Nonlinear Distortion Analysis Research Articles

Analysis of Nonlinear Distortions of Dphemt Structures Based on a GaAs/InGaAs Compound with Double-Sided Delta-Doping

The paper presents the results of studies of C–V characteristics of GaAs/In0.53Ga0.47As HEMT before and after neutron irradiation with a fluence of (6.3 ± 1.3) × 1014 cm–2. Based on the experimentally obtained characteristics, the effective electron distribution profiles of the structure were calculated before and after radiation impact. The effect of radiation defects on the δ-layers of the structure was analyzed.

Reducing black-box nonlinear state-space models: A real-life case study

A known challenge when building nonlinear models from data is to limit the size of the model in terms of the number of parameters. Especially for complex nonlinear systems, which require a substantial number of state variables, the classical formulation of the nonlinear part (e.g. through a basis expansion) tends to lead to a rapid increase in the model size. In this work, we propose two strategies to counter this effect:1) The introduction of a novel nonlinear-state selection algorithm. The method relies on the non-parametric nonlinear distortion analysis of the Best Linear Approximation framework to identify the state variables which are the most impacted by nonlinearities. Pre-selecting only the most appropriate states when constructing the nonlinear terms results in a considerable reduction of the model size.2) The use of so-called ‘decoupled’ functions directly in the model estimation procedure. While it is known that function decoupling can reduce the model size in a secondary step, we show how a decoupled formulation can be imposed to advantage from the start. The results of this approach are benchmarked with the state-of-the-art a posteriori decoupling technique.Our strategies are demonstrated on real-life data of a multiple-input, multiple-output (MIMO) ground vibration test of an F-16 aircraft, a prime complex and nonlinear dynamic system.

Analysis of Nonlinear Distortions of DpHEMT Structures Based on a GaAs/In0.53Ga0.47As Compound with Double-Sided Delta-Doping

Analysis of Nonlinear Distortions of DpHEMT Structures Based on a GaAs/In0.53Ga0.47As Compound with Double-Sided Delta-Doping

Modeling and Simulation of Magnetic Balance Current Sensor Based on Magnetic Scalar Potential Volume Integral

In this paper, a field–circuit combined simulation method, based on the magnetic scalar potential volume integral equation (MSP-VIE) and its fast algorithms, are proposed for the transient simulation and nonlinear distortion analysis of the magnetic balance current sensor. The magnetic part of the sensor is modeled and simulated by MSP-VIE with the field matrices extracted by the method of moments. By directly implementing the magnetic field equation in the circuit, these field matrices can be regarded as equivalent circuit parameters of the magnetic part, to construct the corresponding SPICE model. Finally, the field–circuit combined model of the entire sensor is unified in a circuit, so with the SPICE solver, the transient simulation is accomplished in the time domain. Moreover, aiming at the time-consuming problem, this paper presents a corresponding fast method to accelerate the simulation. The comparison of measurement and simulation demonstrates that the proposed method not only realizes the transient simulation of the whole sensor, but also simulates some hidden performance details; thus, it can be applied to practical engineering, to guide and test the early design of the product.

Pseudo-Signal Interference Regularity of Single-Frequency Electromagnetic Radiation to Stepped-Frequency Radar

When typical radar equipment is subjected to single-frequency electromagnetic radiation, the radar display interface forms a pseudo-signal, resulting in the misjudgment of real targets. Based on the working principle of stepped-frequency radar ranging, the effect mechanism of radar equipment pseudo-signal interference is revealed. Taking a Ku band stepped-frequency ranging radar as the test object, the pseudo-signal interference effect test of single-frequency electromagnetic radiation is carried out in this study. The pseudo-signal level value of 6 dBmV is selected as the sensitive criterion of the pseudo-signal interference effect. Through experiments, the variation curves of the pseudo-signal level values of the sensitive frequency bands and the typical frequency points inside and outside the band with the field strength of the single-frequency interference are obtained. Based on the nonlinear distortion analysis of the receiving circuit, the variation laws of the pseudo-signal level values inside and outside the band are explained, respectively. The experimental results show that there are at least seven pseudo-signal interference-sensitive bands in the tested radar, and the first pseudo-signal strength is only related to the interference signal strength. The essence of the second type of pseudo-signal interference is intermodulation interference, and the pseudo-signal level is related to the interference signal and the useful signal strength.

