Phase-locked Oscillator Research Articles

Specifying Upper Bounds on Phase Noise in Phase-Locked Oscillators in Electronic Warfare Systems–Part I [Application Notes

The purpose of this article is to present simple relations that allow one to find the upper bound on the phase noise of a phase-locked oscillator (PLO), its frequency stability, mean-square incidental phase noise modulation (Φ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and phase jitter. Simple closed-form equations are derived that are not intend ed as design tools, but are intended to establish upper limit specifications for the phase noise levels of PLOs used in wideband electronic attack (EA) and electronic warfare (EW) systems. A block diagram of a hypothetical system is used to illustrate how an EA system is susceptible to degradation due to phase noise of PLOs. This part presents a technique to model the phase noise spectral density of a manufacturer's PLO. Based on the manufacturer's specifications, the model allows the prediction of the total phase noise, phase jitter and predicted frequency uncertainty (Allan Variance) of the PLO considered. Part II (to appear in the February 2012 issue of IEEE Microwave Magazine) will present a technique to calculate the common-mode coupling of the oscillator phase noise into the following intermedi ate frequency (IF) section of a mixer. The coupled noise may increase the noise figure of a receiver. A method to estimate the increase in phase noise due to vibration will also be presented. Some basic definitions and performance characteristics are described in "Performance Metrics for Electronic Warfare Receivers".

Towards the observation of phase-locked Bloch oscillations in arrays of small Josephson junctions

We have designed an experiment and performed extensive simulations and preliminary measurements to identify a set of realistic circuit parameters that should allow the observation of constant-current steps at I=2ef in short arrays of small Josephson junctions under external AC drive of frequency f. Observation of these steps demonstrating phase lock of the Bloch oscillations with the external drive requires a high-impedance environment for the array, which is provided by on-chip resistors close to the junctions. We show that the width and shape of the steps crucially depend on the shape of the drive and the electron temperature in the resistors.

Analysis of synchronized regimes for injection-locked spin-transfer nano-oscillators

The large-angle magnetization dynamics of an injection-locked spin-transfer nano-oscillator (STNO) is studied. The magnetic system is subject to the action of time-varying spin-polarized currents and external magnetic fields. The uniform mode theory is developed and describes the hysteretic synchronization mechanism in terms of bifurcations of equilibria and limit cycles of appropriate dynamical systems. Analytical predictions of control parameters for the synchronization between the magnetization self-oscillation and the external microwave excitations (current, field) are provided. The effect of temperature on the locking band and the hysteretic character of the oscillation response is analyzed. An analytical approach is developed to determine the thermally induced sidebands in the power spectral density of phase-locked oscillations as a function of control parameters. The analytical predictions are in good agreement with the results of numerical simulations.

Research on Processing Techniques of Logging-While-Drilling Signal Based on BPSK Continuous Wave

The system of Logging-While-Drilling based on BPSK continuous wave is important for horizontal well prospecting. In this paper, the processing techniques of BPSK signal received on the ground have been studied. However, it is difficult to acquire the useful signals, since including most of reflective and mud pump noises. Based on the signal’s characteristic of sine, a new difference filter method, which is in the time field, is put forward. The method combines with the band-pass filter, which is in the frequency field, to reject the noises. Costas phase-locked loop technology and number control oscillator have been used in decoding technology, which can demodulate phase information and decode the BPSK signal. By the analyses in theory and experiment, the signal can be correctly decoded.

Bifurcation, amplitude death and oscillation patterns in a system of three coupled van der Pol oscillators with diffusively delayed velocity coupling

In this paper, we study a system of three coupled van der Pol oscillators that are coupled through the damping terms. Hopf bifurcations and amplitude death induced by the coupling time delay are first investigated by analyzing the related characteristic equation. Then the oscillation patterns of these bifurcating periodic oscillations are determined and we find that there are two kinds of critical values of the coupling time delay: one is related to the synchronous periodic oscillations, the other is related to eight branches of asynchronous periodic solutions bifurcating simultaneously from the zero solution. The stability of these bifurcating periodic solutions are also explicitly determined by calculating the normal forms on center manifolds, and the stable synchronous and stable phase-locked periodic solutions are found. Finally, some numerical simulations are employed to illustrate and extend our obtained theoretical results and numerical studies also describe the switches of stable synchronous and phase-locked periodic oscillations.

