Showing papers on "Frequency drift published in 2021"

A Third-Order MAF Based QT1-PLL That is Robust Against Harmonically Distorted Grid Voltage With Frequency Deviation

Abstract: The quasi-type-l phase-locked loop (QT1-PLL) is a grid synchronization technique that has become very popular in recent years thanks to its attractive performance such as easy implementation, fast dynamic response, and good accuracy in steady-state operation. However, it is still vulnerable to operation under harmonically distorted grid voltages with frequency drift. This paper proposes a novel QT1-PLL based synchronization algorithm that makes an appropriate combination of two filters’ types: an in-loop third-order moving average filter (MAF) with a reduced window width, and a simplified second-order fast delayed signal cancellation (FDSC) based prefiltering stage. The proposed PLL is named third-order MAF based QT1-PLL (TQT1-PLL). Though both TQT1-PLL's filters do not need any adaptive algorithm, it is able to reject non-triplen odd-harmonics and the fundamental frequency negative sequence (FFNS) even under grid frequency drift. Its correct operation is confirmed through numerical simulations and real-time implementation on a digital signal processor (DSP). Moreover, the obtained results confirm its ability to reduce the ripple in the estimated frequency and phase under distorted grid voltages and off-nominal frequency operation. Authors show also through an analytical development that the topology of the proposed TQT1-PLL can be extended to enable the rejection of the DC-offset.

Advanced Type-1c FLL for Enhancing Converters Synchronization During Frequency Drift

Abstract: This paper introduces a novel out-loop compensation scheme with a selective filtering stage for Type-1 Frequency Locked Loop (FLL) to obtain the same features of Type-2 FLL in response to frequency drift. The proposed scheme can eliminate the phase angle error during frequency drift without compromising its benefits of the low order control system. The performance of the proposed Type1-c FLL is evaluated with alternatively employed Delayed Signal Cancellation (DSC), Low Pass Filter (LPF) with selective harmonics filtering and multiple second-order generalized integrator (MSOGI) as a pre-filtering stage under the various grid disturbances. The effects of each filtering scheme on the dynamic response and harmonics mitigation are identified. As each filter has a distinct advantage in response to each grid disturbance, a selective control approach is used to insert the most suitable filter based on the severity of the grid disturbance to achieve the best performance. A comprehensive study is conducted to demonstrate the superior performance of the proposed schemes with both simulation and experimental validation. In addition, the potential application of the proposed Type-1c FLL for enhancing the islanded microgrid operation has been presented and verified.

A Low-Jitter and Low-Reference-Spur Ring-VCO- Based Injection-Locked Clock Multiplier Using a Triple-Point Background Calibrator

Abstract: This work presents a low-jitter, low-reference-spur ring voltage-controlled oscillator (ring VCO)-based injection-locked clock multiplier (ILCM). Since the proposed triple-point frequency/phase/slope calibrator (TP-FPSC) can accurately remove the three root causes of the frequency errors of ILCMs (i.e., frequency drift, phase offset, and slope modulation), the ILCM of this work is able to achieve a low-level-reference spur. In addition, the calibrating loop for the frequency drift of the TP-FPSC offers an additional suppression to the in-band phase noise of the output signal. This capability of the TP-FPSC and the naturally wide bandwidth of the injection-locking mechanism allows the ILCM to achieve a very low-RMS jitter. The ILCM was fabricated in a 65-nm CMOS technology. The measured reference spur and RMS jitter of the 2.4-GHz output signal were −72 dBc and 140 fs, respectively, both of which are the best among the state-of-the-art ILCMs. The active silicon area was 0.055 mm2, and the power consumption was 11.0 mW.

