High-impedance Load Research Articles

Conversion of high explosive chemical energy into energy of powerful nanosecond high-current pulses

This study is a contribution into the development of physicotechnical foundations for generation of powerful nanosecond high-current pulses on the basis of explosively driven magnetic flux compression generators. This problem is solved by using inductive storage of energy for matching comparatively low-voltage explosively driven magnetic flux compression generators and high-impedance loads; short forming lines and vacuum diodes. Experimental data of charging of forming lines are given.

A Highly Efficient Dual-Mode 3G/4G Linear CMOS Stacked-FET Power Amplifier Using Active-Bypass

A highly efficient dual-mode linear CMOS stacked-FET power amplifier (PA) is implemented for 3G UMTS and 4G LTE handset applications. High efficiency is achieved at a backed-off output power (P out ) below 12 dBm by employing an active-bypass amplifier, which consumes very low quiescent current and has high load-impedance. The output paths between high-and low-power modes of the PA are effectively isolated by using a bypass switch, thus no RF performance degradation occurs at high-power mode operation. The fabricated 900 MHz CMOS PA using silicon-on-insulator(SOI) CMOS process operates with an idel current of 5.5 mA and show power-added efficiency (PAE) of 20.5%/43.5% at P out = 12.4/28.2dBm while maintaining an adjacent channel leakage ratio (ACLR) better than -39dBc, using the 3GPP uplink W-CDMA signal. The PA also exhibits PAE of 35.1% and ACLR E-UTRA of-33 dBc at P out = 26.5 dBm, using the 20 MHz bandwidth 16-QAM LTE signal.

A CMOS Micro-power and Area Efficient Neural Recording and Stimulation Front-End for Biomedical Applications

This paper presents an ultra-low power and small area analog front-end for an implantable multichannel neural signal recording and stimulation interface, to be used in wirelessly powered implantable Brain-Machine Interfaces. For a given functionality and performance, area, power, and noise-response are the three critical parameters that define the suitability of a design for implantation. The three main components of a typical neural implant are the analog front-end, the digital processor, and the wireless data and power transceiver. Among them, neural front-end is the most power and area hungry module. This paper presents an 8-channel analog front-end prototype for simultaneous recording and stimulation, employing a novel architecture which significantly improves power and area consumption of the chip over current state of the art. In contrast to published architectures, the multichannel recording path is centered on a single super-performing tunable gain-bandwidth amplifier instead of employing a separate stand-alone amplifier for each electrode. The resulting circuitry requires smaller area and less power compared to all previously published designs. Designed in 0.5 $$\upmu $$μm CMOS with VDD of 1.8 V, the 8-channel recording path consume a total of 77 $$\upmu $$μW of power and a net area of 0.24 mm$$^{2}$$2, allowing scalability to a high channel count. The stimulation path utilizes 8 stimulators, each employing an 8-bit multibias DAC with a current amplifier to drive electrode---electrolyte high impedance load. Each stimulator consumes full scale power of 224 $$\upmu $$μW and entire stimulation path occupies an area of 0.32 mm$$^{2}$$2.

A Dual-Band Millimeter-Wave Direct-Conversion Transmitter With Quadrature Error Correction

The analysis and implementation of a dual-band direct-conversion millimeter-wave transmitter is presented. The proposed dual-band modulator uses high-impedance loads at two frequencies for the local oscillator driving amplifiers and power amplifier (PA) pre-amplifiers. To correct the amplitude and phase imbalance of the in-phase and quadrature channels at Q- and W-bands, the paper suggests a digitally controlled quadrature error correction stage to finely calibrate these errors and lower the error vector magnitude (EVM) without increasing the baseband digital-to-analog converter resolution. The transmitter is fabricated in 0.12- μm silicon-germanium BiCMOS process and occupies an area of 5.5 mm 2 . At 45-GHz carrier frequency, error correction improves the sideband suppression ratio (SSR) by 10 dB at 2.4-MHz IF frequency. The EVM is lowered from 3.21% to 2.38% for a 64-QAM constellation at a 2.4-Ms/s symbol rate. At 94-GHz carrier frequency, the SSR is improved from 24 to 41 dBc at 2.4-MHz IF frequency, and the EVM is lowered by more than 1% for a 16-QAM constellation at 3-Ms/s symbol rate. A dual-band PA breakout measurement indicates the peak power-added efficiency of 15% with 14-dBm maximum saturated power (Psat) at 43 GHz and 9-dBm Psat at 82 GHz is achieved.

