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In this work, a new adaptive digital predistorter (DPD) is proposed to linearize radio frequency power amplifiers (PA). The DPD structure is composed of two sub-models. A Feedback–Wiener sub-model, describing the main inverse nonlinearities of the PA, combined with a second sub-model based on a memory polynomial (MP) model. The interest of this structure is that only the MP model is identified in real time to compensate deviations from the initial behavior and thus further improve the linearization. The identification architecture combines offline measurement and online parameter estimation with small number of coefficients in the MP sub-model to track the changes in the PA characteristics. The proposed structure is used to linearize a class AB 75 W PA, designed by Telerad society for aeronautical communications in Ultra High Frequency (UHF) / Very High Frequency (VHF) bands. The obtained results, in terms of identification of optimal DPD and the performances of the digital processing, show a good trade-off between linearization performances and computational complexity.

Le système comptable financier dans ses directives en termes d’opérations libellées en monnaie étrangères qui se convergent dans une grande partie avec la norme IAS 21 "Effets des variations des cours des monnaies étrangères " ont donné la propriété à la réalité économique. L’objectif vise était de voir le mode de traitement spécifique dans le cadre des opérations de consolidation, surtout celles menées dans un environnement autre de celui de l’entreprise mère et selon une monnaie différente, ce qui impose un traitement particulier pour atteindre cet objectif la nécessite impérieuse de mettre en place une démarche approprié pour aboutir à des états financiers selon ce qui a été prescrit. Les entreprises qui détiennent des entités autonomes et non autonomes doivent faire la part des choses aux fins de tirer des conclusions surtout sur la performance en faisant une lecture approfondie de l’impact du cours du change. Mots Clés: directives , démarche, consolidation, autonomes , non-automnes Abstract : The financial accounting system in its directives in terms of foreign currency-denominated operations that largely converge with the IAS 21 "Effects of changes in the prices of foreign currencies" have given ownership to economic reality. The objective was to see the specific method of treatment in the context of consolidation operations, especially those carried out in an environment other than that of the parent company and in a different currency, which requires special treatment to achieve this objective, requiring the urgent need to put in place an appropriate approach to arrive at financial statements as prescribed. Companies that own stand-alone and non-fall entities must make the difference in order to draw conclusions, especially on performance, by making a thorough reading of the impact of the exchange rate.

Nonlinear behavior and power efficiency of the Power Amplifier (PA) contradictorily depend on the input signal amplitude distribution. The transmitted signal in multi-carrier modulation exhibits high Peak-to-Average Power Ratio (PAPR) and large bandwidths, leading to the degradation of the radio link and additional generation out-of-band interferences, which degrade the quality of the transmission. Practical solutions exist, like a power back-off, but with unacceptable efficiency performances of the transmitter. This paper deals with efficiency and linearity improvement using a new PAPR reduction method based on the combination of Discrete Cosine Transform and shaping technique. The main principle is to determine an optimal coding scheme according to a trade-off between coding complexity and performance benefits in the presence of PA nonlinearities. Simulation and experimental results in the context of OFDM signal and using a 20 W–3.7 GHz Radio-Frequency Power Amplifier show an improvement on PAPR reduction of about 3.25 dB. Also, the communication criteria like Bit Error Rate and Error Vector Magnitude are improved by about one decade and a half and $$8\%$$ 8 % , respectively.

This paper proposes the design of a precoder in MIMO systems dedicated to JPEG Wireless (JPWL) (ISO/IEC 15444-11) image transmission which jointly takes into account the channel noise and the nonlinear distortions due to the high power amplifier (HPA) used in the transmitter. MIMO-OFDM (Orthogonal Frequency Division Multiplexing) systems dedicated to image transmission rely only on the Channel State Information (CSI) and the image content to design their precoding solutions. However, the nonlinear behavior of the HPA used at the front-end is not taken into account when designing the current precoders. In order to ensure the QoS of the transmitted image, a large level back-off is usually applied to avoid the nonlinear distortions generated by the HPA. In addition, the Input Back-off (IBO) value is statically chosen and does not depend on the other parameters of the link such as the instantaneous MIMO channel status, the modulation order and the scalability of the JPWL content. This may reduce both the global energy efficiency and the transmission quality of the Radio-Frequency (RF) link. Therefore, this work proposes a new precoding scheme to allocate the total available power while dynamically adjusting the optimal power IBO value according to the HPA parameters, the instantaneous channel status and the image content to be transmitted. Numerical results using a commercial HPA model under the IEEE 802.11n standard show that the proposed power allocation algorithm improves the visual quality of the received JPWL images compared to the state-of-the-art over a realistic radio channel model.

