Free-running Oscillator Research Articles

Multichannel microwave interferometer for the levitated dipole experiment

A four-channel microwave interferometer (center frequency: 60 GHz) has been constructed to measure plasma density profiles in the levitated dipole experiment (LDX). The LDX interferometer has a unique design owing to the unique geometry of LDX. The main design features of the interferometer are: (1) the transmitted beam traverses the plasma entirely in O-mode; (2) the interferometer is a heterodyne system employing two free-running oscillators; (3) four signals of data are received from just on transmitted beam; (4) phase shifts are detected in quadrature. Calibration tests demonstrate that the interferometer measures phase shifts with an uncertainty of approximately 5 degrees . Plasma densities in LDX corresponding to phase shifts of up to 5pi are routinely and successfully measured.

A Tail-Injected Divide-by-4 SiGe HBT Injection Locked Frequency Divider

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This letter presents a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) divide-by-4 injection locked frequency divider (ILFD). The ILFD is based on a single-stage voltage-controlled oscillator with active-inductor, and was fabricated in the 0.35 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex> </formula>m SiGe 3P3M BiCMOS technology. The divide-by-4 function is performed by injecting a signal to the base of the tail HBT. Measurement results show that when the supply voltage <formula formulatype="inline"><tex Notation="TeX">${\rm V}_{\rm DD}$</tex></formula> is 3.1 V and the tuning voltage is tuned from 2.0 to 2.8 V, the divider free-running oscillation frequency is tunable from 2.12 to 2.76 GHz, and at the incident power of 0 dBm the operation range is about 1.15 GHz, from the incident frequency 8.55 to 9.7 GHz. The die area is 0.65<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex> </formula>0.435 mm<formula formulatype="inline"><tex Notation="TeX">$^{2}$</tex> </formula>. </para>

Cdc14-release Oscillation is Separable from Cell-cycle Progression, and Modulated by Clb-Cdk

A free-running Cyclin oscillator suggests that the oscillation of Cyclin dependent kinase(Cdk) activity can lead to periodicity of cell-cycle events. In budding yeast S. cerevisiae mitotic Cyclin activity is primarily antagonised by the phosphatase Cdc14 which is released from nucleolus in late mitosis and becomes active to promote exit from mitosis. We devised a quantitative assay to study the effect of B-Cyclin on Cdc14 localization. By introducing physiological concentration of nondegradable Clb2-kd into the cell, we found that Cdc14-localization status became oscillating and uncoupled from cell-cycle progression.

HBAR-Based 3.6 GHz oscillator with low power consumption and low phase noise

We have designed and built 2 oscillators at 1.2 and 3.6 GHz based on high-overtone bulk acoustic resonators (HBARs) for application in chip-scale atomic clocks (CSACs). The measured phase noise of the 3.6 GHz oscillator is -67 dBc/Hz at 300 Hz offset and -100 dBc/Hz at 10 kHz offset. The Allan deviation of the free-running oscillator is 1.5 x 10(-9) at one second integration time and the power consumption is 3.2 mW. The low phase noise allows the oscillator to be locked to a CSAC physics package without significantly degrading the clock performance.

A 52 $\mu$W Wake-Up Receiver With $-$72 dBm Sensitivity Using an Uncertain-IF Architecture

A dedicated wake-up receiver may be used in wireless sensor nodes to control duty cycle and reduce network latency. However, its power dissipation must be extremely low to minimize the power consumption of the overall link. This paper describes the design of a 2 GHz receiver using a novel ldquouncertain-IFrdquo architecture, which combines MEMS-based high-Q filtering and a free-running CMOS ring oscillator as the RF LO. The receiver prototype, implemented in 90 nm CMOS technology, achieves a sensitivity of -72 dBm at 100 kbps (10-3 bit error rate) while consuming just 52 muW from the 0.5 V supply.

Modeling the Injection-Locked Behavior of a Quantum Dash Semiconductor Laser

Using the conventional rate equations describing an injection-locked system, a novel modulation response function is derived, which implicitly incorporates nonlinear gain through the free-running relaxation oscillation frequency and damping rate of the slave laser. In this paper, it is shown that the model presented can be used to extract the characteristic parameters of the coupled system from experimental data. The number of fitting parameters in the model is reduced by determining the fundamental slave parameters through the conventional free-running response function; these parameters are considered to be constant during the curve-fitting of the injection-locked system. Furthermore, in order to reduce the number of possible solutions generated during the least-squares-fitting process, the remaining fitting parameters are tightly constrained based on the physical limits of the coupled system. By reducing the number of unknown fitting parameters and constraining the remaining terms, a stronger confidence in the extracted parameters is achieved. Using a series of response curves measured from an injection-locked quantum dash laser, characteristic parameters of the system are extracted and validity of the model is examined. The verified model is used to analyze the impact of the linewidth enhancement factor on the characteristics of the response function in the microwave domain.

