Rectangular Waveform Research Articles

Development of a low-cost non-invasive neurostimulator for applications in post stroke hemiplegics

A noninvasive low-cost, programmable single channel stimulator with generating various patterns of waveforms for Functional Electrical Stimulation (FES) applications has been developed. The prototype is small, battery-operated, and flexible for various clinical applications in home and in clinics. A microcontroller is heart of the stimulator used for generating rectangular waveforms and natural pattern of Tibialis Anterior (TA) muscle waveform and controls the pulse rate and frequency. This FES system is used for rehabilitation of persons who suffered a central nervous system lesion and lost voluntary control over muscles necessary for standing, walking, hand-grasp etc., and to regain lost functions.

A Model of the Flickermeter for Frequency Modulation of the Input Voltage

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Flickermeter is a term used for a system that measures the obnoxiousness of flicker caused by voltage fluctuations. The processing performed by a signal chain of this system is very complicated. Thus, it is not easy to obtain the output values only by analytical mean. The aim of this paper is to obtain a simple model of a flickermeter for a case of frequency modulation (FM) of the input signal. There is still a lack of a International Electrotechnical Commission flickermeter standard specification for that case. In this paper, a proposal was made to determine such a model at FM with slowly varying signals and signals in a frequency range from 1 Hz to 155 Hz. The quality of characteristic approximation evaluated was based on numerical simulations with sinusoidal as well as rectangular waveforms as input signals. The presented model makes it possible to clearly understand the flickermeter signal chain operation and helps to verify the functioning of a real measuring device in the considered frequency range. </para>

Spectrally Shaped DS–CDMA with Dual Sideband Combining for Increased Diversity on Dispersive Fading Channels

A new modulation scheme is proposed in this paper. This scheme uses sinusoidal chip waveforms to shape the spectrum of a direct sequence spread spectrum (DS-SS) signal such that the transmitted signal has two distinct spectral lobes, one from a lower sideband (LSB) and the other from an upper sideband (USB). By properly selecting the frequency of the sinusoidal chip waveforms, the two sideband signals can be made to undergo independent fading in a dispersive fading channel. These two independent sideband signals, when combined at the receiver, provide diversity gain. Our analysis and simulation results show that the bit error ratio (BER) performance of the proposed scheme is superior to that of the equivalent DS-SS system that uses conventional rectangular chip waveforms for severely faded channels.

Linear quadrupoles in mass spectrometry

The use of linear quadrupoles in mass spectrometry as mass filters and ion guides is reviewed. Following a tutorial review of the principles of mass filter operation, methods of mass analysis are reviewed. Discussed are extensions of quadrupole mass filters to higher masses, scanning with frequency sweeps of the quadrupole waveform, operation in higher stability regions, and operation with rectangular or other periodic waveforms. Two relatively new methods of mass analysis the use of "islands of stability" and "mass selective axial ejection" are then reviewed. The optimal electrode geometry for a quadrupole mass filter constructed with round rods is discussed. The use of collisional cooling in quadrupole ion guides is discussed along with ion guides that have axial fields. Finally, mass analysis with quadrupoles that have large distortions to the geometry and fields is discussed. An Appendix gives a brief tutorial review of definitions of electrical potentials and fields, as well as the units used in this article.

Deposition of Multiwall Carbon Nanotubes Using Low Frequency Alternating Electrophoretic Deposition

In this paper, electrophoretic deposition of multiwall carbon nanotubes (MWNTs) using low frequency (0.01-1000 Hz) AC electric fields, is reported. The effect of depositing parameters such as frequency and waveform on deposit yield is investigated. Results show that the deposit yield decreases with frequency. The rectangular waveform yields more deposit yield than sinusoidal and triangular waveforms. The deposition pattern is also different in AC and DC electric fields. This technique may be used for deposition of MWNTs thick films.

Performance of Gaussian waveform in OvTDM

Waveforms play a key role in overlapping time division multiplexing (OvTDM) system. The OvTDM has been proved to be a novel transmission technique that can utilize time diversity to improve the bit error ratio (BER) performance in Rayleigh channel. According to the resulted law, the BER performance of Gaussian waveform in OvTDM also improves with the increase in the waveform parameter monotonically, and the rectangular waveform is the worst case of Gaussian waveform. In contrast, the spectrum effectiveness of Gaussian waveform OvTDM decreases with the increase in the waveform parameter. In the study, it is obtained that waveforms can achieve the best performance when the smallest correlation coefficient between neighbor symbols is e −1.

