Joint compensation of multiple RF impairments in MIMO STBC systems

In this paper, we propose a compensation method for the joint effect of high-power amplifier (HPA) nonlinearity, in-phase/quadrature-phase (I/Q) imbalance and crosstalk in multiple-input multiple-output (MIMO) orthogonal space-time block coding (OSTBC) systems. The performance of the MIMO OSTBC equipped with the proposed compensation mechanism is evaluated in terms of average symbol error probability and system capacity, in Rayleigh fading channels. Numerical results are provided and show the effects on performance of several system parameters, namely, the HPA parameters, image-leakage ratio, crosstalk, numbers of antennas, and phase-shift keying modulation order.

Analysis and compensation for the joint effects of HPA nonlinearity, I/Q imbalance and crosstalk in MIMO beamforming systems

In this paper, we investigate the joint effects of high-power amplifier (HPA) nonlinearity, in-phase/quadrature-phase (I/Q) imbalance and crosstalk, on the performance of multiple-input multiple-output (MIMO) transmit beamforming (TB) systems, and propose a compensation method for the three impairments together. The performance of the MIMO TB system equipped with the proposed compensation scheme is evaluated in terms of average symbol error probability and capacity when transmissions are performed over uncorrelated Rayleigh fading channels. Numerical results are provided and show the effects on performance of several system parameters, namely, the HPA parameters, image-leakage ratio, crosstalk, numbers of antennas, length of pilot symbols and phase-shift keying modulation order.

Compensation for HPA nonlinearity and I/Q imbalance in MIMO beamforming systems

In this paper, we investigate the effects of high-power amplifier (HPA) nonlinearity and in-phase and quadrature-phase (I/Q) imbalance on the performance of multiple-input multiple-output (MIMO) transmit beamforming (TB) systems. Specifically, we propose a compensation method for HPA nonlinearity and I/Q imbalance together in MIMO TB systems. The performance of the MIMO TB system under study is evaluated in terms of the average symbol error probability (SEP) and system capacity, considering transmission over uncorrelated frequency-flat Rayleigh fading channels. Numerical results are provided and show the effects of several system parameters, such as the HPA parameters, image-leakage ratio, numbers of transmit and receive antennas, length of pilot symbols, and modulation order of phase-shift keying (PSK), on performance.

Single-carrier frequency domain equalisation for hammerstein communication systems using complex-valued neural networks

Single-carrier (SC) block transmission with frequency-domain equalisation (FDE) offers a viable transmission technology for combating the adverse effects of long dispersive channels encountered in high-rate broadband wireless communication systems. However, for high bandwidthefficiency and high power-efficiency systems, the channel can generally be modelled by the Hammerstein system that includes the nonlinear distortion effects of the high power amplifier (HPA) at transmitter. For such nonlinear Hammerstein channels, the standard SC-FDE scheme no longer works. This paper advocates a complex-valued (CV) B-spline neural network based nonlinear SC-FDE scheme for Hammerstein channels. Specifically, We model the nonlinear HPA, which represents the CV static nonlinearity of the Hammerstein channel, by a CV B-spline neural network, and we develop two efficient alternating least squares schemes for estimating the parameters of the Hammerstein channel, including both the channel impulse response coefficients and the parameters of the CV B-spline model. We also use another CV B-spline neural network to model the inversion of the nonlinear HPA, and the parameters of this inverting B-spline model can easily be estimated using the standard least squares algorithm based on the pseudo training data obtained as a natural byproduct of the Hammerstein channel identification. Equalisation of the SC Hammerstein channel can then be accomplished by the usual one-tap linear equalisation in frequency domain as well as the inverse B-spline neural network model obtained in time domain. Extensive simulation results are included to demonstrate the effectiveness of our nonlinear SC-FDE scheme for Hammerstein channels.

