Triangular Pulse Train Research Articles

Sistema de rehabilitación basado en una férula electrónica para recuperación de lesiones de muñeca y nervio radial

En este trabajo, se presenta un sistema de rehabilitación basado en una férula electrónica para personas que han sufrido lesiones del nervio radial. El sistema se compone de dos partes: la férula electrónica y el electroestimulador. La electroestimulación se realiza utilizando corriente eléctrica controlada a una frecuencia de 18 a 83Hz con un tren de pulsos triangular con una intensidad de 7mA. La férula se ha realizado con acero quirúrgico y materiales textiles para que sea más cómoda para el paciente. La férula se mueve de arriba a abajo y de izquierda a derecha mediante servomotores controlados por Matlab. La información del sistema de rehabilitación se almacena en una base de datos para ser analizada, incluso de forma remota, por un fisioterapeuta.

A Modulator-Free Photonic Triangular Pulse Generator Based on Semiconductor Lasers

A modulator-free photonic triangular pulse generator is proposed and demonstrated based on two semiconductor lasers. In this method, a direct-modulated semiconductor laser is employed to generate a fundamental frequency component. Meanwhile, a third-order harmonic signal is generated by external optical injection together with 1/3 subharmonic microwave modulation of another semiconductor laser. After properly setting the amplitude and time delay between the fundamental and third-order harmonics, the combined signal composes a triangular waveform. The generation of a 11.4-GHz triangular pulse train is experimentally demonstrated. Without using any modulator, the proposed approach is a promising method for triangular pulse generation with low cost and simple structure.

Generation of Triangular-Shaped Waveform With Frequency Doubling

A novel approach for triangular-shaped waveform generation based on a dual-polarization quadrature phase shift keying (DP-QPSK) modulator and balanced photo-detection is proposed and demonstrated by simulation and experiment. By properly biasing the child Mach–Zehnder modulators, the optical carrier and the ±4th-order sidebands can be obtained in the upper arm (X-polarization) of the DP-QPSK modulator and the ±2nd-order sidebands in the lower arm (Y-polarization). The polarization multiplexed optical signal is injected to a balanced photo-detector to generate full-duty triangular-shaped waveform. The repetition rate of the detected triangular-shaped waveform can be double frequency of the driving signal. In the simulation and experiment, a 10-GHz triangular pulse train is successfully generated using a 5-GHz driving signal.

Triangular Pulse Generation by Polarization Multiplexed Optoelectronic Oscillator

A novel triangular pulse generator is proposed based on a polarization multiplexed optoelectronic oscillator (OEO). Employing a dual-polarization modulator, the proposed OEO can simultaneously oscillate at two frequencies of $f$ and $3f$ along the two orthogonal polarizations of the same optical carrier. Thanks to the harmonic injection coupling between the two OEO oscillations, the generated two signals have an exact frequency ratio of 1:3 and can be tuned to be in phase with each other. By properly setting the amplitudes of the two signals, a triangular pulse train can be generated. The generation of a 4.44-GHz triangular pulse train is experimentally demonstrated. A very clean electrical spectrum incorporating the 4.44- and 13.32-GHz components is obtained, and the two tones have good phase noises of −100.6 dBc/Hz at 10 kHz and −99.2 dBc/Hz at 10 kHz, respectively. The generated triangular waveform is very close to an ideal waveform, and the root-mean-square error between the generated and the ideal waveforms is $5.145\times 10^{-4}$ .

Photonic Generation of Triangular Pulses Based on Phase Modulation and Spectrum Manipulation

A photonic triangular pulse generation method based on spectrum manipulation of phase-modulated signals is proposed and experimentally demonstrated. A light wave is first phase modulated by a sinusoidal signal to generate optical sidebands. Then, the optical spectra are manipulated by attenuating the optical carrier and one of the first-order sidebands with the same suppression ratio. By choosing a proper modulation index, a full-duty-cycle triangular pulse train with a repetition rate equal to the frequency of the drive signal can be generated. To improve the practical feasibility and the repetition-rate tunability, the spectrum manipulation is realized using a Sagnac loop and a fiber Bragg grating (FBG). In the experiment, four full-duty-cycle triangular pulse trains with different repetition rates (3–6 GHz) are successfully generated, and the repetition rate can be further improved if larger bandwidth measuring instruments are used. In addition to the large and tunable repetition rate, the proposed scheme also features the advantages of simple structure, low cost, and freedom from bias drift.

