Temperature-compensated Crystal Oscillator Research Articles

Design of Light, Small, and High-precision Digital Servo Clock for LEO Constellation

Modern low earth orbit (LEO) satellite systems have placed increasingly stringent requirements on spaceborne time-frequency systems in the fields of constellation autonomous management, distributed synthetic aperture radar (SAR) imaging, and navigation time service. Admittedly, the original high-stability constant-temperature crystal oscillator and high-stability temperature-compensated crystal oscillator can no longer comply with the indicator requirements of clock source frequency characteristics and clock synchronization accuracy. Likewise, traditional satellites use atomic clocks (rubidium atomic clocks and cesium atomic clocks). On account of their inherent characteristics, the ground receiving system needs to observe and count the clock parameter characteristics for a long time after the satellite enters orbit and frequently modify the future working state parameters. The features of being expensive and bulky increase the operation and maintenance costs of the ground system and the complexity of engineering implementation. In this paper, a kind of light and small high-precision digital servo clock based on the deep coupling of the global navigation satellite system (GNSS) is designed for the LEO satellite constellation. The tame clock is deeply coupled with the GNSS navigation receiver, and the high precision time-frequency difference between the local clock frequency source and GNSS is obtained by using the carrier and pseudo-range measurement information of visible satellite and carrier phase measurement information of the receiver. It not only utilizes the short-term high stability of OCXO but also employs the long-term time-frequency maintenance ability of GNSS so that the tamed OCXO is locked in GNSS for a long time, which can achieve frequency calibration of local clock sources and long-term output to various space-borne systems. The system is small in size and low in power consumption, with output frequency stability better than 3E-13 (10000 s), accuracy better than ±2E-13, and timing accuracy better than ±10 ns, which is comparable to the key technical indexes of spaceborne miniaturized rubidium clocks, in line with the current demand of miniaturization, low power consumption, and low cost of LEO constellations.

A High Precision Analog Temperature Compensated Crystal Oscillator Using a New Temperature Compensated Multiplier

The development and application of various precision electronic devices require a large number of high-precision and low-cost temperature-compensated crystal oscillators (TCXO) to generate frequency references. In order to achieve higher compensation accuracy at lower cost, a new fully integrated analog-TCXO (ATCXO) is proposed in this paper. It uses an innovative temperature-compensated multiplier to generate cubic and quintic voltages. The experimental results show that it can achieve the ultra-high fitting of the frequency-temperature characteristic curve of the crystal. This effectively improves the compensation accuracy of the TCXO. The proposed ATCXO achieves a frequency stability of ± 0.8 ppm in the temperature range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40\,\,^{\circ }\text{C}$ </tex-math></inline-formula> to 95 °C. At the same time, the gain-temperature error of the proposed temperature compensated analog multiplier is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\le 0.13$ </tex-math></inline-formula> dB. This paper is based on SMIC 130 nm process, the core area of the chip is only 0.124 mm2. Multiple modules such as bandgap circuit, n-th power voltage generation circuit, summation circuit, gain control circuit and voltage controlled oscillator using variable capacitor array are integrated.

A Temperature-Compensated Crystal Oscillator With Piecewise Polynomial Varactor Compensation Achieving ±3.75-ppm Inaccuracy From −30°C to 90°C

This brief presents a low-complexity temperature-compensated crystal oscillator (TCXO). The frequency error compensation over temperature is realized by employing the proposed piecewise polynomial varactor (PPV). The PPV operation is determined by a temperature-dependent voltage generator. The temperature compensation is achieved without using an accurate mapping table and high-resolution data converters. In addition, an amplitude-control loop (ACL) is incorporated to maintain a stable XO operation under process, temperature, and supply voltage variations. This brief is fabricated in a 180-nm CMOS process. The frequency inaccuracy of the proposed 40-MHz TCXO is ±3.75 ppm from −30°C to 90 °C. Operating from a 1.8-V supply, the overall current consumption, including the proposed compensation and ACL, is 0.3 mA.