In brief

PAGE 886 Researchers in South Korea present a near-field sheet-like wave-guide as a transmitter, and cylindrical wave-cavity as a receiver, for a wireless power/data transfer device. The device is designed to sustain transmission capabilities despite the variations in thickness of metal walls. The system operates at 25 Mhz and achieves data transfer rates of 50 Mbps. PAGE 853 A technique that significantly reduces the radiated field generated by wireless powered biomedical implants has been proposed in work from the US. The reduction in the radiated field is achieved using a multi-coil wireless power transfer (WPT) system instead of a traditional two-coil WPT design, achieving higher power transfer efficiency, with the same voltage gain and frequency bandwidth, over the same operating distance as a two-coil system. The wireless power/data transfer device is aimed at applications in the shipping industry to alleviate cabling installation issues PAGE 881 Researchers in Germany present the first implementation of integrated mm-wave circuits as radiation sources and detectors for high-resolution mm-wave gas spectroscopy. The results offer a path towards a very compact, low-cost system for gas spectroscopy, using advanced SiGe BiCMOS technology with potential security, forensic and medical applications, including breath analysis. The proposed technique reduces radiated fields generated by wirelessly powered biomedical implants PAGE 850 Work in Australia addresses issues faced by researchers in building effective, compact, microwave-based brain stroke detection systems requiring low profile, compact, directive, wideband antennas for imaging. Utilising the plane of magnetic symmetry, the antenna reported reduces space requirements by half, allowing the diagnostic system to allocate twice the number of antenna elements in the array. Increased data collection results in clearer images for stroke detection. Millimetre wave circuits as radiation sources and detectors utilised in gas spectroscopy may have security and medical applications PAGE 859 The Blumlein configuration is an effective approach to generate high voltage short pulses. Researchers in the United States present on chip Blumlein generators, along with an on-chip broadband Klophenstein taper, to convert high-impedance loads to 50 Ω. This simple and compact Blumlein pulse generator may be implemented in MEMS/NEMS actuation and biomedical studies. Proposed antenna allows clearer images to be produced for detection of strokes in patients Simple and compact Blumlein pulse generator may be implemented in micro/nano-electromechanical systems

On‐chip Blumlein pulse generator

A CMOS Blumlein generator including a two-stacked-metal–oxide semiconductor field effect transistor high-voltage switch, a Blumlein pulse-forming-line (PFL) network and an on-chip Klophenstein taper is presented. The Klophenstein taper is used to convert the high-impedance load to 50 Ω. The Blumlein pulse generator is fabricated in a 0.13 µm CMOS process. Gaussian-like pulses of 725 mV peak-to-peak amplitude, ∼126 ps duration and 3.18 GHz bandwidth are measured on a 50 Ω load (including the losses of the probes, cables and pads). After de-embedding the connection system and Klophenstein taper, the pulses of 1.88 V and 114 ps duration are obtained, which are higher than the rated operating power supply of the given process.

Development of a low-cost frequency shift keying signal Transmitter for digital signal processing

A transmitter consists of an oscillator that generates a carrier frequency followed by a buffer amplifier which provides a high impedance load to minimise drifts, and modulated with an amplified intelligence signal. The development of a low cost frequency shift keying (fsk) transmitter is the concern of this work. The fsk signal forming the base band signal is low - level modulated with a carrier, within the mark and space frequencies. The output from the frequency shift keying circuit at a space frequency of 10kHz and a mark frequency of 20kHz was modulated with a 500kHz single frequency carrier using a diode AM modulating circuit. The transmitter circuit was designed with the use of active devices with few passive components. The measured resonant frequency is 478.63 kHz at 13.427dB, while the calculated resonant frequency is 485 kHz. The calculated carrier power is 1.62W, and the total power radiated out from the antenna is 2.35W. The signal noise was calculated to be 5.228dB while the measured signal noise was 5.399dB. The amplified signal is connected to an antenna, with the response of the design simulated on Multism -12 application software. This development can be used to encode digital signals for information transfer in an area within a 5 kilometre radius with precision.