New mobile applications require the use of Radio Frequency Power Amplifiers (RF PA) in a context of reconfigurability and adaptability. In this paper, we propose a modeling study of RF PA in this context. The proposed approach is a combination of a Feedback-Wiener (FW) structure with a Memory Polynomial (MP) model, which gives a pruned Volterra series. A FIR filter is used in the FW model as a feedback path to reproduce the PA memory effects. Also, a recursive identification algorithm based on the key-term separation principle is proposed and used for an experimental characterization of an LDMOS PA (50W–500MHz to 2.5GHz), with different carrier frequencies, bandwidths and output powers. The comparison with a conventional Generalized Memory Polynomial model (GMP) shows that the proposed model presents the same performances in term of behavioral modeling, with the advantage of a reduced number of parameters.

International audience; Orthogonal Frequency Division Multiplexing (OFDM) has been shown to be an effective technique in wireless communications. It has been successfully used for Radio Frequency applications. However, reducing its main drawback known as PAPR (Peak-to-Average Power Ratio) is one of the main challenges to use efficiently the High Frequency Power Amplifier at the transmitter. As one of attractive technique, interleaving method can be used in PAPR reduction for multicarrier signals without spectrum distortion, but with additional Side-Information. In this paper, we propose to extend the possibilities of interleaving to improve PAPR reduction and make possible the downward compatibility by transmitting interleaver code via null-subcarriers. Simulation in the context of WLAN 802.11a standard in presence of a nonlinear Power Amplifier (PA) model with memory has been performed. Results show a PAPR reduction of about 5,2 dB and an improvement of about 1 decade in BER (Bit Error Rate) and 4% in EVM (Error Vector Magnitude), while respecting the spectral mask.

International audience; In this paper, we propose a new PAPR reduction method using interleaving technique without data rate loss. The main idea is to set up all possibility of interleaving to get the best reduction of PAPR and to transmit the resulting information via null-subcarriers (NS) available in OFDM (Orthogonal Frequency Division Multiplexing) standards. Thus, we develop a new coding of interleaver key based on mapping symbols at the transmitter and a robust decoding procedure at the receiver. Simulation results in the context of WLAN IEEE 802.11a standard show an improvement of PAPR reduction about 5,2 dB, with the same performance in BER (Bit Error Rate), while respecting the communication criteria (Data Rate and spectrum specification).

This article presents a new analog predistortion linearizer to reduce non-linearity effects of Ku-band power amplifier. The structure is composed of Schottky diodes which create combinations of magnitude and phase distortions as function of biasing voltage. This method is compatible with different kind of amplifiers and broadband applications. Tested on a 250W travelling wave tube amplifier (TWTA), a maximum C/I 3 (Carrier to 3rd order intermodulation ratio) and NPR (Noise Power Ratio) improvement of about 17dB and 10dB is obtained, respectively, over 750MHz bandwidth.

International audience; The transmission of highly scalable image and video codestream over error-prone networks can be ensured by using Unequal Power Allocation (UPA) in MIMO-OFDM systems. However, UPA schemes are usually designed without taking into account the High Power Amplifier (HPA) nonlinearity, especially in MIMO-OFDM systems which are known to generate signals with a high Peak-to-Average Power Ratio (PAPR). This paper aims to evaluate the impact of HPA nonlinearity on the transmission of scalable image cotents over a precoded Closed-Loop MIMO-OFDM system when the well-known Content-Based Precoder (CBP) is used for UPA. For PAPR reduction, we have considered the Tone Reservation Using Null Subcarriers (TRNS) technique. Simulations are performed under the IEEE 802.11n standard in a realistic urban environment in presence of a commercial 2W class-AB memoryless HPA from RF Micro Devices. The experimental results in terms of Bit Error Rate (BER) and visual quality show that the error-protection of the most sensitive parts of the codestream against channel distortions achieved using UPA is significantly disturbed in presence of HPA nonlinearity. These results highlight the influence of HPA nonlinearity on the scalable image transmission.

