Bipolar Pulse Generator Research Articles

Nine-channel mid-power bipolar pulse generator based on a field programmable gate array

Many channel arbitrary pulse sequence generation is required for the electro-optic reconfiguration of optical waveguide networks in Lithium Niobate. Here we describe a scalable solution to the requirement for mid-power bipolar parallel outputs, based on pulse patterns generated by an externally clocked field programmable gate array. Positive and negative pulses can be generated at repetition rates up to 80 MHz with pulse width adjustable in increments of 1.6 ns across nine independent outputs. Each channel can provide 1.5 W of RF power and can be synchronised with the operation of other components in an optical network such as light sources and detectors through an external clock with adjustable delay.

Effect of inductance in micro EDM using high frequency bipolar pulse generator

In this work, effect of inductance was investigated in micro EDM using high frequency bipolar pulse generator used for electrolytic corrosion prevention in deionized water. To understand behaviors of the pulses during machining according to inductance, capacitor voltage which is equal to gap voltage and inductor current were analyzed both theoretically and experimentally. Inductance affected the pulse behaviors as well as machining characteristics. In the case of high inductance, inductor current increased after discharge occurred. This increased inductor current also increased both capacitor voltage and discharge current. So, machining time decreased, and tool wear as well as side gap increased with high inductance. However, this peak value shift could lead fluctuation of gap distance and servo voltage, thus, deteriorated controllability. On the other hand, constant discharge current was achieved in the case of low inductance. Low tool wear, small side gap and fine surface were achieved with low inductance.

Design of a Bipolar Magnetic Pulse Generator and Experimental Study on Its Anti-scaling Effect

Design of a Bipolar Magnetic Pulse Generator and Experimental Study on Its Anti-scaling Effect

Discharge in the saline solutions in a vicinity of the threshold voltages

This paper deals with the discharge in saline solution (0.9 % NaCl) in coaxial electrode system at voltages up to several hundred volts. The discharge was powered by bipolar pulsed generator with a pulse repetition rate of 100 kHz and by a generator of negative voltage pulses. At voltages less than a threshold value (less than 300 V)' different types of gas microcavities are formed at the surface of active electrode: the microbubble' the conglomerates of microbubbles (thin gas layers) and a macrobubble with diameter of about 1 mm and less. In a vicinity of threshold voltage the breakdown in the gas cavities occur. For negative polarity at the metal electrode the discharge burns in a form of microsparks of short duration. At positive voltage pulses' the glow-type discharge is sustained in the microcavities.

A source of high-power pulses of elliptically polarized ultrawideband radiation.

Here, we describe a source of high-power ultrawideband radiation with elliptical polarization. The source consisting of a monopolar pulse generator, a bipolar pulse former, and a helical antenna placed into a radioparent container may be used in tests for electromagnetic compatibility. In the source, the helical antenna with the number of turns N = 4 is excited with a high-voltage bipolar pulse. Preliminary, we examined helical antennas at a low-voltage source aiming to select an optimal N and to estimate a radiation center position and boundary of a far-field zone. Finally, characteristics of the source in the operating mode at a pulse repetition rate of 100 Hz are presented in the paper as well. Energy efficiency of the antenna is 0.75 at the axial ratio equal to 1.3. The effective potential of radiation of the source at the voltage amplitudes of the bipolar pulse generator equal to -175/+200 kV reaches 280 kV.

A low-frequency high-power arbitrary-shape voltage pulse generator

A circuit diagram and design of the arbitrary-shape bipolar voltage pulse generator with amplitudes up to 800 V and a peak output on a matched load of 400 kW are described. The generator is based on car rechargeable batteries and power insulated-gate bipolar transistors (IGBTs). Results of the experiments aimed at producing high-power harmonic signals with frequencies of 50 Hz and 1 kHz are presented.

