two sensors allows precise temperature sensing abilities by removing the thermal lag between the DETF resonator and the accelerometer. Tests are held in the −20 °C and 60 °C range by operating both sensors simultaneously in a temperature-controlled oven. The measurement results indicate temperature coefficient of frequency (TCf) of 480 ppm/K for the integrated resonator and temperature dependence of 1,164 µg/K for the accelerometer output, which is decreased to 1.4 µg /K after temperature compensation. Improved noise performances indicate the bias instability of 30 µg and the velocity random walk of 24 µg/sqrt(Hz) with the removal of the temperature ramp (after 30 seconds) in Allan-deviation plot.

Interference wave signal removing device, gnss reception apparatus, mobile terminal, interference wave signal removing program and interference wave removing method

Abstract: An interference wave signal removing device that can surely remove an interference wave signal is provided. An interference wave signal remover includes a controller, a notch filter, an entire-range frequency scanner, and a local frequency scanner. The controller detects the interference wave signal based on a frequency scanning result by the entire-range frequency scanner, and sets the notch filter to attenuate the interference wave signal frequency. Based on input signals to the notch filter, the local frequency scanner frequency-scans in a local frequency band including an attenuation band of the notch filter. The controller detects a frequency drift of the interference wave signal frequency based on the frequency scanning result by the local frequency scanner, and updates the setting of the notch filter to attenuate the interference wave signal frequency after the frequency drift.

The drop of the coherence of the lower kilohertz quasi-periodic brightness variations is also observed in xte j1701−462

Abstract: We investigate the quality factor and root mean square (rms) amplitude of the lower kilohertz quasi-periodic brightness variations (kHz QPOs) from XTE J1701–462, a unique X-ray source which was observed in both the so-called Z and atoll states. Correcting for the frequency drift of the QPO, we show that, as in all sources for which such a correction can be applied, the quality factor and rms amplitude drops sharply above a critical frequency. For XTE J1701–462, this frequency is estimated to be ~800 Hz, where the quality factor reaches a maximum of ~200 (e.g., a value consistent with the one observed from more classical systems, such as 4U 1636–536). Such a drop has been interpreted as the signature of the innermost stable circular orbit, and that interpretation is consistent with the observations we report here. The kHz QPOs in the Z state are much less coherent and lower amplitude than they are in the atoll state. We argue that the change of the QPO properties between the two source states is related to the change of the scale height of the accretion disk; a prediction of the toy model proposed by Barret et al. As a by-product of our analysis, we also increased the significance of the upper kHz QPO detected in the atoll phase up to 4.8σ (single trial significance) and show that the frequency separation (266.5 ± 13.1 Hz) is comparable with the one measured from simultaneous twin QPOs in the Z phase.