International audience; This paper presents a new time-domain model of radio frequency power amplifiers (RF PA) for wideband applications. The proposed model identification requires a set of characterization procedures of a memory polynomial model with delay taps for a two-tone test. This first characterized model is described using amplitude AM/AM and phase AM/PM characteristics including delay and gain parameters, which is able to reproduce distortion sideband asymmetries. A two-tone signal with varying tone spacings is used to find the frequency response of parameters on each nonlinearity order. These response are used to estimate equivalent digital filters giving the final structure of a wideband model. The measurement tests on a Class AB-$1.85\,$GHz RF PA from Advanced semiconductor business with various multitone signals show that the proposed architecture describes PA nonlinearities and memory effects with a high level of accuracy

In this paper, we present a new technique for modeling and characterization of Power Amplifier (PA) by parameter estimation using continuous-time representation. Firstly, we study a continuous model which takes into account nonlinearities and PA filtering. The filter structure includes a non linear polynomial representing amplitude and phase conversion in addition to a MIMO Laplace plant. Then, we propose a new approach for PA model characterization based on parameter estimation with several excitations. Using time-domain measurements, this method deduces recursively an optimal estimation with Non Linear Programming technique. The experimental results show good agreement and demonstrate the possibility of this technique to explain power amplifier dynamics.

La presentation de l'etat de l'art 1 des travaux menes dans le cadre du GdR ME 2 MS sur la modelisation et le diagnostic des defauts de la machine asynchrone a cage, forme l'objectif principal de cet article. Nous y exposons les principales methodes de modelisation fine de la machine asynchrone a cage defectueuse comme le modele de Park etendu, la methode des circuits electriques magnetiquement couples, la methode des reseaux de permeances ainsi que la methode des elements finis. Du point de vue des methodes de diagnostic proprement dites, nous passerons en revue celles basees sur l'analyse spectrale du courant de phase statorique, celles basees sur l'estimation parametrique ainsi que celles mettant en oeuvre des techniques heuristiques telles que la reconnaissance des formes, la logique floue et les reseaux neuronaux. Ces differentes methodes de diagnostic et de modelisation fine pour le diagnostic sont illustrees dans le cas d'un defaut de rupture de barres et d'un defaut de court-circuit interspires dans les bobinages statoriques.

Tone Reservation (TR) is a method used to reduce the Peak to Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, we assess the importance of considering an improved model of the power amplifier (PA) to accurately evaluate the performance of TR method based on Conjugate-Gradient algorithm. Simulation results were carried out in the context of WLAN IEEE 802.11a standard in presence of two memoryless models and nonlinear polynomial model with memory. These models are obtained by an experimental based method, including measurements and parameters identification with a 2.4 GHz class AB PA from RF Micro Devices. The evaluation results as well as the experimental comparison show that TR method considerably improves the transmission quality, in terms of Bit Error Rate (BER) and Error Vector Magnitude (EVM). These results highlight the importance of considering memory effects in PA modelling.

International audience; Correct modeling of radio frequency power amplifiers (RF PA) is difficult, as nonlinear characteristics are not only statics but also dynamics and strongly depend on input signal frequencies. Recent studies in PA behavioral model have shown the interest of structures based on memory polynomial functions with sparse delay taps between instantaneous and previous input signal. The extension of such structures is proposed in this work to achieve a measurement based wideband model of PA for digital wireless communication systems. The model uses Infinite Impulse Response filters which describe the frequency response of each nonlinearity order. The characterization of this new model structure includes direct calculation of polynomial parameters and delay taps with two-tone test for different frequencies and parameter estimation of equivalents filters in frequency domain using least mean square algorithm and Instrumental Variable method. The obtained architecture improves memory effect description and provides computational efficiency suitable for dynamic time-domain PA studies. This new approach is validated using a 1.85GHz RF PA from Advanced semiconductor business with various modulations such as two-tone test, WCDMA and WiMax signals.