Decentralized Frequency Alignment for Collaborative Beamforming in Distributed Phased Arrays

Abstract: A new approach to distributed synchronization (frequency alignment) for the coordination of nodes in open loop coherent distributed antenna arrays to enable distributed beamforming is presented. This approach makes use of the concept of consensus optimization among nodes without requiring centralized control. Decentralized frequency consensus can be achieved through iterative frequency exchange among nodes. We derive a model of the signal received from a coherent distributed array and analyze the effects on beamforming of phase errors induced by oscillator frequency drift. We introduce and discuss the average consensus protocol for frequency transfer in undirected networks where each node transmits and receives frequency information from other nodes. We analyze the following cases: 1) undirected networks with a static topology; 2) undirected networks with a dynamic topology, where connections between nodes are made and lost dynamically; and 3) undirected networks with oscillator frequency drift. We show that all the nodes in a given network achieve average consensus and the number of iterations needed to achieve consensus can be minimized for a given cluster of nodes. We derive the theoretical phase error resulting from both processing noise and measurement noise, and derive an optimal update interval that minimizes the error. Numerical simulations demonstrate that the consensus algorithm enables tolerable errors to obtain high coherent gain of greater than 90% of the ideal gain in an error-free distributed phased array.

Resonant interaction of relativistic electrons with realistic electromagnetic ion–cyclotron wave packets

Abstract: We study the influence of real structure of electromagnetic ion-cyclotron wave packets in the Earth’s radiation belts on precipitation of relativistic electrons. Automatic algorithm is used to distinguish isolated elements (wave packets) and obtain their amplitude and frequency profiles from satellite observations by Van Allen Probe B. We focus on rising-tone EMIC wave packets in the proton band, with a maximum amplitude of 1.2–1.6 nT. The resonant interaction of the considered wave packets with relativistic electrons 1.5–9 MeV is studied by numerical simulations. The precipitating fluxes are formed as a result of both linear and nonlinear interaction; for energies 2–5 MeV precipitating fluxes are close to the strong diffusion limit. The evolution of precipitating fluxes is influenced by generation of higher-frequency waves at the packet trailing edge near the equator and dissipation of lower-frequency waves in the $$\text {He}^+$$ cyclotron resonance region at the leading edge. The wave packet amplitude modulation leads to a significant change of precipitated particles energy spectrum during short intervals of less than 1 minute. For short time intervals about 10–15 s, the approximation of each local amplitude maximum of the wave packet by a Gaussian amplitude profile and a linear frequency drift gives a satisfactory description of the resonant interaction.

A modified Active Frequency Drift Method for Islanding Detection

Abstract: Among active islanding detection methods (IDM), active frequency drift (AFD) is the most IDM applied in the literatures. Recently, an improved active frequency drift (IAFD) was presented in the literature, which has lower total harmonic distortion (THD) injected to the system compared with conventional AFD. IAFD uses a constant step change in 2nd and 4th quarters of the inverter reference current. In this paper, an adaptive step change is proposed to improve the performance of IAFD method, where a positive feedback of voltage frequency is used in this work to change the distortion factor of IAFD. The proposed method is theoretically analyzed and modeled using MATLAB/Simulink environment. As a result, the proposed method improves the performance of IAFD regarding to the Non-detection zone (NDZ).

Adaptive Frequency Tracking Control with Fuzzy PI Compound Controller for Magnetically Coupled Resonant Wireless Power Transfer

Abstract: In the magnetically coupled resonant wireless power transfer (MCR-WPT) system, parameter variations of the resonant network will cause the resonant frequency drift, which will make the system in the detuning state. The detuning will increase the required capacity of the power supply and reduce the transfer efficiency of the system. To solve this problem, this paper analyzes the relation between the input impedance angle of the primary side and the resonant state and proposes an adaptive frequency tracking control (AFTC) method based on the fuzzy PI compound controller. In this method, a fuzzy PI compound controller is used to control the impedance angle (θ = 0), which can make the operating frequency to track the resonant frequency, so that the MCR-WPT system can maintain in the resonant state. The experimental results show that the AFTC method can make the operating frequency to track the resonant frequency faster and accurately during the parameter variations so that the MCR-WPT system can maintain in the resonant state and achieve the higher output power and system efficiency.

