Rectangular Waveform Research Articles

Multi-Signal Generator Design

Signal generator is electronic equipment which can produce standard signals, and it often is used in industrial production electronic laboratories and the electronic equipment. Signal generator can achieve in a variety of methods, and the higher frequency and the more waveform is the better the signal generator condition. We can consider its implementation from the production and using areas. This paper will use function in the external circuit chip ICL8038 and electronic way to produce triangle wave, sine wave, rectangular wave,which are three basic rectangular waveforms, then the wave through ICM7216D, crystal, capacitors, switches and LED digital which are composed of the circuit to show the frequency and makes the sine wave produce a frequency modulation wave through FM circuit.

Core loss behavior in high frequency high power transformers—II: Arbitrary excitation

High frequency high power transformers used in power electronic converters are frequently subjected to non-sinusoidal excitations. The main purpose of this paper is to study the effects of some general arbitrary waveforms on magnetic core loss in these transformers. First, using well-known empirical equations, general expressions were derived based on the parameters of the waveforms. Second, the impacts of different orders of voltage harmonics were investigated. Finally, capabilities of nanocrystalline and amorphous magnetic materials were compared. It is shown that the loss inside the core is highly sensitive to the rise time and duty cycle of trapezoidal and rectangular waveforms, respectively. Furthermore, although amorphous materials have higher saturation flux density, the total core loss inside the transformer designed using nanocrystalline material is considerably lower than the similar transformer with amorphous materials.

Prediction of iron losses in doubly salient permanent magnet machine with rectangular current waveform

Iron losses in doubly salient permanent magnet (DSPM) machine are difficult to predict, as the flux waveforms are complex and dc bias existed. This paper measures iron losses at no load for different rotor speeds and these measured loss data are used to calibrate the iron loss model of the DSPM machine. Then the iron losses at rated load are predicted under three phase rectangular currents exerting on the armature windings. The result shows that small increment of iron losses is in the rotor at rated load which do benefit to the rotor thermal dissipation design.

The development of charge detection-quadrupole ion trap mass spectrometry driven by rectangular and triangular waves

In this article, the charge detection quadrupole mass spectrometry (CD-ITMS) driven by rectangular and triangular waveforms (rect-CD-ITMS and tri-CD-ITMS) was developed for the characterization of microparticles. Since the frequency scan of rectangular and triangular waveform could be realized easier than that of sinusoidal waveform, this research intends to provide simpler operation modes for CD-ITMS. In order to demonstrate the feasibility of rect-CD-ITMS and tri-CD-ITMS, the discharge onset voltage, ejection point of analyzed particles, and the achieved mass resolution were analyzed and compared with the case in conventional sinusoidal CD-ITMS (sin-CD-ITMS). The results indicated that the rect-CD-ITMS and tri-CD-ITMS can work well for the mass measurement of microparticles by using frequency scan. Identical mass resolutions were achieved under the same root mean square (RMS) voltage of different waveforms. The mass resolution was further improved by increasing the applied voltage and signal-to-noise ratio (S/N) of charge detector. Moreover, the rect-CD-ITMS and tri-CD-ITMS were applied to characterize red blood cells (RBCs). According to the obtained mean masses and mass distributions, normal and anemic RBCs were distinguished successfully.

A Multimode/Multiband Envelope Tracking Transmitter With Broadband Saturated Amplifier

