Relevant bibliographies by topics / Q modulator impairments

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Academic literature on the topic 'Q modulator impairments'

Author: Grafiati
Published: 8 June 2022

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Journal articles on the topic "Q modulator impairments"

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Anttila, Lauri, Peter Händel, Olli Mylläri, and Mikko Valkama. "Recursive learning-based joint digital predistorter for power amplifier and I/Q modulator impairments." International Journal of Microwave and Wireless Technologies 2, no. 2 (April 2010): 173–82. http://dx.doi.org/10.1017/s1759078710000280.

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The main implementation impairments degrading the performance of direct-conversion radio transmitters are in-phase/quadrature (I/Q) mismatch, local oscillator (LO) leakage, and power amplifier (PA) nonlinear distortion. In this article, we propose a recursive least-squares-based learning algorithm for joint digital predistortion (PD) of frequency-dependent PA and I/Q modulator impairments. The predistorter is composed of a parallel connection of two parallel Hammerstein (PH) predistorters and an LO leakage compensator, yielding a predistorter which as a whole is fully linear in the parameters. In the parameter estimation stage, proper feedback signal from the transmitter radio frequency (RF) stage back to the digital parts is deployed, combined with the indirect learning architecture and recursive least-squares training. The proposed structure is one of the first techniques to explicitly consider the joint estimation and mitigation of frequency-dependent PA and I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficiency of the proposed PD technique. In general, the obtained results demonstrate linearization and I/Q modulator calibration performance clearly exceeding the performance of current state-of-the-art reference techniques.
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Anttila, Lauri, Peter Handel, and Mikko Valkama. "Joint Mitigation of Power Amplifier and I/Q Modulator Impairments in Broadband Direct-Conversion Transmitters." IEEE Transactions on Microwave Theory and Techniques 58, no. 4 (April 2010): 730–39. http://dx.doi.org/10.1109/tmtt.2010.2041579.

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Anastasijevic, Ana, Duska Coja, Natasa Neskovic, Aleksandar Neskovic, and Djuradj Budimir. "Joint power amplifier and I/Q modulator impairments modelling and compensation for LTE transmitters using artificial neural networks." AEU - International Journal of Electronics and Communications 69, no. 2 (February 2015): 529–38. http://dx.doi.org/10.1016/j.aeue.2014.11.005.

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Tyagi, Rishita. "Simulation and Performance Analysis of RoF System Using Fiber Impairments." International Journal for Research in Applied Science and Engineering Technology 10, no. 5 (May 31, 2022): 2055–61. http://dx.doi.org/10.22214/ijraset.2022.42759.

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Abstract: A Radio over Fiber (RoF) system has a unique feature of containing both a fiber optic link and a free space radio path. Fiber based wireless access facilitates high-capacity multimedia services in a real-time basis. In this research paper, the RoF system is simulated in the presence of fiber impairments, namely, Polarization Mode Dispersion (PMD) and Cross Phase Modulation (XPM) and Four-Wave Mixing (FWM) with the help of OptiSystem simulation tool. The variations in Quality factor (Q factor) and Bit Error Rate (BER) with respect to wavelength of 1552 nm and bit rates of 10 Gb/s of input signal is analyzed in the presence of the linear and non-linear impairments of the fiber. Keywords: Radio over Fiber (RoF), Polarization Mode Dispersion (PMD), Cross Phase Modulation (XPM), Four-Wave Mixing (FWM), OptiSystem, Bit Error Rate (BER), Q factor.
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Wu, Yibo, Ulf Gustavsson, Alexandre Graell I. Amat, and Henk Wymeersch. "Low Complexity Joint Impairment Mitigation of I/Q Modulator and PA Using Neural Networks." IEEE Journal on Selected Areas in Communications 40, no. 1 (January 2022): 54–64. http://dx.doi.org/10.1109/jsac.2021.3126024.

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Muhammad, Fazal, Farman Ali, Usman Habib, Muhammad Usman, Imran Khan, and Sunghwan Kim. "Time Domain Equalization and Digital Back-Propagation Method-Based Receiver for Fiber Optic Communication Systems." International Journal of Optics 2020 (February 12, 2020): 1–13. http://dx.doi.org/10.1155/2020/3146374.

