Nonlinear Harmonic Distortion Research Articles

Characteristic analysis and data comparative of linear and nonlinear low frequency sweep in vibroseis

Abstract Low-frequency seismic data plays a crucial role in seismic data processing and seismic wave inversion. At present, there are two methods to realize the low-frequency excitation of vibrators: one is that the low-frequency vibrators are excited by linear sweep signals, and the other is that the conventional vibrators are excited by nonlinear low-frequency sweep signals. The cost of exploration using low-frequency vibroseis is high, and it is challenging to obtain sufficient low-frequency information using traditional vibrators. To this end, this paper comparatively studies the low-frequency sweep signal characteristics and data effects of low-frequency vibrator and traditional vibrator. Therefore, three kinds of linear and nonlinear low-frequency sweep signals are designed. Theoretical analysis shows that there are certain differences between linear and nonlinear in design methods, signal shapes, etc., but after correlation calculation, the signal spectrums reflecting the seismic response and the related wavelet shapes are basically consistent. Besides, the actual force signal data shows that the linear and nonlinear harmonic distortion are basically equivalent. Finally, based on the forward simulation of three sweep signals and the comparative analysis of field test data, it can be considered that the linear and nonlinear low-frequency sweep signals of vibrator have almost the same denoising ability under the basic conditions of spectrum and wavelet. Both can achieve low-frequency excitation and obtain rich low-frequency information, and the quality of seismic data is basically the same, so they can be applied in practical production.

Performance Analysis of a Backward/Forward Algorithm Adjusted to a Distribution Network with Nonlinear Loads and a Photovoltaic System

Context: The backward/forward (BF) algorithm is a sweep-type technique that has recently been used as a strategy for the power flow analysis of ill-conditioned networks. The purpose of this study is to evaluate the performance of the BF algorithm compared to that of a computational tool such as Simulink, with both strategies adjusted to the operating conditions of a distribution network with nonlinear components (loads and photovoltaic system), unbalanced loads, and harmonic distortion in the voltage and current signals. Method: The study case is a low-voltage distribution network with a radial topology, unbalanced loads, and nonlinear components. The BF algorithm is adjusted to consider two approaches of the Norton model: a coupled admittance matrix and a decoupled admittance matrix. The latter is also used in the network model created in Simulink. The performance of the algorithm is evaluated by analyzing 18 operation scenarios defined according to the presence and use intensity of the loads and solar irradiance levels (low and high). Results: In general, the three strategies could successfully determine the waveform and RMS values of the voltage signals with errors of less than 0,8 and 1,3%, respectively. However, the performance of the strategies for the estimation of current signals and power parameters shows errors of 5-300% depending on the level of solar irradiance at which the photovoltaic system operates. Conclusions: The results show that the BF strategy can be used to analyze unbalanced power grids with increasing penetration of renewable generation and the integration of nonlinear devices, but the performance of this strategy depends on the load model applied to represent the behavior of nonlinear devices and generation systems.

High level sound transmission through cadaver human ears—On the influence of bone conduction and hearing protective devices

High level sound exposure can cause substantial injury to the auditory system, motivating efforts to predict and prevent this injury. Measurement techniques using acoustic manikins are effective for low and moderate sound levels, but nonlinear effects in the middle ear and alternate sound transmission pathways to the inner ear limit their utility at higher sound pressure levels. Here, we describe results from a series of measurements made in cadaveric human ears conducted in our laboratory over the last several years. We quantified sound transmission to the inner ear by measuring the difference in sound pressure level across the cochlear partition near the base of the cochlea, which drives basilar membrane motion. We describe measurements quantifying sound transmission through the human middle ear, which is limited by suspensory ligaments for sounds above approximately 130 dB SPL, resulting in nonlinear (harmonic) distortion of sounds in the cochlea at higher sound pressure levels. Similarly, we describe observations of sound transmission to the cochlea via bone conduction from vibratory transducers, as well as high level sound and impulse noise/blast exposures. The implications of these measurements for hearing loss predictions, effectiveness of hearing protective devices, and injury mechanisms are discussed.