A multimode/multiband envelope tracking (ET) transmitter consisting of a hybrid switching amplifier (HSA) and a broadband saturated power amplifier (PA) is developed for operation across 1.3 to 2.7 GHz. For the various standard signals with different bandwidth (BW) and peak-to-average power ratio, the HSA efficiently provides supply signals to the PA by changing the reference value of the hysteresis comparator. The saturated amplifier employs the nonlinear output capacitor to shape the voltage waveform, resulting in the half-sinusoidal or rectangular waveform. Since the nonlinear capacitor generates large out-of-phased second harmonic component with small higher order harmonics, the voltage shaping is mainly carried out by the capacitor and slightly supported by the harmonic loading circuit. Thus, with the harmonic load higher than that of output capacitor, the saturated amplifier can operate with high efficiency. This characteristic enables the saturated PA to operate with broadband characteristic and high efficiency because the design is mainly focused on the fundamental matching problem while the harmonics can be easily kept out of a low efficiency region through the subsequent optimization of the matching circuit. The broadband saturated PA is implemented based on load/source-pull methodology. The broadband matching networks for the high efficiency are synthesized using the simplified real frequency technique. For the BW from 1.3 to 2.7 GHz (70% fractional BW), the measured output power, drain efficiency, and power-added efficiency (PAE) performances are between 39.8-42.0 dBm, 55.8-69.7%, and 51.2-65.3%, respectively. The multimode/multiband ET transmitter with the designed broadband saturated PA is demonstrated at 1.8425-GHz long-term evolution (LTE), 2.14-GHz wideband code division multiple access (WCDMA), and 2.6-GHz mobile world wide interoperability for microwave access (m-WiMAX) applications. This transmitter delivers a PAE of 32.16, 37.24, and 28.75% for LTE, WCDMA, and m-WiMAX applications.

Experimental Demonstration of Symmetrical Waveform Generation Based on Amplitude-Only Modulation in a Fiber-Based Temporal Pulse Shaping System

We experimentally demonstrate the photonic generation of symmetrical waveforms based on amplitude-only modulation in a fiber-based temporal pulse shaping (TPS) system. A rectangular waveform with a 3-dB width of 18.8 ps and a triangular waveform with a 3-dB width of 6.7 ps are experimentally generated.

Numerical simulation of instability conditions in multiple pinion drives

Multiple pinion drives, parallel arrangements of the pinions for large torque transmission, are widely utilized in various heavy-duty industrial applications. For such multi-mesh gear systems, periodic mesh stiffnesses could possibly cause parametric instabilities and server vibrations. Based on the Floquet–Lyapunov theory, numerical simulations are conducted to determine the parametric instability status. For rectangular waveforms assumption of the mesh stiffness variations, the primary, secondary, and combination instabilities of the multiple pinion drives are studied. The effects of mesh stiffness parameters, including mesh frequencies, stiffness variation amplitudes, and mesh phasing, on these instabilities are yielded. Unstable regions are also indicated for different gear pair configurations. Instability conditions of three-pinion drives are obtained and compared with those of the three-stage gear train.

Numerical Simulation of the Rational Loading Waveform in Large Diameter SHPB Dynamic Test for Rock-Like Materials

For rock-like materials, large diameter SHPB (Split Hopkinson Pressure Bar,SHPB) is necessary and essential in dynamic test. Based on the finite element software ANSYS/LS- DYNA, the transmission of different stress pulse waveform in large diameter bar was simulated and the loading waveform dispersion effect was investigated in this paper. Three typical stress pulses (rectangular waveform, triangular waveform and half-sine waveform) with the same duration time and maximum stress amplitude value were loaded on input bar of SHPB. The time-stress curves of different transmission distance on input bar were traced and recorded and four specific aspects were discussed respectively. Compared with rectangular waveform and triangular waveform, the results of numerical analysis indicated that there isn’t pulse waveform dispersion for half-sine waveform to transmit in large diameter SHPB and there is enough increased time to satify stress equilibrium before rock-like materials failure. The half-sine stress wave is able to meet the one-dimensional assumptions in the propagation process and can be used in large diameter SHPB test.

Experimental and simulation research on the influence of voltage amplitude, frequency and carrier gas flow rate on the performance of FAIMS

A micro sensor chip of High-field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) was designed and fabricated by inductively coupled plasma (ICP) etching on the both sides of silicon and double silicon-glass bonding, with dimensions of 18.8 mm×12.4 mm×1.2mm. The sample ions were created at ambient pressure by VUV lamp ion source, which was equipped with a 10.6 eV photo discharge lamp (λ=116.5 nm). The 2-pentanone was adopted to illustrate the influences of high-field rectangular asymmetric waveform voltage amplitude, frequency and carrier gas flow rate on the performance of FAIMS sensor chip. The experiment results showed that with the frequency or carrier gas flow rate increasing, or voltage amplitude decreasing, the FAIMS sensitivity increases, and that the resolution decreases with the increasing of the frequency or flow rate. The FAIMS simulation results based on the SIMION software was in agreement with the experimental results. The FAIMS detection sensitivity experiment showed that the FAIMS sensor chip can detect positive and negative ions simultaneously, and has detection sensitivity as low as 0.1 ppm for acetic acid.

