Wideband Dual-Polarized Cross-Shaped Vivaldi Antenna

This communication presents a wideband, dual-polarized Vivaldi antenna or tapered slot antenna with over a decade (10.7:1) of bandwidth. The dual-polarized antenna structure is achieved by inserting two orthogonal Vivaldi antennas in a cross-shaped form without a galvanic contact. The measured - 10,\hbox {dB} impedance bandwidth ( {S_{11}} ) is approximately from 0.7 up to 7.30 GHz, corresponding to a 166% relative frequency bandwidth. The isolation ( {S_{21}} ) between the antenna ports is better than 30 dB, and the measured maximum gain is 3.8 11.2 dB at the aforementioned frequency bandwidth. Orthogonal polarizations have the same maximum gain within the 0.7 3.6 GHz band, and a slight variation up from 3.6 GHz. The cross-polarization discrimination (XPD) is better than 19 dB across the measured 0.7 6.0 GHz frequency bandwidth, and better than 25 dB up to 4.5 GHz. The measured results are compared with the numerical ones in terms of S -parameters, maximum gain, and XPD.The authors would like to thank Dr. T. Brown from University of Surrey for proofreading the manuscript, and the anonymous reviewers for the dedicated work to help improve this paper. They would also like to thank T. Jaasko from Pulse Finland for performing the Vivaldi prototype antenna measurements. M. Sonkki would like to thank the Nokia Foundation and Infotech Oulu Doctoral Program for financially supporting his Ph.D. studies. This technology has been licensed by industry.Sonkki, M.; Sánchez Escuderos, D.; Hovinen, V.; Salonen, E.; Ferrando Bataller, M. (2015). Wideband Dual-Polarized Cross-Shaped Vivaldi Antenna. IEEE Transactions on Antennas and Propagation. 63(6):2813-2819. doi:10.1109/TAP.2015.2415521S2813281963

Prediction model for the diurnal behavior of the tropospheric scintillation variance

Tropospheric scintillation is caused by variations of the refractive index due to turbulence. The only meteorological input parameter for two common current scintillation models by Karasawa et al. (1988) and by the ITU-R is the monthly average of the wet part of the refractivity Nwet at ground level, which is not directly associated with turbulence. The diurnal correlation between Nwet and scintillation variance is very weak. Because clouds and cloud formation are closely associated with the turbulence, quantitative cloud parameters were looked for. Cloud type information based on edited synoptic cloud reports are available from the common database of CDIAC and NCAR. Both diurnal and seasonal variations between scintillation variance and average amount of Cumulus type clouds are well correlated. Using this cloud information together with Nwet, a new method for tropospheric scintillation variance predicting also the diurnal variations is introduced. This model is derived and tested using scintillation measurements at four sites in different climates in Finland, United Kingdom, Japan, and Texa

Prediction model for the diurnal behavior of the tropospheric scintillation variance

Tropospheric scintillation is caused by variations of the refractive index due to turbulence. The only meteorological input parameter for two common current scintillation models by Karasawa et al. (1988) and by the ITU-R is the monthly average of the wet part of the refractivity Nwet at ground level, which is not directly associated with turbulence. The diurnal correlation between Nwet and scintillation variance is very weak. Because clouds and cloud formation are closely associated with the turbulence, quantitative cloud parameters were looked for. Cloud type information based on edited synoptic cloud reports are available from the common database of CDIAC and NCAR. Both diurnal and seasonal variations between scintillation variance and average amount of Cumulus type clouds are well correlated. Using this cloud information together with Nwet, a new method for tropospheric scintillation variance predicting also the diurnal variations is introduced. This model is derived and tested using scintillation measurements at four sites in different climates in Finland, United Kingdom, Japan, and Texa

Improved models for long-term prediction of tropospheric scintillation on slant paths