Creation and FFT Analysis of Periodic Waveform

We created periodically varying waveforms, which are rectangular, trapezoidal, triangular, and quasi-sinusoidal waveforms, by using the originally presented equations and we have investigated the effect of waveform on the frequency characteristics by FFT analysis. Under a excitation vibration having a symmetric quasi-sinusoidal waveform, the fundamental frequency of the system and frequencies at its odd numbered cycles appear. The fundamental frequency of the system and its integral-multiple frequencies appear under excitation vibration having an asymmetric quasi-sinusoidal waveform with the peaks shifted to right or left. Under vibration having a quasi-sinusoidal waveform, an angular frequency of 1 appears in addition to the excitation frequency when damping terms are not included, but it does not appear when damping terms are included.

평판형 전극으로 구성된 유전체 배리어 방전 반응기를 이용한 톨루엔 저감 특성

A plate-type dielectric barrier discharge (DBD) reactor was designed and tested for removal of gaseous toluene. The DBD reactor consisted of 9 parallel plate electrodes, four of which were grounded. An AC voltage of rectangular waveform (<TEX>$5{\sim}8.5kV$</TEX>, <TEX>$60{\sim}1,000Hz$</TEX>), was applied to the other five electrodes. The gaseous toluene passed through the DBD reactor and its concentration was measured by a real-time gas analyzer. The carbon monoxide (CO) and carbon dioxide (<TEX>$CO_2$</TEX>) which were produced by decomposition of toluene in the DBD reactor, were sampled and analyzed by a micro gas chromatography. The maximum toluene removal efficiency was 51.4%.

Modeling of grain size and hardness for pulse current electroplating

A mathematical model was developed to describe the effect of the current shape waveform on the grain size, formation, growth rate, and deposits hardness for progressive nucleation (simultaneous nucleation and growth) when four pulse current waveforms are applied: rectangular, ramp up, ramp down, and triangular waveforms. In the model, it is considered that species diffusion across the limit layer is the rate determinant step. The Hall-Petch expression was used to relate the grain size in the metal to its hardness. The model results are compared with the experimental data for nickel electrodeposit hardness, which were presented by Wong et al. (K.P. Wong, K.C. Chan, T.M. Yue, J. Appl. Electrochem. 31 (2001) 25). The model predictions are consistent with the experimental results for the four current waveforms, with an average hardness deviation of about 10% for currents between 1 and 6 kA/m 2.

Symbol Error Rate Performance of QS-CDMA over Frequency Selective Time Non-Selective Multipath Generalized Gamma Fading Channels

Quasisynchronous (QS) Code Division Multiple Access (CDMA) is currently being considered for a variety of wireless applications and services because QS-CDMA enables information transmission with a good quality of service. In this paper, for M-ary signaling, the Symbol Error Rate (SER) performance of QS-CDMA communication system with a maximal ratio combiner (MRC) over frequency-selective, time-nonselective multipath Generalized Gamma (GG3) fading channels is derived not only for any deterministic spreading sequences but also for any chip-limited chip waveforms, and it is investigated for Rectangular, Half-Sine, and Raised-Cosine chip waveforms by means of numerical and simulation results. Numerical and simulation results show that the performance of QS-CDMA is as good as or slightly better than synchronous CDMA (S-CDMA) when the maximum quasisynchronous delays do not need to be less than some specific values depending on the path power scattering. With this flexibility of quasisynchronous delays, both the transmitter and receiver complexities are reduced as quasisynchronous communication is a challenging task for researchers. Additionally, since not only the spreading sequences but also the partial autocorrelation functions of the chip waveform are influential on the performance of multipath QS-CDMA, a measure, Partial Power Ratio (PPR) is defined based on these partial autocorrelation functions in order to select or design a chip waveform for quasisynchronous communication. Furthermore, results show that QS-CDMA using the chip waveform whose PPR is greater has better performance.

Plastic complementary microelectromechanical switches

We have fabricated plastic complementary microelectromechanical switches by using ink-jet printing technologies. Two vertically stacked regular plastic microelectromechanical switches that are complementary to each other realize the function of an inverter. While rectangular voltage waveforms were periodically applied to the control electrodes in the air, the delay times and durability were examined systematically. The frequency response was 50 Hz for an operation voltage of 60 V. When the number of periodic cycles exceeded 106, the changes in the on resistance of the top and bottom switches were 9% and 43%, respectively.