Experimental Study of Heat Flux Distribution of Arc Driven by AC Magnetic Field

The authors earlier developed a model to predict the heat flux distribution in an arc driven by an AC magnetic field. That theoretical model implied that the heat flux distribution depended on waveforms of the imposed AC magnetic field. Experiments were conducted in this study to validate that theoretical prediction. Theoretical calculations of heat flux distribution in the arc driven by AC magnetic field were conducted using the heat flux profile in the arc root obtained from the measurement under no magnetic field. The heat flux distributions in arcs driven by AC magnetic fields were measured by imposing two AC magnetic fields with sinusoidal and rectangular waveforms. Agreement between experimental and theoretical heat flux distributions was good. Results confirm that heat flux profiles of various types are producible by controlling the imposed magnetic flux density and its waveform.

The effects of low frequency pulsed magnetic fields with different waveforms on cardiac microvascular endothelial cells

Objective To investigate the effects of low frequency pulsed magnetic fields (LF-PMFs) on proliferation, the cell cycle, apoptosis, migration, cytoskeleton formation and nitric oxide (NO) secretion in cardiac microvascular endothelial cells (CMECs). Methods LF-PMFs with rectangular and triangular waveforms at 15 Hz were tested. The CMECs were randomly divided into a control group, 0.6 mT group, 1.2 mT group, 1.8 mT group and 2.4 mT group. Except for the control group, the CMECs were exposed to LF-PMFs 4 h/day for 5 days. Results After 5 days of intervention with rectangular wave LF-PMFs the proliferation of CMECs accelerated and NO secretion was enhanced significantly. The percentages of cells at ( S+G2 ) phase increased significantly, whereas apoptosis rates were significantly lower than in the control group. The migration of CMECs was facilitated, stress fibers increased and cytoskeleton components were reorganized. After 5 days of intervention with triangular wave LF-PMFs proliferation of CMECs accelerated and NO secretion was significantly enhanced. The percentages of cells at(S+G2)phase and migration increased, while apoptosis was inhibited. Cytoskeleton components were reorganized after exposure to 0.6 mT and 2.4 mT triangular waveform LF-PMFs. No significant change was detected with 1.2 mT and 1.8 mT triangular waveform LF-PMFs with regard to these variables. Conclusions The effects of LF-PMFs on proliferation, the cell cycle, apoptosis, migration, cytoskeleton formation and NO secretion function of CMECs were infiuenced by the waveform in addition to it's intensity and frequency. Key words: Low frequency pulsed magnetic fields; Cardiac microvascular endothelial cells; Proliferation; Cell cycle; Apoptosis; Migration; Cytoskeleton; Nitric oxide

Interfacial evaluation and hydrophobicity of multi-functional Ni-nanopowder/epoxycomposites for self-sensing and actuation

Electrical and interfacial properties of Ni-nanopowder/epoxy composites were investigatedfor self-sensing and actuation. Contact resistance and electrical resistivity were measuredusing a micro-specimen with a gradient grid of electrical contact on its length. Thespecimens’ self-sensing characteristics were monitored reasonably well under applied cyclicloading. Actuation in an electromagnetic field was evaluated by measurement of inducedstrain for three wavefunction voltages, i.e. sine, triangular and square. Due to the presenceof hydrophobic domains on the heterogeneous surface, the static contact angleof Ni-nanopowder/epoxy composites exhibited hydrophobicity. The specimensresponded well in both self-sensing and actuation tests, in electromagnetic fields,due to the intrinsic metallic property of Ni-nanopowder. Displacement of theactuator was evaluated to attain optimum performance as functions of wave type,frequency and voltage. The strain response followed the shape of the applied voltagesbetter, and was much smoother and less erratic for applied voltages with sine andtriangular waveforms than it was for voltages with a rectangular waveform. This isattributed to the sudden changes in voltage in the latter case. Such self-sensing andactuation, in conductive Ni-nanopowder/epoxy composites, might find uses inmulti-functional composite devices such as biomimetic and micro-size generators.

