Literatura científica selecionada sobre o tema "RF reception chain"

Though MIMO systems improve performance of a wireless communication network by the usage of multiple antennas, demand of distinct set of RF chain (i.e., electronic components required for antenna transmission and reception, in wireless communication) for all the antennas leads to an increase in complexity and cost. Antenna selection technique of MIMO has proved to be a good means to solve this issue. Antenna Selection methods find optimal number of antennas required out of the total antennas present in the MIMO (Multiple Input Multiple Output) system. The selection of antenna can be performed at both ends of the communication network i.e., transmitter or receiver. In this paper, an overview of various Transmit Antenna Selection techniques for various MIMO systems is presented.

Since its inception, the electronics industry has mass-produced equipment. The fast evolution of electronic technologies made obsolete the entire generation of products and even technologies. Until the government issued regulations and guidelines on how to address the issue of reuse of obsolete electronic equipment, with special regard to the ones still operating (e.g., give it to family/friends, donate to charity, or sell to individuals or recycling companies), most of it was thrown out with usual rubbish, with a destructive effect on the environment. This paper presents the design techniques and methods for revaluation of obsolete vacuum tube analog receivers, with a focus on the manufacturing steps of a high-performance receiver. The choice of receiver type is not accidental at all, since tube technology is still a real success among audiophiles many providers offer vacuum tube amplifiers at considerably high prices. The redesign implied the original FM unit replacement with a DSP-based AM/FM tuner while the AM RF vacuum tube section has been preserved with the original architecture to allow the reception of the broadcast stations for the long-wave band and the alternative operation with the silicon tuner for the medium-wave and short-wave bands. The electrical performances of the modified receiver in terms of reliability, sensitivity, selectivity, and distortions on the reception chain are clearly superior to the original one, while the power consumption of the RF section is reduced more than 10 times from 11.5 W–15.5 W to 1 W. Last, but not least important, the proposed solution implied the use of few additional parts and resources and extended significantly the lifetime of the original vacuum tubes receiver. The work has been developed to serve as an example of how obsolete electronic equipment can be redesigned and reused avoiding its complete recycling or even worse, its disposal with usual rubbish. It has been imagined and performed as the initial step in launching a professional student contest on the reuse/redesign of obsolete equipment aimed at raising awareness regarding the issue of pollution with e-waste amongst students from the electronic departments of Romanian technical universities.

Abstract During neonatal life, Ig diversity is limited in many respects. The absence of terminal deoxynucleotidyl transferase (TdT) expression with the consequent lack of nontemplated addition during the neonatal period, coupled with the predominant usage of a single DH reading frame (RF), leads to severe limitations of diversity in the CDR3 region of Ig heavy (H) chains. The neonatal Ig H chain repertoire is also characterized by restricted VH usage, with predominant expression of certain VH segments, such as VH81x, that are rarely evident during adult life. In this report, we examine the effect of enforced TdT expression on the neonatal repertoire of VH81xDJH rearrangements. We find that TdT synthesis abrogates DH RF bias during the fetal/neonatal period through a Ig-receptor-independent mechanism. These findings suggest that DH RF bias during neonatal life is determined largely by homology-directed joining. We also find that TdT synthesis alters the selection of productively rearranged VH81xDJH alleles in the neonatal spleen through a Ig-receptor-dependent mechanism. Analysis of predicted CDR3 amino acid sequences indicates that positive selection of VH81x-encoded H chains is correlated with the presence of a consensus sequence immediately adjacent to the VH segment. These data support the hypothesis that the CDR3 region is critical in determining the ability of VH81x-encoded H chains to form functional receptors that support positive selection of B lymphocytes. Together, our results demonstrate that TdT can indirectly influence the Ig repertoire by influencing both receptor-dependent and receptor-independent selection processes.

