Narrow Results

There has been intensive research in memoryless nonlinear behavioral modeling of power amplifiers (PAs). But in broadband communication systems, memory effects of PAs can no longer be ignored and traditional memoryless model cannot accurately characterize the input-output relationship of PAs. In order to treat memory effects and reduce the complexity of general Volterra model, a new behavioral PA model based on modified Volterra series is proposed. Since the characteristics of power amplifiers change during transmission time, a recursive least squares algorithm with size-fixed observation matrices is developed to update the parameters of the PA model. This identification algorithm, which uses only the latest sample data to identify the parameters, can decrease computational complexity and data storage space needed for identification. Simulations are carried out to validate the performances of the proposed PA model and identification algorithm.

An open loop voltage buffer with an exact unity gain using a positive local feedback technique with a conventional source follower is proposed. Stability of the buffer is determined by evaluating the location of the poles and zeros and its linearity is studied using Volterra series expansion. The proposed buffer is laid out in 0.35-μm standard CMOS technology. Post layout simulations demonstrate that the buffer gain is close to unity with less than 0.2% error. The power consumption is 10 mw from a 3.3 V power supply and the achieved total harmonic distortion is -78 dB for a 10 MHz input frequency. Also Monte-Carlo simulations are carried out to investigate effects of random mismatches on the circuit operation.

A nonlinear spatio-temporal system identification and analysis approach is used to study the dynamical behavior of the Belousov–Zhabotinsky (BZ) chemical reaction process. In our previous study [Guo et al., 2010],, the dynamical behavior of the BZ reaction in the spatial-temporal domain has been analyzed by identifying a coupled map lattice (CML) model of the process directly from experimental data from a real BZ reaction experiment. In this paper, the frequency domain analysis of the dynamics near equilibrium is carried out by mapping the obtained CML model into higher order spatial frequency response functions to reveal the nonlinear coupling and modulation between the various initial spectral components in the process. As far as we are aware, this is the first study of any real spatio-temporal system using a spatio-temporal domain identification and frequency domain analysis approach.

This paper presents the study of the behavior of a soil deposit formed by a single layer subjected to a bedrock excitation strong enough to induce a nonlinear behavior. The soil deposit will be modeled as a Single Degree of Freedom system. The equation of motion that describes the behavior of the system when a seismic wave travels from the bedrock to the surface is developed. The shear modulus and damping ratio of the soil are nonlinear functions of the shear strain. The response of the system is calculated using the proposed method and a nonlinear step-by-step integration scheme. The hysteretic damping model predicts that the dissipation of energy is independent of frequency. The dissipation of energy in soils is practically independent of frequency, and then the hysteretic damping is a better model to describe the soil behavior. If the hysteretic damping model is used, the analysis has to be done in the frequency domain. Up to the third order kernel of the Volterra series in the frequency domain is developed. An inverse Fourier transforms is needed to retrieve the response in the time domain. The examples showed that the HOFRF method could be employed to calculate the response of a single layer soil deposit subjected to a prescribed acceleration of seismic origin strong enough to induce a nonlinear response in the medium.

We present a novel simulation model based on the proposed segmented Volterra series transfer function (S-VSTF) for advanced optical communication systems. The S-VSTF model is used to obtain analytic solution of the nonlinear Schröndinger (NLS) wave equation. Simulated results are compared with those using the well-known split-step Fourier method and it is confirmed that the model is efficient and accurate for optical pulse transmission systems.