Differential Mobility Separation of Ions Using a Rectangular Asymmetric Waveform

The performance of a planar differential mobility spectrometer (DMS) is investigated when operated in air at ambient pressure and driven by a rectangular asymmetric waveform, limited to frequencies of <1.2 MHz and voltage pulse amplitudes of <1 kV with steep rise times of the order of approximately 15 ns. Independent control of frequency, voltage pulse amplitude, and duty cycle allow for characterizing the DMS in terms of transmission, resolution and separation. The tradeoff between sensitivity and resolution and the effect of duty cycle on instrument performance are demonstrated experimentally. The dependence of ion mobility on the magnitude of the electric field determines the displacement of ions measured by the DC compensation voltage as a function of the duty cycle. Optimum values for the duty cycle exist for the separation of A- and C-type ions, while, B-type ions exhibit a more complex behavior. An analytical expression for describing the effect of duty cycle on the separation of the ions, determined by variations in the compensation voltage, is developed and compared to experimental results obtained in air below 75 Td using estimated alpha parameters for a set of ketones. In this context, errors associated with the calculation of alpha parameters using polynomials of even powers are highlighted.

Low operation voltage of inkjet-printed plastic sheet-type micromechanical switches

We have fabricated plastic micromechanical switches using inkjet printing technologies. By reducing the device dimensions, particularly the spacing between the electrodes for electrostatic attraction, the operation voltage is reduced to 6.6V. The frequency response exceeds 1kHz when the operation voltage is above 20V. When the number of periodic cycles of the rectangular voltage waveforms that are applied to the control electrodes in air exceeds 2×106, the on resistance changes slightly from 25to30Ω, thereby demonstrating the reliability and stability of the present plastic switches.

Mapping the Stability Diagram of a Digital Ion Trap (DIT) Mass Spectrometer Varying the Duty Cycle of the Trapping Rectangular Waveform

In a digital ion trap the beta(r) and beta(z) boundary lines of the stability diagram are determined experimentally using an innovative approach. In the rectangular waveform-driven digital ion trap (DIT) manipulation of the waveform duty cycle allows introduction of a precisely defined DC quadrupole component into the main trapping field. Variation of the duty cycle can be controlled at software level without any hardware modification. The data generated use peptide ions, which produce stability diagrams in good agreement with the theoretical stability diagrams previously determined by simulation studies.

Examination of the S–D curve for magnetic stimulation used in the treatment of urinary incontinence using an experimental eddy current waveform

Abstract Strength–Duration Curves (S–D Curves) for the intra-urethral sphincter muscle of the rat were measured using the rectangular waveform and the pseudo-eddy current waveform, which approximate the stimulation current waveform on magnetic stimulation. Finally, the pulse duration for minimum energy using magnetic stimulation is obtained from the measurement results of the S–D curve. The eddy current waveform differs from the rectangular current waveform commonly used in electrical applications. No basic study has examined the effects of magnetic stimulation on threshold values and other aspects of the eddy current waveforms. Magnetic stimulation has been reported to have good efficacy in the treatment of urinary incontinence. It is desirable that the eddy current density produced by a change in the strength of a magnetic field be greater than the excitability threshold of the muscles or nerves to be stimulated. However, effective magnetic stimulation requires the input of a large current into the stimulation coil. The requisite equipment is therefore large and costly, and so it is necessary to develop magnetic stimulators that can more efficiently stimulate tissues and that are more convenient to use than those that are currently available.

Improvement of Lock-in Electrical Bio-Impedance Analyzer for Implantable Medical Devices

A novel solution for improving lock-in electrical bio-impedance (EBI) analyzers by suppressing errors caused by higher odd harmonics of rectangular wave pulses is proposed. The solution is based on a newly developed method of shortening the rectangular full duty cycle pulses, which are commonly used in correlation-type lock-in EBI measurements. Comparison of the proposed method to a common method of regular rectangular waveforms is given. The results show that the measurement errors of the three-element EBI equivalent become several tens of times smaller when shortening the excitation and reference signals separately by different values, for example, by 30 deg and 18deg. Shortening of only a single signal (either excitation or reference) can also give significant progress. Improved accuracy of the EBI phasor measurement makes the proposed method reliable for most clinical applications. Due to its simplicity, the method is appropriate for on-chip realization in implantable devices