On the Dynamics of Regenerative Frequency Dividers

A comprehensive analytical study of regenerative frequency dividers (RFD) is presented. The study includes two fundamental modes of operation in RFDs, namely locked (or stable) and quasi-locked modes, and the study also covers the transition from free-running oscillation to quasi-locked, and ultimately to locked operation mode. Differential equations characterizing the RFD behavior for both operation modes as well as the transition between the two are derived. An RFD circuit for Bluetooth applications was designed and fabricated in a 65-nm CMOS process with a supply voltage of 1.2 V. Measurement results of the RFD prototype verify the accuracy of the proposed analytical models

호흡 및 심박수 측정을 위한 비접촉 방식의 CW 바이오 레이더 시스템의 잡음 분석 및 측정

본 논문에서는 호흡 및 심박수 측정을 위한 CW 바이오 레이더 시스템의 잡음을 분석하고, 이 중 위상 잡음에 대한 측정 결과를 제시하였다. 바이오 레이더 시스템은 기존의 무선 통신 방식이나 RFID 시스템과 달리, 수신신호의 주파수 및 반송파 주파수간의 차가 수 Hz에 불과하며, 수신 신호의 레벨 역시 매우 작으므로 위상 잡음을 포함한 모든 잡음원의 영향을 분석하는 것이 매우 중요하다. 본 논문에서는 CW 방식의 바이오 레이더 시스템의 잡음을 시스템의 SNR 측면에서 그 영향을 정량적으로 분석하였고, 분석 결과로부터 송신 안테나와 수신안테나 사이의 누설 전력량에 의한 위상 잡음이 가장 큰 잡음원이 됨을 확인하였으며, 이는 위상 잡음의 거리상관 효과의 함수임을 확인하였다. 따라서 거리 상관 효과에 따른 위상 잡음을 측정하고 이론과 비교하였다. 측정 결과, 본 논문에서 제안한 위상 잡음 측정 방식이 반송파 주파수에 근접한 위상 잡음을 측정할 수 있음을 확인하였다. 이를 통해 50 cm의 인식 거리를 가지며 1 mW의 저출력에서 동작하는 2.4 GHz에서 바이오 레이더 시스템을 PLL 회로 없이 체계적으로 설계할 수 있었다. In this paper, we present a noise analysis and measurement results of a bio-radar system that can detect human heartbeat and respiration signals. The noise analysis including various phase noise effects is very important in designing the bio-radar system, since the frequency difference between the received signal and local oscillator is very small and the received power is very low. All of the noise components in a bio-radar system are considered from the point of view of SNR. From this analysis, it can be concluded that the phase noise due to antenna leakage is a dominant factor and is a function of range correlation. Therefore, the phase noise component with range correlation effect, which is the most important noise contribution, is measured using the measurement setup and compared with the calculated results. From the measurement results, our measurement setup can measure a closed-in phase noise of a free-running oscillator. Based on these results, it is possible to design a 2.4 GHz bio-radar system quantitatively which has a detection range of 50 cm and low power of 1 mW without additional PLL circuits.

Effects of frequency chirp on magnetron injection locking

The injection locking of a magnetron is theoretically analyzed when either the free running oscillator or the drive signal has a frequency chirp. It is found that complete phase locking of the signal cannot be achieved in either case. However, as long as the locking condition of Adler is well-satisfied instantaneously, a high degree of locking occurs during a major duration of the frequency chirps. The expected output phase variation is computed in terms of the noise in the free-running magnetron oscillator for the case of constant drive frequency.

Low-Cost Optoelectronic Self-Injection-Locked Oscillators

We demonstrate a new configuration for an optoelectronic self-injection-locked (SIL) oscillator, where a part of the electrical output signal is self-injected after passing through a long optical delay line for output phase-noise reduction. The SIL oscillator consists of an electrical free-running oscillator and a long optical feedback loop. For the compact and low cost configuration, the free-running oscillator is realized with an InP HPT-based monolithic oscillator and electrical-to-optical conversion is carried out by two low-speed and low-cost laser diodes. With this new configuration, we achieve more than 55-dB phase-noise reduction at 10-kHz frequency offset from the center frequency of about 10.8 GHz by injecting 8-dBm optical signals without using any high-speed optoelectronic components.

A digitally controlled 2.4-GHz oscillator in 65-nm CMOS

This paper presents a 2.4-GHz digitally controlled oscillator (DCO). The circuit is designed using a 65-nm six-metal CMOS technology with an operating voltage of 1.2 V. The DCO comprises an LC oscillator core and the digital interface logic. It has a frequency range of about 200 MHz covering the 2.4-GHz ISM band, with around 5 MHz available for frequency modulation. Its frequency quantization step is approximately 20 kHz, with a digital SigmaDelta-modulator used to allow a 5-bit fractional digital control and provide an effective frequency resolution better than 1 kHz. Its free running oscillation phase noise is -125 dBc/Hz at 1 MHz frequency offset with 4.8 mA biasing current. The power consumption is adjustable from 1.8 mW to 12 mW.