In the search for enhanced wireless communication systems, multibeam phased array receivers have gained prominence. They promise to significantly boost data rates, reduce latency, and improve reliability. However, implementing multibeam receivers with traditional beamforming techniques can be challenging due to the high computational demands and the need for multiple radio frequency (RF) chains. Hybrid beamforming combines the advantages of digital and analog beamforming to strike a balance between performance and complexity. Our research delves into the following aspects of Hybrid beamforming for multibeam phased array receivers: Reduced Hardware Complexity: By blending digital and analog beamforming, we reduce the number of required RF chains, making multibeam receivers more cost-effective. Enhanced Beam Steering: Hybrid beamforming maintains precise control over multiple beams, ensuring efficient signal reception and transmission. Real-World Applications: We discuss practical applications in 5G and beyond, satellite communications, and radar systems. The paper delves into the fundamental concepts of analog and digital beamforming, illustrating their respective strengths and limitations. It then presents the architecture of hybrid beamforming systems, emphasizing the synergistic integration of analog and digital components. Special attention is given to the design considerations of beamforming networks, antenna arrays, and the beam steering mechanism. KEYWORDS Hybrid Beamforming , Phased Array , Multi-Beam , Analog Beamforming , Digital Beamforming , Beamforming Networks , Antenna Array , Beam Steering , Spatial Multiplexing , Precoding , Channel Estimation , Interference Mitigation , Power Consumption , Millimeter Wave (mmWave) , 5G and Beyond .

Abstract Analysis of the immunoglobulin receptor (IGR) variable heavy- and light-chain sequences on 17 hepatitis C virus (HCV)-associated non-Hodgkin lymphomas (NHLs) (9 patients also had type II mixed cryoglobulinemia [MC] syndrome and 8 had NHL unrelated to MC) and analysis of intraclonal diversity on 8 of them suggest that such malignant lymphoproliferations derive from an antigen-driven pathologic process, with a selective pressure for the maintenance of a functional IgR and a negative pressure for additional amino acid mutations in the framework regions (FRs). For almost all NHLs, both heavy- and light-chain complementarity-determining regions (CDR3) showed the highest similarity to antibodies with rheumatoid factor (RF) activity that have been found in the MC syndrome, thus suggesting that a common antigenic stimulus is involved in MC syndrome and in HCV-associated lymphomagenesis. Moreover, because HCV is the recognized pathologic agent of MC and the CDR3 amino acid sequences of some HCV-associated NHLs also present a high homology for antibody specific for the E2 protein of HCV, it may be reasonable to speculate that HCV E2 protein is one of the chronic antigenic stimuli involved in the lymphomagenetic process. Finally, the use of specific segments, in particular the D segment, in assembling the IgH chain of IgR seems to confer B-cell disorders with the property to produce antibody with RF activity, which may contribute to the manifestation of an overt MC syndrome.

Analysis of the immunoglobulin receptor (IGR) variable heavy- and light-chain sequences on 17 hepatitis C virus (HCV)-associated non-Hodgkin lymphomas (NHLs) (9 patients also had type II mixed cryoglobulinemia [MC] syndrome and 8 had NHL unrelated to MC) and analysis of intraclonal diversity on 8 of them suggest that such malignant lymphoproliferations derive from an antigen-driven pathologic process, with a selective pressure for the maintenance of a functional IgR and a negative pressure for additional amino acid mutations in the framework regions (FRs). For almost all NHLs, both heavy- and light-chain complementarity-determining regions (CDR3) showed the highest similarity to antibodies with rheumatoid factor (RF) activity that have been found in the MC syndrome, thus suggesting that a common antigenic stimulus is involved in MC syndrome and in HCV-associated lymphomagenesis. Moreover, because HCV is the recognized pathologic agent of MC and the CDR3 amino acid sequences of some HCV-associated NHLs also present a high homology for antibody specific for the E2 protein of HCV, it may be reasonable to speculate that HCV E2 protein is one of the chronic antigenic stimuli involved in the lymphomagenetic process. Finally, the use of specific segments, in particular the D segment, in assembling the IgH chain of IgR seems to confer B-cell disorders with the property to produce antibody with RF activity, which may contribute to the manifestation of an overt MC syndrome.

Objective. It has been stated that brain cancers are an increasingly serious issue in many parts of the world. The aim of our study was to determine a possible relationship between Vitamin D receptor (VDR) gene polymorphisms and the risk of glioma and meningioma.Methods. We investigated the VDR Taq-I and VDR Fok-I gene polymorphisms in 100 brain cancer patients (including 44 meningioma cases and 56 glioma cases) and 122 age-matched healthy control subjects. This study was performed by polymerase chain reaction-based restriction fragment length polymorphism (RF LP).Results. VDR Fok-I ff genotype was significantly increased in meningioma patients (15.9%) compared with controls (2.5%), and carriers of Fok-I ff genotype had a 6.47-fold increased risk for meningioma cases. There was no significant difference between patients and controls for VDR Taq-I genotypes and alleles.Conclusions. We suggest that VDR Fok-I genotypes might affect the development of meningioma.