Fiber-Optik Haberleşme Sistemlerinin Bant Genişliğinin Artırılması için Yeni Bir Yaklaşım

In this study, a theoretical systematic approach is introduced as a solution of the bandwidth problem of multi-tone network systems. This systematic approach proposes the use of unused harmonic components of non-linear harmonic distortion produced by the semiconductor laser diode, which is used as a source in the infrastructure of the fiber optic communication system. In order to separate these unused harmonic distortion frequency components from the others, it is possible to add a protocol to each harmonic distortion difference frequency signal, or by intermodulation distortion (IMD) phase modulation, or to use both protocol and IMD phase modulation together. Thus, all harmonic distortion frequency components can be separated theoretically. Thus, it is recommended to use IMD difference frequency components in multi-tone-input subcarrier fiber optic or similar communication systems in the same transmission medium. We think that if this technique is used, it will make a great contribution to increasing the bandwidth of fiber optic communication and network systems.

Nonlinear Harmonic Distortion of Complementary Golay Codes.

Recent advances in electronics miniaturization have led to the development of low-power, low-cost, point-of-care ultrasound scanners. Low-cost systems employing simple bi-level pulse generation devices need only utilize binary phase modulated coded excitations to significantly improve sensitivity; however the performance of complementary codes in the presence of nonlinear harmonic distortion has not been thoroughly investigated. Through simulation, it was found that nonlinear propagation media with little attenuative properties can significantly deteriorate the Peak Sidelobe Level (PSL) performance of complementary Golay coded pulse compression, resulting in PSL levels of -62 dB using nonlinear acoustics theory contrasted with -198 dB in the linear case. Simulations of 96 complementary pairs revealed that some pairs are more robust to sidelobe degradation from nonlinear harmonic distortion than others, up to a maximum PSL difference of 17 dB between the best and worst performing codes. It is recommended that users consider the effects of nonlinear harmonic distortion when implementing binary phase modulated complementary Golay coded excitations.

Enhanced Linearity in FD-SOI CMOS Body-Input Analog Circuits – Application to Voltage-Controlled Ring Oscillators and Frequency-Based ΣΔ ADCs

This paper investigates the use of the body terminal of MOS transistors to improve the linearity of some key circuits used to implement analog and mixed-signal circuits integrated in Fully Depleted Silicon on Insulator (FD-SOI) CMOS. This technology allows to increase the body factor with respect to conventional (bulk) CMOS processes. This effect is analyzed in basic analog building blocks – such as switches, simple-stage transconductors and Voltage-Controlled Ring Oscillators (VCROs). Approximated expressions are derived for the nonlinear characteristics and harmonic distortion of some of these circuits. As an application, transistor-level simulations of two VCRO-based $\Sigma \Delta $ modulators designed in a 28-nm FD-SOI CMOS technology are shown in order to demonstrate the benefits of the presented techniques.

A Reduced Complexity Random Fourier Filter Based Nonlinear Multichannel Narrowband Active Noise Control System

Linear-in-the-parameters nonlinear controllers are widely used for active noise cancellation (ANC) in the presence of nonlinearities in the system. However, the performance of such controllers deteriorates significantly in highly nonlinear systems and also in the presence of nonlinear harmonic distortion. To overcome these issues, a kernel filtered-x least mean square (KFxLMS) algorithm based narrowband ANC system has been recently reported in the literature. We observe that the large memory size and high computational complexity of the KFxLMS algorithm hinder its implementation in real-time ANC systems. To alleviate these issues, a single channel random Fourier filter based FxLMS (RFFxLMS) algorithm is proposed in this brief. The above formulation is then extended to the multichannel scenario, and an RFF based multichannel narrowband ANC system is developed to achieve noise reduction over a broader area. The computational load of the proposed multichannel approach is further reduced by using a partial updating method. The simulation study shows that the overall performance of the proposed schemes is significantly better than the existing nonlinear methods.

Features of the Nonlinear Harmonic Distortion in AOSTFTs

In this article, we present the analysis of the nonlinear harmonic distortion (HD) characteristics for two kinds of amorphous oxide semiconductor thin film transistors (AOSTFTs) based on SiO2/indium–gallium–zinc oxide (IGZO) and HfO2/hafnium–indium–zinc oxide (HIZO), applying the integral function method (IFM). An analysis of the distortion of the transistors used as quasi-linear resistor and the variation in HD as a function of the parameter ${g}_{m}/{I}_{\text {DS}}$ are also included. As far as we know, this kind of study has not been reported before. It is shown that parameter HD2 does not present a minimum as in MOSFETs, because the transfer characteristic does not present an inflection point. The value of HD2 is higher than that of HD3 in the whole operating ranges. When the transistor is used as quasi-linear resistor for different ${V}_{G}$ bias, HD2 is greater than HD3 in more than 50 dB. Because HD2 is significantly greater than HD3, the total HD (THD) parameter can be considered practically equal to HD2. In addition, the behavior of HD around the low-power operating region is shown.