A photonic-assisted periodic triangular-shaped pulses generator based on FWM effect in an SOA

We propose a photonic-assisted triangular-shaped pulse train generator based on four-wave mixing effect (FWM) in a semiconductor optical amplifier (SOA). A dual-parallel Mach–Zehnder operated at quadrupling RF modulation is employed to generate two primary sidebands (±2nd) in spectrum of the triangular-shaped pulse. Then the FWM effect leads to generation of two new frequency components. By setting the modulation index and bias current of the SOA properly, the generated harmonics of optical intensity can be corresponding to the Fourier components of typical periodic triangular pulses. Finally, a triangular pulse train with tunable repetition rate can be obtained. Numerical simulations have been taken to evaluate the impact of several key parameters to make the scheme more practical.

Triangular pulse generation using a dual-parallel Mach–Zehnder modulator driven by a single-frequency radio frequency signal

A simple scheme for the generation of full-duty-cycle triangular pulses is proposed and experimentally demonstrated using a dual-parallel Mach-Zehnder modulator driven by a single-frequency RF signal. By properly setting the bias voltages and the RF power, even-order harmonics in the optical intensity are suppressed, and the amplitude of the first-order harmonic is 9 times of that of the third-order harmonic. A periodical triangular pulse train is obtained in the time domain. 2.5, 5, and 10 GHz triangular pulse trains are experimentally generated, which verifies the feasibility of the proposed scheme.

Circulatory dynamics during periodic intracranial hypertension in fetal sheep.

The human fetal head is periodically compressed during labor. The resulting increase in intracranial pressure (ICP) may exceed the hydrostatic increase in mean arterial pressure (MAP), thereby decreasing cerebral perfusion pressure (CPP). We determined whether the cardiovascular system of near-term fetal sheep is capable of rapidly increasing MAP during periodic increases in ICP. In 12 chronically instrumented fetuses, we produced sinusoidal oscillations in ICP with a maximum of 52 +/- 1 mmHg (baseline MAP) and a minimum of 4 +/- 1 mmHg at a 3-min periodicity by ventricular fluid infusion and withdrawal. Phasic increases in MAP and decreases in electromagnetically determined renal blood flow tracked behind ICP by 0.3-0.5 min. By the sixth cycle, tonic peripheral vasoconstriction that occurred attenuated by the reduction in CPP during subsequent ICP oscillations. By the 10th cycle, plasma catecholamines and vasopressin increased 20-fold. To more closely simulate the pattern during labor, we produced an ICP triangular pulse train with 5-min periodicity and pulse duration of 1.5 min in six other fetuses. The MAP response was nearly out of phase with this more rapid rise of ICP. Thus the phasic component of the fetal pressor response is inadequate for maintaining CPP when ICP is increased to baseline MAP in less than 0.75 min. However, when the ICP pulse duration and frequency are sufficiently high, a tonic pressor response that may be humorally mediated acts to minimize transient cerebral ischemia.

Response of Viscoelastic Materials to Piecewise Continuous Excitations

A general method is presented for predicting the response of a linear viscoelastic material to piecewise continuous excitations in terms of its known response to the standard excitation functions, i.e., in terms of the relaxation modulus and the creep compliance in case of non-periodic excitations, or the real and imaginary parts of the complex modulus and complex compliance in case of the steady-state response to a periodic non-sinusoidal excitation. To illustrate typical behavior, the response is used of a three-parameter Maxwell model to staircase, pyramid, triangular pulse, and triangular pulse train excitations.