Lars Olsson

Switchable Frequency Selective Surface for Reconfigurable Electromagnetic Architecture of Buildings

A frequency selective surface (FSS) that is electronically switchable between reflective and transparent states is tested. It can be used to provide a spatial filter solution to reconfigure the electromagnetic architecture of buildings. The FSS measurements show that the frequency response of the filter does not change significantly when the wave polarization changes or the angle of incidence changes up to ±45° from normal. The FSS is based on square loop aperture geometry, with each unit cell having four PIN diodes across the aperture at 90 degree intervals. Experiments demonstrated that almost 10 dB additional transmission loss can be introduced on average at the resonance frequency, for both polarizations, by switching PIN diodes to on from off state.

Cross-Dipole Bandpass Frequency Selective Surface for Energy-Saving Glass Used in Buildings

Energy-saving glass is becoming very popular in building design due to their effective shielding of building interior against heat entering the building with infrared (IR) waves. This is obtained by depositing a thin layer of metallic-oxide on the glass surface using special sputtering processes. This layer attenuates IR waves and hence keeps buildings cooler in summer and warmer in winter. However, this resistive coating also attenuates useful microwave/RF signals required for mobile phone, GPS and personal communication systems etc. by as much as 30 dB. To overcome this drawback, a bandpass aperture type cross-dipole frequency selective surface (FSS) is designed and etched in the coatings of energy-saving glass to improve the transmission of useful signals while preserving IR attenuation as much as possible. With this FSS, 15-18 dB peak transmission improvement can be achieved, for waves incident with ±45° from normal for both TE and TM polarizations. Theoretical and measured results are presented.

Glass Characterization for Designing Frequency Selective Surfaces to Improve Transmission through Energy Saving Glass Windows

This paper reports initial work on creating frequency selective surfaces (FSS) on modern day glass windows to improve the transmission of wireless/mobile/cellular communication signals through the glass. The manufacturers of these glass windows apply very thin layers of metallic oxides on one side of glass to provide extra thermal insulation. These coatings block the infrared and ultraviolet waves to provide thermal insulation, but they also attenuate communication signlas such as GSM 900, GSM 1800/1900, UMTS and 3G mobile signals. This creates a major communication problem when buildings are constructed using mostly such type of glass. A bandpass FSS can provide a solution to increase the transmission of useful bands through the coated glass. In order to design an appropriate FSS, the relative permittivity and conductivity of glass should be measured accurately. Moreover, electrical properties of the coated layer must also be known in order to obtain a resonance in the desired band. In this work, we used two different methods of measuring the permittivity and conductivity of glass. Electrical properties of one of the common glass windows (Optithermtrade SN) are presented. Simulations of Optitherm glass shows about 35 dB transmission loss over 900-2200 MHz frequency band.

Outdoor microcell measurements at 1700 MHz

An attempt is made to determine how different physical parameters affect the magnitude of the slopes and the location of the breakpoint for loss in both line-of-sight (LOS) and in non-line-of-sight (NLOS). A model for NLOS propagation using piecewise exponential functions is also presented. Multiparameter regression with the squared error between calculated and measured loss as minimizing function is performed to give the optimum fit between measured data and model parameters.<<ETX>>

Transmission analysis of energy saving glass windows for the purpose of providing FSS solutions at microwave frequencies

An inherent transmission problem associated with modern energy-saving glass windows is analyzed. These windows are used in building design to provide thermal insulation which keeps the interior warmer in the winter and cooler in the summer. This thermal insulation is achieved by employing a very thin layer of metallic oxide on one side of the ordinary (float) glass. This layer attenuates infrared waves while remaining transparent to ultraviolet frequencies. But this metallic oxide coating also attenuates the transmission of useful RF/microwave signals (GSM, GPS etc) through the glass window. We have investigated the transmission of microwave frequencies through OptithermtradeSN glass window manufactured by Pilkington. At average, about 30 dB attenuation is observed from 800 MHz to 6 GHz for both TE and TM polarizations at normal incidence. Theoretical and measured results are presented.

Time dispersion measurement system for radio propagation at 1800 MHz and results from typical indoor environments

A high resolution time dispersion measurement system at 1800 MHz has been designed and implemented. More than 3000 impulse responses have been measured in different environments and statistics of the instantaneous rms delay spread /spl tau//sub rms/ show that there is no general increase at longer antenna separations. However, /spl tau//sub rms/ values increase with room size and number of reflectors, which makes it necessary to characterize different indoor propagation environments separately.<<ETX>>

A comparison of solutions to the problem of diffraction of a plane wave by a dielectric wedge

The problem of diffraction of an E-polarized plane wave by a dielectric wedge with nonzero conductivity is considered. Two approximate solutions to the problem, a solution based on impedance boundary conditions (Maliuzhinetss solution) and a heuristic solution, are compared to the exact solution. Maliuzhinetss solution is in good agreement with the exact solution provided that the magnitude of refractive index of the wedge is large compared to unity. The accuracy of the heuristic solution is generally poor, except in the vicinity of the shadow and reflection boundaries. This study is limited to the case of a rectilinear wedge and the scattered field is not determined for the whole space around the wedge.<<ETX>>

The spiral aftereffect technique (SAT) can differentiate between depressive and somatoform disorder patients

This study examined how differences in visuo-perceptual patterns are related to psychopathology. Fifty-six patients (37 women, 19 men; M age = 43.8 yr., SD = 13.4) with a main diagnosis of unipolar depression and 42 patients (22 women, 20 men; M age = 42.0 yr., SD = 11.1) with a main diagnosis of somatoform disorder were compared. The duration and trend of a visual motion aftereffect were measured with the Spiral Aftereffect Technique (SAT). The results indicated that successively increasing aftereffect durations characterized the depressive patients, whereas patterns of very short or short final aftereffect preceded by successively decreasing aftereffect durations characterized the patients with a somatoform disorder. The SAT is thus a valuable tool for linking objectively measured perceptual-personality characteristics with some mental disorders.

Swedish Working-Class History

Interest in the history of the Swedish labor movement is almost as old as the movement itself. The Social Democratic Labor party was founded in 1889, and the Central Trade Union Organization (LO) in 1898. And by 1902 the Archives ofthe Labor Movement had been established in Stockholm to preserve the memory of the pioneers of the movement for future generations. The Swedish labor movement has continued to show considerable interest in its own history, and innumerable histories of party organizations and union locals have been published to celebrate anniversaries. Influential individuals have con tributed to their interest, including Sigfrid Hansson, brother of the party leader and Prime Minister, Per-Albin Hansson. Interest among rank-and-file members also has been substantial. At the universities, interest in labor history can be traced to the 1920s. John Lindgrens pioneering book on the formative years ofthe Social Democratic Labor party in the 1880s (1927) was followed in the 1930s by G. Hilding Nordstr?m s study of the partys history (1938) and Tage Lindboms work on the early trade union movement (1938). Historical interest within the labor movement and the academic world was