Active phased array antenna (APAA) is a representative of complex electronic equipment, and it plays significant roles in scenarios such as battlefield situation perception, aviation guidance, and communication. It has become the core equipment in land, navigation, and aeronautical applications. With the continuous improvement of technical changes and military requirements, the working frequency band, pointing accuracy, gain, and low sidelobe level of APAA increase, and the multi-disciplinary design contradiction between antenna electrical performance and structure and temperature becomes increasingly prominent. As a result, the electrical performance of APAA in service is prone to be affected by the external complex environments. The structural-electromagnetic-thermal (SET) coupling problem has become a key problem restricting the development of APAA. This paper has summarized the structural features and environmental loads of advanced APAA on different platforms and provided design basis and principle for antenna designer. And then the SET coupling theory of APAA has been introduced, which can be applied in both the design and manufacturing stage, as well as the performance control technology in service environment of APAA. This theory helps to analyze the impact of environmental factors, such as antenna structure deformation, radome high-temperature ablation, and feed errors, on the antenna's performance. For 128 × 768 spaceborne array antenna, in the range of 25∼85°C, the gain of antenna decreases with the increase of operating temperature and decreases by 0.015 dB with each increase of 1°C. The key design parameters in the fields of antenna manufacturing accuracy, efficient heat dissipation, and lightweight design are also analysed; for 32 × 32 rectangular planar phased array antenna, the gain of antenna decreases by 2.715 dB when the random error of installation position in x, y, and z direction reaches 1/10 of the wavelength. In addition, condition monitoring, displacement field reconstruction, and electrical performance compensation of APAA have also been touched to help engineers maintain and guarantee the antenna performance throughout its life cycle. Finally, the future research direction of SET technology of APAA has been discussed, and SET technology is extended to more fields such as antenna parameter uncertainty, high-frequency circuit electronics manufacturing, and electronic equipment performance guarantee.
Embarqué sur la plateforme ENVISAT, le spectro-imageur MERIS développé par Thales Alenia Space a permis de mesurer, à partir de 1993 et jusqu’en 2012 les paramètres environnementaux notamment de la couleur de l’Océan au large et sur les zones côtières. Avec le programme Copernicus de l’Union Européenne s’est ouvert en 2014 une évolution vers des mesures opérationnelles grâce aux satellites Sentinel 3 dédiés aux océans et équipés d’une nouvelle génération de spectro-imageurs, OLCI, héritiers de MERIS; quatre satellites sont programmée afin d’assurer la continuité des mesures sur de longues séries temporelles. A l’horizon 2029, le programme Copernicus va se diversifier avec un satellite d’imagerie hyperspectrale confié à Thales Alenia Space, Sentinel-10 ou CHIME (Copernicus Hyperspectral Imaging Mission for the Environment). Cet ensemble de réalisations complété par le développement de sondeurs atmosphériques hyperspectraux comme IASI sur METOP et IRS sur METEOSAT, constituent une expertise technique de pointe, unique au monde.
Instruments and machines, Applied optics. Photonics
The rapid development of the sensor equipment has promoted the rapid growth of the Internet of Things (IoT). The IoT has been widely employed in the multidimensional signal processing and gradually formed the IoT networks. Mobile communication promotes the wide application of the IoT networks. In this study, the transmit antenna selection (TAS) scheme is employed to investigate the average symbol error probability (ASEP) performance of mobile IoT networks over the 2-Rayleigh channels. We first employ moment-generating function (MGF) approach to derive the exact ASEP expressions. We also investigate the outage probability (OP) performance and derive OP expressions. Employing the deep neural network (DNN), an OP intelligent prediction algorithm is proposed. Then, the numerical simulations are conducted to confirm the ASEP and OP performance analysis. The effect of different channel parameters is also analyzed. Compared with Nakagami and Rayleigh channel models, the 2-Rayleigh model has 83.6% and 59.1% increase in ASEP values, respectively. Compared with ELM and RBF models, the DNN model has 31.7% and 22.5% increase in OP prediction accuracy, respectively.