An Improved Difference Temperature Compensation Method for MEMS Resonant Accelerometers.

Abstract: Resonant accelerometers are promising because of their wide dynamic range and long-term stability. With quasi-digital frequency output, the outputs of resonant accelerometers are less vulnerable to the noise from circuits and ambience. Differential structure is usually adopted in a resonant accelerometer to achieve higher sensitivity to acceleration and to reduce common noise at the same time. Ideally, a resonant accelerometer is only sensitive to external acceleration. However, temperature has a great impact on resonant accelerometers, causing unexcepted frequency drift. In order to cancel out the frequency drift caused by temperature change, an improved temperature compensation method for differential vibrating accelerometers without additional temperature sensors is presented in this paper. Experiment results demonstrate that the temperature sensitivity of the prototype sensor is reduced from 43.16 ppm/°C to 0.83 ppm/°C within the temperature range of −10 °C to 70 °C using the proposed method.

Characterization of a multifunctional active demultiplexer for optical frequency combs

Abstract: We report on a multifunctional active demultiplexer for optical frequency combs. The proposed technique, based on injection locking, combines the functionality of a tunable demultiplexer, gain equalizer and an optical amplifier, all in one device. Validation of the concept is experimentally demonstrated through simultaneous demultiplexing and amplification of combs with various free spectral ranges (2.5 to 15 GHz), achieving an adjacent channel suppression ratio > 35 dB and an output power of 7.5 dBm. The functionality of the demultiplexer is extended to that of a gain equalizer, by filtering comb tones with powers 10 dB below the spectral peak, whilst maintaining a suppression ratio > 30 dB and a constant output power. This feature increases the number of comb lines suited for data modulation (i.e. usable lines), by a factor of ~1.7. Finally, we test the stability of such a demultiplexer, by measuring the frequency drift, beat tone power variations and phase correlation between demultiplexed tones.

A Bluetooth 5 Transceiver With a Phase-Tracking RX and Its Corresponding Digital Baseband in 40-nm CMOS

Abstract: A 0.8-V Bluetooth 5 (BT5) digitally intensive transceiver with a phase-tracking RX and a digital TX in 40-nm CMOS is presented. For the phase-tracking RX, a hybrid loop filter with a loop-delay compensation is proposed to suppress digitally controlled oscillator (DCO) sidelobe energy, enhancing interference resilience. To facilitate the DCO-based phase-tracking RX for the reception of BT5 signals, a corresponding digital baseband is implemented with a carrier frequency offset (CFO) calibration to remove the initial static CFO error during the preamble, while an automatic frequency calibration tackles the frequency drift during the payload. An all-digital phase-locked loop (ADPLL)-based digital frequency-modulation (FM) interface shared between TX and RX provides a precise deviation frequency control, ensuring the quality of signal transmission and reception. In the RX mode, the chip consumes 2.3 mW from a 0.8-V supply, achieving a figure of merit (FoM) of 180 dB with −91-/−94-dBm sensitivity at 2/1 Mb/s. In the TX mode, it consumes 6.1 mW when delivering a maximum 1.8-dBm output power, resulting in 25% TX system efficiency.

Frequency drift mitigation of Φ-OTDR using difference-fitting method.

Abstract: A difference-fitting method is proposed to mitigate the low frequency drift of a phase-sensitive optical time domain reflectometry (Φ-OTDR) system caused by laser phase noise. The effective difference region for phase demodulation is theoretically analyzed and experimentally verified, which should be greater than the convolution of the spatial resolution and the length of disturbed optical fiber. Then, a median-fitting algorithm is used to obtain the phase noise of the differential region. The vibration signal of 0.2 Hz is first demodulated with the SNR of 41.79 dB on the optical fiber of 11 km. The low-frequency vibration signals of 0.05 Hz and 0.02 Hz are then successfully restored by using the difference-fitting method, which can effectively eliminate the influence of low frequency drift.