Studying the nonlinear performance of an amplifying reflectarray antenna

In this paper, significance of studying the nonlinear performance of amplifying reflectarray antenna is clarified by showing nonlinear behavior of the unit cell. Furthermore, the procedure for nonlinear analysis of amplifying reflectarray antenna is described and nonlinear analysis is verified by ADS software simulation. Moreover, a typical amplifying reflectarray antenna is designed considering the nonlinear behavior. Nonlinear analysis of the active aperture-coupled patch unit cell is performed using harmonic balance method considering nonlinear model of the amplifier. Then, the effect of nonlinear element in radiation pattern of the antenna is studied. Passive unit cell is simulated using full-wave analysis method considering infinite array approach, and scattering parameters of the unit cell is obtained. Next, these scattering parameters are transformed to admittance parameters and used in obtaining nonlinear response and harmonic distortion of the unit cell containing amplifier. Obtained results show up to 3.4 dB error in predicting pattern of the antenna with linear modeling of the active element.

A method based on spindle motor current harmonic distortion measurements for tool wear monitoring

This paper deals with an indirect measurement of tool wear from spindle motor current. The main focus of this paper is on harmonic analysis of motor current. In this research, the nonlinear harmonic distortion caused by tool breakage and tool wear in the turning process is scrutinized. Representation of fundamental and harmonic components of the signals indicates that the amplitude of fundamental and odd order harmonic components of the signal for worn tool is higher than sharp tool. As the result of increasing harmonics the waveform of AC current signal becomes more distorted. The total harmonic distortion and crest factor measurements, which indicate the level of distortion in the current signal, are proposed as the measures for detecting tool wear and tool breakage by measuring electric current signal. The results show that the total harmonic distortion and crest factor measures increases as tool wear occurs and abruptly increases when there is tool breakage.

(Invited) Total Harmonic Distortion for PEM Fuel Cell

Electrochemical Impedance Spectroscopy (EIS) is well developed and widely applied for the study of electrode/electrolyte interfaces, films, coatings, and ion-transport mechanisms, among others. Measurement and analysis of traditional EIS is based on linear response in voltage or current to a sinusoidal perturbation. Small perturbations with linear responses are used in traditional EIS. Larger perturbations applied to nonlinear systems require a new set of tools. In the present study, we focus on the larger amplitude modulation and analysis of the harmonic response with the purpose of improving signal-to-noise ratio, and deriving additional information about the electrochemical system. Traditional EIS is extended to include Total Harmonic Distortion (THD) analysis. Non-linear harmonic distortion, instrument noise, and perturbation amplitude effects are discussed relative to monitoring oxygen concentration and operation status of a PEM fuel cell (PEMFC). Alternative approaches such as Intermodulation Distortion (IMD) are also introduced.

A method to decrease the harmonic distortion in Mn-Zn ferrite/PZT and Ni-Zn ferrite/PZT layered composite rings exhibiting high magnetoelectric effects

We have investigated the magnetoelectric (ME) effect in layered composite rings subjected to circumferential AC magnetic fields and DC magnetic fields in radial, axial, or circumferential directions. Bilayer samples were obtained combining different grades of commercial Mn-Zn ferrites or Ni-Zn ferrites with commercial lead zirconate titanate (PZT). Mn-Zn ferrites with low magnetostriction saturation (λs<10−6) and low magneto-crystalline anisotropy constants show high ME capabilities when associated with PZT in ring structures. In certain conditions, these ME effects are higher than those obtained with Terfenol-D/PZT composites in the same layered ring structure. Magnetostrictive and mechanical characterizations have given results that explain these high ME performances. Nevertheless, Mn-Zn ferrite/PZT composites exhibit voltages responses with low linearity especially at high signal level. Based on the particular structure of the ME device, a method to decrease the nonlinear harmonic distortion of the ME voltages is proposed. Harmonic distortion analysis of ME voltages measured in different configurations allows us to explain the phenomenon.