Switchable amplification of vibrational circular dichroism as a probe of local chiral structure

A new method to detect the vibrational circular dichroism (VCD) of a localized part of a chiral molecular system is reported. A local VCD amplifier was implemented, and the distance dependence of the amplification was investigated in a series of peptides. The results indicate a characteristic distance of 2.0±0.3 bonds, which suggests that the amplification is a localized phenomenon. The amplifier can be covalently coupled to a specific part of a molecule, and can be switched ON and OFF electrochemically. By subtracting the VCD spectra obtained when the amplifier is in the ON and OFF states, the VCD of the local environment of the amplifier can be separated from the total VCD spectrum. Switchable local VCD amplification thus makes it possible to “zoom in” on a specific part of a chiral molecule.

Nonlinear equalization of Hammerstein OFDM systems

A practical orthogonal frequency-division multiplexing (OFDM) system can generally be modelled by the Hammerstein system that includes the nonlinear distortion effects of the high power amplifier (HPA) at transmitter. In this contribution, we advocate a novel nonlinear equalization scheme for OFDM Hammerstein systems. We model the nonlinear HPA, which represents the static nonlinearity of the OFDM Hammerstein channel, by a B-spline neural network, and we develop a highly effective alternating least squares algorithm for estimating the parameters of the OFDM Hammerstein channel, including channel impulse response coefficients and the parameters of the B-spline model. Moreover, we also use another B-spline neural network to model the inversion of the HPA’s nonlinearity, and the parameters of this inverting B-spline model can easily be estimated using the standard least squares algorithm based on the pseudo training data obtained as a byproduct of the Hammerstein channel identification. Equalization of the OFDM Hammerstein channel can then be accomplished by the usual one-tap linear equalization as well as the inverse B-spline neural network model obtained. The effectiveness of our nonlinear equalization scheme for OFDM Hammerstein channels is demonstrated by simulation results.

B-spline neural network based single-carrier frequency domain equalisation for Hammerstein channels

A practical single-carrier (SC) block transmission with frequency domain equalisation (FDE) system can generally be modelled by the Hammerstein system that includes the nonlinear distortion effects of the high power amplifier (HPA) at transmitter. For such Hammerstein channels, the standard SC-FDE scheme no longer works. We propose a novel Bspline neural network based nonlinear SC-FDE scheme for Hammerstein channels. In particular, we model the nonlinear HPA, which represents the complex-valued static nonlinearity of the Hammerstein channel, by two real-valued B-spline neural networks, one for modelling the nonlinear amplitude response of the HPA and the other for the nonlinear phase response of the HPA. We then develop an efficient alternating least squares algorithm for estimating the parameters of the Hammerstein channel, including the channel impulse response coefficients and the parameters of the two B-spline models. Moreover, we also use another real-valued B-spline neural network to model the inversion of the HPA’s nonlinear amplitude response, and the parameters of this inverting B-spline model can be estimated using the standard least squares algorithm based on the pseudo training data obtained as a byproduct of the Hammerstein channel identification. Equalisation of the SC Hammerstein channel can then be accomplished by the usual one-tap linear equalisation in frequency domain as well as the inverse Bspline neural network model obtained in time domain. The effectiveness of our nonlinear SC-FDE scheme for Hammerstein channels is demonstrated in a simulation study.

Two-way CSI-assisted AF relaying with HPA nonlinearity

In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying in the presence of high-power amplifier (HPA) nonlinearity at relays. The expression for the end-to-end signal-to-noise ratio (SNR) is derived as per the modified system model by taking into account the interference caused by relaying scheme and HPA nonlinearity. The system performance of the considered relaying network is evaluated in terms of average symbol error probability (SEP) in Nakagami-$m$ fading channels, by making use of the moment-generating function (MGF) approach. Numerical results are provided and show the effects of several parameters, such as quadrature amplitude modulation (QAM) order, number of relays, HPA parameters, and Nakagami parameter, on performance.