A 300 nW 10 kHz Relaxation Oscillator with 105 ppm/ $$^{\circ }$$ ∘ C Temperature Coefficient

Abstract: An on-chip nanopower RC relaxation oscillator is developed in a 180-nm standard CMOS process, consuming 300 nW while running at 10 kHz. Employing a frequency compensation scheme that reduces the frequency drift introduced by comparator offset and delay, the proposed oscillator achieves a significant low temperature coefficient. Furthermore, a supply regulation structure is used to reduce the frequency sensitivity to supply voltage variations. Post-simulation results show that the frequency variation against temperature is 105 ppm/ $$^{\circ }$$ C in the temperature range from 0 to 85 $$^{\circ }$$ C, and the line sensitivity is 2.19%/V with the supply voltage changing from 1.05 to 1.45 V. At offset frequencies of 100 Hz and 1 kHz, the simulated phase noises are −50 and −71 dBc/Hz, respectively.

Locking Multi-Laser Frequencies to a Precision Wavelength Meter: Application to Cold Atoms.

Abstract: We herein report a simultaneous frequency stabilization of two 780-nm external cavity diode lasers using a precision wavelength meter (WLM). The laser lock performance is characterized by the Allan deviation measurement in which we find σy=10−12 at an averaging time of 1000 s. We also obtain spectral profiles through a heterodyne spectroscopy, identifying the contribution of white and flicker noises to the laser linewidth. The frequency drift of the WLM is measured to be about 2.0(4) MHz over 36 h. Utilizing the two lasers as a cooling and repumping field, we demonstrate a magneto-optical trap of 87Rb atoms near a high-finesse optical cavity. Our laser stabilization technique operates at broad wavelength range without a radio frequency element.

Phase-Sensitive Optical Time-Domain Reflectometric System Based on Optical Synchronous Heterodyne

Abstract: Aiming at the frequency drift of the laser and acousto-optic modulator in the traditional phase-sensitive optical time domain reflectometric ( $\Phi $ -OTDR), a $\Phi $ -OTDR system based on optical synchronous heterodyne is proposed and demonstrated. The method of optical synchronization heterodyne is used to follow the beat frequency signal to eliminate the interference of frequency shift fluctuation in the phase information and the ubiquitous residual frequency before the optical path heterodyne. The signal-to-noise ratio (SNR) is more than 31.4 dB on a 10 km sensing optical fiber with a probe light pulses of 5 kHz repetition rate and 100 ns pulse width. The error between the demodulated signal amplitude and the actual signal amplitude is less than 1%, and the maximum harmonic amplitude is about 28.3 dB less than the actual signal amplitude. While improving the real-time performance, this research greatly improves the demodulation characteristics of the system, which is of great significance to the advancement of the practical process of the phase-sensitive optical time domain reflectometric system.

Compendious Concurrent Dual-Band Receiver Based on Multiport Interferometric Architecture

Abstract: A distinct usage of the conventional multiport architecture is introduced in this work to explore the compendious scheme of a concurrent dual-band interferometric receiver. Dual RF signals at individual frequency channels are received simultaneously, and only a single low-power local oscillator (LO) source is deployed for frequency translation or conversion to the same intermediate frequency (IF) band. Although these signals are spectrally overlapped, they can be extracted with a simple and efficient algorithm with good channel-to-channel isolations. Compared to the conventional multiport configuration, the power detectors are replaced by analog-to-digital converters (ADCs) to process the signals in this proposed scheme. The underlying physics of the concurrent receiving operation is explained and derived analytically. Some experiments are also presented to investigate various performance indexes, including signal linearity, noise behavior, interchannel interference, and so forth. Lastly, multiple $M$ -quadratic-amplitude modulation (QAM) signals are applied to evaluate the communication behavior of the proposed receiver architecture. Distortions due to frequency drift, channel imbalance, and in-phase and quadrature (IQ) imbalance are studied, and bit-error-rates (BER) are measured and compared with their theoretical counterparts. All obtained results confirm that the proposed interferometric receiver provides good communication performances.