A wavelet-based method for measuring the oscillatory dynamics of resting-state functional connectivity in MEG

Determining the dynamics of functional connectivity is critical for understanding the brain. Recent functional magnetic resonance imaging (fMRI) studies demonstrate that measuring correlations between brain regions in resting-state activity can be used to reveal intrinsic neural networks. To study the oscillatory dynamics that underlie intrinsic functional connectivity between regions requires high temporal resolution measures of electrophysiological brain activity, such as magnetoencephalography (MEG). However, there is a lack of consensus as to the best method for examining connectivity in resting-state MEG data. Here we adapted a wavelet-based method for measuring phase-locking with respect to the frequency of neural oscillations. This method employs anatomical MRI information combined with MEG data using the minimum norm estimate inverse solution to produce functional connectivity maps from a “seed” region to all other locations on the cortical surface at any and all frequencies of interest. We test this method by simulating phase-locked oscillations at various points on the cortical surface, which illustrates a substantial artifact that results from imperfections in the inverse solution. We demonstrate that normalizing resting-state MEG data using phase-locking values computed on empty room data reduces much of the effects of this artifact. We then use this method with eight subjects to reveal intrinsic interhemispheric connectivity in the auditory network in the alpha frequency band in a silent environment. This spectral resting-state functional connectivity imaging method may allow us to better understand the oscillatory dynamics underlying intrinsic functional connectivity in the human brain.

Experimental Compensation for FWM Induced Crosstalk with Digital Coherent Detection

Four-wave mixing (FWM) compensation using digital coherent detection is experimentally demonstrated. Two lights and the induced FWM components are combined with phase-locked local oscillator lights and received individually. The received signals are combined electrically and the signal-to-FWM crosstalk ratio is improved to more than 30dB by backward propagation.

Dynamics of directed interactions between brain regions during interburst–burst EEG patterns in quiet sleep of full-term neonates

The study investigates time-variant directed interactions between brain regions during the interburst–burst EEG pattern (tracé alternant) characteristic of quiet sleep in healthy neonates. The transition from interburst to burst is of particular interest as the generation of the EEG characteristics at burst onset reflects timing and time-variant interplay between the cortical and the thalamo-cortical brain structures. To study the dynamics of the interactions, time-variant partial directed coherence (PDC), a measure of effective connectivity, was used which allows analysis in the time–frequency range. The main results of the grand mean PDC analysis are: (1) PDC time–frequency patterns are frequently associated with phase-locked oscillations. (2) Interhemispheric interactions are dominant between frontal, central and occipital electrodes and intrahemispheric interactions are much less substantial. (3) An interaction breakdown for the frequency ranges 1–4Hz (Fp1⇒Fp2) and 0.5–3Hz (Fp2⇒Fp1) exists which lasts about 2.5s and which is located at about burst onset. (4) Strong interactions in the high-frequency range 3.5–4.5Hz between the frontal electrodes can be observed for both directions at the burst onset. It can be concluded that the evolution of strong interactions in the high-frequency range, which starts shortly before or at the burst onset from frontal regions to anteroposterior directions as well as the frontal interhemispheric interactions, are associated with the burst onset generation. Additionally, the collapsing of the interactions before burst onset and after the burst are indicative of neuronal reorganisation processes.

Analysis and Design of Open-Loop Multiphase Local-Oscillator Generator for Wireless Applications

Multiphase local-oscillator (LO) generators have been widely adopted in modern wireless communication systems. This paper describes the analysis and design of two open-loop multiphase (quadri and octave) LO generators, which can lead to speed relaxation of the phase-locked loop and voltage-controlled oscillator when compared with conventional frequency-division methods. The mathematical model, sizing considerations, and two design examples targeting mobile-TV applications are presented. The first one is an octave-phase LO generator designed in 90-nm CMOS featuring multiple switchable phase correctors in cascade. It covers the VHF-III and UHF bands with an optimized phase precision within 0.8° . The second one combines quadri- and octave-phase LO generation to cover the full band of mobile TV from 170 to 1700 MHz. Optimized in 65-nm CMOS, it can be operated in octave-phase mode for image-reject harmonic-reject downconversion or in quadri-phase mode for simple image-reject downconversion. Extensive simulations accounting for process variations show that the achieved phase precisions are within 1.5° (quadri) and 1° (octave). The phase-noise performance is comparable with state-of-the-art solutions.

A Rigorous Analysis of a Phase-Locked Oscillator Under Injection

This study presents injection-pulling effects on a local oscillator (LO) for wireless applications. A discrete-time analysis is provided to predict output spectra of the LO pulled by a sinusoidal and angle-modulated injection signal. A phase-locked loop synthesizer with an injection signal is analyzed in frequency domain to account for the inherent bandpass filtering on the injection signal. In addition, a phase noise model is developed by using the proposed frequency-domain approach to characterize the overall phase noise of a phase-locked oscillator under injection. Comparison between theoretical predictions and experimental results shows excellent agreement.

