Pulse Jitter Research Articles

Research of Radar Waveform Based on Pulse Position Jitter and Relative LPI Performance Analysis

The low probability of intercept (LPI) radar waveform is reflected in a lower pulse power and complex structure of the pulse series. The previous one ensures that it avoids being intercepted by the electronic measures system (ESM) carried by the goal; the latter makes it difficult for ESM to separate and identify. As for pulse position jitter pulse array, because of pulse position's random jitter in a specific pulse interval of the pulse repetition interval (PRI), the spectrum broadens and spectral density reduces, making it hard for the ESM to intercept. Meanwhile, because the waveform doesn't have a fixed PRI, it's also difficult to be sorted or identified Therefore pulse position jitter waveform is a rational LPI waveform. Combined with a design about the LPI radar signal waveform, this paper carries out a research on PRI jitter waveform, and provides a waveform generating and echo signal processing method; then the paper simulates the LPI characteristics and comes to a conclusion which has an important applying value .

40-GHz $S$-and $L$-Band Dual-Wavelength Pulse Source Using Fiber Optical Parametric Oscillator

We demonstrate a 40-GHz dual-wavelength pulse source in S-and L-band on the basis of harmonically mode-locked fiber optical parametric oscillator. Through leveraging, a 150-m highly-nonlinear dispersion-shifted fiber with a positive β(4), good quality, and low timing jitter pulse trains in both S- and L-band can be generated simultaneously. Its tuning range is as wide as 71 nm, from 1507 to 1542 nm and from 1570 to 1606 nm, with a wavelength span of ~100 nm. The proposed scheme has the potential to become an efficient high repetition rate pulse source for optical communication beyond conventional wavelength band.

Fiber optic picosecond laser pulse transmission line for hydrogen ion beam longitudinal profile measurement

We present a fiber optic laser pulse transmission line for nonintrusive longitudinal profile measurement of the hydrogen ion (H(-)) beam at the front-end of the Spallation Neutron Source accelerator. The 80.5 MHz, 2.5 ps, multikilowatt optical pulses are delivered to the accelerator beam line through a large-mode-area polarization-maintaining optical fiber to ensure high measurement stability. The transmission efficiency, output laser beam quality, pulse jitter, and pulse width broadening over a 30 m long fiber line are experimentally investigated. A successful measurement of the H(-) beam microbunch (~130 ps) profile is obtained. The experiment is the first demonstration to our knowledge of particle beam profile diagnostics using a fiber optic laser pulse transmission line.

Attosecond timing jitter pulse trains from semiconductor saturable absorber mode-locked Cr:LiSAF lasers

The timing jitter of optical pulse trains from diode-pumped, semiconductor saturable absorber mode-locked femtosecond Cr:LiSAF lasers is characterized by a single-crystal balanced optical cross-correlator with an equivalent sensitivity in phase noise of -235 dBc/Hz. The RMS timing jitter is 30 attoseconds integrated from 10 kHz to 50 MHz, the Nyquist frequency of the 100 MHz repetition rate oscillator. The AM-to-PM conversion induced excess phase noise is calculated and compared with experiment. The self-steepening effect is proven to be the dominant AM-to-PM coupling mechanism, whereas the semiconductor saturable absorber operation does not adversely affect timing jitter. The results show that ultrafast Cr:LiSAF lasers are promising compact and efficient ultralow-jitter sources.

Control of the repetition rate and reduction of the jitter of the pulses of passively Q-switched solid-state miniature lasers using periodic diode-pump modulation

Based on an extended point laser model, the lasing of passively Q-switched Nd : YAG minilasers has been numerically analysed. We have shown that periodically modulated diode pump may be used to control the pulse repetition rate and substantially reduce the timing pulse jitter. When the pump is modulated with rectangular pulses, switching from a high pump level to a low one upon generation of a successive laser pulse improves the stability of the pulse repetition rate relative to variations of the average pump level andbroadens the range of repetition frequencies whereby they may be locked to the pulse modulation frequency. The feasibility of lowering the timing jitter and locking the pulse repetition frequency to the pump modulation frequency has been confirmed experimentally. For repetition rates ∼1 kHz, the relative standard deviation of the pulse-repetition period is reduced from several percent for acontinuous pumping to 0.06 % by applying "truncation" of modulation pulses. The experimental results agree well with simulations.