Drift Correction for Active Hydrogen MASERs

Abstract: The drift characteristics of well-aged Hydrogen MASERs may be reasonably modeled as linear over periods greater than two weeks. There are several broad strategies used to manage drift: a) quantify and acknowledge drift in a system error budget, b) compensate using post-processing methods, c) apply a linear correction, or d) steer the MASER output frequency to a superior reference. The selection of drift management method greatly depends upon the requirements of a user’s system. Users, such as radio astronomers, may de-emphasize active drift management as their primary concern is 1-to-100 second stability. These users often prefer to compensate for frequency drift after passing a predefined frequency offset threshold. This removal takes the form of a manual frequency adjustment on the MASER. However, time-scale users, who require exact characterization and compensation of drift, will need to intervene using post-processing methods to avoid tampering with a characterized MASER which may be contributing to local UTC. This paper will discuss the underlying processes that may cause linear drift, how this drift is quantified, and then give an overview of the design implications of each drift handling method. For illustration purposes, a MASER’s drift will be characterized, and a linear drift correction will be applied. This illustration covers the use case when a MASER will perform as a standalone standard with moderate long-term stability requirements.

Demonstration of a 50G-PON with a 45-dB power budget using an IQ-interleaved coherent detection scheme.

Abstract: The application of traditional coherent detection technology to optical access networks has been undermined due to its high complexity and high cost. In this paper, we propose a novel IQ-interleaved detection method which uses the preset frequency offset of the lasers at the transmitter and receiver to obtain the in-phase and quadrature components of the received signal. It keeps the simple structure of heterodyne detection and avoids the down-conversion process. Without Nyquist pulse shaping, the received signal bandwidth of the proposed scheme is theoretically 0.5B smaller than that of heterodyne detection for signal with a symbol rate of B. The 50-Gb/s NRZ transmission experiment proves that by using the proposed scheme, the receiving sensitivity and the frequency drift tolerance can be improved by ∼1 dB and 1 GHz compared with heterodyne detection under strong bandwidth limitation. Without pulse shaping, the receiving sensitivity, frequency drift tolerance (1-dB sensitivity penalty) and link power budget for 20-km fiber transmission are -31.8 dBm, 11 GHz and 43.5 dB, respectively. A higher power budget of 45 dB can be achieved when Nyquist pulse shaping is applied. The proposed scheme provides a low-complexity potential solution for a next-generation coherent PON.

Drifts of the marginally stable burning frequency in the X-ray binaries 4U 1608-52 and Aql X-1

Abstract: We detect millihertz quasi-periodic oscillations (mHz QPOs) using the Rossi X-ray Time Explorer (RXTE) from the atoll neutron-star (NS) low-mass X-ray binaries 4U 1608--52 and Aql X--1. From the analysis of all RXTE observations of 4U 1608--52 and Aql X--1, we find mHz QPOs with a significance level $>3\sigma$ in 49 and 47 observations, respectively. The QPO frequency is constrained between $\sim$ 4.2 and 13.4 mHz. These types of mHz QPOs have been interpreted as being the result of marginally stable nuclear burning of He on the NS surface. We also report the discovery of a downward frequency drift in three observations of 4U 1608--52, making it the third source that shows this behaviour. We only find strong evidence of frequency drift in one occasion in Aql X--1, probably because the observations were too short to measure a significant drift. Finally, the mHz QPOs are mainly detected when both sources are in the soft or intermediate states; the cases that show frequency drift only occur when the sources are in intermediate states. Our results are consistent with the phenomenology observed for the NS systems 4U 1636--53 and EXO 0748--676, suggesting that all four sources can reach the conditions for marginally stable burning of He on the NS surface. These conditions depend on the source state in the same manner in all four systems.