Er:YAl(3)(BO(3))(4) glassy thin films from polymeric precursor and sol-gel methods: Waveguides for integrated optics

This paper presents the characterization of single-mode waveguides for 980 and 1550 nm wavelengths. High quality planar waveguide structure was fabricated from Y(1-x)Er(x)Al(3)(BO(3))(4) multilayer thin films with x = 0.02, 0.05, 0.1, 0.3, and 0.5, prepared through the polymeric precursor and sol-gel methods using spin-coating. The propagation losses of the planar waveguides varying from 0.63 to 0.88 dB/cm were measured at 632.8 and 1550 nm. The photoluminescence spectra and radiative lifetimes of the Er(3+) (4)I(13/2) energy level were measured in waveguiding geometry. For most samples the photoluminescence decay was single exponential with lifetimes in between 640 mu s and 200 mu s, depending on the erbium concentration and synthesis method. These results indicate that Er doped YAl(3)(BO(3))(4) compounds are promising for low loss waveguides. (C) 2009 Elsevier B.V. All fights reserved.

Beleza e poder na Ginástica Rítmica: reflexões para a educação física

La beauté dans la Gymnastique Rythmique (GR) s est esquissée comme condition de son existence. Pour son analyse, nous avons eu recourt au discours sur le pouvoir de Foucault (1971, 1979, 1987, 1988, 1997, 2003) et à sa relation avec la production de savoirs. Basés sur cette compréhension, nous avons réfléchi sur les relations de pouvoir dans la GR qui se sont établies et consolidées grâce à la réglementation de sa pratique, dans lequel le Code de Pointage a un rôle prépondérant. Ainsi, la GR a construit sa beauté à travers les temps au moyen de jeux de force où la gestualité de corps performatiques, à travers la discipline, a été prépondérant. Cette dernière a configuré des sens attelés à la coercition-résistence des corps: la production de discours. C est en pensant à une beauté comme ume trame de discours construits par ces relations de pouvoir-savoir des investissements du corps dans la Gymanstique Rythmique que nous nous posons les questions: Comment le Code de Pointage réglemente la gymanstique rythmique et sportive au sujet de la construction de la beauté ? Quelle est la relation entre les pouvoirs et les savoirs impliqués dans cette réglementation ? Nous avons donc pour objectifs de rechercher la beauté dans la Gymnastique Rythmique comme savoir produit à partir des relations du pouvoir circonscrites dans les règles de la modalité et de discuter la beauté à partir de la relation pouvoir/savoir comme réflexion pour le milieu de l éducation physique. Nous avons utilisé comme méthodologie la technique de l analyse de contenu (Bardin, 1977) afin d analyser le Code de Pointage de la GR dans sa version 2005-2008. Nous avons également fait usage des images de gymnastes comme moyen analogique pour amplifier le sens des discussions. La lecture fluctuante nous a permis de sélectionner des unités significatives et d organiser nos discussions en trois axes thématiques qui composent le premier chapitre intitulé « La beauté réglementée ». Dans ce chapitre, nous discutons les spécificités de la GR, la prescription de l utilisation du temps et de l espace et la configuration du geste technique à partir de l analyse de son code de ponctuation. Dans le deuxième chapitre, « Le corps beau transcende la règle », nous réalisons quelques réflexions destinées à l éducation physique à partir de la discussion du chapitre antérieur en prenant pour cible trois sujets : Pouvoirs et Savoirs, Technique et Style, Beauté et Éducation. Nous avons ainsi constaté que la beauté de la Gymnastique Rythmique contemporaine est entourée par sa réglementation, mais a été et continue à être dessinée par des mécanismes de pouvoir-savoir tout au long de sa trajectoire historique. Malgré l existence de conditions pour la beauté dans le Code de Pointage de la GR, il existe la possibilité de la création du propre style par la gymnaste, par la possibilité de vivre l improvisé et l imprévu, de sensibiliser le public, parce que le pouvoir crée des savoirs et le corps, qui se dépasse, créera toujours de nouvelles formes d être beau. La constatation que le Code de Pointage produit une beauté et que la gymnaste la reconstruit continuellement en en réactualisant les règles est une réflexion importante pour l éducation physique: elle réaffirme que le corps n est jamais seulement soumis, que même dans la soumission il est capable de produir du savoir, d être beau et de créer de nouveaux sens pour la Culture de Mouvements

Modelagem em SystemC-AMS de uma plataforma compatível com o sistema de coleta de dados brasileiro