Neural ITD coding with bilateral cochlear implants: effect of binaurally coherent jitter

Poor sensitivity to the interaural time difference (ITD) constrains the ability of human bilateral cochlear implant users to listen in everyday noisy acoustic environments. ITD sensitivity to periodic pulse trains degrades sharply with increasing pulse rate but can be restored at high pulse rates by jittering the interpulse intervals in a binaurally coherent manner (Laback and Majdak. Binaural jitter improves interaural time-difference sensitivity of cochlear implantees at high pulse rates. Proc Natl Acad Sci USA 105: 814-817, 2008). We investigated the neural basis of the jitter effect by recording from single inferior colliculus (IC) neurons in bilaterally implanted, anesthetized cats. Neural responses to trains of biphasic pulses were measured as a function of pulse rate, jitter, and ITD. An effect of jitter on neural responses was most prominent for pulse rates above 300 pulses/s. High-rate periodic trains evoked only an onset response in most IC neurons, but introducing jitter increased ongoing firing rates in about half of these neurons. Neurons that had sustained responses to jittered high-rate pulse trains showed ITD tuning comparable with that produced by low-rate periodic pulse trains. Thus, jitter appears to improve neural ITD sensitivity by restoring sustained firing in many IC neurons. The effect of jitter on IC responses is qualitatively consistent with human psychophysics. Action potentials tended to occur reproducibly at sparse, preferred times across repeated presentations of high-rate jittered pulse trains. Spike triggered averaging of responses to jittered pulse trains revealed that firing was triggered by very short interpulse intervals. This suggests it may be possible to restore ITD sensitivity to periodic carriers by simply inserting short interpulse intervals at select times.

Single-Event Soft Errors in CMOS Logic

In this article, various mechanisms for combinational logic-related radiation induced soft errors such as SE-induced soft delays, SE clock jitter and clock pulse, and SE crosstalk effects have been discussed. Our analysis shows that increasing SE crosstalk noise and delay effects occur with smaller technologies. This work has finally discussed hardening techniques for SE crosstalk noise and delay. Results are shown using HSpice Simulations with interconnect and device parameters derived from Predictive Technology Model for 65 nm.

Profile-shape stability and phase-jitter analyses of millisecond pulsars

Millisecond pulsars (MSPs) have been studied in detail since their discovery in 1982. The integrated pulse profiles of MSPs appear to be stable, which enables precision monitoring of the pulse times of arrival (TOAs). However, for individual pulses the shape and arrival phase can vary dramatically, which is known as pulse jitter. In this paper, we investigate the stability of integrated pulse profiles for 5 MSPs, and estimate the amount of jitter for PSR J0437-4715. We do not detect intrinsic profile shape variation based on integration times from ~10 to ~100 s with the provided instrumental sensitivity. For PSR J0437-4715 we calculate the jitter parameter to be f_J=0.067+-0.002, and demonstrate that the result is not significantly affected by instrumental TOA uncertainties. Jitter noise is also found to be independent of observing frequency and bandwidth around 1.4 GHz on frequency scales of <100 MHz, which supports the idea that pulses within narrow frequency scale are equally jittered. In addition, we point out that pulse jitter would limit TOA calculation for the timing observations with future telescopes like the Square Kilometre Array and the Five hundred metre Aperture Spherical Telescope. A quantitative understanding of pulse profile stability and the contribution of jitter would enable improved TOA calculations, which are essential for the ongoing endeavours in pulsar timing, such as the detection of the stochastic gravitational wave background.

Single-cycle radio-frequency pulse generation by an optoelectronic oscillator

We demonstrate experimentally passive mode-locking of an optoelectronic oscillator which generates a single-cycle radio-frequency pulse train. The measured pulse to pulse jitter was less than 5 ppm of the round-trip duration. The pulse waveform was repeated each round-trip. This result indicates that the relative phase between the pulse envelope and the carrier wave is autonomously locked. The results demonstrate, for the first time, that single-cycle pulses can be directly generated by a passive mode-locked oscillator. The passive mode-locked optoelectronic oscillator is important for developing novel radars and radio-frequency pulsed sources and it enables studying directly the physics of single-cycle pulse generation.

