String Of Pulses Research Articles

Gyrating solitons in a necklace of optical waveguides

We consider light pulses in a circular array of $2N$ coupled nonlinear optical waveguides. The waveguides are either hermitian or alternate gain and loss in a $\mathcal{PT}$-symmetric fashion. Simple patterns in the array include a ring of $2N$ pulses travelling abreast, and a breather -- a string of pulses where all even and all odd waveguides flash in turn. In addition, the structure displays solitons gyrating around the necklace by switching from one waveguide to the next. Some of the gyrating solitons are stable while other ones are weakly unstable and evolve into gyrating multiflash strings. By tuning the gain-loss coefficient, the gyration of solitons in a nonhermitian array may be reversed without changing the direction of their translational motion.

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2 ABSTRACT: Because of advances in solid state power devices and microprocessors pulse width modulation (PWM) is widely used in power electronics and variable speed drives to digitize the power signal so that a string of voltage pulses can be procreated by the electronic switching devices like choppers. The PWM technique has been the main choice in power inverters and DC to AC converters for decades. Forasmuch of its circuit naivety and disparate control scheme PWM technique is oftentimes used in power applications such as in motor controllers and inverters etc. The preferment of PWM rooted switching power converter upon linear power amplifier in view of lower power dissipation, easy to implement and control, no temperature variation and aging-caused drifting or degradation in linearity and Compatible with today's digital systems. Unexpectedly because of the uses of power converters and variable speed drivers neither the voltage nor the current waveform remains impeccable. They endure harmonic contamination in addition with power losses and high frequency noise. These harmonic must be removed or minimized in the system to curtail and detract harmful effect on power supply system. In this document the concept of Pulse Width Modulation (PWM) for single-phase inverters, operating principles and effect of harmonic are analyzed. The results are comprised with simulation results for a single-phase inverter.

A 10.2 Mbps Pulse Harmonic Modulation Based Transceiver for Implantable Medical Devices

A low power wireless transceiver has been presented for near-field data transmission across inductive telemetry links, which operates based on pulse harmonic modulation (PHM). This PHM transceiver uses on-off keying (OOK) of a pattern of pulses to suppress inter-symbol interference (ISI), and its characteristics are suitable for low-power high-bandwidth telemetry in implantable neuroprosthetic devices. To transmit each bit across a pair of high-Q LC-tank circuits, the PHM transmitter generates a string of narrow pulses with specific amplitudes and timing. Each pulse generates a decaying oscillation at the harmonic frequency that the receiver LC-tank is tuned at, which is then superimposed with other oscillations across the receiver at the same frequency, to minimize the ISI. This allows for reaching high data rates without reducing the inductive link quality factor (to extend its bandwidth), which significantly improves the range and selectivity of the link. The PHM receiver architecture is based on non-coherent energy detection with programmable bandwidth and adjustable gain. The PHM transceiver was fabricated in a 0.5- μm standard CMOS process, occupying 1.8 mm2. The transceiver achieved a measured 10.2 Mbps data rate with a bit error rate (BER) of 6.3×10-8 at 1 cm distance using planar implant sized (1 cm2) figure-8 coils. The PHM transmitter power consumption was 345 pJ/bit and 8.85 pJ/bit at 1 cm and zero link distances, respectively. The receiver dissipates 3 mW at 3.3 V supply voltage.

Research on a Pulsed Approach for Electrical Impedance Spectroscopy Measurement

For the application of electrical impedance spectroscopy to the anomaly detection of composite material component, a pulsed method for impedance spectroscopy measurement, different from the traditional swept frequency methods, is presented. A string of square-wave pulses is digitally generated as the exciting signal to the sensing electrodes. A step sampling method for collecting the instantaneous response current curves is realized on the basis of a field programmable gate array (FPGA) chip. The collected curves are further processed to obtain the impedance spectroscopy. Experiments are carried out for the measurement of electrical impedance spectroscopy of the demo electric circuits in order to verify the feasibility and practicability validity of the pulsed measurement system. The preliminary experimental results indicate that the pulsed measurement system can effectively extract the electrical impedance spectroscopy information of the detected object. The proposed approach is feasible and practicable for evaluating the electrical impedance spectroscopy of the detected object.

RESHAPING-INDUCED CONTROL OF CHAOS AND CRISIS PHENOMENA IN A DAMPED, PARAMETRICALLY DRIVEN PENDULUM

The behavior of a damped pendulum parametrically excited by a periodic string of symmetric pulses of finite width and amplitude is investigated. Analytical (Melnikov method) and numerical (bifurcation diagrams) results show that chaos and crises are reliably controlled over a wide range of parameters by hump-doubling of a parametric excitation which is initially formed by a periodic string of single-humped symmetric pulses. In particular, the analysis reveals that the chaotic threshold amplitude when altering solely the pulse shape presents a minimum as a single-humped pulse transforms into a double-humped pulse, the remaining parameters being held constant. Additionally, the mechanism underlying the hump-doubling-induced crises is discussed with the help of a two-dimensional map.

