Voltage-controlled Crystal Oscillator Research Articles

Model-free adaptive frequency calibration for voltage-controlled oscillators

The operating frequency accuracy of the local oscillators is critical for the overall system performance in the communication systems. However, the high-precision oscillators could be too expensive for civil applications. In this paper, we propose a model-free adaptive frequency calibration framework for a voltage-controlled crystal oscillator (VCO) equipped with a time to digital converter (TDC), which can significantly improve the frequency accuracy of the VCO thus calibrated. The idea is to utilize a high-precision TDC to directly measure the VCO period which is then passed to a model-free method for working frequency calibration. One advantage of this method is that the working frequency calibration employs the system history of input/output (I/O) data, instead of establishing an accurate VCO voltage-controlled oscillator model. Another advantage is the lightweight calibration method with low complexity such that it can be implemented on an MCU with limited computation capabilities. Experimental results show that the proposed calibration method can improve the frequency accuracy of a VCO from ±20 ppm to ±10 ppb, which indicates the promise of the modelfree adaptive frequency calibrator for VCOs.

Technical Evaluation of Engineering Model of Ultra-Small Transmitter Mounted on Sweetpotato Hornworm

The authors are making a prototype flexible board of a radio-frequency transmitter for measuring an electromyogram (EMG) of a flying moth and plan to apply for an experimental station license from the Ministry of Internal Affairs and Communications of Japan in the summer of 2022. The goal is to create a continuous low-dose exposure standard that incorporates scientific and physiological functional assessments to replace the current standard based on lethal dose 50. This paper describes the technical evaluation of the hardware. The signal of a bipolar EMG electrode is amplified by an operational amplifier. This potential is added to a voltage-controlled crystal oscillator (27 MHz, bandwidth: 4 kHz), frequency-converted, and transmitted from an antenna about 10 cm long (diameter: 0.03 mm). The power source is a 1.55-V wristwatch battery that has a total weight of about 0.3 g (one dry battery and analog circuit) and an expected operating time of 20 minutes. The output power is −7 dBm and the effective isotropic radiated power is −40 dBm. The signal is received by a dual-whip antenna (2.15 dBi) at a distance of about 100 m from the moth. The link margin of the communication circuit is above 30 dB within 100 m. The concepts of this hardware and the measurement data are presented in this paper. This will be the first biological data transmission from a moth with an official license. In future, this telemetry system will improve the detection of physiological abnormalities of moths.

Clock tuning technique for a disciplined high medium–long-stability GNSS oscillator with precise clock drifts for LEO users

A crucial issue of low earth orbit (LEO) navigation augmentation satellite constellation is to obtain a satellite clock of high medium–long stability (i.e., averaging time of 10–10,000 s) using a disciplined oscillator to reduce satellite size, weight, power consumption and cost, instead of using a large, heavy and expensive space atomic clock. To resolve this difficulty, we propose a new global navigation satellite system (GNSS) clock discipline technique via a stand-alone GNSS receiver. Consequently, high medium–long stability can be attained with the disciplined receiver oscillator. Based on the Doppler measurements calculated from carrier phases, precise clock drifts of the receiver oscillator are derived. According to the motion state of the LEO GNSS receiver, a precise clock drift estimation model is chosen to have good adaptability to the receiver's high dynamic movement. Then, the receiver oscillator is properly tuned to its nominal frequency at each epoch without loss of lock. An automatic closed-loop frequency control system using a third-order frequency-locked loop filter is proposed to periodically compensate the instantaneous frequency offsets of the user clock with respect to its nominal frequency. A nonlinear frequency steering method is proposed to overcome the receiver lost lock problem during the oscillator discipline process. The correctness and effectiveness of the proposed clock tuning technique were numerically verified with MATLAB first. Then, the oscillator discipline performances were tested with a VCH-1008 passive hydrogen maser, a LEO GNSS receiver and a PicoTime clock stability analyzer. With static real GPS data of a static receiver as well as with hardware simulated data of a LEO receiver, both the medium-term and long-term frequency stabilities of the disciplined oscillator were confirmed. Finally, the proposed oscillator discipline technique was implemented in a self-developed LEO GNSS receiver. A high-quality voltage-controlled crystal oscillator mounted on an onboard LEO receiver was used for our test both in a static situation and in a LEO dynamic environment. The experiment results show that the overlapping Allan deviation of the disciplined GNSS oscillator could be less than 7E-12 over periods of 1 to 4,000 s in both the static situation and the LEO moving situation for a 1070 km orbit with 1 Hz epoch sampling rate at the testing stage.