Retraction notice Dynamic stability of a planetary gear train under the influence of variable meshing stiffnesses

The main source of vibration and noise in planetary gear train systems is the parametric instability caused by variable meshing stiffnesses. The operating conditions leading to parametric instability are investigated for planetary gear trains with three and four planets. Perturbation technique is used to study the primary, secondary, and combination instabilities. The effects of mesh stiffness parameters, including stiffness variation amplitudes, contact ratios, and mesh phasing, on these instabilities are identified. A rectangular waveform is used to describe the mesh stiffness variation. The boundaries separating stable and unstable conditions are obtained as simple expressions in terms of mesh parameters. These expressions allow the suppression of particular instabilities by adjusting the contact ratios and mesh phasing.

Measurement and modeling of pulsatile flow in microchannel

An experimental study of pulsatile flow in microchannel is reported in this paper. Such a study is important because time-varying flows are frequently encountered in microdevices. The hydraulic diameter of the microchannel is 144 μm and deionized water is the working fluid. The pressure drop across the microchannel as a function of time is recorded, from which the average and r.m.s. pressure drops are obtained. The experiments have been performed in the quasi-steady flow regime for a wide range of flow rate, frequency of pulsations, and duty cycle. The results suggest that the pressure with pulsations lies between the minimum and maximum steady state pressure values. The average pressure drop with pulsation is approximately linear with respect to the flow rate. The theoretical expression for pressure has also been derived wherever possible and the experimental data is found to lie below the corresponding theoretical values. The difference with respect to the theoretical value increases with an increase in frequency and a decrease in flow rate, with a maximum difference of 32.7%. This is attributed to the small size of the microchannel. An increase in frequency of square waveform leads to a larger reduction in pressure drop as compared to rectangular waveform, irrespective of the duty cycle. The results can be interpreted with the help of a first-order model proposed here; the model results are found to compare well against the experimental results. A correlation for friction factor in terms of the other non-dimensional governing parameters is also proposed. Experimental study of mass-driven pulsatile flow in microchannel is being conducted for the first time at these scales and the results are of both fundamental and practical importance.

Digital Asymmetric Waveform Isolation (DAWI) in a Digital Linear Ion Trap

Traditionally, in a quadrupole mass filter, ion isolation is achieved by scanning the rf and DC voltages with a fixed ratio. In this paper, we describe an innovative procedure implemented in a digitally driven linear ion trap termed digital asymmetric waveform isolation (DAWI) in which ion isolation is obtained by manipulation of the duty cycle of the rectangular waveforms. Variation of the waveform duty cycle allows introduction of a precisely defined DC quadrupole component into the main trapping field of the quadrupole ion filter. The DAWI method is completely controlled at software level and does not require any hardware modification.

Alias-Suppressed Oscillators Based on Differentiated Polynomial Waveforms

An efficient approach to the generation of classical synthesizer waveforms with reduced aliasing is proposed. This paper introduces two new classes of polynomial waveforms that can be differentiated one or more times to obtain an improved version of the sampled sawtooth and triangular signals. The differentiated polynomial waveforms (DPW) extend the previous differentiated parabolic wave method to higher polynomial orders, providing improved alias-suppression. Suitable polynomials of order higher than two can be derived either by analytically integrating a previous lower order polynomial or by solving the polynomial coefficients directly from a set of equations based on constraints. We also show how rectangular waveforms can be easily produced by differentiating a triangular signal. Bandlimited impulse trains can be obtained by differentiating the sawtooth or the rectangular signal. An objective evaluation using masking and hearing threshold models shows that a fourth-order DPW method is perceptually alias-free over the whole register of the grand piano. The proposed methods are applicable in digital implementations of subtractive sound synthesis.