Excitation-Reshaping-Induced Chaotic Escape from a Potential Well

The chaotic escape of a nonlinearly damped oscillator excited by a periodic string of symmetric pulses from a cubic potential well is investigated. Analytical (Melnikov analysis) and numerical results show that chaotic escapes are typically induced over a wide range of parameters by hump-doubling of an external excitation which is initially formed by a periodic string of single-humped symmetric pulses. The role of a nonlinear damping term, proportional to the nth power of the velocity, on the hump-doubling scenario is also discussed.

A CMOS 1<tex>$times$</tex>–16<tex>$times$</tex>Speed DVD Write Channel IC

Optical recording demands a meticulous write strategy to control the laser beam power and regulate the phase change layer temperature tightly. The width, height, and delay of a string of short pulses applied to the laser diode need to be adjusted in fine steps, and the writing speed varies widely per applications. A multi-phase phase-locked loop (PLL) tracks a wide range of clock frequencies, and provides a low-jitter time base for write pulses. With two enabling circuit concepts, PLL loop filter voltage folding/unfolding and switch-in of parallel MOS resistors in delay cells, it is possible to operate a PLL to cover a frequency range spanning over three octaves with one VCO. A 10-stage differential VCO is phase-locked to the input channel clock ranging from 26 to 420 MHz (1/spl times/-16/spl times/ DVD speed), and its 20-phase outputs are used to generate write pulses. The pulsewidth and delay are programmed with 120 /spl plusmn/ 40 ps time resolution. The prototype chip fabricated in 0.35 /spl mu/m CMOS occupies 3.5/spl times/3.3 mm/sup 2/, and consumes 294 mW at 3.3 V.

RESHAPING-INDUCED CHAOTIC ESCAPE FROM A POTENTIAL WELL

The chaotic escape of a damped oscillator excited by a periodic string of symmetric pulses of finite width and amplitude from a cubic potential well that typically models a metastable system close to a fold is investigated. Analytical (Melnikov analysis) and numerical results show that chaotic escapes are typically induced over a wide range of parameters by hump-doubling of an external excitation which is initially formed by a periodic string of single-humped symmetric pulses. The analysis reveals that the threshold amplitude for chaotic escape when altering solely the pulse shape presents a minimum as a single-humped pulse transforms into a double-humped pulse, the remaining parameters being held constant. We discuss a physical mechanism concerning the impulse transmitted by the pulse which explains the aforementioned results.

Calibration system based on a laser interferometer for kinematic accuracy assessment on machine tools

This paper deals with a method for the dynamic calibration of the kinematic accuracy of lathes and thread grinding machines in screw-cutting mode but free of load. It utilizes a precision polygon mounted on the spindle, in conjunction with a trigger device to generate angular pulses. A laser interferometer system assesses the longitudinal position of the saddle with respect to a cube-corner affixed on the chuck. As the spindle rotates, a string of pulses is generated by the angular trigger device. These pulses are used for triggering the laser interferometer. A software package has been elaborated to enable on-the-fly data acquisition and to display the kinematic errors in graphical form. The components of the kinematic error considered are the progressive pitch error, the cyclic error and spindle-free float. Application of this kinematic error calibrator on a universal and a CNC lathe has been carried out. Test results are presented and commented.

Hump-Doubling-Induced Bifurcations and Chaos in a Damped Driven Pendulum

The onset of homoclinic chaos in a damped driven pendulum by hump-doubling of an ac force which is initially formed by a periodic string of single-humped symmetric pulses is theoretically demonstrated by means of Melnikov's method. The analysis reveals that the chaotic threshold amplitude when altering solely the pulse shape presents a minimum as a single-humped pulse transforms into a double-humped pulse, the remaining parameters being held constant. Computer simulations show that the corresponding order-chaos route appears to be especially rich, including different types of crises.

Well-behaved dynamics in a dissipative nonideal periodically kicked rotator.

Well-behaved dynamical properties are found in a dissipative kicked rotator subjected to a periodic string of asymmetric pulses of finite amplitude and width. The stability boundaries of the equilibrium are determined to arbitrary approximation for trigonometric pulses by means of circular harmonic balance, and to first approximation for general elliptic pulses by means of an elliptic harmonic balance method. The bifurcation behavior at the stability boundaries is determined numerically. We show how the extension of the instability region of the equilibrium in pulse parameter space reaches a maximum as the pulse width is varied. We also characterize the dependence of the mean duration of the transients to the equilibrium on the pulse width. The evolution of the basins of attraction of chaotic attractors when solely the pulse width is varied is characterized numerically. Finally, we show that the order-chaos route when solely the width of the pulses is altered appears to be especially rich, including different types of crises. The mechanism underlying these reshaping-induced crises is discussed with the aid of a two-dimensional map.

Changes in syllable magnitude and timing due to repeated correction

In a semi-spontaneous conversational setting, subjects were made to repeat the same correction of one digit in a three-digit sequence consisting of “five” or “nine” followed by “Pine Street”. Articulatory and acoustic signals were recorded by the University of Wisconsin Microbeam Facility for four speakers of American English. By analyzing jaw movements, syllable magnitude and time values were evaluated, to represent the rhythmic organization of the utterance by a linear string of syllable pulses. Preliminary results suggest that not only does the magnitude of the corrected syllable increase by the correction of a digit, but also, in most cases, there is some systematic increase of syllable magnitude both in the corrected digit and other digits in the same utterance, as the same correction is repeated. Considerable difference among different speakers is observed and discussed in terms of syllable magnitude and timing patterns.