Clusia: Holy Grail and enigma

Clusia is the only genus with bona fide dicotyledonous trees performing Crassulacean acid metabolism (CAM). Clusia minor L. is extraordinarily flexible, being C(3)/CAM intermediate and expressing the photosynthetic modes C(3), CAM, CAM-cycling, and CAM-idling. C(3) photosynthesis and CAM can be observed simultaneously in two opposite leaves on a node and possibly even within the same leaf in the interveinal lamina and the major vein tissue, respectively. The relative activity of photosystem II (PhiPSII) indicating photosynthetic energy use, is larger under photorespiratory than under non-photorespiratory conditions due to the particular energy demand of photorespiration. The heterogeneity of PhiPSII over the leaves as visualized by chlorophyll fluorescence imaging in the C(3) mode is larger under non-photorespiratory conditions than under photorespiratory conditions. These observations indicate that photorespiration, presumably by its particular energy demand, synchronizes photosynthetic activity over the leaves. In the CAM mode, the heterogeneity of PhiPSII is more dependent on the transitions between CAM phases. Free-running circadian oscillations of photosynthesis are strongly dampened in both the C(3) and the CAM mode. Photorespiration is under circadian clock control in both the C(3) and the CAM mode. PhiPSII and the heterogeneity of PhiPSII oscillate in phase with CO(2) uptake and photorespiration only under non-photorespiratory conditions. Under photorespiratory conditions, PhiPSII does not oscillate and there is no heterogeneity, again indicating the stabilizing function of photorespiration. Plants acclimatized to perform CAM switch to C(3) photosynthesis during free-running oscillations while subjected to constant illumination.

Electrical Silencing of PDF Neurons Advances the Phase of non-PDF Clock Neurons inDrosophila

Drosophila clock neurons exhibit self-sustaining cellular oscillations that rely in part on rhythmic transcriptional feedback loops. We have previously determined that electrical silencing of the pigment dispersing factor (PDF)-expressing lateral-ventral (LN(V)) pacemaker subset of fly clock neurons via expression of an inward-rectifier K(+) channel (Kir2.1) severely disrupts free-running rhythms of locomotor activity-most flies are arrhythmic and those that are not exhibit weak short-period rhythms-and abolishes LN(V) molecular oscillation in constant darkness. PDF is known to be an important LN(V) output signal. Here we examine the effects of electrical silencing of the LN(V) pacemakers on molecular rhythms in other, nonsilenced, subsets of clock neurons. In contrast to previously described cell-autonomous abolition of free-running molecular rhythms, we find that electrical silencing of the LN(V) pacemakers via Kir2.1 expression does not impair molecular rhythms in LN(D), DN1, and DN2 subsets of clock neurons. However, free-running molecular rhythms in these non-LN(V) clock neurons occur with advanced phase. Electrical silencing of LN(V)s phenocopies PDF null mutation (pdf (01) ) at both behavioral and molecular levels except for the complete abolition of free-running cellular oscillation in the LN(V)s themselves. LN(V) electrically silenced or pdf 01 flies exhibit weak free-running behavioral rhythms with short period, and the molecular oscillation in non-LN(V) neurons phase advances in constant darkness. That LN( V) electrical silencing leads to the same behavioral and non-LN( V) molecular phenotypes as pdf 01 suggests that persistence of LN(V) molecular oscillation in pdf 01 flies has no functional effect, either on behavioral rhythms or on non-LN(V) molecular rhythms. We thus conclude that functionally relevant signals from LN(V)s to non-LN(V) clock neurons and other downstream targets rely both on PDF signaling and LN(V) electrical activity, and that LN( V)s do not ordinarily send functionally relevant signals via PDF-independent mechanisms.

A Model for Stability, Noise, and Angle Modulation Analysis of Injection-Locked Oscillators

A model is presented for an injection-locked oscillator. It is derived from a perturbation of the free-running oscillator steady state, which is accurately determined from a harmonic balance (HB) simulation. As a first application, the proposed model is used to trace the existing solutions of the injection-locked system and their stability. It is then extended to include the effect of noise on the stability. Finally, the injection-locked system performance is studied under phase modulation. Sinusoidal phase modulation is considered and the stability of the modulated solutions is examined by Floquet theory. The validity of the model is verified for a 4.422-GHz oscillator, by HB and envelope transient simulations, as well as measurements.

