Impulse generator

About: Impulse generator is a research topic. Over the lifetime, 1479 publications have been published within this topic receiving 8831 citations.

Body monitoring and imaging apparatus and method

Abstract: A non-acoustic pulse-echo radar monitor is employed in the repetitive mode, whereby a large number of reflected pulses are averaged to produce a voltage that modulates an audio oscillator to produce a tone that corresponds to the heart motion. The antenna used in this monitor generally comprises two flat copper foils, thus permitting the antenna to be housed in a substantially flat housing. The monitor converts the detected voltage to an audible signal with both amplitude modulation and Doppler effect. It further uses a dual time constant to reduce the effect of gross sensor-to-surface movement. The monitor detects the movement of one or more internal body parts, such as the heart, lungs, arteries, and vocal chords, and includes a pulse generator for simultaneously inputting a sequence of pulses to a transmit path and a gating path. The pulses transmitted along the transmit path drive an impulse generator and provide corresponding transmit pulses that are applied to a transmit antenna. The gating path includes a range delay generator which generates timed gating pulses. The timed gating pulses cause the receive path to selectively conduct pulses reflected from the body parts and received by a receive antenna. The monitor output potential can be separated into a cardiac output indicative of the physical movement of the heart, and a pulmonary output indicative of the physical movement of the lung.

Behaviour of grounding systems excited by high impulse currents: the model and its validation

Abstract: The behaviour of grounding systems excited by high impulse currents (such as lightning strokes or phase to ground faults) considerably differs from that at low-frequency and at low-current: inductive behaviour can become more and more important with respect to resistive behaviour and, in addition, these currents can generate soil breakdown (which makes the impulse response typically nonlinear). Many experimental tests confirm these aspects. In order to obtain a correct design of electrical systems, with respect to the protection of installations against anomalous events, it is fundamental to predict the impulse characteristics of grounding systems. An efficient solution to this problem may be obtained by a mathematical model based on a circuit approach. The development of this model (which is able to simulate complex grounding systems when nonlinear ionization phenomena take place) is described in this paper. The model has been validated by comparing the numerical results both with experimental tests and with the simulations executed by various approaches.

Effects of converter pulses on the electrical insulation in low and medium voltage motors

Abstract: A new IEC test specification is under development for the insulation systems used in converter-driven machines with the aim of providing manufacturers with a reliable means to quality insulation systems for use in converter-fed machines and users with confidence that the machines they purchase contain insulation that is fit for their intended purposes. Much of the qualification testing for insulation systems subject to converter voltages may be undertaken with existing 50/60 Hz equipment. However, for testing of complete coils in low voltage machines, an impulse generator and an impulse PD test set are required. For large machines, which have stress-graded endwindings, it will be necessary for a source of converter voltage to be available.

Subpicosecond electro-optic shock waves

Abstract: When an extremely short optical pulse is focused into an electro‐optic material, a moving polarization is produced which radiates in a Cerenkov‐like cone. At the boundary of this shock wave, the electric field consists of an extremely fast electrical transient with a correspondingly wide spectral distribution extending well into the far infrared. When appropriately coupled out of the material, this shock wave can be used as a fast electronic impulse generator or far‐infrared source without requiring subminiature transmission structures to guide the signal.

Waveform adaptive ultra-wideband transmitter

Abstract: A waveform adaptive transmitter that conditions and/or modulates the phase, frequency, bandwidth, amplitude and/or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and/or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and/or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and/or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.