Statistical Modeling and Analysis of Power Amplifier Nonlinearities in Communication Systems

Hardware impairments in general and amplifier nonlinearity in particular severely limit the performance of communication links. This paper analytically provides statistical results on how a nonlinear amplifier affects the quality of signals in communication systems. In particular, we propose a statistical model that describes the nonlinear distortion as a function of the input signal’s average and instantaneous power and captures the pulse-shaping and matched filters’ effects. We show through simulations and complementary measurements that the proposed model can provide an authentic connection between the communication system parameters, power amplifier nonlinearity characteristics, and the communication system performance. It serves not only as a reliable model for nonlinear distortion analysis but also as a design tool that allows optimization of signal and filter characteristics with respect to nonlinear distortion.

Analysis of nonlinear distortions of DpHEMT structures based on the GaAs/InGaAs compound with double-sided delta-doping

Computational and experimental studies of the characteristics of a high-power AlGaAs/InGaAs/GaAs DpHEMT were performed. A self-consistent numerical solution of the Schrodinger and Poisson equations was used to calculate the band diagram and the electron concentration in the channel of the transistor under study. The electron mobility in the transistor channel was estimated experimentally at 9300 cm2/V·s. The obtained transfer current--voltage characteristic of the transistor was used to calculate the parameters of a model differential amplifier (small-signal gain and third-order non-linear distortion factor). Keywords: AlGaAs/InGaAs/GaAs DpHEMT, nonlinear distortion, spacer layers.

Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies

Integrated CMOS neural amplifiers are key elements of modern large-scale neuroelectronic interfaces. The neural amplifiers are routinely AC-coupled to electrodes to remove the DC voltage. The large resistances required for the AC coupling circuit are usually realized using MOSFETs that are nonlinear. Specifically, designs with tunable cutoff frequency of the input high‑pass filter may suffer from excessive nonlinearity, since the gate-source voltages of the transistors forming the pseudoresistors vary following the signal being amplified. Consequently, the nonlinear distortion in such circuits may be high for signal frequencies close to the cutoff frequency of the input filter. Here we propose a simple modification of the architecture of a tunable AC-coupled amplifier, in which the bias voltages Vgs of the transistors forming the pseudoresistor are kept constant independently of the signal levels, what results in significantly improved linearity. Based on numerical simulations of the proposed circuit designed in 180 nm technology we analyze the Total Harmonic Distortion levels as a function of signal frequency and amplitude. We also investigate the impact of basic amplifier parameters—gain, cutoff frequency of the AC coupling circuit, and silicon area—on the distortion and noise performance. The post-layout simulations of the complete test ASIC show that the distortion is very significantly reduced at frequencies near the cutoff frequency, when compared to the commonly used circuits. The THD values are below 1.17% for signal frequencies 1 Hz–10 kHz and signal amplitudes up to 10 mV peak-to-peak. The preamplifier area is only 0.0046 mm2 and the noise is 8.3 µVrms in the 1 Hz–10 kHz range. To our knowledge this is the first report on a CMOS neural amplifier with systematic characterization of THD across complete range of frequencies and amplitudes of neuronal signals recorded by extracellular electrodes.

A nonlinear model of vortex-induced forces on an oscillating cylinder in a fluid flow

A nonlinear model relating the imposed motion of a circular cylinder, submerged in a fluid flow, to the transverse force coefficient is presented. The nonlinear fluid system, featuring vortex shedding patterns, limit cycle oscillations and synchronisation, is studied both for swept sine and multisine excitation. A nonparametric nonlinear distortion analysis (FAST) is used to distinguish odd from even nonlinear behaviour. The information which is obtained from the nonlinear analysis is explicitly used in constructing a nonlinear model of the polynomial nonlinear state-space (PNLSS) type. The latter results in a reduction of the number of parameters and an increased accuracy compared to the generic modelling approach where typically no such information of the nonlinearity is used. The obtained model is able to accurately simulate time series of the transverse force coefficient over a wide range of the frequency–amplitude plane of imposed cylinder motion.