This work presents simulation results of an identification platform compatible with the INPE Brazilian Data Collection System, modeled with SystemC-AMS. SystemC-AMS that is a library of C++ classes dedicated to the simulation of heterogeneous systems, offering a powerful resource to describe models in digital, analog and RF domains, as well as mechanical and optic. The designed model was divided in four parts. The first block takes into account the satellite s orbit, necessary to correctly model the propagation channel, including Doppler effect, attenuation and thermal noise. The identification block detects the satellite presence. It is composed by low noise amplifier, band pass filter, power detector and logic comparator. The controller block is responsible for enabling the RF transmitter when the presence of the satellite is detected. The controller was modeled as a Petri net, due to the asynchronous nature of the system. The fourth block is the RF transmitter unit, which performs the modulation of the information in BPSK ±60o. This block is composed by oscillator, mixer, adder and amplifier. The whole system was simulated simultaneously. The results are being used to specify system components and to elaborate testbenchs for design verification

Metodologia de Verificação Funcional para Circuitos Analógicos

This work proposes a new methodology to verify those analog circuits, providing an automated tools to help the verifiers to have a more truthful result. This work presents the development of new methodology for analog circuits verification. The main goal is to provide a more automated verification process to certify analog circuits functional behavior. The proposed methodology is based on the golden model technique. A verification environment based on this methodology was built and results of a study case based on the validation of an operational amplifier design are offered as a confirmation of its effectiveness. The results had shown that the verification process was more truthful because of the automation provided by the tool developed

Medidas e análise estatística em sinais bioelétricos sobre pontos de acupuntura

In the 20th century, the acupuncture has spread on occident as a complementary practice of heath care. This fact has motivated the international scientific community to invest in research that seek to understand why acupuncture works. In this work we compare statistically volt age fluctuation of bioelectric signals caught on the skin at an acupuncture point (IG 4) another nearby on acupuncture point. The acquisition of these signals was performed utilizing an electronic interface with a computer, which was based on an instrumentation amplifier designed with adequate specifications to this end. On the collected signals from a sample of 30 volunteers we have calculated major statistics and submitted them to pairing t-test with significance leveI a = O, 05. We have estimated to bioelectric signals the following parameters: standard deviation, asymmetry and curtose. Moreover, we have calculated the self-correlation function matched by on exponential curve we have observed that the signal decays more rapidly from a non-acupoint then from an acupoint. This fact is an indicative of the existence of information in the acupoint

g-acceleration of gravity: its measurement from the shape of water by using a computerized rotational system

This paper proposes a different experimental setup compared with the traditional ones, in order to determine the acceleration of gravity, which is carried out by using a fluid at a constant rotation. A computerized rotational system-by using a data acquisition system with specific software, a power amplifier and a rotary motion sensor-is employed in order to evaluate the angular velocity and g. An equation to determine g is inferred from fluid mechanics. For this purpose, the fluid's parabolic shape inside a cylindrical receptacle is considered using a rotational movement.

Aspectos metodológicos relacionados aos sistemas manométricos utilizados em estudos hemodinâmicos

Atualmente, diante das técnicas atuais, a manometria tem sido relegada a plano secundário durante a cateterização cardíaca. No entanto, ainda fornece importantes informações para identificação e avaliação das doenças cardiovasculares. Os dados coletados durante os exames possibilitam a obtenção de variáveis quantitativas e qualitativas, as quais podem ser comparadas aos padrões normais. Os sistemas manométricos são compostos por transdutor, amplificador e registrador, que, em conjunto, devem espelhar com fidelidade a morfologia e os valores das variáveis analisadas. Para atingir esse objetivo, é necessário desempenho adequado de todos os componentes. Se uma determinada informação é de extrema relevância, o operador deve gastar tempo suficiente para obtê-la de maneira inequívoca. Assim, o operador deve estar familiarizado com os sistemas manométricos e com as fontes de erro relacionadas com as técnicas de registro, cateteres, conectores e fluidos. Com os fundamentos analisados neste manuscrito, salientamos que deve ser dispensada atenção às ondas de pressão usadas nas interpretações da fisiopatologia das doenças cardiovasculares.