Superstitious perceptions of a face revealed by non phase-locked gamma oscillations in the human brain

Superstitious perceptions of a face revealed by non phase-locked gamma oscillations in the human brain

Expiration: The moment we experience retronasal olfaction in flavor

Respiration is essential for smell perception. Previously we found that 8–12-Hz cortical rhythms were phase-locked to inspiration onset during the presentation of odor stimuli; this is referred to as inspiration phase-locked alpha band oscillation (I-α). Generators of I-α estimated with a dipole fitting model were found in the piriform, the entorhinal cortex (ENT), the amygdala (AMG), the hippocampus (HI) and the orbitofrontal cortex (OFC). Such olfactory perception is said to occur via the orthonasal olfaction route. Another route is the retronasal olfaction route. In this study, we investigated the link between respiration phase and retronasal olfactory perception. Electroencephalograph (EEG) and respiratory flows (separately measured with mouth and nose) were simultaneously recorded during stimulation of subjects’ tongues with liquids of chocolate, sucrose and water. The percentage of subjects correctly identifying the chocolate taste was higher when subjects were asked to breathe through the nose than when they were breathing through the mouth. In the averaged EEGs triggered by the onset of expiration measured from the flow through the nose, a 8–12-Hz oscillation was observed. Generators of this potential were found in the left ENT, HI, AMG and OFC in the order of milliseconds after expiration onset. Perception of retronasal olfaction is dependent on expiration, and combining retronasal olfactory information with gustatory information and somatosensation enable us to identify flavors when drinking and feeding.

Phase-Noise Measurement of Microwave Oscillators Using Phase-Shifterless Delay-Line Discriminator

In this paper, a modified method based on the frequency discriminator technique for measuring phase noise of microwave oscillators is presented. In the proposed method, the phase shifter is omitted. In contrast, a 90° hybrid with one more channel containing a phase detector, and a low-noise amplifier is added to the measurement setup. It can be said that an in-phase/quadrature phase-noise detection has been developed. With the proposed method, tuning of the variable phase shifter is not needed anymore. Therefore, the measurement is done automatically, and as a result, the measurement time is decreased. Another considerable advantage of this method is that the method is theoretically self-calibrated. For verifying the accuracy of the method, a measurement setup based on the proposed method was established. Two relatively low phase-noise phase-locked oscillators at frequencies of 2.8 and 4.9 GHz were designed. Their phase noise was measured by the proposed method, the conventional delay-line method, and the two-oscillator technique. Comparison of the measured data of the three methods shows the validity of the proposed method.

Fundamental wave phase-locked dual-band push-push DRO using out-of-phase Wilkinson power combiner

A new push-push phase-locked dielectric resonator oscillator (PLDRO) with dual-band (C/Ku) output capability is presented. An out-of-phase Wilkinson power combiner is used to provide the fundamental ( f 0 ) output. The phase-locking is implemented at f 0 as an alternative to direct locking the push-push output frequency (2 f 0 ) using prescalers. The push-push PLDRO has shown a fundamental suppression of 35.12 dBc and a second-harmonic suppression of 34.77 dBc at the 2 f 0 output and the f 0 output, respectively. Experimental results also indicate a maximum spur level of -77.4 dBc, and phase noise values of -109.6 and -143 dBc/Hz at 10 kHz and 1 MHz offsets, respectively, from a 12.6 GHz carrier.

Vibrational circular dichroism signal enhancement using self-heterodyning with elliptically polarized laser pulses

Vibrational circular dichroism (VCD) spectra were recorded using elliptically polarized ultrashort laser pulses, produced with the help of a photoelastic modulator. The short polarization axis of the elliptical light acts as a phase-locked local oscillator field, heterodyning the chiral signal generated by the field along the long polarization axis. This leads to VCD signals that increase linearly with the ellipticity of the probe pulses and enhanced signal to noise, which is expected to improve recently reported transient VCD scans. An analogous scheme allows for vibrational optical rotary dispersion measurements. The techniques are compared with similar approaches using both a linear response picture and the Jones matrix calculus.

