Arnaud Soury

A new behavioral model taking into account nonlinear memory effects and transient behaviors in wideband SSPAs

Accurate and non quasi-static behavioral models of SSPAs taking into account nonlinear memory effects become of prime importance for a breakthrough in system level analysis and design of wideband digital communication systems. This paper describes a new method to characterize and integrate memory effects in nonlinear behavioral models of SSPAs allowing to reproduce both transient and steady state behaviors.

Behavioral modeling of RF and microwave circuit blocks for hierarchical simulation of modern transceivers

The development of simulation and macro-modeling techniques for RF and microwave communication systems has been a high priority research subject for several years. If one observed this last years an impressive improvement of simulation tools performances, the full chip simulation of modern TX-RX chains remains a real stumbling block, as the transistor count has considerably increased. This paper discusses the hierarchical RF simulation issue using the same harmonic balance or envelope transient simulation engine for both transistor level description and circuit block macro-models. This method can reduce the size of the problem to enable accurate and fast simulation of large size circuits. The concept requires however to develop macro-modeling techniques taking into account impedance mismatch effects, which are discussed here.

Measurement based modeling of power amplifiers for reliable design of modern communication systems

The characterization and the modeling of nonlinear memory effects are, nowadays, an integral part of the design process of modern communication systems. Notably, the nonlinear long term memory effects occurring in solid state devices impact considerably system performances. Recently, a new method to characterize and integrate low frequency memory effects in nonlinear behavioral models of SSPAs has been presented. This paper presents a detailed mathematical study and a measurement based extraction principle of the proposed behavioral model. Calibrated time-domain envelope measurements are used for the model extraction and verification procedures. The extraction technique is illustrated by the modeling of a L-Band HFET amplifier.

A Two-Kernel Nonlinear Impulse Response Model for Handling Long Term Memory Effects in RF and Microwave Solid State Circuits.

Accurate modeling of the memory effects in nonlinear RF and microwave devices is of prime importance in the design process for the new generations of communications systems. This is particularly important for the design of power amplifier, predistorter and linearizer, and the prediction of system intermodulation distortion as well as power budget. This paper extends previous works and provides a comprehensive mathematical foundation for envelope-domain and band-pass nonlinear impulse response of RF and microwave blocs. The new model shows significant accuracy improvements in modeling long-term memory effects, especially self-heating. Besides the paper presents a new kernel identification technique that is faster and more accurate as it requires only frequency-domain measurements or harmonic-balance simulation

Time-domain envelope measurements for characterization and behavioral modeling of nonlinear devices with memory

This paper presents a calibrated four-channel measurement system for the characterization of nonlinear RF devices such as power amplifiers. The main goal of this study is to perform the characterization of the bandpass response of a nonlinear device-under-test (DUT) driven by modulated carriers. The proposed setup enables the generation of L- or S-band (1-4 GHz) carriers with a modulation bandwidth up to 100 MHz. The carrier harmonics generated by the nonlinear DUT are ignored and considered to be sufficiently filtered. This characterization setup enables calibrated time-domain measurements of the complex envelopes of both incoming and outgoing RF waves at the input and output of the DUT. This means that the fundamental and harmonic frequencies of the envelope are measured and processed. A large set of modulation formats can be generated by using a computer-controlled arbitrary waveform generator. Complex envelopes are measured by using a four-channel sampling scope. The proposed calibrated setup can be used to study or to validate linearization techniques of power amplifiers. This characterization tool is also well suited for the extraction and validation of behavioral bilateral models of nonlinear RF analog equipment exhibiting memory effects

Modeling memory effects in nonlinear subsystems by dynamic Volterra series

Design challenges resulting from single chip integration of RF and microwave transceivers is requiring both more powerful analog simulation techniques and more accurate behavioral models that allow efficient hierarchical simulation. Today system level models are limited by their inability to effectively cope with nonlinear memory effects. We describe a modeling approach based on modified Volterra series, which accounts efficiently for memory effects in nonlinear subsystems.

Implementation of Behavioral Models in System Simulator and RF Circuit/System Co-Simulation

The verification of the system performances becomes of prime importance and notably with the emergence of the SoC, in which, the spurious couplings between the functional circuits can be critical. The needs in terms of system simulation tools become thus very important. This paper is divided into two parts, the first part presents a method to implement the Volterra and nonlinear impulse response models in Matlab/Simulink environment. The second part presents a co-simulation interface between Matlab/Simulink and Xepedion/Goldengate circuit simulator

Modeling long term memory effects in microwave power amplifiers for system level simulations

Accurate and dynamic behavioral models of SSPAS become of prime importance in system level analysis and design of modern communication and detection systems. This paper describes a new method to characterize and reproduce nonlinear memory effects in behavioral models ofSspas. We highlight, in a first section, the detailed mathematical development, whose the starting point is the Volterra series expansion, and ends to the nonlinear impulse response notion. The new model extraction relies on envelope transient simulations or time-domain measurements of complex envelopes at externDut reference accesses. This modeling technique is simple and enables a good prediction of nonlinear memory effects and especially long term memory effects and nonlinear transient behaviors. Simulations and measurements based extractions of this model are presented through significant amplifier examples.RésuméLes modèles comportementaux dynamiques précis d’amplificateurs de puissance deviennent de première importance dans l’analyse et la conception de systèmes de détection et de communication modernes. Ce papier décrit une nouvelle méthode pour caractériser et reproduire les effets de mémoire non linéaires dans les amplificateurs de puissance. Nous présentons dans une première section un développement mathématique détaillé dont le point de départ est le développement en séries de Volterra et qui se conclut par la notion de réponse impulsionnelle non linéaire. L’extraction du nouveau modèle repose sur des simulations en transitoire d’enveloppe ou des mesures dans le domaine temporel des enveloppes complexes présentes aux accès du dispositif sous test (Dst). Cette technique de modélisation est simple et permet une bonne prédiction des effets de mémoire non linéaires et notamment des effets de mémoire à long terme et des comportements transitoires non linéaires. Des extractions de ce modèle basées sur des simulations et des mesures expérimentales sont présentées aux travers d’exemples d’amplificateurs significatifs.

Implementation of Volterra Model in System Simulation Environments and RF Circuit/System Co-Simulation

The verification of the system performances becomes of prime importance and notably with the emergence of the SoC, in which, the spurious couplings between the functional circuits can be critical. The needs in terms of system simulation tools become thus very important. This paper is divided into two parts, the first part presents a method to implement the Volterra and nonlinear impulse response models in Matlab/Simulink environment. The second part presents a co-simulation interface between Matlab/Simulink and Xepedion/Goldengate circuit simulator

Modeling envelope-tracking RF amplifiers

In the past years, the design of modern RF transceivers has been widely driven by strict and contrasting design specifications (linearity, efficiency, etc.). This is especially true for the advent of the new 4G (LTE) and of the next 5G standards. In this context, power amplifiers (PAs) have received a particular attention and we have seen the promotion of various pre-distortion techniques (DPD). In parallel, envelope tracking techniques recently allowed significant improvements in terms of power consumption. While some methods capturing the preformatting of the DC bias voltage have been proposed, the majority are based on static observations. Unfortunately, the design on new IC processes, either small-scale CMOS or GaN, is very sensitive to nonlinear memory effects. Those effects may alter the quality of the correction. This paper proposes a way to characterize those effects.