Theoretical study on nonlinear magnetoelectric effect and harmonic distortion behavior in laminated composite

A theoretical model is established for nonlinear magnetoelectric (ME) effect and harmonic distortion behavior in laminated composite, in which the complex nonlinear mechanical-thermo-magnetic characteristics of magnetostrictive phase are taken into consideration. Both the low-frequency and the resonant ME effects are derived by the elastic mechanics method. In this model, the output ME voltage is divided into three parts: a dc term, a linear ac term and a nonlinear ac term. Considering the temperature effect, this model is adopted to predict the dependences of ac voltages on bias magnetic field, frequency of ac magnetic field, the volume fraction of piezoelectric phase and interfacial parameter. Then, the competition relationship between linear and nonlinear ac voltages is discussed. To clearly describe the nonlinear characteristics of the proposed sample, a distortion factor θ is used for characterizing the harmonic distortion behaviors. The dependences of θ on the frequency of ac magnetic field and temperature under different ac magnetic fields are also studied. Finally, the predictions of harmonic distortion behaviors with changing bias magnetic field are obtained. The calculated linear ME coefficient shows a good agreement with the previous experimental data. It showed that: linear ac voltage and linear piezomagnetic coefficient present the same trend as the bias magnetic field increases, and nonlinear ac voltage shows the same trend as the absolute value of nonlinear piezomagnetic coefficient with increasing bias magnetic field; with temperature increasing, the output ME voltages decrease; operating temperature has a minimal effect on the required magnetic field corresponding to the optimal value of the output ME voltages, while it cannot alter the optimal value of piezoelectric phase's volume fraction; the nonlinear ac voltage presents more resonant frequencies than the linear one in the same range. Also, a definite multiple relationship is observed between the corresponding resonant frequencies of linear and nonlinear voltages; a larger θ leads to a more serious harmonic distortion, which is influenced by the frequency of ac magnetic field and temperature; bias magnetic field can be applied to adjust the harmonic distortion behaviors.

Power Amplifier Linearizer for High Frequency Medical Ultrasound Applications.

Power amplifiers (PAs) are used to produce high-voltage excitation signals to drive ultrasonic transducers. A larger dynamic range of linear PAs allows higher contrast resolution, a highly desirable characteristic in ultrasonic imaging. The linearity of PAs can be improved by reducing the nonlinear harmonic distortion components of high-voltage output signals. In this paper, a linearizer circuit is proposed to reduce output signal harmonics when working in conjunction with a PA. The PA performance with and without the linearizer was measured by comparing the output power 1-dB compression point (OP1dB), and the second- and third-order harmonic distortions (HD2 and HD3, respectively). The results show that the PA with the linearizer circuit had higher OP1dB (31.7 dB) and lower HD2 (-61.0 dB) and HD3 (-42.7 dB) compared to those of the PA alone (OP1dB (27.1 dB), HD2 (-38.2 dB), and HD3 (-36.8 dB)) at 140 MHz. A pulse-echo measurement was also performed to further evaluate the capability of the linearizer circuit. The HD2 of the echo signal received by the transducer using a PA with the linearizer (-24.8 dB) was lower than that obtained for the PA alone (-16.6 dB). The linearizer circuit is capable of improving the linearity performance of PA by lowering harmonic distortions.

Nonlinear harmonic distortion effect in magnetoelectric laminate composites

Magnetoelectric (ME) harmonic distortion behavior in layered piezoelectric/magnetostrictive composites was investigated in this study. Taking into account the quadratic magnetostrictive effect, a nonlinear distortion coefficient was proposed to quantitatively describe the distortion of ME frequency response. It was revealed that the ME distortion was the competition result of linear piezomagnetic and quadratic magnetostrictive effect. Theoretical predictions of their dependences on dc bias field and frequency of ac drive field showed good agreement with experiment. Moreover, the diagram of competition mechanism for these two effects was established, demonstrating that the nonlinear distortion could be tuned by interplay between frequency doubling and mechanical resonance effect, which was significant for the development of tunable nonlinear ME devices.