Background: Outcomes of nursing interventions following discharge for recipients of transcatheter aortic valve replacement (TAVR) are scarce. Purpose: This quality improvement project was a retrospective cohort design to evaluate the effectiveness of a follow-up telephone call on reducing 30-day hospital readmission for patients recovering from the TAVR procedure. Methods and Results: A convenience sample of 50 patients was used, 25 who received the follow up phone calls and 25 who did not. Twenty-five patients were selected from those TAVR patients who did received a follow-up telephone call between January 20 - May 20, 2017 and 25 TAVR patients from those who were not exposed to the intervention between January 20 - May 20, 2016. The cohorts were matched based on sex and NYHA CHF classification at time of the hospital admission. Both hospital length of stay and postoperative length of stay were shorter in the intervention group than the control group. Patients who received the follow-up telephone call post discharge spent on average 2.20 days less in the hospital than those who did not receive the follow up telephone call, 3.92 ± 1.9 days vs 6.12 ± 3.95 days respectively, t = 2.53 (34), p = 0.01. Patients who received the follow-up telephone call post-discharge spent on average 1.28 days less in the hospital after their procedure than those who did not receive the follow-up telephone call, 2.84 ± 1.7 days vs 4.12 ± 2.57 days respectively, t = 2.07 (48), p = 0.01. However, there was no significant difference in readmissions within 30 days of discharge in those received the follow-up phone call post-discharge (n=4, 8%) and those who did not receive the follow-up phone call post-discharge (n=4, 8%). Conclusions: The quality improvement follow-up telephone call initiative did not reduce the rate of hospital readmission. Although, this program did not evaluate patient reported outcomes, future projects should not only consider hospital readmissions but other quality measures as well.
Jayshri Kulkarni, Raju Seenivasan, V. Abhaikumar
et al.
This paper presents a triple band monopole antenna design with an overall size of 21 × 8 mm2 for WLAN/WiMAX Multiple Input and Multiple Output (MIMO) applications in the laptop computer. It comprises of three monopole radiating elements, along with two rectangular open-ended tuning stubs. This structure excites 2.4/5.2/5.8 GHz WLAN and 2.3/3.3/5.5 GHz WiMAX bands. The prototype testing of proposed antenna array formed by using the same antenna design shows that, it has measured -10dB impedance bandwidth of 11.86% (2.22-2.50 GHz) in a lower band (fl), 5% (3.25-3.42 GHz) in medium band (fm) and 16.84% (5.00-5.92 GHz) in upper band (fu). The measured gain and radiation efficiency are well above 3.65 dBi and 75%, respectively, throughout the operating bands. Also, the measured isolation between two antennas is better than -20dB and envelope correlation coefficient (ECC) is less than 0.004 across the three bands of interest. This confirms the applicability of the proposed antenna array for MIMO applications in the laptop computer.
A circularly polarized (CP) wearable antenna based on the FDM (fused deposition modeling) technology is proposed. Conductive fabric is used to realize conductive parts of the patch antenna on the NinjaFlex substrate. The antenna is encapsulated with additional layers of NinjaFlex. Modified patch ensures the CP character at 2.45 GHz. Bending and washing tests are conducted to check the performance stability, and good agreement between simulated and measured results is observed. The experimental results illustrate that the antenna holds 11% 10 dB S11 bandwidth and around 70 MHz 3 dB axial ratio bandwidth. In addition, surface current analysis is also given to understand the operating mechanism of CP wave.
Ayman S. Al-Zayed, Mohammed A. Kourah, Samir F. Mahmoud
The design of a frequency reconfigurable dual-band H-shaped microstrip antenna fed by two coaxial probes is presented. Each probe excites one of the two fundamental modes of the antenna which are linearly polarized and orthogonal to each other. The antenna is symmetrically loaded with four varactor diodes to simultaneously tune these two modes. Simulation results show that the tunable range of the first mode is between 1.69 and 2.19 GHz (1.3 : 1 tuning ratio), whereas it is between 1.94 and 2.72 GHz (1.4 : 1 tuning ratio) for the second mode. In the range between 1.94 and 2.19 GHz, the radiation of the proposed antenna can be switched between two orthogonal linear polarizations by a simple adjustment to the capacitance of the varactor diodes. The proposed antenna achieves a good performance in terms of port-to-port isolation, directivity, and cross-polarization.
A band-notched UWB antenna is presented, which can switch between two notch bands and tune the central frequency simultaneously. It is the first time that the switchable and tunable behaviours are combined together in band-notched UWB antennas. In the band-notched structure, PIN diodes are used to switch the lower and upper frequency bands, while varactors could vary the central frequency of each notch band continuously. Measurement results show that the notch bands could switch between 4.2 GHz and 5.8 GHz when the state of varactors is fixed, and the ranges of tuning are 4.2–4.8 GHz and 5.8–6.5 GHz when the state of PIN diodes is ON and OFF, respectively.
