Search results for " Modulation"
showing 10 items of 496 documents
Suppression of soliton self-frequency shift by up-shifted filtering
2002
We propose an efficient method for suppressing the soliton self-frequency shift in high-speed transmission lines by means of up-shifted filters.
Nonlinear polarization effects in optical fibers: polarization attraction and modulation instability [Invited]
2014
We review polarization stabilization techniques based on the polarization attraction effect in low-birefringence fibers. Polarization attraction or pulling may be based on cross-polarization modulation, on parametric amplification, and on Raman or Brillouin scattering. We also review methods for laser frequency conversion based on polarization modulation instabilities in low- and high-birefringence fibers, and photonic crystal fibers. Polarization instabilities in nonlinear fibers may also be exploited for sensing applications.
Innovative Computational Approach to Harmonic Mitigation for Seven-level Cascaded H-Bridge Inverters
2020
Low frequency modulation strategies are a good solution to increase the energy conversion efficiency in high power applications. The paper is devoted to presents an innovative way to low order harmonics mitigation for seven-level Cascaded H-Bridge Inverters. In particular, this approach is based on the mitigation of selected harmonics without solve non-linear equations for an extended range of the fundamental amplitude. In fact, in real-Time operation to evaluate the control angles the polynomial equations have been identified. Through circuit simulation analysis in MatLab/PLECS environment, the effectiveness of the harmonic mitigation method has been tested and compared with theoretical re…
Design and performance evaluation of a high power density EMI filter for PWM inverter-fed induction motor drives
2015
This paper presents the design of an electromagnetic interference (EMI) filter for a low voltage high current induction motor drives supplied by DC power grids, such as those used in several vehicle applications. In order to effectively design the EMI filter a suitable Common Mode/Differential Mode (CM/DM) separation technique has been used. In consideration of the high operating currents, a software based separation technique using time domain measurements has been applied. The proposed technique allows the CM and DM sections of the EMI filter to be properly selected in a more economical way, i.e. without the need of dedicated hardware or costly radio frequency (RF) instrumentation. The de…
Breast cancer cells exhibit selective modulation induced by different collagen substrates.
2008
During the invasive phase of malignant tumors, neoplastic cells break into the basal lamina and enter in contact with the underlying connective tissue, which concurrently undergoes extensive modifications. The aim of our present minireview is to focus the changes in the collagenous matrix occurring during breast cancer progression and to explore the possible effects of different collagen substrates on breast cancer cell behavior and proteomic modulation.
Hypoxia-induced dysfunction of rat diaphragm
2004
Contains fulltext : 47331.pdf (Publisher’s version ) (Closed access) Oxidants may play a role in hypoxia-induced respiratory muscle dysfunction. In the present study we hypothesized that hypoxia-induced impairment in diaphragm contractility is associated with elevated peroxynitrite generation. In addition, we hypothesized that strenuous contractility of the diaphragm increases peroxynitrite formation. In vitro force-frequency relationship, isotonic fatigability, and nitrotyrosine levels were assessed under hypoxic (Po(2) approximately 6.5 kPa) and hyperoxic (Po(2) approximately 88.2 kPa) control conditions and also in the presence of authentic peroxynitrite (60 min), ebselen (60 min), and t…
Combining super-orthogonal space-frequency trellis coding, constellation shaping by shell mapping, and OFDM for high data rate broadband mobile commu…
2014
In this paper, we seamlessly combine three transmission techniques to design an improved performance broadband mobile communication system with two transmit antennas. In so doing, we took inspiration from the V.34 data modem toolbox designed for public switched telephone network. We modified the constellation shaping by shell mapping algorithm to apply it only to the orthogonal frequency division multiplexing (OFDM) frame sent by the first antenna, in such a way that the peak-to-average power ratio (PAPR) is also reduced for the second antenna. We use a 24-point quadrature amplitude modulation (QAM) signal constellation on each subcarrier, while the reference system employs 16 QAM for the s…
Performance Analysis of Cooperative Communication Systems with Imperfect Channel Estimation
2009
This paper investigates the effects of channel estimation errors on the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and- forward (AF) mode. A pilot symbol assisted modulation scheme with linear minimum mean square estimation (LMMSE) is used for the channel estimation. An accurate and easy-to-evaluate SER expression is presented for uncoded cooperative communication systems with quadrature amplitude modulation (QAM) and phase-shift keying (PSK) constellations. Numerical simulations are conducted to verify the correctness of the proposed analytical formulation. It is shown that the performance loss caused by channel estimation errors incre…
Reducing the peak and average power for OFDM systems using QAM by constellation shaping
2009
In this paper, we present a shell mapping scheme to reduce the peak and average power of orthogonal frequency division multiplexing (OFDM) signals using quadrature amplitude modulation (QAM) by constellation shaping. Our approach can be considered as an extension of the shell mapping technique introduced originally in the V.34 recommendation of ITU-T. The shell mapping method uses multiple cost functions, each having the OFDM block length N as a parameter. The cost functions are presented in closed form for any N. The main advantage of the proposed scheme is that the peak and average power can be reduced without sacrificing the data rate, and no side information is needed at the receive sid…
Protecting quantum resources via frequency modulation of qubits in leaky cavities
2018
Finding strategies to preserve quantum resources in open systems is nowadays a main requirement for reliable quantum-enhanced technologies. We address this issue by considering structured cavities embedding qubits driven by a control technique known as frequency modulation. We first study a single qubit in a lossy cavity to determine optimal modulation parameters and qubit-cavity coupling regime allowing a gain of four orders of magnitude concerning coherence lifetimes. We relate this behavior to the inhibition of the qubit effective decay rate rather than to stronger memory effects (non-Markovianity) of the system. We then exploit these findings in a system of noninteracting qubits embedde…