Search results for "BAND"
showing 10 items of 2610 documents
Baseband predistorter using direct spline computation
2005
A baseband predistorter is presented. Key features of the predistorter reside in the use of cubic spline interpolation to generate predistorted input data to the power amplifier, without time convergence problems of classical approaches, with the goal of a reduction in the computational effort. Simulated behaviour of the proposed scheme is presented, demonstrating the effectiveness of the approach.
Full-wave FDTD design and analysis of wideband microstrip-to-waveguide transitions
2003
Wideband transitions are designed and analysed by using two different approaches of the finite-difference time-domain (FDTD) method, in combination with the theory of nonuniform transmission lines. These transitions consist of a ridged waveguide-based taper between a shielded microstrip and a standard X-band rectangular waveguide. In the first step, a full-wave 2D-FDTD scheme is used to calculate the dispersion characteristics, as well as the geometry dependence of the impedance in the double ridged waveguide. Once these design curves have been obtained, the stepped transmission line transformer theory is used to design the tapers. In a former step, the nonuniform 3D-FDTD technique is appli…
Quasifractal planar microstrip resonators for microwave circuits
1999
We propose a new shape for microwave planar circuits using the self-similarity of the fractal geometry. This new shape allows the generation of numerous resonant frequencies for this microwave planar resonator due to the surface's encasing. The resonant frequency assessment can be useful for the concept of filters or wide frequency band matching loads as examples, without consuming circuit surface. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 433–436, 1999.
Detection of defective elements in an X band array antenna from its near field measurements
2007
An algorithm has been used to detect defective elements errors in array antennas. It has been applied to an X band slot array antenna and good results have been obtained. These have enabled the detection of errors in the manufacture process. We have used spherical near field measurements of the radiated field of the antenna. Then, once the equivalent currents are be obtained, an analysis of these results will be made in order to detect possible mistakes.
Fatigue life prediction under wide band random loading
2004
In this paper, a method for the high-cycle fatigue life prediction of components subjected to gaussian, stationary, wide band random loading is presented. It allows the user to evaluate the fatigue life of components subjected to uniaxial stress states directly from the stress power spectral density (PSD), avoiding onerous simulations in time domain. The proposed method can be applied to random stress processes having PSD of any shape, and the fatigue life predictions obtained are more accurate than that provided by most of the frequency domain techniques proposed in literature.
Electrical-optical characterization of multijunction solar cells under 2000X concentration
2014
In the framework of the FAE "Fotovoltaico ad Alta Efficienza" ("High Efficiency Photovoltaic") Research Project (PO FESR Sicilia 2007/2013 4.1.1.1), we have performed electrical and optical characterizations of commercial InGaP/InGaAs/Ge triple-junction solar cells (1 cm2) mounted on a prototype HCPV module, installed in Palermo (Italy). This system uses a reflective optics based on rectangular off-axis parabolic mirror with aperture 45×45 cm2 leading to a geometrical concentration ratio of 2025. In this study, we report the I-V curve measured under incident power of about 700 W/m2 resulting in an electrical power at maximum point (PMP) of 41.4 W. We also investigated the optical properties…
A DRO-based X-band injection-locked amplifier without input non-reciprocal elements
2009
Conventional design of injection-locked amplifiers (ILA's) implies the use of a non-reciprocal (ferrite, usually) element for separating the input signal from the synchronized output signal. In this paper a novel topological structure is proposed which permitted the realization of a wide-band, transmission-type, ILA with no need for separating input-port isolator or preamplifier. The prototype, realized in HMIC technology, while intended only as demonstrator of the newly proposed approach in the design of ILA's, shows quite satisfactory performances at X-band, with a simple, compact and low-cost structure.
The design of measurement-based underwater acoustic channel simulators using the INLSA algorithm
2015
This paper utilizes the iterative nonlinear least square approximation (INLSA) algorithm for designing measurement-based wideband shallow underwater acoustic (UWA) channel simulators. Measurement-based channel simulators are essential for the test, optimization, and performance analysis of UWA communication systems. The aim is to fit the time-variant channel impulse response (TVCIR) of the simulation model to that of the measured UWA channel. The performance of the designed UWA channel simulator is assessed by comparing the time-frequency correlation function (TFCF), the power delay profile (PDP), and the probability density function (PDF) of the channel envelope with the corresponding quan…
Temporal Dispersion Characterization of Over-Building Propagation Applied to Iso-Frequency Repeaters
2009
This letter presents the results of a measurements campaign carried out at 2050 MHz with the aim of characterizing the time dispersion of multipath propagation when the transmit and receive antennas are placed near and situated on rooftops or mounted on masts. The measurements were taken in four separate locations within the urban area of Madrid, Spain. From the measured data, the root mean square (RMS) value of the delay spread and the delay interval that characterize the time dispersion propagation of the environment under study are analyzed. An average power delay profile (PDP), representative of the time dispersion, is proposed so as to extrapolate these results to other similar environ…
Narrowband power line communications for medium voltage smart grids
2014
The aim of the paper is to show how narrowband power line communications (NB-PLCs) can be a valid solution for medium voltage grids. Advantages and drawbacks of this solution are analyzed, starting from some experimental communication results, which were carried out on the medium power system networks of the islands of Ustica and Favignana, in the presence of the net voltage. Furthermore, some communication architectures and hardware prototypes based on NB-PLCs are proposed for different smart grids applications.