A Wideband Power Amplifier in 45 nm CMOS SOI Technology for X Band Applications

A fully-integrated wideband power amplifier (PA) operating in 9-15 GHz range is implemented in a standard 45 nm CMOS SOI technology. The PA is designed with three dynamically-biased stacked Cascode cells (6 stacked transistors) to overcome the low breakdown voltages of nanoscale CMOS transistors. The stacked Cascode cells ensure stable operation and facilitate high gain, and high optimum load impedance, leading to high output power, high efficiency and good linearity characteristics over the entire bandwidth. The unbalanced amplitude and phase of drain-source voltage signals caused by internodal parasitic capacitance are equalized by adjusting the sizing of transistors. With a supply voltage of 4.8 V at 12 GHz, the measured saturated output power and linear power are 22.5 dBm and 19.2 dBm, respectively, while the peak power-added efficiency (PAE) is 19.2%. At a reduced power supply of 3.6 V, the PA achieves peak PAE of 25.7% where the drain efficiency reaches 40.7%. Including its pads, the PA occupies a compact chip area of 0.22 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Fast insertion impedance of 2G HTS superconductors for megawatt AC and repetitive pulsed power operation

Within the past few years a newer, more robust type of superconductor known as 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> Generation (2G) High Temperature Superconductors (HTS) wire capable to operate in LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has become available in sufficient quantity and lengths for developers to build prototype devices and test their capabilities. 2G HTS made possible to reduce size, weight and volume of electrical apparatus in few orders of magnitude and provide a fast switching power and energy transitions with negligible impedance in superconducting stage and fast transitions impedances in resistive stage. This transition is typically called quenching and is useful for driving high impedance loads, limiting fault currents and developing large steep insertion impedances useful in many pulsed power applications. Electrical equipments made out of copper or aluminum typically shows high current transitions, inrush and short circuiting faults currents that can reach 100's of kA. There is a need for having repeatable fast insertion impedance to transform high current transitions, useful for impedance matching, stabilization, robustness of large current transients and proper dielectric operation in Megawatt installations. Development of Superconducting Fault Current Limiters (SFCLs) has been pursued for decades and has been limited thermally and/or mechanically by the available superconducting materials performance characteristics. However, this new 2G material has re-invigorated the worldwide race to develop a successful SFCL device that meets the stringent demands of Megawatt power equipment. SuperPower is pursuing the development of modular SFCL based on its proprietary 2G HTS wire and SFCL technologies. We will discuss testing and improvements made to optimize Recovery Under Load (RUL) performance. We also discuss high power tests and the influence of the different variables that have an important impact in RUL. A wide operating RUL window has been tested in order to define where RUL is feasible. We will show the manufacturing and latest tests and capabilities of sub-cooled of the SFCL device and modules designed for distribution and transmission lines. We show the advantages and superior performance of the new 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> Generation HTS superconductors under sub-cooled liquid nitrogen operation when used in SFCL.