A Novel Hardware-Based All-Digital Phase-Locked Loop Applied to Grid-Connected Power Converters

For grid-connected power converters, the frequency and phase angle of the grid voltage, which are essential to the system operations, must be quickly and accurately obtained even if the utility voltage is distorted or unbalanced. In this paper, a novel hardware-based all-digital phase-locked loop (ADPLL) is proposed for grid interface converters to detect the frequency and phase angle based on the voltage zero crossings. The proposed ADPLL features wide track-in range and fast pull-in time, and it can easily be integrated with the digital controller for grid-connected power converters. A discrete small-signal model is presented to investigate the performance and parameter dependence of the ADPLL. As expected, the output phase error and pulse jitter are minimized by selecting a high clock frequency and proper regulator parameters. With additional voltage sensors, the ADPLL can be readily extended into applications with grid disturbances. Experimental results verify the analysis and the effectiveness of the ADPLL.

Automated Noise Measurement System for Radar and EW Transmitter Components

AbstractThe development of a 2–18 GHz instrument for radar and electronic warfare (EW) transmitter test and measurement is reported. The transmitter component analyzer was developed by NSWC Crane to measure critical performance parameters of the AN/SPY‐1 radar's components. Typical measurements include clutter attenuation, clutter improvement factor, intrapulse noise, moving target indicator residues, random pulse jitter, systematic pulse jitter, phase noise, and amplitude noise.

Reduction of Parametric Amplified Noise in Nonlinear Fiber Channels by Use of Wiener Filtering

As a parametric amplified noise, nonlinear phase noise limits the channel capacity in multispan fiber-optics transmissions. In this paper, the reduction of nonlinear phase noise by use of Wiener filtering is studied. Extracting signal from time-domain concepts, parametric amplified noise covering signal spectrum in frequency domain can be suppressed considerably. Timing jitter and ghost pulses due to intrachannel nonlinearities can also be compensated. Nonparametric Wiener filtering is used at the end of six configurations of dispersion compensation (DC) transmission lines: pre- and postlumped DC, distributed DC without optical phase conjugation (OPC), dispersion inversion (DI) about midlink OPC with, respectively, one-for-multispan, single type span and alternate type span on each side of OPC. It is found that single-DI and alternate-DI schemes have higher input power capacity than one-for-multi-DI scheme. Further reductions in the nonlinear phase noise accumulation for all these DC maps are obtained with Wiener filtering, and higher absolute dispersion can decrease signal fluctuation due to nonlinear phase noise, as well.

Low-Time-Jitter Short-Pulse Generator Using Compact Gain-Switching Laser Diode Module With Optical Feedback Fiber Line

On the basis of a self-pulse feedback mechanism, an ultralow-time-jitter and flexible repetitious rate optical pulse generator module with a simple and compact design was developed. Using a compact design self-seeding distributed feedback laser diode module, a low time jitter pulse on the order of sub-picoseconds was successfully observed within any modulation frequency range from 1 to 2 GHz. A pulse compression technique based on the nonlinear effect in optical fiber was used. A pulse width of 1.9 ps and a jitter of 0.5 ps were obtained with neither waveform degradation nor jitter increase.

FIRST SIMULATIONS RESULTS ON LASER PULSE JITTER AND MICROBUNCHING INSTABILITY AT SPARXINO

In the frame of the R&amp;D activity foreseen for the first phase of the SPARX project, the SPARXINO test facility is meant to provide an ultra-high electron beam at 1.2-1.5 GeV, able to drive SASE and seeded FEL experiments in the 10-3 nm range. The proposed layout is analyzed regarding its sensitivity to laser pulse jitter effects and microbunching instability limitations. First simulation results are presented.

Effects of synchronization of laser induced fluorescence and corona induced fluorescence in a pulsed corona reactor

Corona-induced fluorescence (CIF) of nitric oxide (NO) reveals that NO(A/sup 2//spl Sigma//sup +/) is primarily excited through N/sub 2/(A/sup 3//spl Sigma//sub u//sup +/) produced in a pulsed corona rector (PCR). The charge voltage in PCR, the time delay of the high-voltage pulse applied to the reactor, and its time jitter vary from gas composition to gas composition. This is because the reactor electric equivalent resistance in an OFF state has different values for different gas components. The PCR pulse jitter, typically a few tenths of a microsecond, for the same gas composition, varies with the frequency of high-voltage pulses due to changes in feed composition. A precise time synchronization of CIF with the laser induced fluorescence (LIF), the intensified charge-coupled device (ICCD) detector and the PCR pulse reveals that NO molecules stay in the vibrational levels of the ground state for about 700 /spl mu/s.

