Showing papers on "Frequency drift published in 2022"

Improving the Ensemble Time Scale by Eliminating Frequency Drifts of Hydrogen Masers

Abstract: The long-term stability of the time scale is affected by the large frequency drifts of hydrogen masers. It is necessary to calibrate the hydrogen maser’s drift before it is used to keep time. To calibrate drift, a reference with negligible drift is needed. Traceability links are established in timekeeping laboratories to get clock differences between local time scales and remote time scales. Drifts of remote time scales are negligible. Therefore, remote time scales can be used as reference for drift calibration. In this article, the concept of remote virtual clock is proposed and the model is constructed. The remote virtual clock is involved in the local clock ensemble on timekeeping. With the help of the negligible frequency drift of virtual clock, drifts of local clocks can be calibrated. Meanwhile, a time scale algorithm based on drift calibration is proposed to generate the ensemble time scale. The final results of simulation and experiment demonstrate that the frequency drift can be calibrated and long-term stability can be improved by one order of magnitude.

Temperature compensated ring oscillator based VCO

Abstract: Frequency drift due to temperature variations is a crucial design consideration and cannot always be compensated by a phase-locked loop especially when low-gain, multiband oscillators are employed. A ring oscillator architecture with reduced frequency drift over temperature is presented in this paper. The oscillator is incorporated in a phase locked loop (PLL) to produce a stable clock within the required frequency range under process, voltage, and temperature variations. The output frequency of the oscillator is compensated through a proportional to absolute temperature (PTAT) current in order to eliminate the frequency drift. A proof-of-concept PLL has been designed and fabricated in a 180 nm CMOS technology operating with 3.3 V supply voltage and providing a 480 MHz frequency. Measurement results of the fabricated chip show a frequency variation of the VCO from −1.5 % to + 0.4 % from the center frequency across the temperature range from −40 °C to 120 °C meeting the requirements for most consumer market applications. The duty cycle distortion is less than 1% across the temperature range. The phase noise of the oscillator was measured at −107 dBc/Hz.

A Fixed-Frequency, Tunable Dielectric Resonator Oscillator With Phase-Locked Loop Stabilization

Abstract: Highly stable oscillators used for microwave measurement systems require both excellent long-term and short-term stability. The dielectric resonator oscillator (DRO) offers a unique combination of high performance and simple construction. Its drift and noise are already comparably low, but can be further reduced by phase-locked loop stabilization. In this work, the design and measurement of a low-cost DRO concept with a phase noise of −107.2 dBc/Hz at 10 kHz offset frequency and 12.8 GHz output frequency is presented. An electronic control loop reduces drift and phase noise of the oscillator resulting in a very low jitter of 29 fs.

MeerKAT Observations of the Reversing Drifting Subpulses in PSR J1750-3503

Abstract: We present an analysis of the subpulse drift in PSR J1750−3503, which is characterized by abrupt transitions of drift direction. As the pulsar does not exhibit other mode changes or clear nulling, it is an ideal candidate system for studying the phenomenon of drift direction change. For ∼80% of the time, the subpulses are characterized by positive drift—from early to later longitudes—while the drift direction is negative in the other ∼20%. The subpulse separation for single pulses with positive drift, P 2 = (18.8 ± 0.1)°, is higher than for single pulses with negative drift, P 2 = (17.5 ± 0.2)°. When the drift is stable, the measured repetition time of the drift pattern is P 3 obs = (43.5 ± 0.4)P, where P is the pulsar period. We show that the observed data can be reproduced by a carousel models with subpulse rotation around the magnetic axis using a purely dipolar configuration of the surface magnetic field. The observed drift characteristics can be modeled assuming that the actual repetition time P 3 < 2P, such that we observe its aliased value. A small variation in P 3, of the order of 6% (or less assuming higher alias orders), is enough to reproduce the characteristic drift direction changes we observe.

A Low Frequency Drift LC-DCO with Wide Temperature Range

Abstract: A 2.4GHz LC-DCO with low frequency drift is presented to support frequency synthesizer under narrow band system like BLE. In the LC-DCO, a comprehensive temperature compensation scheme, which includes a Proportional To Absolute Temperature (PTAT) current bias and the varactor arrays varying linearly with voltage, is proposed to reduces the frequency drift of LC-DCO as a result of temperature fluctuations. By applying the circuit, frequency drift is reduced from 31MHz (without compensation) to 6MHz within the temperature from -40°C to 120 °C. And the results show that no extra in-band noise is added to LC tank. It consumes 860uW from a 0.9V supply in 40nm CMOS process technology.