Systems based on Orthogonal Frequency Division Multiplexing (OFDM) take advantages of multicarrier modulations. Properties in term of dynamic spectrum adjustment make OFDM a promising technology for Cognitive Radio systems. An OFDM modulation suffers from high power peaks, which significantly degrade the power efficiency and the linearity of the transmitter. In this paper, the Tone Reservation method is used to reduce the Peak-To-Average Power-Ratio (PAPR) in OFDM systems. We intend to consider an adaptive algorithm to improve speed convergence and PAPR reduction gain, taking into account the complexity of the algorithm. The proposed approach is based on the Conjugate-gradient method which is a powerful gradient descent algorithm, reliable and efficient on a wide range of optimization problems. The radio-frequency Power Amplifier (PA) being the most sensitive element to envelope fluctuations, a class AB 2.4GHz-2W InGaP PA is used to evaluate the performance of the proposed method in terms of Bit Error Rate and Error Vector Magnitude.

International audience; Systems based on Orthogonal Frequency Division Multiplexing (OFDM) take advantages of multicarrier modulations. Properties in term of dynamic spectrum adjustment make OFDM a promising technology for Cognitive Radio systems. An OFDM modulation suffers from high power peaks, which significantly degrade the power efficiency and the linearity of the transmitter. In this paper, the Tone Reservation method is used to reduce the Peak-To-Average Power-Ratio (PAPR) in OFDM systems. We intend to consider an adaptive algorithm to improve speed convergence and PAPR reduction gain, taking into account the complexity of the algorithm. The proposed approach is based on the Conjugate-gradient method which is a powerful gradient descent algorithm, reliable and efficient on a wide range of optimization problems. The radio-frequency Power Amplifier (PA) being the most sensitive element to envelope fluctuations, a class AB 2.4 GHz-2 W InGaP PA is used to evaluate the performance of the proposed method in terms of Bit Error Rate and Error Vector Magnitude.

International audience; The aim of this paper is to evaluate and compare different optimization algorithms for Peak to Average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems. Based on Tone Reservation (TR) method, we exploit the unused subcarriers of the studied standard to generate the peak canceling signal without data rate loss. Gradient, Conjugate-Gradient with two directions search and Quasi-Newton methods have been investigated and evaluated on the basis of spectral regrowth, convergence speed and ability to improve the high peak-to-average reduction in multicarriers systems. As an example, the simulations are performed in the case of Local Area Network WLAN (IEEE 802.11a standard). Simulation results show that a PAPR reduction gain around 3 dB can be achieved.

International audience; In this paper, we present a new method for the modeling and characterization of oscillator circuit with a Van Der Pol (VDP) model using parameter identification. We also discussed and investigated the problem of estimation in nonlinear system based on time domain data. The approach is based on an appropriate state space representation of Van der Pol oscillator that allows an optimal parameter estimation. Using sampled output voltage signal, model parameters are obtained by an iterative identification algorithm based on Output Error method. Normalization issues are fixed by an appropriate transformation allowing a quickly global minimum search. Finally, the proposed estimation method is tested and validated using simulation data from a 1 GHz oscillator circuit in GaAs technology.

International audience; In the present paper, the nonlinear Internal Model Control (IMC) method is introduced and applied to linearize high frequency power amplifiers (PAs). The IMC is based on the description of a process model and of a controller. It is shown that baseband frequency descriptions are suitable for the model and the controller. Their description parameters are derived from input and output modulation signals processed in Cartesian form. Simulation results are given to illustrate the design procedure and to demonstrate the performances of the IMC linearizer.

International audience; In this paper, a new linearization algorithm of Power Amplifier, based on Kalman filtering theory is proposed for obtaining fast convergence of the adaptive digital predistortion. The proposed method uses the real-time digital processing of baseband signals to compensate the nonlinearities and memory effects in radio-frequency Power Amplifier. To reduce the complexity of computing in classical Kalman Filtering, a sliding time-window has been inserted which combines off-line measurement and on-line parameter estimation with high sampling time to track the changes in the PA characteristics. We evaluated the performance of the proposed linearization scheme through simulation and experiments. Using digital signal processing, experimental results with commercial power amplifier are presented for multicarrier signals to demonstrate the effectiveness of this new approach.

International audience; In this paper, we present a new method for characterization of radio frequency Power Amplifier (PA) in the presence of nonlinear distortions which affect the modulated signal in Radiocommunication transmission system. The proposed procedure uses a gray box model where PA dynamics are modeled with a MIMO continuous filter and the nonlinear characteristics are described as general polynomial functions, approximated by means of Taylor series. Using the baseband input and output data, model parameters are obtained by an iterative identification algorithm based on Output Error method. Initialization and excitation problems are resolved by an association of a new technique using initial values extraction with a multi-level binary sequence input exciting all PA dynamics. Finally, the proposed estimation method is tested and validated on experimental data.