A Way for High-Voltage $\mu\hbox{s}$ -Range Square Pulse Generation

In this paper, a new way for high-voltage μs -range quasi-square pulse generation based on a ns source pulser and a chopping spark gap is introduced. The source pulser delivered high-voltage source pulse with front edge at ns range to the chopping gap, and the chopping gap chopped the long flat back edge of the source pulse, so that a quasi-square pulse was formed on a high-impedance load. The breakdown-delay characteristics of the chopping gap, which was the most important, were studied in detail. Results of the experiments showed that when the pulse voltage peaked by the first peaking gap was a little lower than or approximate to the breakdown voltage of the chopping gap, the chopping gap broke down at the back edge of the peaked pulse so that the breakdown-delay time can increase from 30 ns to several μs. The breakdown-delay time of chopping gap is confined to the flat top of the peaked pulse. By using this mechanism of breakdown delay, a quasi-square pulse with pulse width of 1.95 μs, amplitude of 55 kV, and front edge of 22 ns was produced on a 1.15-kΩ load. Repetitive chopping pulses at 0.2 Hz were provided to demonstrate the feasibility of the chopping gap. By contrast to the conventional chopping, four essential conditions were concluded. Based on these results, a controllable trigatron-type chopping gap system is introduced to ensure chopping stability. It provides an important new way for μs-range high-voltage square pulse generation.

Efficient Estimation of Crosstalk Statistics in Random Wire Bundles With Lacing Cords

This paper deals with crosstalk estimation in a set of individually insulated wires laced together to form a bundle, and running above a ground plane. A simplified and numerically efficient multiconductor transmission line model is developed, involving a single reference cross section with pseudocircular shape and staircase approximation for the wire trajectories. The presence of lacing cords along the bundle is modeled as a sinusoidal modulation of the reference cross-section dimension. It is shown that crosstalk in wire bundles is mainly affected by the relative positions of the generator and receptor wires, whose paths are to be accurately represented as smooth curved trajectories, whereas it results to be substantially insensitive to rough modeling of the paths of the remaining wires. The weak random nonuniformity of the generator and receptor wires proves to be the fundamental property to be reproduced in order to obtain physically sound crosstalk predictions. This is enforced by deducing the staircase approximation of the generator and receptor wires from a preliminary representation of only that wire pair in terms of splines with a very small number of nodes. Differently, the staircase trajectories of the remaining wires are obtained by direct mapping onto the reference cross section. Model performance is assessed by comparing crosstalk predictions versus measurement data and theoretical results available in the technical literature. Predictions compare appreciably well with measurements, also in the most critical case of high-impedance loads. The coupling distribution shows nonsymmetrical structure and a long tail to the right, as several other crosstalk analyses have shown.

Compact and Tunable Matching of High Impedance Loads at microwave frequencies using metamaterials

Compact and Tunable Matching of High Impedance Loads at microwave frequencies using metamaterials

A helical-radial magnetic cumulation fast-growing current pulse generator

A design-experimental study of a magnetic cumulation generator (further referred to as generator) with flat helical is performed. This generator combines advantages of both spiral-cylindrical and disk generators. As to speed of operation, the spiral-radial generator is equivalent to the disk generator, but can operate in high-impedance loads. To calculate characteristics of spiral-radial generators, including external-excitation generators, a semiempirical procedure for determining laws of variations of the inductances and mutual inductance of helical of the generator is developed. The procedure is based on measuring the current oscillation frequency in the course of the magnetic-field compression, while the helix is loaded into a small capacitance. A satisfactory compliance of the experimental data and semiempirical calculations is obtained. The experimental effective time values of the current buildup of the spiral-radial generators do not exceed the same characteristic for spiral-cylindrical generators with an axial charge initiation of the explosive material. A possibility of further decreasing the effective time is shown for the plane-parallel throwing of liner plates.

Repetitive Pulsed High-Voltage Generator Using Semiconductor Opening Switch for Atmospheric Discharge

Atmospheric pulsed gas discharge requires very short duration high-voltage pulse delivered to the electrodes. Moreover, atmospheric gas discharge of very short pulse is usually a high impedance load. Pulsed power technology based on inductive energy storage (IES) is suitable for this application. In this paper, we present a repetitive pulsed high-voltage generator with IES. It uses semiconductor opening switch, combined with magnetic switches and insulated-gate bipolar transistors. Experimental tests were carried out with 30-cm-long plate-to-knife discharge load. An output voltage of ~ 50 kV with a pulse duration of ~10 ns was obtained for a gap distance of 1 cm in air. The generator has been operated at a repetition rate up to 250 Hz. Uniform discharge plasma has been identified.