Overactivation of immune responses is a hallmark of autoimmune disease pathogenesis. This includes the heightened production of inflammatory cytokines such as Tumor Necrosis Factor α (TNFα), and the secretion of autoantibodies such as isotypes of rheumatoid factor (RF) and anticitrullinated protein antibody (ACPA). Fcγ receptors (FcγR) expressed on the surface of myeloid cells bind Immunoglobulin G (IgG) immune complexes. Recognition of autoantigen-antibody complexes by FcγR induces an inflammatory phenotype that results in tissue damage and further escalation of the inflammatory response. Bromodomain and extra-terminal protein (BET) inhibition is associated with reduced immune responses, making the BET family a potential therapeutic target for autoimmune diseases such as rheumatoid arthritis (RA). In this paper, we examined the BET inhibitor PLX51107 and its effect on regulating FcγR expression and function in RA. PLX51107 significantly downregulated expression of FcγRIIa, FcγRIIb, FcγRIIIa, and the common γ-chain, FcϵR1-γ, in both healthy donor and RA patient monocytes. Consistent with this, PLX51107 treatment attenuated signaling events downstream of FcγR activation. This was accompanied by a significant decrease in phagocytosis and TNFα production. Finally, in a collagen-induced arthritis model, PLX51107-treatment reduced FcγR expression in vivo accompanied by a significant reduction in footpad swelling. These results suggest that BET inhibition is a novel therapeutic approach that requires further exploration as a treatment for patients with RA.

Background: Rheumatoid Arthritis (RA) is a chronic disorder characterized by an inflammation of synovial tissue in joints resulting in pain, deformities and affects the quality of life. The gene for protein tyrosine phosphatase non-receptor type 22 (PTPN22) encodes a lymphoid specific phosphatase (LYP), which serves as a negative regulator of T lymphocyte activation and is associated with a number of autoimmune/chronic diseases in various ethnic groups. Objective: This study was undertaken to investigate an association between PTPN22 gene functional polymorphism (C1858T; rs2476601) and rheumatoid arthritis (RA) in Kuwaiti Arabs. The frequency of this candidate locus was compared between Kuwaiti RA patients and the controls and with that reported from other populations. Methods: The study was carried out in 191 Kuwaiti RA patients and 214 healthy controls. The diagnosis of RA was carried out according to the guidelines of the American College of Rheumatology (ACR). The genotypes of PTPN22 gene (C1858T) polymorphism were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by DNA sequence analysis in RA patients and controls. Results: The TT genotype of PTPN22 gene functional polymorphism C1858T was found in 2/191 (1%) in RA patients compared to 2/214 (1%) in the controls (P = 1.0). In contrast, heterozygous CT genotype was detected in 3/191 (1.57%) RA patients compared to 32/214 (14.9%) in the controls. The CC genotype was detected in 186/191 (97.38%), RA patients while it was detected in 180/214 (84.1%) of the controls. The two RA patients who carried the homozygous variant (TT) genotype were both positive for rheumatoid factor (RF) and did not have any extra-articular manifestations. Amongst the Kuwaiti RA patients, 27% had a family history of RA. No correlation was found between the activity/severity of the disease and PTPN22 gene polymorphism genotypes. Conclusion: This study did not find an association between the PTPN22 gene functional polymorphism (C1858T) and clinical manifestation and activity/severity of RA in Kuwaiti Arabs. This is in sharp contrast to previous reports from Caucasian and some other populations in which a positive association of PTPN22 gene (C1858T) polymorphism with genetic susceptibility to RA has been reported.