A $W$-band Injection-Locked Frequency Divider Using GaAs pHEMTs and Cascode Circuit Topology

This study presents a W-band injection-locked frequency divider (ILFD) with a wide locking range characteristic by using 0.15 mum GaAs pHEMT techniques. Based on the cascode circuit topology, the oscillation and the injection parts can be designed individually without the trade-off between the input matching and the oscillation condition. Including with a characteristic of the active capacitance in this ILFD, a free-running oscillation frequency about 50 GHz was obtained with a frequency tuning function, in which the tuning range was about 1.2 GHz (50.5-49.3 GHz). By injecting a signal of around 100 GHz into this ILFD, the maximum locking range was measured up to 400 MHz, while the injected power was set to -5 dBm under a 3 V supply with a power consumption of 21 mW in the ILFD core.

Intracellular Ca2+Regulates Free-Running Circadian Clock OscillationIn Vivo

Although circadian oscillation in dynamics of intracellular Ca2+ signals has been observed in both plant and animal cells, it has remained unknown whether Ca2+ signals play an in vivo role in cellular oscillation itself. To address this question, we modified the dynamics of intracellular Ca2+ signals in circadian pacemaker neurons in vivo by targeted expression of varying doses of a Ca2+ buffer protein in transgenic Drosophila melanogaster. Intracellular Ca2+ buffering in pacemaker neurons results in dose-dependent slowing of free-running behavioral rhythms, with average period >3 h longer than control at the highest dose. The rhythmic nuclear accumulation of a transcription factor known to be essential for cellular circadian oscillation is also slowed. We also determined that Ca2+ buffering interacts synergistically with genetic manipulations that interfere with either calmodulin or calmodulin-dependent protein kinase II function. These results suggest a role for intracellular Ca2+ signaling in regulating intrinsic cellular oscillation in vivo.

A New $X$-Band Low Phase-Noise Multiple-Device Oscillator Based on the Extended-Resonance Technique

A novel multiple-device oscillator based on the extended-resonance technique is proposed. This oscillator achieves low phase noise through optimizing the circuit's group delay. Based on this technique, an X-band four-device SiGe HBT oscillator has been designed, fabricated, and tested. The measured phase noise is - 119 dBc at 100-kHz offset frequency. To the authors' best knowledge, this oscillator shows the lowest phase-noise performance among other reported X-band microwave planar hybrid free-running oscillators.

Effects of Phase Noise on OFDM Systems With and Without PLL: Characterization and Compensation

In this paper, we propose an algorithm for suppressing intercarrier interference due to phase noise in coded orthogonal frequency division multiplexing (OFDM) systems. The algorithm approximates the phase-noise waveform by using a Fourier series approximation for the current phase-noise realization. Thereby, it cancels the effects of the phase noise beyond the standard common phase error correction used in contemporary OFDM standards. The algorithm requires that the correlation properties of the intercarrier interference are known. We calculate these properties in terms of the phase-noise spectral correlation matrix for both Wiener and Ornstein-Uhlenbeck phase-noise models, respectively. This modeling corresponds to a free-running oscillator, as well as a phase-locked loop realization of the local oscillator in orthogonal frequency division multiplexing transceivers. For both transceiver configurations, we investigate the performance of the proposed algorithm. It is demonstrated that the new algorithm achieves as much as one order of magnitude better performance in terms of packet/bit error rate when compared to a receiver with only the common phase error suppression.

Phase and Amplitude Noise Analysis in Microwave Oscillators Using Nodal Harmonic Balance

In this paper, a nodal harmonic balance (HB) formulation is presented for the phase and amplitude noise analysis of free-running oscillators. The implications of using different constraints in the resolution of the perturbed-oscillator equations are studied. The obtained formulation allows the prediction of the possible spectrum resonances without ill conditioning at low frequency offset from the carrier. The noise spectrum is meaningfully expressed in terms of the eigenvalues of a newly defined matrix, obtained from the linearization of the nodal HB system about the steady-state solution. The cases of real or complex-conjugate dominant eigenvalues are distinguished. The developed phase-noise formulation is extended to a system of two coupled oscillators. The phase and amplitude noise analyses have been applied to a push-push oscillator at 18 GHz, a bipolar oscillator at 1 GHz, and a coupled system of two field-effect transistor oscillators at 6 GHz.

On the Dynamics of Regenerative Frequency Dividers

A comprehensive analytical study of regenerative frequency dividers (RFD) is presented. The study includes two fundamental modes of operation in RFDs, namely locked (or stable) and quasi-locked modes, and the study also covers the transition from free-running oscillation to quasi-locked, and ultimately to locked operation mode. Differential equations characterizing the RFD behavior for both operation modes as well as the transition between the two are derived. An RFD circuit for Bluetooth applications was designed and fabricated in a 65-nm CMOS process with a supply voltage of 1.2 V. Measurement results of the RFD prototype verify the accuracy of the proposed analytical models