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.

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.

A differential coupled frequency doubling voltage-controlled crystal oscillator in a 0.35 μm CMOS process

This paper presents a high-performance differential coupled frequency doubling voltage-controlled crystal oscillator (VCXO). Frequency doubling and low phase noise are realized through a novel gm-boosted differential Colpitts oscillator. Distributed varactor arrays are used to obtain wide frequency tuning range and high tuning linearity simultaneously. The proposed VCXO is fabricated in a 0.35 μm 2P3M standard complementary metal-oxide semiconductor process at a supply voltage of 3.3 V, and the power dissipation is 7 mW. Measurement results show that the designed VCXO achieves ±135 ppm output frequency variation range with 5 % linearity and ?133 dBc/Hz phase noise at 1 kHz frequency offset by using a 40 MHz fundamental AT-cut crystal resonator.

Design of Phase Identification System to Support Three-Phase Loading Balance of Distribution Feeders

In this paper, a phase identification system (PIS) is designed to incorporate a fuzzy microprocessor-based controller for phase measurement of underground transformers. The proposed fuzzy calibration algorithm used in the controller aims to solve the offset and gain of frequency deviation of the real-time clock, which was generated by a voltage-controlled crystal oscillator (VCXO) to maintain the timing lock with respect to the 1 pulse per second signal of the global positioning system before phase measurement is executed. According to the field test of the PIS design, the phase deviation of the real-time clock with embedded VCXO can be improved from 46.27° to 0.98° by applying the fuzzy calibration algorithm. The PIS has been applied for field measurement of underground distribution transformers to identify their phases and correct the corresponding attributes of the automated mapping faulty management (AM/FM) system in Taipower. By retrieving the information of the line segments and transformers from the AM/FM, the network modeling of distribution feeders is derived to analyze the three-phase unbalance. The rephasing strategy of laterals and distribution transformers has been derived and executed by Taipower engineers. By comparing the phase currents and neutral current of a test feeder before and after rephasing, the three-phase balance of the distribution system can be significantly enhanced with the PIS to identify the phasing of distribution transformers for deriving the rephasing strategy of the distribution feeders.

Ultrastable Frequency Dissemination via Optical Fiber at NICT

We have developed a radio-frequency (RF) dissemination system using optical fibers. The phase noise induced during the transmission is actively cancelled by the compensation system with a voltage-controlled crystal oscillator. A first proving test was conducted on an urban telecom fiber link with a length of 10 km, and a frequency stability of 1 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-17</sup> was achieved at an averaging time of one day. As an application of ultrastable frequency dissemination, a 1-GHz signal based on a cryogenic sapphire oscillator was transferred through a 25-km fiber and used as a microwave reference for an optical frequency comb. A fractional frequency stability of an ultranarrow clock laser for a Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion optical frequency standard was measured by the comb as 9 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> at 1 s, which included both laser stability and transferred reference stability.