Development of a Bipolar Pulse Generator for High-Frequency Ultrasound Imaging System

The pulse generator is the critical component in high-frequency ultrasound imaging systems. Currently, there still exist some shortcomings about commercial ultrasound image systems and devices such as 5900 PR …etc.. However, to achieve a higher sensitivity and high performance, a programmable pulser generator is desired to match the requirements of high frequency ultrasound image system. In this study, we utilized a novel bipolar pulse generator method to overcome those issues in developed high resolution image system. As the needs of application in clinic, a real –time of high-frequency ultrasound imaging systems, including pulse generator, high speed scanning mechanism, high voltage protection and FPGA trigger control circuit, was developed in our Laboratory. This paper will focus to compare the performance of the bipolar generator and unipolar generator as used in pulse generator device respectively. Finally, the developed bipolar pulse generator show the better performance than the unipolar generator does. The bipolar system can generate clean N-cycle bipolar pulses and improve the center frequency of transducer up to 60 MHz. The axial resolution of scan system has been improved to around 60 μm. In addition, the result indicated that the proposed bipolar pulser could increase 4 dB for pulse/echo waveforms amplitude.

Photonic generation of ultra-wideband doublet pulse using a semiconductor-optical-amplifier based polarization-diversified loop

We propose and demonstrate a novel scheme of ultra-wideband (UWB) doublet pulse generation using a semiconductor optical amplifier (SOA) based polarization-diversified loop (PDL) without any assistant light. In our scheme, the incoming gaussian pulse is split into two parts by the PDL, and each of them is intensity modulated by the other due to cross-gain modulation (XGM) in the SOA. Then, both parts are recombined with incoherent summation to form a UWB doublet pulse. Bi-polar UWB doublet pulse generation is demonstrated using an inverted gaussian pulse injection. Moreover, pulse amplitude modulation of UWB doublet is also experimentally demonstrated. Our scheme shows some advantages, such as simple implementation without assistant light and single optical carrier operation with good fiber dispersion tolerance.

Solid state marx modulator with blumlein stack for bipolar pulse generation

Sub-nanosecond bipolar high voltage pulses are a very important tool for food processing, medical treatment, waste water and exhaust gas processing. A Hybrid Modulator for sub-microsecond bipolar pulse generation, comprising an unipolar solidstate Marx generator connected to a load through a stack Blumlein system that produces bipolar pulses and further multiplies the pulse voltage amplitude, is presented. Experimental results from an assembled prototype show the generation of 1000 V amplitude bipolar pulses with 100 ns of pulse width and 1 kHz repetition rate.

Low temperature Si-DLC coatings on fluoro rubber by a bipolar pulse type PBII system

Diamond-like carbon (DLC) films have been attractive materials because of their excellent mechanical properties such as high hardness, low friction coefficient, high wear resistance and more. In order to spread the application of the DLC coatings for polymer materials, it is necessary to make the temperature go down during the coating process. Our group has been studying DLC coatings on several materials with bipolar pulse type PBII (plasma based ion implantation) systems, which consist of positive and negative (or bipolar) pulse generators and a timing controller. Recently we have introduced a new bipolar pulse generator, whose slew-rate is several times larger than that of previous generators, and a controller which can make a very short pulse less than 1 μs. Using the pulse generator and controller, we have tried to make Si incorporated DLC (Si-DLC) coatings on fluoro rubber, which is widely used in many industries, at low temperature. Using the new pulse generator and controller, we can make very short width positive pulse of about 1 μs, and reduce the temperature during Si-DLC coating to about 30 K. The lower temperature makes fewer folds on the sample surface. By using optical indentation microscope system, Meyer hardness (H M) of uncoated and Si-DLC coated fluoro rubber was obtained and the value of H M for Si-DLC coated rubber is about 1.4 times larger than that of uncoated rubber. Coefficient of friction of Si-DLC coated rubber was 0.2 to 0.25 and drastically decreased from 1.3 to 1.9 of uncoated rubber. Wear of uncoated fluoro rubber is apparent, however, wear of Si-DLC coated rubber cannot be observed, except for the creep effect of fluoro rubber substrate. The counter SUJ2 ball surfaces also showed almost no wear. Si-DLC coating can make the tribological property of fluoro rubber to low friction and less wear. Si-DLC coatings are very useful in many applications.

