FDTD analysis of log-periodic flat dipole antennas

LPDA are now widely used for TV, broadcasting and communication in frequency range 0.1…4 GHz. The stand-point of the advantages of this type of antennas is the possibility to achieve permanently high gain in broad band. Up to the early 90th full-series production of LPDA use the technology of welding of metal tubes of different length and diameters. Obtained metal contacts were not reliable or otherwise were too expensive. Especially this regards to the cases when antenna gain is 10dB and more in broad band. The step forward in LPDA-building was made by proposal of new technology [1], which al-lows to increase reliability of antenna and to reproduce the geometry parameters of LPDA with precision not worth than 0.1 mm. Before, most of investigators used method of moments for LPDA modelling. Antenna model was consist of infinitely thin wires connected by hypothetical transmission line in free space. Results were obtained by numerical solution of integral equation for the currents and voltages on vibrators.In this paper a new analysis based on FDTD method is presented

Analysis of 3N parameters with N-N forces

This investigation has a twofold objective, (a) to examine in some detail the effects of various refinements in the input forces on the binding energy (BE) of the triton and the doublet neutron-deuteron scattering length (a<SUB>1/2</SUB>), and (b) to compare the effects of shape variations in the potentials on the evaluation of the same quantities. For this purpose, we calculate the BE and a<SUB>1/2</SUB> with the inclusion of tensor and core effects individually and collectively and give a comprehensive comparison of these results along with those obtained in earlier investigations by various authors. For the second objective, we present the results for an entirely different shape of the separable potentials (viz., form factors of the type &#8730;Q<SUB>0</SUB> which fulfill certain analyticity requirements on the potentials), and compare these predictions with those based on potentials proposed by Yamaguchi and Yukawa. The effects of the shape variation on the results found from the comparison of these potentials, which agree only approximately on the energy shell, persist even with higher-ranked potentials which agree much more closely on the energy shell as a result of the inclusion of repulsive-core terms. The limitations that the effects of shape variations imply on the reliability of three-body calculations with input two-body forces are discussed

An ultra-wideband feed for axisymmetrical reflector antenna

Results of modelling of an ultra-wide feed built on a basis on log-periodic dipole antenna by a finite differences time domain method have been submitted. Structurally the feed is the H-plane array of single log-periodic antennas. Numerical results have been verified by experimental data