Ray Tracing

Abstract— A computational parallel approach for 3D ray-tracing techniques in the radio propagation prediction is presented. This approach considers that the main tasks in a 3D ray-tracing technique can be evaluated in an independent and/or parallel way. The workload distribution ...

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor vertical. Previous theoreti- cal and experimental work has demonstrated how this can result in the internal wave en- ergy being focused

A hybrid method, coupling a ray tracing method and a finite difference approach, is proposed for modelling T-wave propagation from an underwater source to an on-land seismic station. The long-range hydroacoustic wavefield, estimated in the SOFAR channel by the Maslov approach, shows many triplications of propagation with an increasing number of caustics as the range increases. Ray tracing approaches lead to a straightforward analysis of the SOFAR propagation: we find that the duration and the amplitude of the hydroacoustic T waves generated by a source close to the SOFAR axis may be respectively eight times longer and almost seven times higher than the duration and the amplitude of hydroacoustic T waves generated by a source close to the SOFAR limits. The finite difference modelling handles the complex hydroacoustic–seismi c T-wave conversion on atoll shores with an illustration of seismic T waves recorded during the Midplate experiment in 1989. Two different seismic stations, FGA on the Fangataufa Atoll and DIN on the Mururoa Atoll, both in French Polynesia, have recorded the seismic T waves due to an underwater chemical blast at a distance greater than 900 km. Synthetic seismograms computed by our proposed hybrid method are close enough to the real data for quantitative interpretation. We believe that the input model structure is accurate enough to allow such analysis of the seismic T waves. The numerical simulation shows that the seismic T waves recorded at both stations are mainly composed of P phases and Rayleigh phases. The simulation shows that the seismic T-wave duration is often linked to the source depth, although other factors (the continental slope or the distance between the top of the continental slope and the seismic station) may also affect the signal duration.

... and small scale fading in indoor wireless communication channels. Reinaldo A. Valenzuela, Dmitry Chizhik and Jonathan Ling ... References [I] R. A. Valenzuela, 0. Landron, DL Jacobs, "Estimating Local Mean Signal Strength of Indoor Multipath Propagation", IEEE Trans. ...

We report initial measurements of ionospheric propagation parameters, particularly the total electron content (TEC), using the recently launched FORTE satellite. FORTE, which orbits the Earth at an altitude of 800 km and an inclination of 70°, contains a set of wideband radio receivers whose output is digitally recorded. A specialized triggering circuit identifies transient, broadband radio events, which include radiation from lightning, transionospheric pulse pairs, and man-made sources. Event data are transmitted to the ground station for analysis. In this paper we examine signals transmitted from an electromagnetic pulse generator operated at Los Alamos. The transmitter produces nearly impulsive signals in the VHF range. The received signal is dispersed by the ionosphere, and the received signal can be analyzed to deduce the total electron content along the path. By comparing the slant TEC thus measured with results from a ray-tracing code, we can deduce the vertical TEC to 800 km. Data from eight passes are presented. These types of data (in larger quantities) are of interest to operators of radar altimeters, who need data to corroborate their corrections for the ionospheric TEC. The combination of FORTE TEC data to 800 km and TEC measurements to 20,000 km (the Global Positioning System orbital altitude) can provide useful information for assessing the validity of models of plasmaspheric electron density. Initial estimates of the plasmaspheric density, on two daytime passes, are about 6 TECU. The signal received by FORTE, which is linearly polarized at the transmitter, is split into two magnetoionic modes by the ionosphere. The receiving antenna is also linearly polarized and therefore receives both modes. By measuring the beat frequency between the two modes, we can deduce the product of the geomagnetic field and the cosine of the angle between the field and the propagation vector. The possibility of using the measured slant TEC and the beat frequency to geolocate impulsive signals is discussed.

The analysis and simulation of electromagnetic (EM) wave propagation represent a crucial task in planning cellular networks for mobile communication. When an adequate building database is available, deterministic 3D ray tracing techniques are quite useful and accurate to face this problem, but since their computational complexity is time consuming, a preprocessing step is necessary. Such a step allows the practical use of 3D ray tracing simulations so as to achieve the same accuracy of the ray optical approach in short simulation time. The preprocessing phase is independent on the position of the transmitter’s antenna, consequently it can be run once and for all, independently on EM field strength simulations. This strategy makes the technique practical and useful in common cellular network design, such as UMTS cellular planning. During the preprocessing phase, the mutual visibility between the walls and edges of the buildings are pre-evaluated and stored: the mutual visibility is d...

Under the AM1-5g spectrum, the efficiency of a c-Si module can be increased by 0.5-1.5% (relative) by using a silicone encapsulant rather than EVA. This increase is primarily due to photons of wavelengths less than ~400 nm being transmitted by silicone but blocked by EVA. The highest increase in efficiency arises for cells with a good `blue response' and for silicones of a higher refractive index. In this work we show that when calculated for the AM1-5g spectrum, the optical advantage of silicone over EVA tends to be an underestimate of what can be expected in the field. This is because incident spectra are frequently `bluer' than the AM1-5g spectrum, particularly in summer and on cloudy days. In such cases, a larger fraction of photons have a wavelength less than 400 nm. With ray tracing, we find that the relative advantage of silicone over EVA is increased by an additional 0.3% on a sunny summer day in Phoenix AZ, and by 0.7% on a cloudy summer day in Brownsville TX. Still greater increases are expected for maritime climates and for installations with high albedo.

A simulation model for light extraction efficiency (LEE) was proposed, considering the real structure of GaN_based light emitting diodes and absorption of GaN, electrodes and encapsulation materials, as well as the difference between TE and TM modes, the effects of active layer reabsoption and photo recycling. The slope angle and the depth of the pattern were optimized for patterned sapphire substrates (PSSs). Results show fill factor affects the LEE improvement most and air holes buried in the interface between n-GaN and PSS diminish LEE improvement of the pattern. Then a best improvement of 26% is obtained with the optimized pattern. Especially it is noticeable that the simulated result of LEE (39.2%) and the derived internal quantum efficiency (43.9%) agree well with the experimental results (38%, 45.1% respectively). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)