This paper deals with the development of a W-band noise-adding radiometer which combines the millimeter-wave (MMW) radiometric measurements with a high-resolution imager. The offset parabolic antenna is presented to achieve an accurate measurement and a high resolution. To reduce the cross-polarization level of the antenna, a multimode feed horn with a multistep structure is proposed to match the focal region fields of the reflector. It has advantages over the corrugated horns in lower mass and easier manufacturing. In addition, due to an unavoidable settling time for the noise-adding radiometer output signal passing through the low-pass filter, a theoretical criterion for the optimum duty cycle determination to reject extraneous contributions from the transient is proposed in this paper. The appropriate duty cycle threshold is 0.33 for the developed W-band radiometer. Also, a geometric correction method is presented to correct the obtained passive image suffering from a distortion for a better image interpretation. Preliminary experimental results are given to illustrate and verify the presented techniques.
Sébastien Rapinel, Anne Bonis, Johan Oszwald
et al.
La microtopographie, et par extension le régime hydrique joue un rôle primordial dans la répartition spatiale des végétations des zones humides. L'objectif de ce travail est d'évaluer l'intérêt des données topographiques LiDAR pour la cartographie des communautés végétales prairiales. La méthode appliquée repose sur le seuillage du Modèle Numérique de Terrain en fonction des valeurs altimétriques caractérisant les différents relevés phytosociologiques sur un site de 35 ha du Marais Poitevin. Les résultats montrent que les communautés mésophiles, méso-hygrophiles et hygrophiles ont pu être classées automatiquement avec une précision globale de 89.6% (Kappa = 0.83). La cartographie produite au 1:5000ème constitue un support pour le suivi et la gestion des habitats naturels.
Instruments and machines, Applied optics. Photonics
A volume integral equation based fast algorithm using the Fast Fourier Transform of fitting Green’s function (FG-FFT) is proposed in this paper for analysis of electromagnetic scattering from 3D anisotropic dielectric objects. For the anisotropic VIE model, geometric discretization is still implemented by tetrahedron cells and the Schaubert-Wilton-Glisson (SWG) basis functions are also used to represent the electric flux density vectors. Compared with other Fast Fourier Transform based fast methods, using fitting Green’s function technique has higher accuracy and can be applied to a relatively coarse grid, so the Fast Fourier Transform of fitting Green’s function is selected to accelerate anisotropic dielectric model of volume integral equation for solving electromagnetic scattering problems. Besides, the near-field matrix elements in this method are used to construct preconditioner, which has been proved to be effective. At last, several representative numerical experiments proved the validity and efficiency of the proposed method.
Multipath effect is the main factor of deteriorating target detection performance in low grazing angle scenario, which results from reflections on the ground/sea surface. Amplitudes of the received signals fluctuate acutely due to the random phase variations of reflected signals along different paths; thereby the performances of target detection and tracking are heavily influenced. This paper deals with target detection in low grazing angle scenario with orthogonal frequency division multiplexing (OFDM) radar. Realistic physical and statistical effects are incorporated into the multipath propagation model. By taking advantage of multipath propagation that provides spatial diversity of radar system and frequency diversity of OFDM waveform, we derive a detection method based on generalized likelihood ratio test (GLRT). Then, we propose an algorithm to optimally design the transmitted subcarrier weights to improve the detection performance. Simulation results show that the detection performance can be improved due to the multipath effect and adaptive OFDM waveform design.
AbstractA new approach to the steady state detection in the uniformization method ofsolving continuous time Markov chains is introduced. The method is particularlyuseful in solving inhomogenous CTMC’s in multiple steps, where the desirederror bound of the whole solution can be distributed not proportionally to thelengths of the respective intervals, but rather in a way, that maximizes thechances of detecting a steady state. Additionally, the convergence properties ofthe underlying DTMC are used to further enhance the computational savingsdue to the steady state detection. The method is applied to the problem ofmodeling a Call Center using inhomogenous CTMC model of a M(t)/M(t)/s(t)queuing systems.Keywords: Markov processes, OR in service industries, transientsolutions, uniformization, numerical methods, nonstationary,algorithms, Contact Centre1. IntroductionOne of the most important characteristics of the telephone Call Centers istheir varying number of service requests (calls) in time. As the cost of laboris the most signi cant one in such service systems, the problem of adequatescheduling of its employees has a long history in the area of operational re-search. The methods proposed to analyze such time-varying behavior in orderto nd optimal working schedules for given demand forecasts are based mostlyon approximations, by adopting stationary queuing models. Examples of suchwell established methods can be found e.g in Green et al. (2007) or Aksin et al.(2007).However, stationary solutions for generating such schedules are, in manysituations, not adequate. Ingolfsson et al. (2010) demonstrated that such ap-proximations can be either entirely unreliable or deliver results signi cantlydi erent than methods based on inherently transient models. Despite this,
La chartreuse de Villeneuve-lès-Avignon (Gard), fondée au XIVème siècle par le pape Innocent VI, a subi de nombreux bouleversements tout au long de son existence, à l'image de son église. Construite en plusieurs temps, elle a atteint son apogée au XVIIIème siècle, avant d'être vendue puis divisée en lots et occupée par la population pauvre locale. Le XXème siècle marque sa renaissance à travers les expropriations et les restaurations. Elle est aujourd'hui un site touristique et un lieu de résidence pour artistes. Dans le cadre du programme 3D[Monuments] piloté par le Ministère de la Culture et de la Communication, l'église a été le théâtre de campagnes de relevés numériques et photographiques visant à reconstruire en 3D son état actuel. Une restitution hypothétique de son état postrévolutionnaire, basée sur les nombreuses et diverses sources documentaires, a également été proposée. Une base de données contenant la documentation liée aux objets 3D a été mise en place. L'élaboration de la maquette 3D a conduit l'équipe à s'interroger sur la fiabilité des informations transmises par les sources documentaires. La chartreuse a ainsi été choisie comme terrain d'expérimentation privilégié pour l'étude de l'incertitude des données documentaires réalisée dans le cadre d'une thèse de doctorat.