A Novel Grid Forming Control Scheme Revealing a True Inertia Principle

Abstract: This article proposes an unconventional strategy for a grid forming converter, based on a phase restoring control concept by which a constant steady state frequency is achieved. This control scheme is inherently without a phase-locked loop (PLL) and keeps the power system frequency at its nominal value. Under disturbance, the control response mimics infinite virtual inertia since the power system frequency always returns to its nominal value. Therefore, this control presents a physical equivalence to a power system response with substantial inertia provided by synchronous machines. The understanding of frequency drift as a local phenomenon and power system frequency as a global aspect is briefly introduced. Further, the inherent discretization of a converter control as part of the feedback loop over the continuous network system is also considered. The concept has been mathematically investigated in a realistic test bench and global stability of the control is displayed based on the necessary boundary conditions. Simulation results supporting the mathematical hypothesis and visualizing the controller actions are presented. As a beneficial coincidence of these ideas, the control structure ensures similar responses in both electromagnetic transients (EMT) and root mean square (RMS) simulations.

Low-Power GPS-Disciplined Oscillator Module for Distributed Wireless Sensor Nodes

Abstract: Many sensor systems, such as distributed wireless sensor arrays, require high-accuracy timing while maintaining low power consumption. Although the capabilities of chip-scale atomic clocks have advanced significantly, their cost continues to be prohibitive for many applications. GPS signals are commonly used to discipline local oscillators in order to inherit the long-term stability of GPS timing; however, commercially available GPS-disciplined oscillators typically use temperature-controlled oscillators and take an extended period of time to reach their stated accuracy, resulting in a large power consumption, usually over a watt. This has subsequently limited their adoption in low-power applications. Modern temperature-compensated crystal oscillators now have stabilities that enable the possibility of duty cycling a GPS receiver and intermittently correcting the oscillator for drift. Based on this principle, a design for a GPS-disciplined oscillator is presented that achieves an accuracy of 5 μs rms in its operational environment, while consuming only 45 mW of average power. The circuit is implemented in a system called geoPebble, which uses a large grid of wireless sensors to perform glacial reflectometry.

Compact and high reliable frequency-stabilized laser system at 589 nm based on the distributed-feedback laser diodes

Abstract: A compact frequency-stabilized laser system at 589 nm is demonstrated for sodium laser guide star and sodium lidar. The 589 nm laser based on all-fiber devices was generated by the sum frequency generation (SFG) of the distributed-feedback laser diodes (DFB-LD) seed lasers of 1064 nm and 1319 nm. The absolute frequency was locked to the D2a line by adopting the method of saturated absorption. The frequency drift of 589 nm can reach to 1.8 MHz (RMS) over 5000 s. The proposed DFB-LD based frequency stabilization scheme of 589 nm laser is a promising solution for applications that require extremely mobile or miniaturized systems.

Research on Trimming Frequency-Increasing Technology for Quartz Crystal Resonator Using Laser Etching

Abstract: A quartz crystal resonator (QCR) is an indispensable electronic component in the field of the modern electronics industry. By designing and depositing electrodes of different shapes and thicknesses on a quartz wafer with a certain fundamental frequency, the desired target frequency can be obtained. Affected by factors such as the deposition equipment, mask, wafer size and placement position, it is difficult to accurately obtain the target frequency at a given time, especially for mass-produced QCRs. In this work, a laser with a wavelength of 532 nm was used to thin the electrodes of a QCR with a fundamental frequency of 10 MHz. The electrode surface was etched through a preset processing pattern to form a processing method of local thinning of the electrode surface. At the same time, the effect of laser etching on silicon dioxide and resonator performance was analyzed. Satisfactory trimming frequency-increasing results were achieved, such as a frequency modulation accuracy of 1 ppm, frequency distribution with good consistency and equivalent parameters with small changes, by the laser partial etching of the resonator electrode. However, when the surface electrode was etched into using through-holes, the attenuation amplitude of the equivalent parameter became larger, especially in terms of the quality factor (Q), which decreased from 63 K to 1 K, and some resonators which had a serious frequency drift of >40%. In this case, a certain number of QCRs were no longer excited to vibrate, which was due to the disappearance of the piezoelectric effect caused by the local thermal phase change in the quartz wafer.