Machining characteristics of micro EDM in water using high frequency bipolar pulse

Micro EDM using conventional pulse generators such as the RC type or transistor type with water as the dielectric fluid suffers from poor accuracy of machined structures due to electrolytic corrosion. In this study, a new high frequency bipolar pulse generator for micro EDM in water was developed in order to prevent electrolytic corrosion. The new pulse generator produced a high frequency bipolar pulse possessing a positive pulse duration of several hundred nanoseconds with a high repetition rate provided to the machining gap. Discharge characteristics of micro EDM using the new pulse generator were investigated. Machining characteristics were also investigated according to machining conditions such as the repetition rate, positive voltage, capacitance and resistivity. Using the new pulse generator, micro holes without electrolytic corrosion were successfully fabricated in deionized water and tap water. Machining time, tool wear and clearance using the new pulse generator in deionized water decreased compared with those using the RC circuit in kerosene.

A compact subnanosecond high-voltage bipolar pulse generator with spark gaps

Two modifications of the compact subnanosecond high-voltage bipolar pulse generator with an active unit based on a high-impedance charging line, forming line, and two uncontrolled nitrogen spark gaps without gas purging are studied. In both cases, the forming lines are charged with compression of the energies of incident pulses with a ∼160-kV amplitude, a ∼4-ns duration, and a ∼1.5-ns leading edge. The difference of operation modes of the circuits and their efficiency are specified by a point of connecting the load. In conditions of nanosecond prebreakdown overvoltage at a 100-Hz repetition rate, the spark gaps were energized with a relative scatter of ±(100–170) ps, thus specifying the stability of the shape of output bipolar pulses with a voltage difference up to 250 kV.

High-Power Pulse Generator With Flexible Output Pattern

This paper presents a high-voltage bipolar rectangular pulse generator using a solid-state boosting front-end and an H-bridge output stage. The topology generates rectangular pulses with fast enough rise time and allows easy step-up input voltage. In addition, the circuit is able to adjust positive or negative pulsewidth, dead time between two pulses, and operating frequency. The topology can also be controlled to produce unipolar pulses and other pulse patterns without changing its configuration. With an appropriate dc source, the output voltage can also be adjusted to requirements of different applications. The intended application for such a circuit is algal cell membrane rupture for oil extraction, although additional applications, include biotechnology and plasma sciences, medicine, and food industry. A 1 kV/200 A bipolar solid-state pulse generator was fabricated to validate the theoretical analysis presented in this paper. In addition, to validate the analysis with simulations and prototype tests, biological test were conducted in order to examine the technical value of the proposed circuit. These evaluations seem to suggest that oil production rate from bipolar pulses may double that of an equivalent process with unipolar pulses.

Simple modifications to the NMR PGSE technique for investigations in the regime of short diffusion observation times

AbstractSimple modifications to the spin‐echo NMR technique with pulsed magnetic field gradients are proposed. These modifications make it possible to compensate the negative influence of gradient pulse fronts by applying an additional gradient pulse, to eliminate the acoustic effect of gradient pulses on a sample by decoupling the probe and gradient coils, and to simplify the generation of bipolar gradient pulses of the magnetic field using a scheme of two electronic circuits. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 33B: 216–219, 2008

Current Pulse Generation for Transient Electromagnetic Applications

In this article, a novel circuit topology of near rectangular current pulse generation suitable for the transient electromagnetic (TEM) applications is proposed. Satisfactory TEM applications, in general, rely upon a TEM transmitter circuit acting as a current excitation source to produce a high-quality primary magnetic field. This requires that the generated current pulse be of short turn-off delay time, with highly linear falling edge, and fast rising edge. The generation of near rectangular bipolar current pulses is very challenging for high-current high-power applications. The proposed TEM transmitter circuit can be considered as a voltage stabilizing clamp current pulse shaper. Its operation principles are described and guidelines for optimal component selection are also provided. Simulation results show that the proposed circuit demonstrates superior performance compared to other TEM transmitter circuit topologies, such as the improved RCD snubber, IEDD, and the quasi-resonant rectifying circuit.