Self‐tunable chaotic true random bit generator in current‐mode CMOS circuit with nonlinear distortion analysis

SummaryWe discuss the low‐complexity integrated circuit design of a true random bit generator with parametric self‐tuning capabilities. The design targets a mixed‐signal complementary metal‐oxide‐semiconductor (CMOS) current‐mode circuit implementing the Sawtooth chaotic map. Starting from the analysis of the proposed circuit topologies, we investigate how the dynamical system behavior is affected by nonlinear distortions, discussing theoretical simplified models and resorting to qualified numerical simulations. The circuit solutions proposed in this paper and validated with experiments represent an improvement of the designs published in literature, proposing technical solutions to solve stability issues and introducing parametric adjustment capabilities while maintaining a strong link with the studied theoretical models.

Analysis of nonlinear distortion and its reduction using feedback injection schemes in an [formula omitted] transistor laser

In this work, we analyze the third and fifth order intermodulation distortion components and its reduction in an 1.3μm transistor laser by feedback harmonic injection technique. The device is modeled by rate equations, which are numerically solved by fourth order Runge–Kutta method. The second harmonic and IMD3 components available at the collector are added with the base current separately, to reduce the distortions. Modulation Bandwidth of 11 GHz and modulation depth of 92.1% are obtained for Ib=7.5 mA. An improvement of 12.64 dB and 4.3 dB are obtained for IMD3 and IMD5, under second harmonic injection scheme, at a bias current of 7.5 mA. In the case of combined second harmonic and IMD3 feedback injection, a reduction of 13.33 dB and 4.49 dB is obtained. Similarly, SFDR of 63.7 dB/Hz2∕3 and 64 dB/Hz2∕3 are obtained for the first and second schemes respectively.

Nonlinear distortion analysis for single heterojunction GaAs HEMT with frequency and temperature

Nonlinearity analysis using two-tone intermodulation distortion (IMD) technique for 0.5 μm gate-length AlGaAs/GaAs based high electron mobility transistor have been investigated based on biasing conditions, input power, frequency and temperature. The outcomes indicate a significant modification on the output IMD power and as well as the minimum distortion level. The input IMD power effects the output current and subsequently the threshold voltage reduces, resulting to an increment in the output IMD power. Both frequency and temperature reduces the magnitude of the output IMDs. In addition, the threshold voltage response with temperature alters the notch point of the nonlinear output IMD’s accordingly. The aforementioned investigation will help the circuit designers to evaluate the best biasing option in terms of minimum distortion, maximum gain for future design optimizations.

Analysis of different structure and nonlinear distortion of multicore fiber for power over fiber applications

Recently the fiber technology enabled the application in electrical domain for remote access uses. The Power over Fiber technique is a preamble for the same where in the multicore fiber is used as a channel. In this paper, we have designed the five structures like triangular, ring, square, rectangular and hexagonal of multi core fiber and their analysis in term of a number of cores, pitch and power spectrum. The hexagonal MCF has provided maximum power at output –10 dB and maximum power of current cut is 6.340e-001W at 38 mesh point and recommended for power over fiber link. The nonlinear distortions associated with multicore fiber and its impact on the performance of power over fiber link are also discussed. The simulation results are carried out on OptiFDTD 12.0 version platform.

Stability, Noise, and Nonlinear Distortion Analysis of a Sampling OPLL

The behavior of a sampling optical phase-locked loop (OPLL) is analyzed. An equivalent time invariant system model for the sampling OPLL was derived. With the help of the model, the stability of a sampling OPLL was found to depend not only on the sampling frequency but also on the duty cycle of the sampling pulse. In addition, the closed-form solutions for the sampling OPLL output noise and nonlinear distortions were also derived. The theoretical results were validated by numeric simulations.

Fast-scale non-linear distortion analysis of peak-current-controlled buck–boost inverters

ABSTRACTThis paper deals with fast-scale non-linear distortion behaviours including asymmetrical period-doubling bifurcation and zero-crossing distortion in peak-current-controlled buck–boost inverters. The underlying mechanisms of the fast-scale non-linear distortion behaviours in inverters are revealed. The folded bifurcation diagram is presented to analyse the asymmetrical phenomenon of fast-scale period-doubling bifurcation. In view of the effect of phase shift and current ripple, the analytical expressions for one pair of critical phase angles are derived by using the design-oriented geometrical current approach. It is shown that the phase shift between inductor current and capacitor voltage should be responsible for the zero-crossing distortion phenomenon. These results obtained here are useful to optimise the circuit design and improve the circuit performance.