A 43 nW, 32 kHz, ±4.2 ppm Piecewise Linear Temperature-Compensated Crystal Oscillator With ΔΣ-Modulated Load Capacitance

This article describes an ultralow-power (ULP) temperature-compensated crystal oscillator (TCXO) with a pulsed-injection XO driver for IoT applications. Temperature compensation is achieved by changing the load capacitance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{L}$ </tex-math></inline-formula> ) between two values using a delta-sigma modulator ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \Sigma \text{M}$ </tex-math></inline-formula> ). The complex modulation profile across temperature is approximated as piecewise linear elements that is selected by a coarse temperature sensor. As a result, the power and area of fine-grain look-up tables (LUTs) or a polynomial engine used in prior works can be avoided. The proposed pulsed-injection XO driver that directly replenishes the energy of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{L}$ </tex-math></inline-formula> sustains the XO oscillation for the two different <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{L}$ </tex-math></inline-formula> states. Implemented in 40-nm CMOS, the proposed 32.768-kHz TCXO achieves an accuracy of ±4.2 ppm from −20 °C to 85 °C with just three-point trimming and an Allan deviation floor of 34 ppb while consuming 43 nW, which is an approximate 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> improvement over the recent state-of-the-art TCXOs.

In-orbit Timing Calibration of the Insight-Hard X-Ray Modulation Telescope

Abstract We describe the timing system and the timing calibration results of the three payloads on board the Insight-Hard X-ray Modulation Telescope (Insight-HXMT). These three payloads are the High Energy X-ray telescope (HE; 20–250 keV), the Medium Energy X-ray telescope (ME; 5–30 keV), and the Low Energy X-ray telescope (LE; 1–10 keV). We present a method to correct the temperature-dependent period response and the long-term variation of the onboard crystal oscillator, especially for ME, which does not carry a temperature-compensated crystal oscillator. The times of arrival (ToAs) of the Crab pulsar are measured to evaluate the accuracy of the timing system. As the ephemeris of the Crab pulsar given by the Jodrell Bank Observatory has systematic errors around (Rots et al. 2004) 40 μs, we use the quasi-simultaneous observations of the X-ray Timing Instrument (XTI) on board the Neutron star Interior Composition Explorer (NICER) to produce the Crab ephemerides and to verify the timing system of Insight-HXMT. The energy-dependent ToAs’ offsets relative to the NICER measurements including the physical and instrumental origins are about 24.7 μs, 10.1 μs, and 864.7 μs, and the systematic errors of the timing system are determined to be 12.1 μs, 8.6 μs, and 15.8 μs, for HE, ME, and LE, respectively.

Research on light source average wavelength and crystal oscillator frequency for reducing temperature error of the FOG scale factor

Based on the working principle of the digital closed-loop fiber optic gyroscope (FOG), a model for the influence of crystal oscillator frequency on scale factor (SF) temperature error is theoretically derived. Besides, the correlation between the two main light sources average wavelength and the SF temperature error is discussed. The experimental results show that both the crystal oscillator frequency and the light source average wavelength have a greater impact on the FOG SF temperature error. There is a cubic function relationship between crystal oscillator frequency and temperature, the temperature error of the SF is inversely proportional to the crystal oscillator frequency. Using a higher frequency temperature-compensated crystal oscillator, the frequency stability can be improved by two orders of magnitude, from 67.14 ppm to 0.22 ppm, the SF temperature error is also greatly reduced. The SF error is proportional to the relative change in wavelength, and the change caused by the temperature is of the same order of magnitude. Compared with the super luminescent diode (SLD) light source, the Erbium-doped fiber light source has higher average wavelength stability, the SF error caused by it is also smaller. The error can be reduced by 15 ppm and controlled at about 10 ppm after temperature compensation.

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

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.