Leptin, the product of the ob gene, is a pivotal signal in the regulation of neuroendocrine function and fertility. Although much of the action of leptin in the control of the reproductive axis is exerted at the hypothalamic level, some direct effects of leptin on male and female gonads have also been reported. Indeed, recent evidence demonstrated that leptin is able to inhibit testosterone secretion at the testicular level. However, the molecular mechanisms behind this effect remain unclear. The focus of this study was twofold: (1) to identify potential targets for leptin-induced inhibition of steroidogenesis, and (2) to characterize in detail the pattern of expression and cellular distribution of leptin receptor (Ob-R) mRNA in adult rat testis. In pursuit of the first goal, slices of testicular tissue from adult rats were incubated with increasing concentrations of recombinant leptin (10(-9)--10(-7 )M) in the presence of human chorionic gonadotropin (hCG; 10 IU/ml). In this setting, testosterone secretion in vitro was monitored, and expression levels of mRNAs encoding steroidogenic factor 1 (SF-1), steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450 scc) and 17 beta-hydroxysteroid dehydrogenase type III (17 beta-HSD) were assessed by Northern hybridization. In pursuit of the second goal, the pattern of cellular expression of the Ob-R gene in adult rat testis was evaluated by in situ hybridization using a riboprobe complementary to all Ob-R isoforms. In addition, testicular expression levels of the different Ob-R isoforms, previously identified in the hypothalamus, were analyzed by means of semi-quantitative RT-PCR. In keeping with our previous data, recombinant leptin significantly inhibited hCG-stimulated testosterone secretion. In this context, leptin, in a dose-dependent manner, was able to co-ordinately decrease the hCG-stimulated expression levels of SF-1, StAR and P450 scc mRNAs, but it did not affect those of 17 beta-HSD type III. In situ hybridization analysis showed a scattered pattern of cellular expression of the Ob-R gene within the adult rat testis, including Leydig and Sertoli cells. In addition, assessment of the pattern of expression of Ob-R subtypes revealed that the long Ob-Rb isoform was abundantly expressed in adult rat testis. However, variable levels of expression of Ob-Ra, Ob-Re, and Ob-Rf mRNAs were also detected, whereas those of the Ob-Rc variant were nearly negligible. In conclusion, our results indicate that decreased expression of mRNAs encoding several up-stream elements in the steroidogenic pathway may contribute, at least partially, to leptin-induced inhibition of testicular steroidogenesis. In addition, our data on the pattern of testicular expression of Ob-R isoforms and cellular distribution of Ob-R mRNA may help to further elucidate the molecular mechanisms of leptin action in rat testis.

Que ce soit dans un contexte de communications numériques, de radar ou de guerre électronique, les chaînes d’émission et de réception réalisant ces fonctions sont constituées de composants non-linéaires. Ces derniers opèrent sur les signaux d’intérêt les opérations cruciales d’amplification, de transposition en fréquence, et de conversion du monde analogique de propagation de ces signaux, au monde numérique de leur traitement. Dans tous les contextes cités, la dynamique instantanée est un critère de performance clé, déterminant la fuite spectrale à l’émission, contraignant le débit à la réception de signaux de communication, ou encore qualifiant la capacité à recevoir des échos de puissances différentes en radar. L’augmentation de la dynamique instantanée peut se faire au niveau de la conception des chaînes, tant dans le choix des composants que dans leur ordonnancement, et relève alors d’un processus de conception long et fastidieux, résultant en un sacrifice au niveau du coût, de l’encombrement ou de la consommation. L’autre façon d’augmenter la dynamique instantanée, qui fait l’objet de ce manuscrit, est la linéarisation par traitement numérique, basée sur la modélisation comportementale de la chaîne d’émission ou de réception.Cette linéarisation repose sur trois phases intrinsèquement imbriquées, la modélisation comportementale, l’identification des paramètres du modèle, et la compensation des défauts non-linéaires. Après avoir introduit le contexte applicatif de ces travaux, nous débutons ce manuscrit par le développement de modèles à temps continus, basés sur la dérivée du signal. Nous prenons ainsi le parti de s’extraire du formalisme des séries de Volterra, reposant sur le concept d’effet mémoire, afin de retrouver l’intuition physique de la description de la distorsion vis-à-vis des variations instantanées du signal. Nous scindons ensuite l’identification des paramètres de ces modèles en deux phases. La caractérisation tout d’abord, regroupe les méthodes basées sur signaux multi-tons, associant un formalisme relativement simple et une mise en œuvre aisée. Cette première phase est donc appliquée à l’étude du comportement non-linéaire, et au dimensionnement du modèle. La deuxième phase, dite de calibrage, désigne l'identification des paramètres de ce modèle à partir de bruit blanc, par corrélation, nécessitant donc un formalisme plus lourd mais permettant une identification plus exhaustive, destinée à un déploiement embarqué sur FPGA. A ce titre, une première réécriture du modèle proposé est introduite, sur une base de fonctions orthogonales, pour la diagonalisation du système de corrélations. Une deuxième réécriture est effectuée pour appliquer la théorie du filtrage multicadence à l’élimination de la distorsion repliée dans la bande d’échantillonnage. Le dernier objet de ces travaux de thèse est l'application des méthodes présentées à la réalisation d'un calibrage mis en œuvre in situ, de façon à pouvoir s'adapter de façon dynamique à la variation de la distorsion non-linéaire de la chaîne au regard de l'évolution de l'environnement du radar aéroporté. Cette mise en œuvre suppose l'utilisation de la chaîne d'émission afin d'injecter le stimulus de calibrage dans la chaîne de réception. Nous proposons ainsi un procédé permettant la distinction des contributions non-linéaires des chaînes d’émission et de réception à l'observation de la sortie de leur cascade, afin de n'identifier que les défauts de la chaîne de réception, pour la linéarisation du signal capté par l'antenne
Whether in the context of digital communications, radar or electronic warfare, the transmission and reception chains performing these functions are made up of non-linear components. The latter carry out on the signals of interest the crucial operations of amplification, frequency transposition, and conversion from the analog world of propagation of these signals to the digital world of their processing. In all the contexts mentioned, the instantaneous dynamics is a key performance criterion, determining the spectral leakage at transmission, constraining the flow rate at reception of communication signals, or qualifying the capacity to receive echoes of different powers in radar.Increasing the instantaneous dynamics can be done through the design of the chains, both in the choice of components and in their ordering, and then involves a long and tedious design process, resulting in a sacrifice in terms of cost, size or consumption. The other way of increasing the instantaneous dynamics, which is the subject of this manuscript, is linearization by digital processing, based on behavioral modeling of the transmission or reception chain.This linearization is based on three intrinsically intertwined phases, behavioral modeling, identification of model parameters, and compensation of non-linear faults. After introducing the application context of this work, we begin this manuscript with the development of continuous-time models, based on the derivative of the signal. We thus opt to escape from the formalism of the Volterra series, based on the concept of memory effect, in order to rediscover the physical intuition of the description of the distortion with respect to instantaneous variations of the signal. We then split the identification of the parameters of these models into two phases. Characterization, first of all, brings together methods based on multi-tone signals, combining a relatively simple formalism and easy implementation. This first phase is therefore applied to the study of non-linear behavior, and to the sizing of the model. The second phase, calibration, designates the identification of the parameters of this model from white noise, by correlation, therefore requiring a heavier formalism but allowing a more exhaustive identification, intended for an embedded deployment on FPGA. As such, a first rewriting of the proposed model is introduced, on the basis of orthogonal functions, for the diagonalization of the correlation system. A second rewriting is carried out to apply the theory of multi-rate filtering to the elimination of the aliased distortion in the sampling band. The last object of this thesis work is the application of the methods presented to the realization of a calibration implemented in situ, so as to be able to adapt dynamically to the variation of the non-linear distortion of the chain with regard to the evolution of the airborne radar environment. This implementation assumes the use of the transmission chain in order to inject the calibration stimulus into the reception chain. We thus propose a method allowing the distinction of the non-linear contributions of the transmission and reception chains to the observation of the output of their cascade, in order to identify only the defects of the reception chain, for the linearization of the signal captured by the antenna