Design of ring oscillator with temperature compensation effect

Abstract: In this article, a ring oscillator with Temperature Compensation Effect is proposed in 0.18 μm CMOS. The ring oscillator is composed of 31 stages of inverters in series. The change in ambient temperature will cause the oscillator frequency to deviate. Therefore, this research uses a voltage circuit with a positive temperature coefficient as the power supply for the oscillator circuit, so that the ring oscillator can output stable oscillation center frequency regardless of ambient temperature. The ring oscillator has been verified by simulation and experimental testing. The ambient temperature is within the range of −40°C to 80°C. The output frequency of the ring oscillator is stable at 33 kHz ± 0.50 kHz. The frequency error is within 1.6%. Temperature stability was 120 ppm/°C. At 1 MHz off the carrier, the phase noise is as low as −151.2 dBc/Hz and the total power dissipation is 210 μW. Compared with the previous scheme, the chip area and power consumption are lower. This circuit module can provide a clock signal for the timer when the UWB chip sleeps.

Coupled optoelectronic oscillator and its application in 5G communication system

Abstract: The oscillator is the core module of the radio frequency receiving front-end, which directly determines the signal processing capability of the communication system. Optoelectronic Oscillator (OEO) technology has become the main research direction to solve the indicators of improving phase noise and frequency tuning range of RF receiving front-end. In order to better solve the problem of RF reception, this paper studies the coupled opto-electronic oscillator, discusses its application in 5G communication systems, and discusses the voltage-controlled tunable fiber Fabry-Perot Coupled Optoelectronic Oscillator (FFP-COEO); Phase noise phase and frequency tuning model, the oscillator controls the cavity length of the Fabry-Perot cavity by voltage, and the starting frequency can be adjusted. The experimental results show that the oscillator can increase the secondary mode-locked loop by improving the filtering performance of the optical loop, further optimize the phase noise of the system, and improve the side mode suppression ratio and output power.

Ultra-Stable Oscillator Stabilization using an Artificial Neural Network

Abstract: SummaryWe present results from experiments where we attempted to use an array of thermal sensors and an artificial neural network to predict the temperature-induced frequency fluctuations in a low-noise quartz oscillator. We trained the neural network by giving it thermal sensor readings as well as frequency measurements made against a hydrogen maser reference. The temperature vs. frequency model created by the neural network was then tested on separate data where the difference between the predicted frequency and measured frequency was collected. We found that the Allan deviation of this residual frequency difference was up to 10 dB lower than the Allan deviation of the original oscillator frequency. This result demonstrates the potential of using thermal sensors coupled with an artificial neural network to suppress temperature-induced frequency fluctuations in an oscillator without the need for bulky thermal insulation.

Improved frequency stability HBT oscillator with temperature compensation technique

Abstract: Here, we describe a heterojunction bipolar transistor (HBT) voltage-controlled oscillator (VCO) showing extremely low frequency drift with temperature using a compensation capacitor CCO across the base-collector electrodes. CCO has a 5~10 times value of junction capacitor and it efficiently shields resonance frequency stability from junction capacitance fluctuation with temperature. Taking advantage of the added capacitor CCO, we can use smaller capacitors to implement the Clapp-like structure oscillator with a compact layout. Fabricated with 2μm GaAs HBT technology, the oscillator achieves a frequency drift rate < 0.6MHz/℃ and >8dBm output power in 2.5-7.2GHz output frequency band. Excellent 2nd harmonics suppression <-30dBc and superior phase noise of -87dBc/Hz@10KHz and -105dBc/Hz@100KHz are observed at room temperature.

Methane-Based Photonic Microwave Oscillator With Stability Better Than 10−14 at 1–103 s Averaging Times

Abstract: An improved version of the transportable photonic microwave oscillator based on the He–Ne/CH₄ optical frequency standard (OFS) ( $\lambda $ = $3.39 ~\mu \text{m}$ ) and the femtosecond Er fiber laser optical-to-microwave frequency divider ( $\lambda $ = $1.55 ~\mu \text{m}$ ) has been developed. Stable continuous operation of the generator was achieved for several days without operator intervention, and the relative Allan deviation below $1\times10$ ⁻¹⁴ was demonstrated for averaging times 1–10³ s at output frequencies of 1.0 and 9.2 GHz. The choice of frequencies is determined by the implementation of the methane-based photonic microwave oscillator as an interrogation oscillator for Cs (Rb) fountain. The obtained relative frequency instability at averaging times of 1–200 s is lower than that of the best commercial H-masers. Compared to transportable photonic microwave oscillators based on an ultralow expansion Fabry–Perot (FP) cavity, the oscillator described in this article has an order of magnitude less drift and can be attractive for different tasks of coherent radio photonics where a relatively long-term accumulation of weak signals is required.