250 kV sub-nanosecond pulse generator with adjustable pulse-width

This paper details the construction of a sub-nanosecond pulse generator capable of delivering 250 kV into a high impedance load. The pulse width is approximately 600ps with a voltage rise of up to 1 MV/ns. The pulse rise-time can be adjusted by manipulation of a peaking gap, whereas the pulse-width can be changed by adjusting a novel tail-cut switch located close to the load.

Fast High Voltage Switching Using Stacked MOSFETs

Fast switching of high voltage using stacked MOSFETs has been studied. It is shown that the effective drain-source capacitance has a negative influence in the turn-off process, especially when the load impedance is relatively high. In order to solve this problem, an alternative circuit configuration is tested where additional switching modules are used to deal with the drain-source capacitance. The experimental results have demonstrated fast switching performance, even for a high impedance load.

Comparison of five different defibrillators using recommended energy protocols

Biphasic defibrillators represent a great step ahead in defibrillation. The manufacturers claim that biphasic defibrillators are able to compensate for differences in transthoracic impedance. That should mean that all patients should be defibrillated with approximately the same amount of current, regardless of their transthoracic impedance. We assessed one monophasic and four biphasic defibrillators. The defibrillators were discharged into resistive loads of 50, 90 and 130 Omega, simulating transthoracic impedance. For each waveform we used energy protocols recommended by the manufacturers and guidelines 2005. Waveforms were observed with on a digitising oscilloscope on a current sensing resistor. We compared the electrical properties of different waveforms and two defibrillators with the same type of waveform. The influence of different impedance on shape, duration and amplitude of current flow were also observed for each waveform. Measurements showed a significant difference in current flow at different impedance loads. At low impedance the mean current is well above expectations for all the defibrillators studied and at high impedance load we observed a big reduction of current amplitude. We can conclude that the compensating mechanisms of biphasic defibrillators are, from electrical point of view, negligible. From the laws of physics it is practically impossible to keep same level of current at given time with same energy at higher impedance. That is why we should reconsider the use of different energy equivalents between patients with different transthoracic impedance and not between different defibrillation impulses.

Low cost general-purpose microcontroller based multi-channel neuromuscular stimulator

A constant current stimulator for high-impedance loads using a microcontroller is presented. The designed muscle stimulator has the advantage that all the parameters such as amplitude, duration and time period can be adjusted. It can give up to eight independent channels of output at a time with adjustable parameters. It has got the advantage of having a user-friendly interface. The facility for storing the stimulation parameters and making it available for future reference has made. A prototype produces stimulus of amplitude and pulsewidth within 0 ≤ Iskin ≥ 20 mA and 1 ms ≤ Tpulse ≥ 250 ms, respectively. Pulse-repetition spans from 0.1–1000 Hz. Worst case ripple is less than 3% at Iskin = 1 mA. Maximum power consumption is 6.5 W per channel at Iskin = 20 mA.

An Energy Source Based on Helical Explosion–Magnetic Generators for High-Impedance Loads

A transportable standard module developed at the Institute of Experimental Physics as a component of an energy source for modeling current pulses of positive lightning is described. The source is designed as a combination of several unified helical explosion–magnetic generators with output transformers and an inner diameter of the stator of 200 mm. According to our calculations, the source generates current pulses with an amplitude of up to 100 kA in loads with an inductance of ∼100 μH and a resistance of several tens of ohms. The results from testing a typical module operating with a circuit having an inductance of ∼100 μH and a resistance of ∼4 Ω are presented. The experimental data coincide well with the results of a mathematical simulation of the module's operation.

Improved signal-to-noise ratio of silicon microphones by a high-impedance resistor

This paper presents the improvement of the signal-to-noise ratio of a silicon microphone by utilizing a high-impedance load resistor. A model is described which considers the acoustical and electrical parts of the microphone. Based on an equivalent circuit diagram, the model is able to simulate the sensitivity and the noise thus the signal-to-noise ratio. Describing the noise spectrum differentiated by parts, the thermal noise of the load resistor proves to be a main noise source as long as the resistance is relatively low.