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This paper presents a new broadband antenna for satellite communications. It describes the procedure involved in the design of a microstrip antenna array and its multi-level passive feed network that together yield circular polarization and the necessary gain to be used in an earth-satellite link. The designed antenna is notable for its large bandwidth, circular polarization, high gain and small dimensions.
This paper presents the design and simulation processes of an Equiangular Spiral Antenna for the extremely high frequencies between 65 GHz and 170 GHz. A new approach for the analysis of the antenna’s electrical parameters is described. This approach is based on formalism proposed by Rumsey to determine the EM field produced by an equiangular spiral antenna. Analytical expressions of the electrical parameters such as the gain or the directivity are then calculated using well sustained mathematical approximations. The comparison of obtained results with those from numerical integration methods shows a good agreement.
To improve the energy conversion efficiency of solar organic cells, the clue may lie in the development of devices inspired by an efficient light harvesting mechanism of some aquatic photosynthetic microorganisms that are adapted to low light intensity. Consequently, we investigated the pathways of excitation energy transfer (EET) from successive light harvesting pigments to the low energy level inside the phycobiliprotein antenna system of Acaryochloris marina, a cyanobacterium, using a time resolved absorption difference spectroscopy with a resolution time of 200 fs. The objective was to understand the actual biochemical process and pathways that determine the EET mechanism. Anisotropy of the EET pathway was calculated from the absorption change trace in order to determine the contribution of excitonic coupling. The results reveal a new electron energy relaxation pathway of 14 ps inside the phycocyanin component, which runs from phycocyanin to the terminal emitter. The bleaching of the 660 nm band suggests a broader absorption of the terminal emitter between 660 nm and 675 nm. Further, there are trimer depolarization kinetics of 450 fs and 500 fs in high and low ionic strength, respectively, which arise from the relaxation of the β84 and α84 in adjacent monomers of phycocyanin. Under conditions of low ionic strength buffer solution, the evolution of the kinetic amplitude during the depolarization of the trimer is suggestive of trimer conservation within the phycocyanin hexamer. The anisotropy values were 0.38 and 0.40 in high and in low ionic strength, respectively, indicating that there is no excitonic delocalization in the high energy level of phycocyanin hexamers.
We investigated the excitation modes of the light-harvesting protein phycocyanin (PC) from Thermosynechococcus vulcanus in the crystalline state using UV and near-infrared Raman spectroscopy. The spectra revealed the absence of a hydrogen out-of-plane wagging (HOOP) mode in the PC trimer, which suggests that the HOOP mode is activated in the intact PC rod, while it is not active in the PC trimer. Furthermore, in the PC trimer an intense mode at 984 cm−1 is assigned to the C–C stretching vibration while the mode at 454 cm−1 is likely due to ethyl group torsion. In contrast, in the similar chromophore phytochromobilin the C5,10,15-D wag mode at 622 cm−1 does not come from a downshift of the HOOP. Additionally, the absence of modes between 1200 and 1300 cm−1 rules out functional monomerization. A correlation between phycocyanobilin (PCB) and phycoerythrobilin (PEB) suggests that the PCB cofactors of the PC trimer appear in a conformation similar to that of PEB. The conformation of the PC rod is consistent with that of the allophycocyanin (APC) trimer, and thus excitonic flow is facilitated between these two independent light harvesting compounds. This excitonic flow from the PC rod to APC appears to be modulated by the vibration channels during HOOP wagging, C = C stretching, and the N–H rocking in-plan vibration.
Die Alterungsbeständigkeit von geschirmten Kabeln und Kontaktpaaren gewinnt angesichts des zunehmenden Einsatzes elektronischer softwarebasierter Steuerungen in Transportmitteln an Relevanz. Elektro- und Hybridantriebe sowie die Implementierung von Fahrassistenzsystemen bis hin zu autonom fahrenden Fahrzeugen führen zu komplexen Kabelbäumen mit einer großen Zahl von geschirmten Kabeln und Steckverbindern.