International audience; The type of control system used for electrical machines depends on the use (nature of the load, operating states, etc.) to which the machine will be put. The precise type of use determines the control laws which apply. Mechanics are also very important because they affect performance. Another factor of essential importance in industrial applications is operating safety. Finally, the problem of how to control a number of different machines, whose interactions and outputs must be coordinated, is addressed and solutions are presented. These and other issues are addressed here by a range of expert contributors, each of whom are specialists in their particular field. This book is primarily aimed at those involved in complex systems design, but engineers in a range of related fields such as electrical engineering, instrumentation and control, and industrial engineering, will also find this a useful source of information.

International audience; The type of control system used for electrical machines depends on the use (nature of the load, operating states, etc.) to which the machine will be put. The precise type of use determines the control laws which apply. Mechanics are also very important because they affect performance. Another factor of essential importance in industrial applications is operating safety. Finally, the problem of how to control a number of different machines, whose interactions and outputs must be coordinated, is addressed and solutions are presented. These and other issues are addressed here by a range of expert contributors, each of whom are specialists in their particular field. This book is primarily aimed at those involved in complex systems design, but engineers in a range of related fields such as electrical engineering, instrumentation and control, and industrial engineering, will also find this a useful source of information.

International audience; In the present paper, the nonlinear Internal Model Control (IMC) method is introduced and applied to linearize high frequency Power Amplifiers (PAs). The IMC is based on the description of a process model and of a controller. It is shown that baseband frequency descriptions are suitable for the model and the controller. Their description parameters are derived from input and output modulation signals processed in Cartesian form. Simulation results are given to illustrate the design procedure and to demonstrate the performances of the IMC linearizer.

International audience; This article presents a new Low-Pass Delta Sigma Modulators (LPDS) architecture to improve the noise shaping for high frequency applications. The errors resulting from approximations made by calculating with 1/2N coefficients are compensated. Simulations with extracted parasitics of the layout are made and give a SNDR of 111 dB, 3.8 mW power consumption at 4 GHz in 65 nm CMOS technology for UMTS standard.

International audience; In this paper, a method to study and characterize a single-loop, cascaded and 1-bit Band-Pass Delta Sigma modulator for digital transmitter is presented. This technique is based on a combination of digital filter simulation and nonlinear optimization of signal-to-quantization noise. The optimal coefficients of modulator structure are achieved by minimization of a quadratic criterion based on prediction error between desired digital filter and noise transfer model. To demonstrate the effectiveness of this approach, simulated results for a sixth order cascaded structure for WCDMA Band-1 standard are presented. Spurious and ACLR improvement could be achieved for this standard with the proposed characterization technique.

A new adaptive technique for digital predistortion is presented. The proposed method uses the real-time digital processing of baseband signals to compensate the nonlinearities and memory effects in radio-frequency power amplifier. Kalman filtering algorithm with sliding time-window is adapted to track the changes in the PA characteristics. Simulation and measurement results, using digital signal processing, are presented for multicarrier signals to demonstrate the effectiveness of this new approach.

International audience; In this paper, we present a new identification procedure for radio frequency power amplifier (PA) in the presence of nonlinear distortion and memory effects. The proposed procedure uses a continuous-time model where PA dynamics are modeled with a multivariable filter and a general polynomial function. Using the baseband input and output data, model parameters are obtained by an iterative identification algorithm. Finally, the proposed estimation method is tested and validated on experimental data by comparison of the quadrature IQ signals in time domain.

International audience; A new adaptive technique for digital predistortion is presented. The proposed method uses the real-time digital processing of baseband signals to compensate the nonlinearities and memory effects in radio-frequency power amplifier. Kalman filtering algorithm with sliding time-window is adapted to track the changes in the PA characteristics. Simulation and measurement results, using digital signal processing, are presented for multicarrier signals to demonstrate the effectiveness of this new approach.

International audience; In this paper, a new method to optimize the noise shape of a bandpass delta sigma (BPDS) modulator for a digital transmitter is presented. The optimal coefficients of BPDS structure are obtained by minimization of a quadratic criterion based on prediction error. To demonstrate the effectiveness of this approach, simulated results for a 6th order BPDS structure are presented.