"A particularly important aspect of immunology is to develop non-invasive methods of obtaining antibodies which could be a great alternative to traditional ones that based on the harmful procedure of isolation of immunoglobulins from animal blood sera. That’s why the extraction of antibodies from poultry egg yolks (IgY) is the most promising. Due to the fact of variation of IgY structural features that determine the definite immunochemical properties, yolk antibodies in comparison with mammalian immunoglobulins (IgG) does not interact with rheumatoid factor (Rf), contribute to the activation of the complement system, bind to the Fc-receptor (FcR), and also has weak cross-reactivity, which confirms the possibility of their widespread use in medicine and food. Also the presence of phylogenetic distance between chickens and mammalians guarantees immune response against conservative mammalian protein molecules which is highly important for the creation of new generation test systems. The aim of this work is to develop a selective method of producing high-purity immunoglobulin Y preparations from the yolk of chicken eggs. There were adopted selective conditions of isolation of IgY under spontaneous thawing procedure at the room temperature of firstly frozen yolk solution in a sodium-phosphate buffer mixed with water (pH 5.0) in a ratio of 1:6, which leads to receiving a water-soluble fraction further precipitated with the sodium chloride at a concentration of 10% of the solution mass and subsequently concentrated using ultrafiltration with membrane UAM-10, that allows achieving the content of IgY not less than 95% per dry substance in immunoglobulin fraction. It is possible to produce a protein fraction with a protein content of at least 9 g/l. The purity of the immunoglobulin fraction was verified using polyacrylamide gel electrophoresis. The presence of a light chain in the IgY solution was proved to be a low-molecular compound using the method of gel-filtration-chromatography. The immunological activity of IgY was studied with respect to bovine serum albumin (BSA) as an antigen. The enzymatic resistance of IgY against proteolytic enzymes was tested in area of the gastrointestinal tract."