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Fiber optic communication systems (FOCSs) have attained a lot of attention by revolutionizing the telecommunication industry and offering new possibilities with the technical advancements in state-of-the-art high speed digital electronics. Advanced modulation formats make use of the phase, amplitude, and polarization of the optical signals at the same time to provide high spectral efficiency as compared with 1 bit/s/Hz for the intensity modulation direct detection system (IMDD), but are highly prone to transmission impairments. Thus, the effects that add up to the optical fiber impairments such as optical fiber chromatic dispersion (OFCD), polarization model dispersion (PMD), and phase offset and noise (POaN) need to be addressed at the receiver side. The development of components and algorithms to minimize these effects in next generation FOCSs with 100 Gbps data rate and beyond with long-haul transmission is still a challenging issue. In this paper, digital signal processing- (DSP-) assisted dispersion and nonlinear compensation techniques are presented to compensate for physical layer impairments including OFCD, PMD, and POaN. The simulations are performed considering Dual Polarization- (DP-) QPSK modulation format to achieve two-fold data rate to achieve spectral efficiency of 3.28 bits/s/Hz by making use of the polarization diversity and system performance is investigated in terms of bit error rate (BER), constellation diagrams, and quality factor (Q-factor) for different values of optical signal-to-noise ratio (OSNR), launch power (PL), and fiber length.
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Trombley, Paul Q. "Selective Modulation of GABAA Receptors by Aluminum." Journal of Neurophysiology 80, no. 2 (August 1, 1998): 755–61. http://dx.doi.org/10.1152/jn.1998.80.2.755.

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Trombley, Paul Q. Selective modulation of GABAA receptors by aluminum. J. Neurophysiol. 80: 755–761, 1998. Aluminum has been implicated in several neurodegenerative conditions including Alzheimer's disease. Because the mammalian olfactory system has an unusual capacity for the uptake and transneuronal spread of inhaled substances such as aluminum, whole cell recording techniques were used to examine the actions of aluminum on basic membrane properties and amino acid receptors on rat olfactory bulb mitral/tufted (M/T) neurons in culture. Aluminum had little direct effects on M/T neurons. Aluminum (100 μM) did not evoke a membrane current or alter action-potential shape or duration. Aluminum also had no marked effects on the family of voltage-gated membrane currents evoked by a series of 10-mV, 50-ms depolarizing steps. However, aluminum dramatically potentiated the current evoked by 30 μM γ-aminobutyric acid (GABA) at concentrations <100 μM. Conversely, higher concentrations of aluminum blocked the GABA-evoked current. The effects of aluminum on GABA-evoked currents were not voltage dependent. Aluminum (100 μM) equally potentiated both inward currents at −30 mV and outward currents at + 30 mV. At 300 μM, aluminum blocked both inward and outward currents to a similar extent. In some neurons, aluminum only blocked the current and potentiation was not observed. The biphasic action of aluminum on GABA-evoked currents suggests separate binding sites: a high-affinity potentiating site and a low-affinity inhibiting site. Despite its effects on GABA-evoked currents, aluminum did not alter membrane currents evoked by glutamate, N-methyl-d-aspartate, kainate, or glycine. Aluminum also did not reduce spontaneous excitatory synaptic activity, suggesting little, if any, effect on glutamate release. Although a causal role for aluminum in Alzheimer's disease and other neuropathological conditions remains controversial, it is clear that elevated aluminum concentrations in the brain are associated with a variety of cognitive impairments. The present results indicate that aluminum can alter the function of GABAA receptors and may suggest that aluminum can contribute to cognitive impairment through disruption of inhibitory circuits.
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Hosseini-Sharifabad, Ali, Mohammad Reza Mofid, Majid Moradmand, and Mohammad Keimasi. "The Effect of Omega-lycotoxin on the Cognitive Impairment Induced by Kainic Acid in Rats." Iranian Journal of Toxicology 15, no. 1 (January 1, 2021): 49–56. http://dx.doi.org/10.32598/ijt.15.1.740.1.

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Background: Excitotoxicity is a common pathological process in neurodegenerative diseases associated with overactivity of N-methyl-D-aspartate (NMDA) and P/Q type voltage-gated calcium (Cav2.1) channels. Omega-lycotoxin-Gsp2671g is a therapeutic tool to modulate overactive Cav2.1 (P/Q type) channels. Omega-lycotoxin binds to Cav2.1 channels with high affinity and selectivity. This study aimed to investigate the effects of Omega-lycotoxin on the cognitive impairment induced by kainic acid in rats. Methods: The effect of pre-treatment and post-treatment trials of intra-hippocampal Cornu Ammonis-3 administration of omega-lycotoxin (0.5, 1 or 2µg) was studied on the cognitive impairment induced by kainic acid in rats. The rats’ learning and memory were assessed by the passive avoidance and a single-day testing version of the Morris water maze method. Results: Omega-lycotoxin caused a significant increase in the latency of the passive avoidance test and the duration of their presence in the target area of the Morris water maze test compared to the groups treated with kainic acid (P<0.0001). There were statistically significant differences for the effects of various doses of omega-lycotoxin. The post-treatment groups showed a greater improvement than those in the pretreatment groups. Conclusion: The findings demonstrated that a single dose of omega-lycotoxin can prevent or revert the memory impairment caused by kainic acid in rats.
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Mugridge, K. G., M. Perretti, P. Ghiara, C. L. Galeotti, M. Melli, and L. Parente. "Gastric antisecretory and anti-ulcer actions of IL-1 in rat involve different IL-1 receptor types." American Journal of Physiology-Gastrointestinal and Liver Physiology 269, no. 5 (November 1, 1995): G763—G769. http://dx.doi.org/10.1152/ajpgi.1995.269.5.g763.