An Ultra-Low-Power 2.4 GHz All-Digital Phase-Locked Loop With Injection-Locked Frequency Multiplier and Continuous Frequency Tracking

Abstract: This paper presents a 0.46 mW and 2.4 GHz; All-Digital Phase-Locked Loop (ADPLL) through an Injection-Locked Frequency Multiplier (ILFM) and Continuous Frequency Tracking Loop (CFTL) circuitry for low power Internet-of-Thing (IoT) applications. In the proposed ADPLL architecture to save power, the need for Time-to-Digital Converter (TDC) is eliminated through providing the CFTL circuitry. This feature makes the design compact, low power, and suitable for IoT applications. The proposed design is based on a synthesizable pulse injection and frequency-locked loop along with an ultra-low-power LC Digitally-Controlled Oscillator (LC-DCO). The presented CFTL circuit adjusts the frequency of the DCO continuously and prevents the frequency drift after the reference injection. Inside the designed LC-DCO core, the power consumption is minimized by optimizing the $\text{g}_{\mathrm {m}}~/\text{I}_{\mathrm {D}}$ and adjusting the power supply to 0.5 V. The proposed ILFM based ADPLL is fabricated in 55 nm CMOS technology and covers the operational frequency range of 2.402 GHz to 2.480 GHz with a reference frequency of 32 MHz. The measured phase noise performance of the ADPLL is −111.15 dBc/Hz at 1 MHz offset frequency from the carrier frequency of 2.4 GHz. It consumes only 0.46 mW power with an active area of 0.129 mm2.

Detection of Sinusoids with Frequency Drift in White Gaussian Noise

Abstract: In this study, 4 methods of detecting sinusoid targets in white Gaussian noise are investigated. Averaging FFTs coherently and non-coherently is examined. A brute force method is introduced and investigated. Using a single large FFT spanning the observation window is also considered. Detection performance is studied on targets whose frequencies drift over time. It is determined that averaging non-coherent FFTs is a safe choice in a detection system. The preferred size of the FFT used for tone detection as well as the number of spectra to average is driven by the nature of the target tone frequency drift. This information is especially useful when high sample rate detectors are used to find tones from low quality transmitters because making FFTs too large or taking too many averages may hinder detection.

Large-tuning-range frequency stabilization of an ultraviolet laser by an open-loop piezoelectric ceramic controlled Fabry-Pérot cavity.

Abstract: We demonstrate a laser frequency stabilization method with large tuning range to stabilize a UV laser by installing piezoelectric ceramic actuators into a Fabry–Perot cavity with an ultra-low expansion spacer. To suppress piezoelectric drift, a two-layer symmetrical structure is adopted for the piezoelectric actuator, and a 14.7 GHz tuning range is achieved. The short-term drift of the piezoelectric ceramics caused by temperature and creep is eliminated, and the long-term drift is 0.268 MHz/h when the Fabry–Perot cavity is sealed in a chamber without a vacuum environment. The long-term frequency drift is mainly caused by stress release and is eliminated by compensating the cavity voltage with an open loop. Without the need for an external reference or a vacuum environment, the laser frequency stabilization system is greatly simplified, and it can be extended to wavelengths ranging from ultraviolet to infrared. Owing to its simplicity, stability, and large tuning range, it is applicable in cold atom and trapped ion experiments.