Combination of all-optical 2R signal regeneration with fiber-based retiming

We present all-optical signal regeneration using fiber-based retiming to overcome limitation by intrachannel cross-phase modulation-induced timing jitter in 2R regenerated transmission systems. As timing shifts of the optical pulses depend on the sign of the accumulated dispersion, timing jitter can be balanced out by a short piece of fiber with inverse sign of accumulated dispersion as the preceding transmission span. Timing jitter is cancelled out completely. Remaining amplitude jitter and ghost pulses are reduced by 2R-regeneration based on self-phase modulation. Limitation by amplitude jitter of the retiming stage and limitation by timing jitter of the 2R-regeneration cancel out each other. Numerical simulations show that maximum transmission distance is enhanced significantly.

Experimental study of X-pinch in a submicrosecond regime

X-pinch plasmas are known as point-like X-ray sources with the potential application for backlighting diagnostics. X-pinches are commonly driven by large pulsed power generators delivering high-voltage pulses with short rise-times, typically under 100 ns. When operating with slower capacitor banks, X-pinches become less reliable because of the arising X-ray pulse jitter and because of the appearance of two or more X-ray bursts coming from multiple hot spots. In this paper, a very compact inductance-capacitance (LC) generator with the current rise-time of 200 ns was used to drive molybdenum and tungsten wire X-pinches. A single peak, small shot-to-shot jitter emission of X-rays was obtained. Time-integrated penumbral imaging recorded the X-ray source dimension of less than 15 /spl mu/m in the spectral region above 2.4 keV. The total yield of more than 80 mJ was registered with the radiation pulse duration as short as 1.5 ns. The appearance of single- or multiple-source core structures is discussed in correlation with used wire material and X-pinch torsion angle. The results confirm the possibility of using an X-pinch driven by a fast compact capacitor bank for backlighting applications.

Ultrahigh supermode noise suppressing ratio of a semiconductor optical amplifier filtered harmonically mode-locked Erbium-doped fiber laser

The supermode noise suppressing ratio (SMSR) and the phase noise of a harmonically mode-locked Erbium-doped fiber laser (HML-EDFL) with an intra-cavity semiconductor optical amplifier (SOA) and an optical band-pass filter (OBPF) are improved and compared with a state-of-the-art Fabry-Perot laser diode (FPLD) injection-mode-locked EDFL. By driving the intra-cavity SOA based high-pass filter at unitary gain condition, the SMSR of the HML-EDFL is enhanced to 82 dB at the cost of degrading phase noise, increasing jitter, and broadened pulse width. The adding of OBPF further improves the SMSR, pulse width, phase noise, and jitter of the SOA-filtered HML-EDFL to 90 dB, 42 ps, -112 dBc/Hz, and 0.7 ps, respectively. The ultrahigh SMSR of the SOA-filtered HML-EDFL can compete with that of the FPLD injection-mode-locked EDFL without sacrificing its pulse width and jitter performances.

Passively mode-locked glass waveguide laser with 14-fs timing jitter.

Ultralow jitter pulse trains are produced from a passively mode-locked, erbium/ytterbium co-doped, planar waveguide laser by use of high-bandwidth feedback control acting on the physical cavity length and optical pump power. Synchronization of a 750-MHz, fundamentally mode-locked laser to an external clock signal yields an ultralow, root-mean-square relative timing jitter of 14.4 fs integrated from 10 Hz to the Nyquist frequency of 375 MHz.

Synchronization of two passively mode-locked, picosecond lasers within 20 fs for coherent anti-Stokes Raman scattering microscopy

We report on the synchronization of two commercial picosecond Ti:sapphire lasers with unprecedented low temporal jitter between the pulse trains. Pulse jitter is reduced from a few picoseconds to 20 fs with a stability of several hours. The technology enabling the tight pulse synchronization is reviewed in this article. We demonstrate the usefulness of the synchronization scheme by applying the technique to coherent anti-Stokes Raman scattering (CARS) microscopy. It is shown that CARS images can be acquired with a significant improvement in signal-to-noise ratio. This level of performance brings the fluctuations of the CARS signal down to the fundamental photon shot-noise limit. We present detailed statistical analysis of the pulse jitter and CARS noise along with enhanced CARS vibrational images of polymer beads.