A study of nonlinear harmonic distortion in a balanced armature actuator with asymmetrical magnetic flux

This study investigates the nonlinear harmonic distortion caused by the asymmetrical magnetic flux in a balanced armature actuator (BAA). To account for asymmetrical magnetic flux, a set of transduction equations with nonlinear parameters for a BAA is first established. Next, the nonlinear transduction equations are solved correctly and with great efficiency by utilizing the hybrid spline difference method. Unlike symmetrical magnetic flux that leads to odd-order harmonic distortion only, analysis results demonstrate that asymmetrical magnetic flux in the electromagnetic field leads to the simultaneous appearance of even- and odd-order harmonic distortions. Meanwhile, the present study also indicates that the nonlinear harmonic distortion of the BAA can be reduced by adjusting the eccentric position of the armature and the cross-sectional area of the air gap between the permanent magnets and armature. Results presented herein provide valuable information not only on the desired design of a BAA but also on the diagnosis and improvement of its performance.

Advantages of the Graded-Channel SOI FD MOSFET for Application as a Quasi-Linear Resistor

In this paper, we analyze the previously unexpected advantages of asymmetric channel engineering on the MOS resistance behavior in quasi-linear operation, such as used in integrated continuous-time tunable filters. The study of the two major figures of merit in such applications as on-resistance and nonlinear harmonic distortion, is supported by both measurements and simulations of conventional and graded-channel (GC) fully depleted silicon-on-insulator (SOI) MOSFETs. The quasi-linear current-voltage characteristics of GC transistors show a decrease of the on-resistance as the length of the low doped region in the channel is increased, as well as an improvement in the third-order harmonic distortion (HD3), when compared with conventional transistors. A method for full comparison between conventional and GC SOI MOSFETs is presented, considering HD3 evolution with on-resistance tuning under low voltage of operation. Results demonstrate the significant advantages provided by the asymmetrical long channel transistors.

Identification of the Nonlinear Response of Ionic Polymer Actuators using the Volterra Series

Ionic polymer transducers exhibit coupling between three physical domains: electrical, chemical, and mechanical. This coupling enables their use as both sensors and actuators. Because this phenomenon was only recently discovered, the fundamental mechanisms governing the actuation and sensing response are still open for debate. However, since ionic polymers are very compliant, low-voltage transducers have become an increasingly researched intelligent material. In this paper we aim to gain a better understanding of the physical mechanisms involved in the actuation response by studying the nonlinear harmonic distortion. The Volterra series was the chosen identification technique for its potential to extract information about the nonlinearities. Results show that the solvent appears to play a significant role in the actuation response, as evidenced by a changing distortion from different solvents.

Integral function method for determination of nonlinear harmonic distortion

The analysis of harmonic distortion is of prime importance for the analog and mixed integrated circuits. Recently we presented a new integral function method (IFM), based on a completely new principle, which allows the calculation of harmonic distortion using the DC output characteristic of devices or circuits. In this work we complement the integral function method to provide direct calculation of the following distortion figures: total harmonic distortion (THD), second harmonic distortion (HD2) and third harmonic distortion (HD3), voltage intercept points (VIP) and the intermodulation distortion (IMD). The comparison with the same distortion figures calculated by the Fourier coefficients (FC), by direct AC measurements and from FFT in simulators, indicates that results obtained by IFM give an excellent agreement in the full range of the analyzed active regions. The IFM combines simplicity and computer efficiency with accuracy and with the possibility to easily analyze the distortion when varying any of the circuit or device parameters.

Experimental verification of the mechanisms for nonlinear harmonic growth and suppression by harmonic injection in a traveling wave tube.

Understanding the generation and growth of nonlinear harmonic (and intermodulation) distortion in microwave amplifiers such as traveling wave tubes (TWTs), free electron lasers (FELs), and klystrons is of current research interest. Similar to FELs, the nonlinear harmonic growth rate scales with the harmonic number in TWTs. In klystrons, the wave number scaling applies to the nonlinear harmonic bunching and associated nonlinear space-charge waves. Using a custom-modified TWT that has sensors along the helix, we provide the first experimental confirmation of the scaling of nonlinear harmonic growth rate and wave number in TWTs. These scalings of a nonlinearly generated harmonic mode versus an injected linear harmonic mode imply that suppression by harmonic injection occurs at a single axial position that can be located as desired by changing the injected amplitude and phase.