Optimal Online Resonance Suppression in a Drive System Based on a Multifrequency Fast Search Algorithm

Abstract: The resonant frequency drift caused by the change in mechanical parameters will cause the servo mechanism of CNC machine tools, robots and other equipment to produce mechanical resonance again To address this problem, we propose a novel identification method of mechanical resonance based on the Fibonacci principle and a novel design method of notch filters based on optimization theory First, by using a multifrequency sinusoidal signal, we design a fast search algorithm to search for the drift resonance frequency online; then, we optimize the notch filter to achieve fast and real-time resonance suppression by optimization theory Compared with commonly employed passive resonance suppression methods, the proposed method can rapidly identify the parameters, more accurately suppress the resonance, minimize the phase angle loss and maintain the stability of the system Finally, we apply the method to a 2-mass system experimental platform The experimental results show that the proposed method is superior to the conventional passive resonant suppression method under the resonant frequency drift and other states and has strong robust performance

Resilient Ultra Stable CMOS-MEMS Oscillator with Receiver in Intel 22FFL Technology

Abstract: A frequency-scalable reference oscillator based on a Scandium doped Aluminum Nitride-on-silicon contour-mode micromechanical resonator is demonstrated for the first time which utilizes an oscillator receiver implemented in Intel 22FFL node. The oscillator operates at 95 MHz, with a total power consumption of 1 mW including the amplitude/bias control and the shaper circuitry (@1.2 V supply). A phase noise of -107 dBc/Hz @ 1 kHz offset and an RMS jitter of 870 fs over the frequency range of 12kHz-5MHz are measured for this oscillator. Aging is also studied over a period of 25 days with a promising frequency drift of less than 4 ppm. The temperature compensated ScAlN on silicon resonator exhibited a quality factor of 5k and maximum frequency vs temperature variation of 450 ppm over the -40 °C to 125 °C temperature range making the oscillator a viable alternative for reference crystal oscillators in computing systems.

Wideband tunable optoelectronic oscillator based on stimulated Brillouin scattering and a Mach–Zehnder interferometer

Abstract: We propose a novel optoelectronic oscillator (OEO) based on stimulated Brillouin scattering (SBS) and a Mach–Zehnder interferometer (MZI). The SBS and MZI form a microwave photonic filter (MPF), which completes the frequency selection of the OEO. The width of the MPF passband can be changed by adjusting the DC voltage of the MZI. When the gap between the passbands is aligned with the side mode, the side mode can be suppressed; in this way, a single-mode optoelectronic oscillator is achieved. Compared with the previous structure, the proposed structure is more stable and easier to integrate. A stable frequency signal at 9.4 GHz is obtained with a phase noise of −84.05dBc/Hz at 10 kHz, the side-mode-suppression ratio is 42 dB, and the frequency drift is below 50 kHz within 420 s. By adjusting the wavelength of the tunable laser source, a 280 MHz tuning range from 9.25 to 9.53 GHz is obtained. If an independent pump is introduced, a large tuning range is achieved from 9.4 to 24.9 GHz.

Performance Evaluation and Analysis of BeiDou In-Orbit Satellite Atomic Clocks Based on Multiple Source Data

Abstract: As a key payload, the performance of the satellite-based atomic clock will have an important impact on the whole navigation system. At present, the on-orbit performance evaluation of satellite-based atomic clocks is mainly based on the precise clock bias products released by IGS MGEX, iGMAS, and other organizations. Due to the influence of space environment changes, equipment aging, and other factors, there are gross errors in the clock bias data. In this paper, we propose a method of using SAIM clock monitoring telemetry data to assist in the detection and rejection of gross errors in the precision clock products, and then select the typical satellites C19, C20, C36, C37, C41, and C42 of Beidou-3 with different life spans to evaluate and analyze the in-orbit performance of rubidium atomic clocks. The multi-source data of Beidou-3 satellites are from 2019-01-01 to 2020-11-21. On this basis, the in-orbit performance of the rubidium atomic clock is analyzed and evaluated in terms of satellite clock stability, frequency accuracy, frequency drift rate, and other indicators. The evaluation results show that the Beidou C19, C20, C36, C37, C41, C42 satellites 10,000 s frequency stability reached the order of 10−14, frequency drift rate (days) overall in the order of 10−13, frequency accuracy overall in the order of 10−11.