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Limited knowledge exists concerning the interleukin-1 (IL-1) receptor type (IL-1RT) mediating the potent antisecretory and gastro-protective actions of IL-1. In the present study, the gastric actions of IL-1 beta and two related mutant proteins, yIL-1 beta delta 4, an analogue that preferentially binds to IL-1-RTII, and mutant yIL-1 beta N7/Q, an analogue that has equal affinity as IL-1 beta for IL-1RTI and IL-1RTII, have been compared. Modulation of IL-1 gastric actions were also investigated using monoclonal antibody (MAb) preparations raised against IL-1RTI or IL-1RTII. In the pylorus-ligated rat, yIL-1 beta delta 4, yIL-1 beta N7/Q, and IL-1 beta (all at 1 microgram/kg ip) reduced gastric acid secretion (50, 79, and 78%, respectively), indicating the importance of IL-1RTII binding for antisecretory activity. This was further substantiated in experiments using the MAb preparations, which showed that IL-1 beta (1 microgram/kg ip) antisecretory activity was reversed by MAb IL-1RTII (10-50 micrograms/kg sc) but not by MAb IL-1RTI (50 micrograms/kg sc). In contrast, at dosages 10-fold higher (10 micrograms/kg ip) than that used in the study to inhibit acid secretion, IL-1 beta and yIL-1N7/Q equally reduced (approximately 80%) indomethacin-induced gastric damage, but yIL-1 beta delta 4 was ineffective. The results using yIL-1 beta delta 4 indicated that impairment of IL-1RTI binding capacity appeared to be paralleled by a decreased gastroprotective effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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Giacomucci, Giulia, Salvatore Mazzeo, Sonia Padiglioni, Silvia Bagnoli, Laura Belloni, Camilla Ferrari, Laura Bracco, Benedetta Nacmias, Sandro Sorbi, and Valentina Bessi. "Gender differences in cognitive reserve: implication for subjective cognitive decline in women." Neurological Sciences 43, no. 4 (October 8, 2021): 2499–508. http://dx.doi.org/10.1007/s10072-021-05644-x.

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Abstract Background Subjective Cognitive Decline (SCD) is a self-experienced decline in cognitive capacity with normal performance on standardized cognitive tests, showing to increase risk of Alzheimer’s Disease (AD). Cognitive reserve seems to influence the progression from SCD to Mild Cognitive Impairment (MCI) and to AD. The aim of our study was to investigate gender differences in cognitive reserve evaluating how sex might modulate the role of cognitive reserve on SCD. Methods We included 381 SCD patients who underwent clinical evaluation, neuropsychological assessment, evaluation of premorbid intelligence by the Test di Intelligenza Breve (TIB), cognitive complaints by the Memory Assessment Clinics Questionnaire (MAC-Q), and apolipoprotein E (APOE) genotyping. Results The proportion between women and men was significantly different (68.7% [95% CI 63.9–73.4 vs 31.4%, 95% CI 26.6–36.0]). Women were younger than men at onset of SCD and at the baseline visit (p = 0.021), had lower years of education (p = 0.007), lower TIB scores (p < 0.001), and higher MAC-Q scores (p = 0.012). TIB was directly associated with age at onset of SCD in both women and men, while years of education was inversely associated with age at onset only in women. Multivariate analysis showed that sex influences TIB independently from years of education. TIB was directly associated with MAC-Q in men. Conclusions Sex interacts with premorbid intelligence and education level in influencing the age at onset and the severity of SCD. As the effect of education was different between men and women, we speculated that education might act as a minor contributor of cognitive reserve in women.
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Dissertations / Theses on the topic "Q modulator impairments"

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Abdi, Abyaneh Mohammad. "Génération des signaux agrégés en fréquences dans le contexte de LTE-A." Electronic Thesis or Diss., Paris, ENST, 2016. https://pastel.hal.science/tel-03689710.