A low-cost bipolar pulse generator for high-frequency ultrasound applications

A design of a low-cost bipolar pulse generator for high-frequency (HF) ultrasound applications is presented. The pulse generator can produce N cycle (1-255 cycles) bipolar pulses with center frequency over 60 MHz. The measured pulse amplitude was over 160 Vpp, and the pulse ringing was less than 0.3 Vpp (i.e., signal-to-ring ratio is 55 dB). The pulser can be used in high-frequency ultrasound Doppler and B-mode imaging applications with arrays.

Bipolar pulse generator for intense pulsed ion beam accelerator

A new type of pulsed ion beam accelerator named "bipolar pulse accelerator" (BPA) has been proposed in order to improve the purity of intense pulsed ion beams. To confirm the principle of the BPA, we developed a bipolar pulse generator for the bipolar pulse experiment, which consists of a Marx generator and a pulse forming line (PFL) with a rail gap switch on its end. In this article, we report the first experimental result of the bipolar pulse and evaluate the electrical characteristics of the bipolar pulse generator. When the bipolar pulse generator was operated at 70% of the full charge condition of the PFL, the bipolar pulse with the first (-138 kV, 72 ns) and the second pulse (+130 kV, 70 ns) was successfully obtained. The evaluation of the electrical characteristics indicates that the developed generator can produce the bipolar pulse with fast rise time and sharp reversing time.

High-Voltage Rectifier Diodes Used as Photoconductive Device for Microwave Pulse Generation

Generation of unipolar and bipolar pulses by using high- and medium-voltage silicon rectifier diodes is achieved. These components are provided by the French Atomic Energy Commission (CEA). Furthermore, these devices work in the linear mode of photoconducting switches. Generation of electrical unipolar pulses with an amplitude of 10.7 kV and a full-width at half-maximum of 300 ps by using only 1.2 mJ of optical power is demonstrated. This energy value is 10-100 times less than usually published during the past decades. Furthermore, the linear mode running of these devices permits to synchronize several generators with a precision as low as 2 ps. This low timing jitter is useful for bipolar generators in order to control their spectrum with high precision, i.e., bipolar pulses of 3 kV peak-to-peak have been generated with a cycle duration of 400 ps and an optical energy of 1 mJ

High-power bipolar picosecond pulse generation using optically activated traveling wave generator

We demonstrate the generation of multikilovolt bipolar picosecond pulses using an optically activated travelling wave generator into 50Ω load. The spectral content of the output electrical pulse can be modified to favour or reduce low-frequency components. Bipolar pulses of 450 ps of duration with more than 3 kV of peak voltage are produced. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1645–1648, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21713

Removal of 2‐Heptanone by Dielectric Barrier Discharges – The Effect of a Catalyst Support

AbstractSummary: 2‐heptanone is representative of a class of odorous molecules. Recent studies have shown that by adding a catalyst to a dielectric barrier discharge (DBD) plasma, the elimination of 90% of this molecule can be achieved with low consumption of electric energy, at room temperature, for concentrations below 1 000 ppm. In the presented work, the removal of the ketone by DBD, both in dry air and within a slice of a honeycomb monolith of cordierite without a catalyst, was studied. In both experiments, the discharge was operated in a plane‐to‐plane geometry with a discharge volume of 10 cm3. A high voltage, bipolar pulse generator (40 kV max, 1–140 Hz frequency range) was used. In dry air, it was found that 2‐heptanone is almost totally removed (>95%) for a specific deposited energy of about 500 J · l−1, but this elimination is less effective in the porous cordierite reactor (80%) for the same energy. This effect is explained by the very different spatial distribution of the plasma within the discharge volume, as seen using a CCD camera. Moreover, the adsorption‐desorption equilibrium of the molecule at the surface of the material is greatly influenced by the discharge.2‐Heptanone removal as a function of the specific energy for the DBD both in dry air and in the cordierite catalyst support.magnified image2‐Heptanone removal as a function of the specific energy for the DBD both in dry air and in the cordierite catalyst support.