Non-rectangular waveforms for neural stimulation with practical electrodes

Historically the rectangular pulse waveform has been the choice for neural stimulation. The strength–duration curve is thus defined for rectangular pulses. Not much attention has been paid to alternative waveforms to determine if the pulse shape has an effect on the strength–duration relation. Similarly the charge injection capacity of neural electrodes has also been measured with rectangular pulses. In this study we questioned if non-rectangular waveforms can generate a stronger stimulation effect, when applied through practical electrodes, by minimizing the neural activation threshold and maximizing the charge injection capacity of the electrode. First, the activation threshold parameters were studied with seven different pulse shapes using computer simulations of a local membrane model. These waveforms were rectangular, linear increase and decrease, exponential increase and decrease, Gaussian, and sinusoidal. The chronaxie time was found to be longer with all the non-rectangular pulses and some provided more energy efficient stimulation than the rectangular waveform. Second, the charge injection capacity of titanium nitride microelectrodes was measured experimentally for the same waveforms. Linearly decreasing ramp provided the best charge injection for all pulse widths tested from 0.02 to 0.5 ms. Finally, the most efficient waveform that maximized the charge injection capacity of the electrode while providing the lowest threshold charge for neural activation was searched. Linear and exponential decrease, and Gaussian waveforms were found to be the most efficient pulse shapes.

Frequency change-induced alternative potential waveform dependence of membrane damage to cells cultured on an electrode surface

In the present study, alternative potential stimulation with rectangular pulse, sine and triangular waveforms at 10 and 100Hz was applied to cells cultured on an ITO electrode. As a result, we found that the alternating potential waveform dependence induced by the frequency on membrane damage of cells cultured on an electrode surface. The cell membrane damage was promoted by a rectangular pulse wave in comparison with sine and triangular waves, when alternating electrical potentials of 0 to +1.0V at 100Hz were loaded. In contrast, this waveform dependence was not observed when the frequency was 10Hz. Furthermore, it was found that cell membrane damage was induced at positive potentials more than +0.8V under the present experimental conditions.

Effects of Cabling and Grounding Configuration on Surge Voltage in Inverter-Fed Motors

In inverter-fed motor systems, output voltage of the inverter has a rectangular waveform with rise time of a few tens of nanoseconds, and consequently a motor suffers from repetitive surge pulses which may have adverse effect on motor insulation. Therefore the behavior of surge pulses should be clarified to devise the optimum insulation design of a motor. We have investigated how cable structure and grounding wire connecting inverter and motor affect the surge behavior with particular regard to peak voltage between motor input terminal and ground and peak voltage across the first coil in serially connected multi coils. As a result, we discovered phenomena whereby, when cross sectional structure of the cable is asymmetrical, the surge voltage of a specific phase can become higher than that of the other phases resulting from asymmetry among capacitances between feeder line and ground line. And we have confirmed these phenomena can be prevented by the following three methods: using cables that have symmetrical capacitance to ground among 3 phases (e.g., a 3-phase shielded cable), providing the grounding wire as a separate cable to reduce the capacitance, inserting capacitors at motor terminals or inverter terminals to cancel out capacitive asymmetry.

Effects of Ion Beam Waveform on Flyer Acceleration Produced by Pulsed Ion Beam Ablation Plasma

The main objective of the current study is to clarify the influence of ion beam waveform and to investigate the momentum producing capability of flyer acceleration for propulsion applications, which is produced by irradiating target materials with pulsed ion beam. Al thin foil with a thickness of 50 μm was used to form the high-pressure, high-temperature, and high-energy density ablation plasma when it interacts with pulsed ion beam. The analytical procedures are based on one-dimensional hydrodynamic equations together with a real gas equation of state. This paper presents not only the physical parameters of pulsed ion beam interaction with a target, but also shows the effects of ion beam waveform on momentum production. In addition, we describe the mechanism of ablation pressure formation and compare the results obtained for the rectangular and the parabolic waveform of ion beam irradiation. An ion beam with parabolic waveform produces ablation pressure more efficiently than a rectangular waveform. Propulsion performance is also estimated. An impulse bit of 50.7 mNs and a specific impulse of 5200 s are obtained at an electric power consumption of 1677 W.