Method of contour integrals for the analysis of complex nonlinear distortions of narrowband Gaussian random processes

The method of contour integrals can be used to analyze interference in radio equipment of modern broadband radio-access systems resulting from the presence of nonlinear devices (NDs) with amplitude-to-phase conversion. Several nonlinear models of power amplifiers are considered as such devices. The analysis of interference is reduced to the determination of the interference power density at the ND output and the signal-to-interference ratio in the fundamental band of the signal.

Operator o and analysis of harmonic distortion

Abstract It has been shown that the description of mildly nonlinear circuits with the use of an operator o introduced by Meyer and Stephens in their paper published more than forty years ago was flawed. The problem now with their incorrect and imprecise definition is that it is still replicated in one or another form, as, for example, in publications of Palumbo and Pennisi on harmonic distortion calculation in integrated CMOS amplifiers or an article of Shrimali and Chatterjee on nonlinear distortion analysis of a three-terminal MOS-based parametric amplifier. Here, we discuss the versions of o operator presented in the works mentioned above and show points, where mistakes were committed. Also, we derive the correct forms of nonlinear circuit descriptions that should be used.

Comparative analysis of inter-channel nonlinear distortions from PM-QPSK and PS-QPSK interferers

Polarization-Switched QPSK (PS-QPSK) can offer a higher tolerance to fiber nonlinearities than Polarization Multiplexed QPSK (PM-QPSK), albeit with 25% loss of spectral efficiency. While improved performance has been shown experimentally, a thorough study of inter-channel nonlinearities in these systems has not been performed. Here we numerically study two separate manifestations of cross phase modulation (XPM) generated by these two formats; XPM-induced phase noise (XPM-PN) and XPM-induced polarization crosstalk (XPM-PC). We find that in both dispersion-compensated (DC) and dispersion uncompensated (DUC) systems, greater XPM-PN is generated by PS-QPSK interferers, whereas greater XPM-PC is generated by PM-QPSK interferers. While the combined effect of these distortions provides similar penalties in either system, this finding may help inform the design of efficient nonlinear equalizers.

A Novel Decomposition Analysis of Nonlinear Distortion in OFDM Transmitter Systems

In Orthogonal Frequency Division Multiplexing (OFDM) transmitter systems, nonlinear distortion is a major impairment caused by power amplifier (PA). The distortion is constituted by numerous noise-like inter-modulation products (IMPs). Although the overall behavior of nonlinear IMP distortion has been well studied, in large multi-carrier contexts, such as in OFDM, the knowledge of individual IMPs and their quantitative interrelationships, together with the derivation of behavioural knowledge and the predictability of consequences arising from such interrelationships, is a fairly unexplored topic. This is the subject of this paper. The powers of the very numerous individual IMPs generated are analytically derived based on a Bessel-Fourier PA behavioural model, and it is proven that these powers have only a small number of distinct powers. Proven also is that the ratios of these power values are constants, and that these constants are invariant with the particular PA's nonlinearity characteristics or operating point. Further, it is proven that specific types of IMPs dominate nonlinear distortion effects. Finally, it is shown that IMP power spectra can be derived from a simple product of two polynomials, which are quadrature functions of frequency and PA operating point, respectively. Application possibilities for findings presented in this paper, such as their potential to contribute efficiency improvements in OFDM system modulation fidelity calculations (over 1100 times faster than conventional methods), are also outlined in the conclusions.

Analysis of Nonlinear Distortion and SSII Cancellation in EAM-Based IMDD OFDM Transmission

In terms of second-order nonlinearity, nonlinear distortion in an EAM-based IMDD OFDM system is deterministically modeled as subcarrier-to-subcarrier intermixing interference (SSII), such that DSP-based nonlinear compensation can be provided by decision-aided SSII cancellation at the receiver. The effectiveness of SSII cancellation heavily relies on the accuracy of SSII calculation, which is determined mainly by the modulation model adopted. This study made comprehensive comparisons of three small-signal models (constant-chirp, dynamic-chirp, and nonlinear-E/O models). We then combined theory and experiment results to examine the characteristics of SSII estimation and cancellation using various models, such as SSII spectra, regression coefficients, and correlation coefficients between the SSII and the total received errors, as well as the relationship between improvements in performance and the correlation coefficient. The nonlinear-E/O model is the most comprehensive, and as a result presents the flattest regression coefficient and highest correlation coefficient, which results in the most pronounced improvement in performance.