No abstract

of the experiment for both environments A and B; thus, the effectiveness of the simulation is confirmed. CONCLUSIONIndoor propagation has been measured at 30 points in the experimental room (4.525 ϫ 6.220 ϫ 2.700 m) in order to investigate the effectiveness of using an EM-wave absorber to improve a wireless LAN communications environment.A well-reflected environment, where the ceiling and the wall are metal and the floor is concrete, has been compared with one in which one long side wall is replaced by a three-layer absorber consisting of general building materials. The average absorption performance was found to be 10.4 dB (2.4 -2.5 GHz), which makes the average delay spread one-half of that of the well-reflected environment; further replacement of the ceiling with the sound-absorbing rock wool makes the spread equal to one-quarter.Simulation using the ray-tracing method was also performed in this room and the results for number of positions to the normalized delay spread calculated by the simulation are similar to those obtained from the experiment.Useful and necessary extensions of this work for other materials and under different conditions will be presented in future works. Printed array antennas are commonly used for microwave and millimeter-wave applications due to their attractive features such as low profile, ease of integration with other circuits, and conformability to planar or nonplanar surfaces as compared to parabolic reflectors. However, large printed array antennas have severe efficiency limitations at high frequencies (Ku or Ka bands) due to ohmic and dielectric losses, and parasitic radiations in long and complicated feed networks are dominantly increased [1]. Table 1 shows the calculated gain and directivity of the microstrip array and the gain of a dish at 10 GHz [1]. The microstrip array has a dielectric constant of 2.2, thickness of 1.6 mm, and spacing between elements of 0.8 0 ( 0 , is the free-space wavelength). A dish antenna has the same area as the microstrip array and an aperture efficiency of 50%. To overcome the drawbacks of the printed arrays, several high-gain printed arrays are studied [2][3][4]. It is also noticed that larger printed arrays are not practical when reasonable efficiency is required. In this work, a slot-array antenna using waveguide-fed subarrays backed by a single rectangular cavity is made and its characteristics are measured. Slot arrays are the most widely used antennas because they are relatively simple to build and analyze, and can be used for compact antenna systems [5][6][7]. An open slot antenna is free to radiate on both sides. A slot antenna can radiate into one side or have a unidirectional beam by using a cavity.Therefore, a cavity-backed slot antenna is of major interest in phased arrays, satellite-communication systems, and direct-broadcast satellite applications because of its compact size and high efficiency. In arrays containing a large number of elements, it may be impractical to back each slot with its individual cavity.In this study, groups of...

Emission properties of the 173nm lights from the electrical discharge cells of the plasma display panel are investigated. The dimer formation and a theoretical model of 173nm emission are presented. It is shown that the diffusion loss of the excited xenon atoms in the metastable level is one of the most important population depreciation factor of excited xenon atoms. The decay time τd of excited atom number increases from zero, reaches its peak, and then decreases to zero, as the gas pressure p increases from zero, agreeing well with experimental data. A simple analytical expression Y of the total emission intensity is described in terms of the diffusion loss df, the three-body collision η, the gas pressure p, and the xenon mole fraction χ. The emission intensity Y of 173nm photon decreases with an increasing value of parameter df. Moreover, the emission intensity Y increases drastically with an increasing value of the gas pressure p and the xenon mole fraction χ. Results from the theoretical model agree remarkably well with experimental data.

In this paper, a transparent antenna made with a new structure of ITO/Ag/ITO is proposed. Overcoming the physical limitations of transparency and conductivity is an important problem with transparent materials. By studying and comparing previously reported transprent materials, a transparent electrode with thin film Ag inserted between two layers of ITO instead of a single layer is selected for a highly efficient transparent antenna. This electrode has low sheet resistance (3.1 Ω/sq) relative to its high transparency (88 % at 550 nm), which is a factor that can increase the efficiency of the antenna. In general, it is difficult to measure sheet resistance (SR) using a 4-point DC probe for very thin films (thickness of transparent material is less than the skin-depth). Therefore, a form of reverse engineering that can estimate DC sheet resistance using RF SR was presented and verified. As a result, it was possible to predict and design the performance of the transparent antenna with the new material structure. The selected transparent material is applied to design the wideband transparent antenna and the design process for wideband performance is covered in the paper. The proposed antenna with ITO/Ag/ITO was implemented for verification. The peak efficiency of the fabricated antenna was 66 %, and the measured bandwidth was 123 % (from 2.5 GHz to 10.6 GHz), which is the best performance than previously reported transparent antennas.INDEX TERMS Transparent antenna, efficiency improvement, ultra-wideband, ITO/Ag/ITO films.

A simple analytical expression Y of the 173 nm emission intensity is described in terms of the diffusion loss d f, the three-body collision η, the gas pressure p and the xenon mole fraction χ. The emission intensity Y of 173 nm photons decreases with increasing parameter d f. Moreover, Y increases rapidly with the gas pressure p and the xenon mole fraction χ. Results from the theoretical model agree markedly well with experimental data.