X-Band 위성통신을 위한 고안정 위상 동기 발진기 구현

본 논문에서는 두 개의 위상 동기 루프를 구성하여 이중으로 위상 고정시킨 band 위성통신용 국부 발진기를 설계하고 위상 잡음을 분석하였다. 설계된 위상 동기 발진기는 직렬귀환 유전체 공진발진기, 주파수 분주기, 위상검출기, 루프 필터 및 PLL-IC로 구성되어 있으며, 12.6 GHz의 발진 주파수를 2분주시켜 6.3 GHz에서 15.32 dBm의 출력값을 보였다. 제작한 발진기의 위상 잡음은 -81 dBc/Hz@100 Hz, -100.86 dBc/Hz@1 kHz, -111.12 dBc/Hz@10 kHz, -116 dBc/Hz@100 kHz 및 -140.49 dBc/Hz@1 MHz으로 매우 안정되며 우수한 특성을 보였다. In this paper, X-band satellite communication oscillator of double phase locked is implemented by constructing a couple of phased-locked loop, and then we have analyzed the phase noise of designed PLL-DRO. The designed phase-locked oscillator is consist of series feedback DRO, frequency divider, phase detector, loop filter and programmable PLL-IC. By dividing oscillation frequency of 12.6 GHz into two frequencies, it exhibits output power of 15.32 dBm at 6.3 GHz. Phase noises of implemented oscillator are -81 dBc/Hz@100Hz, -100.86 dBc/Hz@1 kHz, -111.12 dBc/Hz@10 kHz, -116 dBc/Hz@100 kHz and -140.49 dBc/Hz@1 MHz respectively. These indicate excellent stable operation of oscillator and very good phase noise characteristics.

Phase Locked BWO System for Open Resonator Measurement in D-Band

The combination of a D-Band phase-locked backward-wave oscillator (BWO) with a spectrum analyzer for measurement of permittivity and low loss-tangent is presented. For measuring low loss tangent material, such as CVD diamond and high purity semi-insulating (HPSI) 4H-SiC , at millimeter wave ranges, it is necessary to precisely measure an increase of a few kHz in a line-width of 200 kHz. We describe a phase-locked loop with frequency conversion that combines a BWO source and a microwave spectrum analyzer to obtain line-width measurements with less than 2 kHz (less than 1%) standard deviation in D-Band millimeter wave.

Synthesis of Distributed Phase-Locked Oscillators

This paper describes a type of distributed oscillator which combines the functions of distributed amplifiers (DAs), distributed transversal filters (DTFs), and distributed mixers (DMs). Nonlinear feedback of the kind used in mode-locked laser (MLL) systems is used in order to obtain phase locking between the resonant frequencies within the oscillator. The theory of operation is given and a tuning procedure for the tap weights of the distributed oscillator aimed at achieving a desired state of oscillation is presented. The impact that the nonideal components of the oscillator have on its performance is discussed. Through simulation it is shown that the effects of transmission line loss, uneven tap weight spacing and terminal impedance mismatch can be mitigated by properly adjusting the tap weights of the oscillator. Examples of waveform synthesis are given in which different periodic waveforms are produced by the oscillator including those found in an MLL and a waveform suitable for impulse based ultra-wideband systems.

Effects of time-lagged niche construction on metapopulation dynamics and environmental heterogeneity

Time-delayed responses to environmental changes and disturbance can beget profound effects on the spatiotemporal dynamics of metapopulations. Here, we first examined the effect of three forms of time-lag (that is, equal-weight, recency and primacy effects) on population dynamics, using a spatially structured lattice model. The time-lag was incorporated in the niche construction process of the system (an organism–environment feedback). Using bifurcations diagrams and numerical simulations, we found that the time-lag can form a phase-locked oscillation. Three typical spatial patterns emerged: spiral wave, spiral-broken wave and circular wave. These spatial patterns gradually become immobile as a result of the self-organized ecological imprinting due to niche construction. Therefore, the phase-locked oscillation and the ecological imprinting process together determine the spatial structure of metapopulations and the environmental heterogeneity.

High-finesse displacement sensor and a theoretical accelerometer model based on a fiber Fabry-Perot interferometer

A displacement sensor based on the fiber Fabry-Perot (F-P) cavity was proposed in this paper. Theoretical and experimental analyses were presented. Displacement resolution was demonstrated by spectrum-domain experiments to obtain the dynamic range of the F-P sensor, and a piezoelectric crystal unit (PZT) was used as the driver. The output signal was modulated by a piezoelectric ceramic ring and demodulated by a phase-locked oscillator. The experimental results show that the displacement resolution of the F-P sensor is less than 5 nm and the dynamic range is more than 100 μm. As acceleration is the second-order differential of displacement, an accelerometer model was proposed using the finite element method (FEM) nd ANSYS software.