Um die Stabilität von Kontaktsystemen hinsichtlich ihrer Stabilität zu prüfen, werden Hochspannungskabel unterschiedlicher Hersteller und Dimensionierung für den Einsatz in Hybridfahrzeugen untersucht. Diese wurden mit Modellsteckern versehen, die die Schimung kontaktierten und hinreichend gewährleisteten.
Impedanz und Schirmwirkungsdämpfung wurden an thermisch belasteten Kabeln und Kontaktpaaren vergleichend zu Neuteilen untersucht. Der Einfluss der in Anlehnung an die LV 214 induzierten thermischen Alterung auf das frequenzabhängige Übertragungsprofil sowie den Gesamtstreuverlust wurde messtechnisch ermittelt. Zusätzlich wurden die Alterungseffekte an den Leitungsmaterialien mittels moderner bildgebender Analytik dokumentiert.
This paper evaluates experimentally the susceptibility of IT-networks under influences and the threats of HPEM (High Power Electromagnetic) and IEMI (Intentional Electromagnetic Interferences). As HPEM source a PBG 5 (Pulse Burst Generator) adapted to a TEM (Transversal Electromagnetic) Horn type antenna and a 90 cm IRA (Impulse Radiating Antenna) type antenna is used. Different network cable types and categories with different lengths are used. The immunity of the IT network is examined and the breakdown failure rate of the system is defined for a PRF (Pulse Repetition Frequency) of 500 s-1 in duration of 10 seconds. Series of measurements were carried out and disturbances of keyboards, mouse, switches, distortions on monitors and failures of the IT network and, even crash of PCs were observed. It is shown amongst other that by increasing the pulse repetition rate or frequency, generic test IT-networks are more susceptible to interference. Obtained results provide another view of the susceptibility analysis of modern generic IT-networks against UWB-Threats.
The possibility to bring the interference source, close to the potential target is characterized by the property of the source as stationary, portable, mobile, very mobile and highly mobile [3]. Starting from the existing and well-known IEME interference or IEMI (Intentional Electromagnetic Interference) and the already existing classifications an analysis of methods based on a comparative study of the methods used to classify the intentional EM environment is carried out, which takes into account the frequency, the cost, the amplitude of the noise signal, the radiated power and the energy of a pulse of radiation.
The deterioration of the shielding performance of electromagnetic interference finger stock gaskets in a corrosive environment is investigated. The visualization of the real contact area shows a drastic reduction of the engaged active contact region between fingers and their mating surfaces in presence of corrosives residues. In fact, additional openings occur besides the “Tlike” holes due to the porous nature of gaskets. This leads to a strong degradation of the shielding effectiveness. Modified Bethe’s theory is used to estimate the equivalent circuit parameters while the shielding effectiveness in terms of ratio between two transfer functions is obtained upon applying the filter theory. Quantitative measurements carried out for different gasket types show a good agreement with calculated results, demonstrating thus the validity of the approach.
At higher frequencies the triaxial cell becomes in principle a cavity resonator which shows different resonance frequencies depending on the dimensions of the cell as well as on the size of the DUT. Above these resonance frequencies propagation of TEM waves is disturbed and measurements of screening attenuation with triaxial test method according to IEC 62153-4-15 are limited. Higher order modes respectively resonance frequencies can be suppressed by using conductive absorber material such as ferrites, nanocrystalline absorbers, magnetic absorbers or foam absorbers, placed in the Triaxial cell. With these absorbers, the frequency range of the screening attenuation measured in Triaxial cell can be extended up to several GHz.
This work presents a spiral antenna array, which can be used in the V- and W-Band. An array equipped with Dolph-Chebychev coefficients is investigated to address issues related to the low gain and side lobe level of the radiating structure. The challenges encountered in this achievement are to provide an antenna that is not only good matched but also presents an appreciable effective bandwidth at the frequency bands of interest. Its radiation properties including the effective bandwidth and the gain are analyzed for the W-Band.