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Dans ce travail de thèse, on a proposé une structure de génération des signaux multi-porteuse afin de créer plusieurs oscillateurs locaux (OL ) tout en utilisant qu’un modulateur I/Q. Ces signaux peuvent être utilisés dans les récepteurs de LTE-A pour la transposition des signaux agrégé en fréquence vers la bande de base. On développe la structure afin de l’utiliser en émetteur répondant aux normes du standard LTE-A. La nouvelle structure nous permet de générer n signaux agrégés en fréquences, de manière simultanée, par une seule chaîne de transmission (c.a.d un modulateur I/Q, un OL). En utilisant cette structure on réduit le nombre de circuits utilisés, en comparaison du cas où n signaux agrégés en fréquences sont générés par n émetteurs. La fréquence d’échantillonnage est réduite dans notre cas par rapport au cas où les signaux sont générés directement de la bande de base à la bande RF avec des convertisseurs analogiques numériques adéquats. Dans la troisième partie, on se concentre sur les imperfections et les non linéarités du modulateur I/Q dans le cadre de notre structure multibande. On modélise le fonctionnement du modulateur multi-bande en utilisant les échantillons en entrée et en sortie. Notre modèle est dérivé de la série de Volterra qui prends en compte les effets non linéaires et les effets mémoires ainsi que les imperfections du modulateur I/Q. Puis, on obtient la fonction "inverse" du modèle et on l’applique à l’entrée du modulateur afin de corriger et linéariser la sortie du modulateur I/Q. La fonction "inverse" est appelée DPD (en anglais : Digital Pre-Distortion). Enfin, on a évalué le modèle et la DPD en simulations et en mesures
In this dissertation, a signal generation structure is proposed using which a multitone Local Oscillator (LO) signal is created by a single I/Q modulator. These LOs can be used in the CA receivers to down-convert the transmitted component carriers simultaneously. The multi-tone LO signal structure is further developed to be used at the transmitter as a CA generation solution. Using the proposed structure n-component carriers can be generated in parallel. This structures requires lower sampling rates with respect to the case where RF signals are synthesized directly by digital-to- analog converters. Moreover, less circuitry is required, because one single I/Q modulator is used to generate n component carriers, instead of n I/Q modulators. This work follows on investigating the origin of impairments and mild nonlinearities in our I/Q modulator. To overcome these problems, we focus on the functionality of the overall system rather than each component of the I/Q modulator. This method is called behavioral modeling. Once the nonlinear model is obtained, if its inverse function is applied to the input, a linearized output is expected. The generation of the inverse function is called Digital Pre-Distortion (DPD). We propose a tri-band behavioral model for nonlinearities and impairments in tri-band CA using our I/Q modulator. Furthermore, the DPD of the model is evaluated in simulations and experiments
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Conference papers on the topic "Q modulator impairments"

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Crespo-Cadenas, Carlos, Javier Reina-Tosina, Maria J. Madero-Ayora, and Juan A. Becerra-Gonzalez. "Relationship between a pruned volterra model structure and impairments in an I/Q modulator." In 2017 12th European Microwave Integrated Circuits Conference (EuMIC). IEEE, 2017. http://dx.doi.org/10.23919/eumic.2017.8230739.

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Crespo-Cadenas, Carlos, Javier Reina-Tosina, Maria J. Madero-Ayora, and Juan A. Becerra-Gonzalez. "Relationship between a pruned volterra model structure and impairments in an I/Q modulator." In 2017 47th European Microwave Conference (EuMC). IEEE, 2017. http://dx.doi.org/10.23919/eumc.2017.8231045.

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Schubert, Benjamin, Ahmet Gokceoglu, Lauri Anttila, and Mikko Valkama. "Augmented Volterra predistortion for the joint mitigation of power amplifier and I/Q modulator impairments in wideband flexible radio." In 2013 IEEE Global Conference on Signal and Information Processing (GlobalSIP). IEEE, 2013. http://dx.doi.org/10.1109/globalsip.2013.6737113.

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Crespo-Cadenas, C., M. J. Madero-Ayora, J. Reina-Tosina, and J. A. Becerra-Gonzalez. "A widely nonlinear approach to compensate impairments in I/Q modulators." In 2015 European Microwave Conference (EuMC 2015). IEEE, 2015. http://dx.doi.org/10.1109/eumc.2015.7345811.

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Madero-Ayora, M. J., J. Reina-Tosina, C. Crespo-Cadenas, and J. A. Becerra-Gonzalez. "On the robustness of a widely nonlinear approach to model impairments in I/Q modulators." In 2015 Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC). IEEE, 2015. http://dx.doi.org/10.1109/inmmic.2015.7330366.

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Tai Xin, Zuo Yongfeng, and Liu Liang. "Baseband signal predistortion based compensation technique for broadband I/Q modulation impairments in vector signal generators." In 2015 12th IEEE International Conference on Electronic Measurement & Instruments (ICEMI). IEEE, 2015. http://dx.doi.org/10.1109/icemi.2015.7494371.

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