Threshold-Switching Delay Controlled by $\hbox{1}/f$ Current Fluctuations in Phase-Change Memory Devices

Threshold switching, i.e., the electrical transition from high to low resistivity in amorphous semiconductors, plays a major role in the program/erase processes of phase-change memory (PCM) devices. Understanding and designing materials and cell structures for optimum memory performance require that accurate models for threshold switching be developed, in both the steady-state and the transient regime. This work presents an experimental and modeling study of threshold switching in amorphous chalcogenide materials for PCM applications. The delay time for the onset of threshold switching from the application of an electrical pulse is explained based on 1/f fluctuations of the subthreshold current. A Monte Carlo model is developed for calculating the statistical distribution of delay times. The model can account for 1) the voltage dependence of the average delay time and 2) the statistical spread of the delay time for both rectangular and triangular voltage waveforms. The delay model is used for a reliability assessment of read disturb in PCM devices.

Separation of Ions from Volatile Organic Compounds Using High-Field Asymmetric Waveform Ion Mobility Spectrometry-Mass Spectrometer

A combination of high-field asymmetric waveform ion mobility spectrometry (FAIMS) with mass spectrometer (MS) was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp (Å = 116.5 nm). The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm × 8 mm × 0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from −30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.

A novel phase-coherent programmable clock for high-precision arbitrary waveform generation applied to digital ion trap mass spectrometry

Digital ion trap (DIT) mass spectrometry requires the ability to precisely and accurately produce waveforms. The quality of the mass spectra produced in terms of resolution and mass accuracy depend on the resolution and precision of the applied waveforms. This publication reveals a novel method for the production of arbitrary waveforms in general and then applies the method to the production of DIT waveforms. Arbitrary waveforms can be created by varying the clock frequency input to a programmable read only memory that is then input to a digital-to-analog converter (DAC). The arbitrary waveform is composed of a defined number of points that are triggered to be written after programmed numbers of clock cycles to define the arbitrary waveform. The novelty introduced here is that the direct digital synthesis (DDS) generated clock frequency can be precisely changed as the arbitrary waveform is written because we have developed a method to rapidly switch the DDS frequency exactly at the end of the output clock cycle allowing exact timing of multiple transitions to produce precise and temporally complex waveforms. Changing the frequency only at the end of the output clock cycle is a phase-coherent process that permits precise timing between each point in the arbitrary waveform. This waveform generation technique was demonstrated by creating a prototype that was used to operate a digital ion trap mass spectrometer. The jitter in the phase-coherent DDS TTL output that was used as the frequency-variable clock was 20 ps. This jitter represents the realizable limit of precision for waveform generation. The rectangular waveforms used to operate the mass spectrometer were created with counters that increased the arbitrary jitter to 100 ps. The mass resolution achieved was 5000 at m/ z = 414. Resolution should improve with increasing mass because the waveforms have longer periods while the jitter should remain constant. Given the current limit of the variable clock resolution, much better mass resolution should be achievable with future generations of the waveform production system. The agility of the DDS function generators permits the phase-coherent variable clock to be switched at a rate up to 250 MHz. This permits arbitrary waveforms to be produced with much more temporal complexity than previously possible.

Excitations of limited-diffraction waves approaching the classical 0-order x-wave by rectangular waveforms

In this paper, an approach for simplifying the experimental arrangement, needed to generate limited diffracting waves through annular ultrasonic arrays, is analyzed in terms mainly of the subsequent acoustic field. The main idea is to approximate the theoretical X-wave electrical excitations to rectangular driving signals in each array annulus, by means of the L2 curve criterion. The differences between theoretical X-wave signals and these approximate signals, related to real excitation effects, were minimized by using the transition times and amplitudes of the rectangular signals as fitting parameters.Acoustic field simulations, based on the impulse response technique, are applied for evaluating the agreement degree between both emitted ultrasonic fields, whit the calculated classical X wave and with the new approximation method proposed here for low-cost limited-diffraction wave generation. In addition, source vibration and ultrasonic field simulated signals were compared with those of the classic x wave under an exact driving, with the purpose of validating the method.The good agreement between the two vibration signals and resulting field distributions, obtained from the classical X wave excitations and those provided by the drastic simplification presented here, can be justified by the filtering effects induced by the transducer elements bands in frequency domain. These results suggest the possibility of achieving limited diffraction waves with relatively simple driving waveforms, which can be implemented with a moderate cost in analogical electronics.