Timing Calibration of the NuSTAR X-Ray Telescope

Abstract The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first focusing X-ray telescope in the hard X-ray (3–79 keV) band. Among the phenomena that can be studied in this energy band, some require high time resolution and stability: rotation-powered and accreting millisecond pulsars, fast variability from black holes and neutron stars, X-ray bursts, and more. Moreover, a good alignment of the timestamps of X-ray photons to UTC is key for multi-instrument studies of fast astrophysical processes. In this paper, we describe the timing calibration of the NuSTAR mission. In particular, we present a method to correct the temperature-dependent frequency response of the on-board temperature-compensated crystal oscillator. Together with measurements of the spacecraft clock offsets obtained during downlinks passes, this allows a precise characterization of the behavior of the oscillator. The calibrated NuSTAR event timestamps for a typical observation are shown to be accurate to a precision of ∼65 μs.

New Method for 100-MHz High-Frequency Temperature-Compensated Crystal Oscillator.

The implementation of high-performance and high-frequency temperature-compensated crystal oscillator (HFTCXO) still faces great challenges. In this article, a new temperature-compensation method for HFTCXO with closed-loop architecture is described. The sample of 100-MHz HFTCXO with the measured temperature stability of ±0.22ppm/-40 °C ~ +85 °C and the phase noise of -151 dBc/Hz@1 kHz and -163 dBc/Hz@10 kHz was designed. Experimental results show that this method can realize real-time high-precision temperature compensation of high-frequency crystal oscillator.

Research on control technology of RS422A differential time-unified signal

RS422A differential signal is a kind of bipolar pulse signal formed by level conversion of TTL signal through RS422A differential transmission device.Using shielded twisted pair transmission, the signal level is determined by the voltage difference between the two twisted pairs at the same time. It has the characteristics of long transmission distance and strong anti-interference ability.The time system signal is a standard RS422 differential signal, which plays an important role in the fire control system. The complex programmable logic device CPLD, the high-precision temperature-compensated crystal oscillator, and the standard RS422A differential transceiver device are used as the control device in this article. The control methods for generating, detecting, sending and receiving, adjusting the pulse width and synchronizing the timing signals are elaborated in detail.This method has the characteristics of simple circuit, high reliability, flexible control, high control accuracy, etc. It is widely used in fire control systems.

Two-way laser regeneration pseudocode rangefinder of intersatellite optical crosslink

The millimeter-level bidirectional long-distance asynchronous ranging has long been a huge challenge in the field of measurement and instrumentation. Correspondingly, a laser pseudocode ranging algorithm based on regenerative synchronization mechanism is proposed to address the problems obstructing precise distance measurement between asynchronous satellites. First, the synchronization strategy of a double-ended asynchronous terminal based on the regenerative pseudocode is discussed. Subsequently, we look at the algorithm of the generation, transmission, detection, and the code phase tracking loop, which forms the base of obtaining high precision of pseudocode ranging. On this basis, the error of laser pseudocode ranging link is analyzed, which mainly incorporates receiver noise and clock error. In terms of receiver noise, the influence of the photodetector carrier-to-noise ratio on random noise distribution is evaluated, and the design of receiver parameters is guided as such. As for the clock error, we look at the constraint relationship between the range and the precision under the action of the clock error, which provides the basis for the selection of the clock. Finally, the optimized system is tested when a double-ended laser link is set up in the laboratory. As a result, the comprehensive accuracy results of 3.47 mm systematic error and ±1.73 mm random error is obtained, and the long-scale measurement performance has been tested by the temperature-compensated crystal oscillator pulse frequency experiment. In conclusion, the experiment is consistent with the theory proposed in this study, which provides a theoretical and experimental basis for long-distance high-precision intersatellite ranging.