High-frequency overtone TCXO based on mixing of dual crystal oscillators

To implement a high-stability and high-frequency overtone temperature-compensated crystal oscillator (TCXO) conveniently, an improved design of the novel overtone TCXO is described in this paper. A 120-MHz TCXO based on mixing of dual crystal oscillators is implemented. It utilizes a 100-MHz AT-cut 5th-overtone crystal oscillator mixed with a 20-MHz AT-cut voltage-controlled crystal oscillator (VCXO). The 120-MHz mixed product is filtered to produce the output signal. The total frequency deviation of 20-MHz and 100-MHz crystal oscillators is compensated by adjusting the output frequency of the 20-MHz oscillator to produce the stable 120-MHz output frequency. In this work, verifying experimental results of the compensation are presented. The stability of the experimental 120-MHz overtone TCXO with microprocessor temperature compensation achieves +/-2 X 10(-7) over the temperature range from -30 degrees C to +70 degrees C. A phase noise level of -133 dBc/Hz at 1 kHz offset has been initially measured for the prototype TCXO. The experimental result demonstrates this approach can conveniently implement the high-frequency overtone temperature compensation with a relatively high stability, and it is available for a wider frequency range as well.

Proposal for a Novel Remote Synchronization System for the On-Board Crystal Oscillator of the Quasi-Zenith Satellite System

ABSTRACT: A remote synchronization system for the on-board crystal oscillator (RESSOX) of the QZSS is proposed. Aimed at offering an alternative architecture for the classic GPS time-keeping system (TKS), the proposed system consists of a synchronization framework where an ultrastable atomic clock, localized at the ground station, is kept synchronized to a second time reference, a voltage-controlled crystal oscillator (VCXO), on-board the QZSS satellite. Based on orbit calculations and delay predictions, feedback and feed-forward control guarantee the correct synchronization of the on-board time reference and the ground-station atomic clock. Compared with the classic GPS TKS, the RESSOX scheme offers several advantages in terms of accuracy, cost, weight, and power consumption. An extensive explanation of this novel design is presented. Differences and advantages of the proposed system are compared with the classic atomic clock scheme.

A fully integrated zero-IF transceiver for GSM-GPRS quad-band application

A fully integrated GSM/GPRS quad-band transceiver is presented. It includes the receiver, the transmitter, the synthesizer, all necessary voltage-controlled oscillators, all loop filters, the voltage regulators, the voltage-controlled crystal oscillator, and the power amplifier controller. The chip meets all GSM specification. The design was done in a BiCMOS SiGe 0.35-μm technology and the die area is 14 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Analog frequency modulation detector for dynamic force microscopy

A new analog frequency modulation (FM) detector (demodulator) for dynamic force microscopy (DFM) is presented. The detector is designed for DFM by utilizing the FM detection method where the resonance frequency shift of the force sensor is kept constant to regulate the distance between a tip and a sample surface. The FM detector employs a phase-locked loop (PLL) circuit using a voltage-controlled crystal oscillator (VCXO) so that the thermal drift of the output signal is negligibly reduced. The PLL is used together with a frequency conversion (heterodyne) circuit allowing the FM detector to be used for a wide variety of force sensors with the resonance frequency ranging from 10 kHz to 10 MHz. The minimum detectable frequency shift was as small as 0.1 Hz at the detection bandwidth of 1 kHz. The detector can track a resonance frequency shift as large as 1 kHz. We also present some experimental results including the observations of the Si(111)-7×7 reconstructed surface and fullerene molecules deposited on the surface by DFM using this FM detector.

A 155-MHz clock recovery delay- and phase-locked loop

The authors describe a completely monolithic delay-locked loop (DLL) which may be used either by itself as a deskewing element or in conjunction with an external voltage-controlled crystal oscillator (VCXO) for a delay- and phase-locked loop (D/PLL) that enables jitter-peaking-free clock recovery by removing the zero from the forward path. The voltage-controlled phase shifter (VCPS) shifts incoming data under loop control to align the data with the clock. The loop amplifier is an integrator so that the DLL is first order. The bandwidth of the loop determines the frequencies over which input jitter may be tracked out. The phase detector is a pattern-and duty-cycle insensitive implementation. The higher-order poles provide additional filtering of phase-detector output ripple to further improve jitter accommodation. >