Instruments and machines, Applied optics. Photonics
Dimitra Zarbouti, George Tsoulos, Georgia Athanasiadou
et al.
Radio channels induce distortions to the radiation pattern of beamforming systems such as beam broadening as well as sidelobe level and null rising. If these effects are ignored, the system performance is overestimated. This paper proposes the simple concept of an effective radiation pattern (ERP) calculated by optimally fitting the “real-world” radiation pattern to the ERP. The proposed ERP method is incorporated into a multicell bad urban 4G LTE operational scenario which employs beamforming for both the BSs and the RNs. The performed simulations provide evidence that the ideal instead of the real radiation pattern overestimates the SIR and capacity by almost 3 dB and 13 Mbps, respectively, for the reference scenario without RNs. It also proves that the ERP method produces almost identical performance results with the real radiation pattern, and hence it is a simple and viable option for realistic performance analysis. Finally, the network performance is studied as a function of the number of RNs with the help of the ERP method. Results show that a beamforming LTE network with RNs that also employ beamforming provides 3 dB SIR gain with the addition of 1 RN per cell and 15 dB gain with 4 RNs per cell.
In the last few years, several antenna designs of rectenna that meet various objectives have been proposed for use in RF energy harvesting. Among various antennas, microstrip patch antennas are widely used because of their low profile, light weight, and planar structure. Conventional patch antennas are rectangular or circular in shape, but variations in their basic design are made for different purposes. This paper begins with an explanation and discussion of different designs, put forward with an aim of miniaturization, harmonic rejection, and reconfigurability. Finally, microstrip patch structured rectennas are evaluated and compared with an emphasis on the various methods adopted to obtain a compact rectenna, harmonic rejection functionality, and frequency and polarization selectivity.
This paper presents optimization problem formulations to design meander-line antennas for passive UHF radio frequency identification tags based on given specifications of input impedance, frequency range, and geometric constraints. In this application, there is a need for directive transponders to select properly the target tag, which in turn must be ideally isotropic. The design of an effective meander-line antenna for RFID purposes requires balancing geometrical characteristics with the microchip impedance. Therefore, there is an issue of optimization in determining the antenna parameters for best performance. The antenna is analyzed by a method of moments. Some results using a deterministic optimization algorithm are shown.
The SVD-aided joint transmitter and receiver design for the uplink of CDMA-based synchronous multiuser Turbo-BLAST systems is proposed in the presence of channel state information (CSI) imperfection. At the transmitter, the beamforming and power allocation schemes are developed to maximize the capacity of the desired user. At the receiver, a suboptimal decorrelating scheme is first proposed to mitigate the multiuser interference (MUI) and decouple the detection of different users with imperfect CSI, and then the iterative detecting algorithm that takes the channel estimation error into account is designed to cancel the coantenna interference (CAI) and enhance the bit error rate (BER) results further. Simulation results show that the proposed uplink CDMA-based multiuser Turbo-BLAST model is effective, the detection from every user is completely independent to each other after decorrelating, and the system performance can be enhanced by the proposed beamforming and power allocation schemes. Furthermore, BER performance can be enhanced by the modified iterative detection. The effect of CSI imperfection is evaluated, which is proved to be a useful tool to assess the system performance with imperfect CSI.