Performance of clock sources and their influence on time synchronization in wireless sensor networks

Wireless sensor networks require time synchronization, which is the coordination of events or actions to make a system operate in unison. In this work, real experiments and a theoretical analysis of the behavior of the clock sources, most used in wireless sensor networks, have been carried out. The experiments have been performed on two real platforms from two different manufacturers in real environments with sudden changes in temperature. Complementary metal-oxide-semiconductor oscillators have a low accuracy, bigger than 500 ppm, and a high dependency with temperature. External crystal oscillators have good accuracy, around 20 ppm, and are stable with temperature. Temperature-compensated crystal oscillators are very accurate, around 5 ppm, and the temperature has no influence in their drift. The use of phase-locked loop circuits minimizes the impact of temperature and stabilizes oscillators. We highlight and demonstrate the importance of the early stages of design, especially the selection of the clock source, because that decision has a great impact on the performance of the time synchronization in wireless sensor networks.

A design of ± 0.28 ppm temperature-compensated crystal oscillator in a 0.35 μm CMOS process

A high-performance temperature-compensated crystal oscillator (TCXO) is presented. This paper proposes a new temperature sensor with a Σ–Δ analog to digital converter, and a voltage-controlled crystal oscillator, respectively, using two sets of independent power supply. The presented TCXO is implemented in a 0.35 μm 2P3 M standard complementary metal-oxide semiconductor process at a power supply of 3.3 V, and the total power dissipation is 21 mW. Measurement results indicate that the designed TCXO achieves ± 16 ppm output frequency tuning range and 135, − 141 dBc/Hz phase noise at 1, 10 kHz frequency offset, respectively, by using a 40 MHz fundamental AT-cut crystal resonator. With the temperature compensation, the frequency deviation is within ± 0.28 ppm over − 40 °C to 85 °C.

Implementation of a Low-Cost Energy and Environment Monitoring System Based on a Hybrid Wireless Sensor Network

A low-cost hybrid wireless sensor network (WSN) that utilizes the 917 MHz band Wireless Smart Utility Network (Wi-SUN) and a 447 MHz band narrow bandwidth communication network is implemented for electric metering and room temperature, humidity, and CO2 gas measurements. A mesh network connection that is commonly utilized for the Internet of Things (IoT) is used for the Wi-SUN under the Contiki OS, and a star connection is used for the narrow bandwidth network. Both a duty-cycling receiver algorithm and a digitally controlled temperature-compensated crystal oscillator algorithm for frequency reference are implemented at the physical layer of the receiver to accomplish low-power and low-cost wireless sensor node design. A two-level temperature-compensation approach, in which first a fixed third-order curve and then a sample-based first-order curve are applied, is proposed using a conventional AT-cut quartz crystal resonator. The developed WSN is installed in a home and provides reliable data collection with low construction complexity and power consumption.

Temperature-compensated crystal oscillator simulation in stress compensated cut crystal resonators

Traditional quartz crystal frequency references include a large, power-starving, oven-controlled crystal oscillator (OCXO), which base stations favor because of their excellent stability. We simulated a temperature-compensated crystal oscillator (TCXO) in the stress-compensated cut (SC-cut) resonator using the C and B mode frequencies. Power-conscious base-station manufacturers use the compensation circuit combination of TCXOs. The large frequency change in the B mode will be employed in temperature compensation for the C mode. First, we examined the circuit that could drive the C mode and B mode by simulation at the same time.

A seafloor electromagnetic receiver for marine magnetotellurics and marine controlled-source electromagnetic sounding

In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that performs well and overcomes the abovementioned problems, we performed forward modeling of the E-field abnormal response and established the receiver’s characteristics. We describe the design optimization and the properties of each component, that is, low-noise induction coil sensor, low-noise Ag/AgCl electrode, low-noise chopper amplifier, digital temperature-compensated crystal oscillator module, acoustic telemetry modem, and burn wire system. Finally, we discuss the results of onshore and offshore field tests to show the effectiveness of the developed seafloor electromagnetic receiver and its performance: typical E-field noise of 0.12 nV/m/rt(Hz) at 0.5 Hz, dynamic range higher than 120 dB, clock drift lower than 1 ms/day, and continuous operation of at least 21 days.