Design and implementation of a CMOS VCXO for FM stereo decoders

A circuit technique to simulate large variable capacitance of both positive and negative polarities over a given frequency range is discussed. The simulated capacitance can be varied by voltage control from -60 to +100 pF. The capacitor-simulating circuit is connected in parallel with a resonator to tune its parallel resonance. An oscillator with grounded resonator is also developed. Together with the variable capacitor, a voltage-controlled crystal oscillator (VCXO) is realized. The oscillation frequency of the oscillator can be tuned continuously from 452 to 461 kHz by voltage control. Detailed analyses to completely characterize the oscillator with a simple expression are presented. The prototype of the VCXO has been fabricated in a 4- mu m standard CMOS process.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gealas laser diode pumped cesium beam frequency standard

A laser diode pumped cesium beam frequency standard had been built. The laser diode used for both optical pumping and detection is frequency-locked at the 4-4 transition of Cs D2 line. The voltage controlled crystal oscillator (VCCO) frequency is locked to the center of the Ramsey pattern of the microwave clock transition after frequency multiplying and synthesizing. The preliminary measurement of the frequency stabilities shows that the results are in agreement with the theory, and better results could be achieved by further improving the frequency stability of the laser diode.

Synchronization Techniques for Digital Networks

A fault-tolerant network clock regenerator (NCR) will be analyzed, which consists of two digital phase-locked loops (DPLL), and which allows a dynamical configuration control and thus is able to meet CCITT's Recommendations concerning permissible slip rates, frequency inaccuracy, as well as phase jitter and wander. The network synchronization scheme will conform to the master-slave principle, in the course of which the reference clock is derived from a national caesium atomic oscillator as master. The NCR's mentioned before serve as slaves which are equipped with highly precise voltage-controlled crystal oscillators and proportional-integral working DPLL's. The results of a field trial in the long-distance communications network of the "Deutsche Bundespost (FRG)" are given and interpreted by a Random Walk Model which describes the time interval errors appearing. For future digital exchanges, an NCR with intelligent configuration control is introduced, which consists of two microprocessor-controlled digital phase-locked loops (MCDPLL) and which has comparable time stability characteristics as the double-DPLL mentioned above at half the circuit volume. Finally, the dominant advantages are shown which result from synchronizing broad-band services by intelligent NCR techniques.

The AR6A Single-Sideband Microwave Radio System: Microwave Carrier Supply

In the AR6A repeater bay, microwave carrier power for both the receiver and the transmitter is derived from a single voltage-controlled crystal oscillator. For long-term stability, this oscillator is phase locked to an external-reference frequency, available at each radio station. From the output signal of this oscillator, an active frequency-multiplier chain generates about +21 dBm power in the 6-GHz band. Part of this power serves as the local oscillator signal for the transmitter directly. The other part is shifted in frequency, to produce the local oscillator signal for the receiver.

New Microwave-Frequency Synthesizers that Exhibit Broader Bandwidths and Increased Spectral Purity

A superior microwave-frequency synthesis technique is treated in this paper, emphasizing improved spectral purity with octave bandwidths in the microwave region. The microwave-frequency synthesizer is discussed in two sections each corresponding to a system unit. The driver unit specifications are analyzed in the first section, showing its voltage-controlled crystal oscillator (VCXO) L(f ) output to be -130 dBc/Hz at 10 kHz. In the second section, the driver VCXO output is translated in the microwave unit to the final X-band frequency by means of a phase-locked loop. An analysis of this phase-locked loop, as described in this paper, shows the final L(f ) equal to -101 dBc/Hz at 10 kHz. Since a worst case situation was assumed, the final L(f ) is quite superior for octave bandwidth microwave-frequency synthesizers.

Comments on "Voltage-controlled crystal oscillators"

Comments on "Voltage-controlled crystal oscillators"

Frequency Stability Analysis of a Grounded-Base Voltage-Controlled Crystal Oscillator

The frequency stability is analyzed for a voltage-controlled grounded-base crystal oscillator by matrix algebra. The validity of the resulting equation was verified by measurements on an oscillator with a 110-MHz fifth-overtone quartz crystal. Sensitivity coefficients for the oscillator are computed with the aid of a time share computer program and its sweep range is drawn by a plotting routine.