Statistical analysis of fiber-optic CDMA communication systems. II. Incorporating multiple optical amplifiers

For pt. I see ibid., vol.20, no.8, p.1304-16 (2002). In this paper, we study and elaborate on the architectural consideration of using multiple optical amplifiers in an all-optical fiber-optic code-division multiple-access (FO-CDMA) network. Our study and considerations are based on obtaining the statistical characteristic functions for photon-counts of a string of output pulses that constitutes the address code in a FO-CDMA network. Optical orthogonal codes (OOCs) with minimum auto-and cross correlation are employed as the address or signature sequence codes. Our analysis is based on chip-synchronous interference only, which provides an upper bound on the system performance. Shot noise, thermal noise, and extinction ratio are considered in this analysis. Bit error rate (BER) results are obtained using two methods, namely, saddle-point and Gaussian approximations. From our BER analysis, we develop some insight into the optimum distribution of optical amplifiers and their corresponding gain setting parameter. Moreover, the effects of source power, code weight, number of users, bit rate, and amplified spontaneous emission noise are investigated.

Statistical analysis of fiber-optic CDMA communication systems. I. Device modeling

In this paper, we present a new methodology for analysis of all-optical fiber-optic code-division multiple-access (FO-CDMA) networks. In this analysis, we propose statistical models, based on photon-counting techniques, for some basic elements of the network, such as splitters, combiners, star couplers, and FO-CDMA passive encoders/decoders. By following the statistical variation of the photon-count of the string of pulses that constitutes the address sequence in an FO-CDMA network, we will be able to reveal the quantum-limited optical signal-to-noise ratio (OSNR) required at the transmitter output to meet the performance limits. Moreover, considering receiver thermal noise and source extinction ratio, we explore the role of using an optical preamplifier before the detector and the dependence of the performance on the transmitted power and the weight of the employed optical orthogonal codes (OOCs).

Chaotic behavior in a dissipative non-ideal periodically kicked rotator

The behavior of a damped kicked rotator subjected to a periodic string of asymmetric pulses of finite amplitude and width is investigated. We discuss physical conditions for the results to be independent of the particular choice of the pulse waveform. Analytical (Melnikov analysis) and numerical (Lyapunov exponents) results show that the extension of chaos in parameter space reaches a maximum as the pulse width is varied.

Bifurcations and chaos in a parametrically damped two-well Duffing oscillator subjected to symmetric periodic pulses

We study a parametrically damped two-well Duffing oscillator, subjected to a periodic string of symmetric pulses. The order-chaos threshold when altering solely the width of the pulses is investigated theoretically through Melnikov analysis. We show analytically and numerically that most of the results appear independent of the particular wave form of the pulses provided that the transmitted impulse is the same. By using this property, the stability boundaries of the stationary solutions are determined to first approximation by means of an elliptic harmonic balance method. Finally, the bifurcation behavior at the stability boundaries is determined numerically.

Spin Echoes after ArbitraryNPulses

Based on the Bloch equations, the general response of a nuclear spin-12 system to multiple RF pulses with arbitrary phases and flip angles is presented. The general solution is expressed in a form including the pathway vectors specifying the magnetization paths generated by a string of pulses. The pathway vectors are useful for predicting the exact positions, magnitudes, and number of echoes. Also, these vectors make it easy to trace the physical origin of an echo formation. It is shown that the maximum number of echoes afterNpulses is (3N−1− 1)/2 using this concept.

Chaos and geometrical resonance in the damped pendulum subjected to periodic pulses

The chaotic behavior of a damped pendulum driven by a periodic string of pulses is studied by means of Melnikov’s analysis. The reduction of homoclinic chaos, in the asymptotic case of infinite period driving, is explained in terms of geometrical resonance.

Inhibition of chaos in Hamiltonian systems by periodic pulses.

It is shown that, depending on their amplitude, period, shape, and initial phase, a time-dependent periodic string of external driving pulses can suppress classical deterministic stochasticity. The analysis is based on a coupled pendulum--harmonic-oscillator system. Similar results are obtained by studying the behavior of the Lyapunov exponent from a simple recursion relation which models an unstable limit cycle affected by a periodic string of pulses.

Pupillary dilation as a measure of attention: a quantitative system analysis

It has long been known that the pupil dilates as a consequence of attentional effort. But the function that relates attentional input to pupillary output has never been the subject of quantitative analysis. We present a system analysis of the pupillary response to attentional input. Attentional input is modeled as a string ofattentional pulses. We show that the system is linear; the effects of input pulses on the pupillary response are additive. The impulse response has essentially a gamma distribution with two free parameters. These parameters are estimated; they are fairly constant over tasks and subjects. The paper presents a method of estimating the string of attentional input pulses, given some average pupillary output. The method involves the technique of deconvolution; it can be implemented with a public-domain software package, Pupil.