Frequency Compensated Crystal-Free 802.15.4 Wireless Radio

Abstract: Crystal-Free radios are susceptible to frequency drifts due to temperature and voltage. Compensation for the frequency drift in the 2.4 GHz local oscillator due to voltage variation was demonstrated for a Crystal-Free radio while powered from a solar cell under 200 mW/cm2 of irradiation and a 0805 capacitor. Without compensation the local oscillator frequency would vary by 2.4 MHz while the 802.15.4 packets were transmitted resulting in a loss of 100B of the payload. With frequency drift compensation that oscillator frequency varied less than 300KHz and the full length 125B 802.15.4 packet was received by an off-the-self component radio.

A 5.0-to-12.5-Gb/s, 1.7-pJ/b, 0.66-μs Lock-time Reference-less Sub-sampling CDR with Beat Detection FLL in 28nm CMOS

Abstract: The primary role of a frequency-locked loop (FLL) is to match the frequency of the recovered clock to the bit-rate clock frequency. Since a perfect match is impossible, there is always a residual frequency even after the FLL is locked. This residual frequency is compensated within the capture range of the phase detector (PD). In practice, the capture range of the PD is usually narrow, and it is desirable to reduce the residual frequency of the FLL as much as possible without sacrificing lock-time, frequency coverage, and energy efficiency.

GPS Disciplined Numerically Controlled Oscillator Based on Xilinx FPGA

Abstract: The high precision frequency standard is important in most frequency and time measurements. Accurate frequency standards are expensive and hard to obtain. Most of the GPS receivers provide 1 pulse per second time standard which can be used to accurately discipline a crystal oscillator with a high short-term stability. The following work uses a high frequency unadjustable crystal oscillator followed by a numerically controlled oscillator in order to obtain a high stability frequency based on 1 pulse per second GPS signal.

Study on crystal oscillator frequency drift model and performance of low orbit satellite

Abstract: Aiming at the problem of frequency drift of crystal oscillator due to temperature and aging characteristics, a mathematical model of clock frequency drift of crystal oscillator was established by analyzing the telemetry data of a solar synchronous orbit satellite over the years. The mathematical models of clock frequency drift of several crystal oscillators are established. The fitting accuracy is taken as the evaluation index to compare several models and determine the optimal model. The model can be used to fit and verify the crystal oscillator output frequency, which can meet the continuous time calibration service of spacecraft when GPS/BD is not available, and can provide reference for on-board autonomous time calibration or long-term management on the ground.

A Low-Drift Laser-Driven FOG Suitable for Trans-Pacific Inertial Navigation

Abstract: We report a laser-driven fiber-optic gyroscope (FOG) with an angle random walk of 0.9 mdeg/√h, an Allan-deviation minimum of 4.9 mdeg/h, and an Allan-deviation maximum (or true drift) of 12.6 mdeg/h. This state-of-the-art performance was achieved by implementing an optical gate and a power-control feedback loop to suppress several sources of drift in the FOG, namely optical spikes that result from the square-wave biasing modulation, the nonlinear Kerr effect, drift in the detected power arising from spurious interferometers in the fiber circuit and laser-power fluctuations, and bias offset drift in the demodulation electronics. The measured output of this FOG was used to simulate 20 10-h trans-Pacific flights of an aircraft guided solely by inertial sensors. 95% of the flights landed within ±10 nmi of their intended destination. To our knowledge, this is the first report of a laser-driven FOG that meets the Federal Aviation Administration's Required Navigation Performance 10 criteria for aircraft navigation.

High Precision RC Relaxation Oscillator for Wide Supply Voltage Swing from 2.5V to 5.5V

Abstract: A low-temperature drift current-mode relaxation oscillator suitable for wide supply voltage swing is presented. The characteristic that the delay of the buffer is proportional to the supply voltage and inversely proportional to the bias current is exploited. The bias of the buffer is provided by the current source that changes with the supply voltage, so as to achieve the purpose that the delay of the buffer is weakly correlated with the supply voltage and suppress the change of the output frequency. A temperature-dependent resistance is used to balance the delay of the buffer with temperature. The experimental results show that the typical frequency of the oscillator is 2MHz. The frequency variation is 0.33%/V for the supply voltage of 2. 5~5.5V and 40.6ppm/°C for temperature of −40~125°C.