The prediction models for tropospheric scintillation on earth-satellite paths from Karasawa, Yamada, and Allnutt and ITU-R are compared with measurement results from satellite links in Europe, the United States, and Japan at frequencies from 7 to 30 GHz and elevation angles of 3 to 33°. The existing prediction models relate the long-term average scintillation intensity to the wet term of refractivity at ground level. The comparison shows that the seasonal variation of scintillation intensity is well predicted by this relation, but for the annual average some additional meteorological information is needed. A much better agreement with measurement results is found when a parameter representing the average water content of heavy clouds is incorporated. This confirms the assumption that scintillation is, at least partly, associated with turbulence inside clouds. The asymmetry between the distributions of signal fade and enhancement can also be explained by turbulence inside clouds. The asymmetry depends on the intensity of the scintillation, which is consistent with the theory assuming a thin layer of cloudy turbulence. A new model based on this theory predicts the distributions of signal fade and enhancement significantly better. © 1999 IEEE

Planar Wideband Polarization Diversity Antenna for Mobile Terminals

This letter presents a planar wideband polarization diversity antenna for mobile terminals. The antenna consists of two orthogonally oriented quasi-complementary antennas (QCA) formed by the combination of an electric dipole and a magnetic slot and located at the separate ends of a mobile ground plane. The studies with a single quasi-complementary antenna element show that the electric dipole and the magnetic slot are partly compensating each other providing large bandwidth and offering good radiation properties. The measured -6-dB impedance bandwidth of the individual QCA is from 1.8 to 4.6 GHz, corresponding to an 87.5% relative bandwidth. The measured S21 is less than - 18 dB within the - 6-dB impedance bandwidth. The average measured total efficiency at the aforementioned bandwidth is - 0.95 dB. The measured radiation patterns are presented at 2 and 4 GHz with orthogonal polarizations. Finally, the measured envelope correlation and effective diversity gain (EDG) as a function of frequency are presented, with a maximum correlation less than 0.01 and EDG better than 8.0 dB. © 2011 IEEE.This work was supported by the Finnish Funding Agency for Technology and Innovation, Nokia Devices Oulu, and Pulse Finland.Tapani Sonkki, M.; Antonino Daviu, E.; Ferrando Bataller, M.; Salonen, E. (2011). Planar Wideband Polarization Diversity Antenna for Mobile Terminals. IEEE Antennas and Wireless Propagation Letters. 10:939-942. doi:10.1109/LAWP.2011.2167589S9399421

Improved Planar Wideband Antenna Element and its Usage in a Mobile MIMO System

A simple antenna structure for a multiple-input-multiple-output (MIMO) system in a mobile terminal with spatial diversity is presented. A single antenna element consists of a combination of an electric dipole and a square magnetic slot. The studies with a single quasi-complementary antenna element show that the electric dipole and the square-shaped magnetic slot are partially compensating the effect of the electric conductor closely spaced to the electric dipole (0.0037-0.01¿). Simulations also show that by scaling antenna structure, a 0.7-2.1-GHz frequency bandwidth can be achieved. The measured -6-dB impedance bandwidth of the MIMO antenna prototype is from 2.0 to 5.6 GHz, corresponding to a 95% relative bandwidth. The measured S 21 is less than -19 dB within the -6-dB impedance bandwidth. The average measured total efficiency at the aforementioned bandwidth is -0.85 dB. The measured radiation patterns are presented at 2 and 5 GHz with a maximum total gain of 2.8 and 5.7 dBi, respectively. The measured envelope correlation of the MIMO antenna is less than 0.04 with 90% MIMO efficiency within the -6-dB impedance bandwidth. © 2002-2011 IEEE.This work was supported by the Finnish Funding Agency for Technology and Innovation, Nokia Devices Oulu, Pulse Finland, and Universitat Politecnica de Valencia under Project PAID-06-09-2868. The work of M. Sonkki was supported by the Tauno Tonning Foundation and Universitat Politecnica de Valencia.Sonkki, M.; Antonino Daviu, E.; Cabedo Fabres, M.; Ferrando Bataller, M.; Salonen, E. (2012). Improved Planar Wideband Antenna Element and its Usage in a Mobile MIMO System. IEEE Antennas and Wireless Propagation Letters. 11:826-829. doi:10.1109/LAWP.2012.2208615S8268291