100-MHz Low-Phase-Noise Microprocessor Temperature-Compensated Crystal Oscillator

An AT-cut third-overtone 100-MHz quartz crystal resonator was used to achieve a 100-MHz low-phase-noise voltage-controlled crystal oscillator prototype. The unloaded quality factor of the used resonator is about 132 K, and the equivalent dynamic capacitance is about 1.2 fF. For the characteristic of the large equivalent dynamic capacitance of the resonator, the design method and the actual measured data of the low-phase-noise oscillator prototype are given. An explanation of why larger equivalent dynamic capacitance and higher voltage-control sensitivity can lead to bad phase noise in half-bandwidth is given. The STM32F103RCT6 MCU is used to read the real-time data of temperature sensor of the microprocessor temperature-compensated crystal oscillator (MTCXO) and the real-time control voltage loading on the MTCXO. Therefore, the real-time communication between a personal computer and an MTCXO is achieved. The control voltage $V$ achieved in this way has already considered both the effect of the actual working condition of the MTCXO circuit and the effect of the MTCXO internal reference voltage that it is not accurate enough. After temperature compensation, the measured temperature performance of the 100-MHz low-phase-noise MTCXO are better than ±0.45 ppm/−30 °C –+50 ° C, and measured phase noise results are better than −157 dBc/Hz at 1 KHz and −170 dBc/Hz at 10 KHz.

Dynamics of temperature-frequency processes in multifrequency crystal oscillators with digital compensations of resonator performance instability

Design and construction peculiarities of multifrequency crystal oscillators technically invariant to temperature effects have been considered. The analysis of thermodynamic characteristics of multifrequency temperature-compensated crystal oscillators was performed in conditions of nonstationarity of the thermal behavior of piezoelectric resonator. The volume density of heat source was determined during the excitation of quartz crystal resonator. Thermodynamic processes occurring in multifrequency crystal oscillators were investigated at the stage of settling of quartz crystal resonator oscillations. The need of taking into account the thermodynamic component during the investigation of high-speed thermal processes taking place in quartz crystal resonators was proved. The efficiency of using a multifrequency-algorithmic approach for ensuring the invariance of piezoresonance devices was estimated. It was shown that the use of this approach makes it possible to essentially reduce the temperature instability of crystal oscillators and reduce the up time of these devices due to a more exact compensation of initial frequency drifts.

Wide dynamic range FPGA-based TDC for monitoring a trigger timing distribution system in linear accelerators

A new field-programmable gate array (FPGA)-based time-to-digital converter (TDC) with a wide dynamic range greater than 20ms has been developed to monitor the timing of various pulsed devices in the trigger timing distribution system of the KEKB injector linac for the Super KEK B-factory project. The pulsed devices are driven by feeding regular as well as any irregular (or event-based) timing pulses. The timing pulses are distributed to these pulsed devices along the linac beam line with fiber-optic links on the basis of the parameters to be set pulse-by-pulse in the event-based timing and control system within 20ms. For monitoring the timing as precisely as possible, a 16-ch FPGA-based TDC has been developed on a Xilinx Spartan-6 FPGA equipped on VME board with a resolution of 1ns. The resolution was achieved by applying a multisampling technique, and the accuracies were 2.6ns (rms) and less than 1ns (rms) within the dynamic ranges of 20ms and 7.5ms, respectively. The various nonlinear effects were improved by implementing a high-precision external clock with a built-in temperature-compensated crystal oscillator.

The low-power potential of oven-controlled mems oscillators

It is shown that oven-controlled micro electromechanical systems (MEMS) oscillators have the potential of attaining a higher frequency stability, with a lower power consumption, than temperature-compensated crystal oscillators (TCXOs) and the currently manufactured MEMS oscillators.