On the Modal Superposition Lying under the MoM Matrix Equations

This paper shows an interesting sight on the correspondence between total current solution obtained by the Method of Moments and by the Characteristic modes respectively. Derivation is based on representation of a matrix in its spectral form. Detailed study of dipole antenna fed under different conditions is presented demonstrating that modal decomposition of currents offers a nice physical insight into behavior of radiating structures

Two-Element PIFA Array Structure for Polarization Diversity in UMTS Mobile Phones

In this paper, we demonstrate the possibility to strongly modify the radiated fields of a UMTS handset by using a phased two-element PIFA array. The structure is composed of a 100x40 mm2 metallic ground plane acting as the Printed Circuit Board (PCB) of the mobile phone. Two UMTS PIFAs are located at the top edge of this PCB. They are fed by a double Quasi-Lumped Coupler able to provide a 360° phase difference between its two outputs. By properly choosing the DC bias of the double QuasiLumped Coupler, we can set a specific phase difference between the two PIFAs. In this way the two-element array is able to radiate different electromagnetic fields. Simulated and measured radiation patterns in the two main planes of the chassis are presented for different phase differences. It is especially revealed that the novel twoantenna structure is able to radiate vertically-polarized electric fields in the azimuthal plane of the phone and horizontally-polarized electric fields in the same plane when changing the phase shift between the antennas from 0° to 180°. Potential applications are polarization-diversity techniques and Specific Absorption Rate reduction for handsets

Wpływ agrowłokniny na produkcyjność ziemniaków wczesnych

During 1999-2001 and in 2003 the effect of white fleece Pegas-agro 17 UV on the yield formation in the early irrigated potatoes (Adora and Impala cvs) was investigated in an early potatoes region of the Czech Republic. The fleece was placed over the crops for 30 days (1999), 49 days (2000), 35 days (2001) or 45 days (2003) after the planting. The fleece significantly increased yield of commercial tubers in the early harvest (02.06.1999 - 52.5%, 31.05.2000 - 21.3%, 07.06.2001 - 33.7% and 04.06.2003 - 463% in comparison with the control in average values of both cultivars). In the later sequential harvests the differences between the variant with fleece and the control variant diminished and at the end of June they were already nonsignificant. Between cultivars the greater yield effect was found in Impala as compared with Adora cv. A favourable influence of the fleece on the soil temperatures was demonstrated and also the heat insulating effect of the fleece during ground frosts was proved.W latach 1999-2001 i 2003, w rejonach korzystnych do uprawy ziemniaków wczesnych w Republice Czeskiej, prowadzono badania nad plonowaniem wczesnych odmian Adora i Impala pod osłoną z agrowłókniny Pegaz-agro 17 UV. Poletka agrowłókniną okryte były od wysadzenia ziemniaków przez 30 dni w roku 1999, 49 dni w roku 2000, 35 dni w 2001 i 45 dni w roku 2003. Zastosowanie agrowłókniny zwiększało plon ziemniaków we wczesnych terminach zbioru, średnio dla obu odmian, w stosunku do plonu uzyskanego bez okrycia, w kolejnych latach badań odpowiednio o 52,2%, 21,3%, 33,7% i nawet 463%. Podczas zbioru w końcu czerwca różnice były już nieistotne. Większy efekt zastosowania agrowłókniny uzyskano u odmiany Impala, niż u odmiany Adora. Stwierdzono pozytywny wpływ agrowłókniny na temperaturę gleby szczególnie w czasie przygruntowych przymrozków