W. Wiesbeck

Ray optical modeling of wireless communications in high-speed railway tunnels

A new deterministic approach for wave propagation modeling in high-speed train tunnels is presented. The model is based on a new ray launching method and results in the polarimetric and complex channel impulse response as well as the Doppler diagram for radio links between on-train stations and tunnel-fixed stations. Different channel simulations under certain propagation conditions are presented.

Aperture-coupled microstrip patch phased arrays in C- and X-band: a contribution to future multi-polarization multi-frequency SAR systems

Future spaceborne SAR systems will use active phased array antennas with multi-polarization and multi-frequency capabilities. For high resolution SAR images of high quality the antennas have to provide a large bandwidth and an extreme polarization purity. These requirements can be met by aperture-coupled microstrip patch phased arrays based on low-permittivity, low-weight and low-cost foam substrates. The paper presents their design and their measured performance in C-band (5.3 GHz) and X-band (9.6 GHz).

Dual polarized L-band microstrip patch array for the AIRSAR/TOPSAR system

Describes the design and initial results of an advanced dual polarized 8x2 element microstrip patch array for the new NASA/JPL dual frequency C- and L-band interferometric SAR. The new dual polarized L-band antenna for the AIRSAR/TOPSAR system consists of aperture-coupled microstrip patch elements on a foam substrate, yielding a high polarization purity, low losses, a good port-to-port isolation and a large bandwidth.

New planning methods for single frequency networks

For analog broadcast networks the planning parameters for frequency, power and site assignment are well known, for digital audio broadcast networks the research into these criteria just started. This paper presents the derivation of protection ratios and fieldstrength levels under worst case conditions for digital audio broadcast systems from the bit error rate of the unprotected propagation channel. This channel is modeled ray optically as a 3D wave propagation channel, based on digital terrain data. Different terrain types, frequencies and temporal/spatial probabilities are considered.

Comparison of channel impulse response measurements and calculations in indoor environments

Emerging radio systems are established in the UHF to EHF. They are also intended for short ranges like in a single building or a scenario of a few buildings. A wave propagation tool for indoor environments is required in order to plan these systems. The wavelength above 1 GHz is small with respect to the dimensions of the physical environment, thus a ray optical approach is valid. At the Institut fur Hochstfrequenztechnik und Elektronik (IHE) at the University of Karlsruhe, a ray optical propagation model for indoor environments has been developed. To verify the model several measurements have to be performed. A measurement system has been developed at the IHE which is based on a vector network analyzer. It measures complex transmission factors in the frequency range from 45 MHz up to 50 GHz limited only by the antenna bandwidth. The channel impulse response results in an inverse Fourier transformation. Additional diversity aspects like the cross covariance of a multi channel system are also investigated by the measurement system. This paper deals with the verification of the model at frequencies from 1 GHz up to mm-wave bands. Some comparisons of channel impulse response measurements and calculations are presented and a variety of diversity results with different antenna systems is shown.

Mutual coupling in aperture-coupled microstrip patch arrays with a sequential feeding technique

Aperture-coupled microstrip patch antennas are very attractive candidates for many polarimetric phased array applications. They offer an excellent electrical performance and are easy to manufacture. Due to their multilayer design an optimum choice can be made for the patch and the feed substrate. Low-permittivity patch substrates yield a high bandwidth as well as high radiation efficiency. Dual linear polarization can be achieved by either crossed slot or offset slot configurations. Depending on the bandwidth the typical polarization isolation of dual polarized aperture-coupled antenna elements on low-permittivity substrates is about -25 dB. However, for several phased array applications a even higher polarization isolation is required. By sequential feeding techniques a significant improvement of the polarization purity at the array level with values of better than -45 dB is achieved. However, microstrip patch arrays with sequentially rotated antenna elements show a different coupling and scan behavior than arrays with unidirectional aligned antenna elements. This paper investigates microstrip patch arrays for phased array applications in the C-band with a sequential feeding technique.

Ray optical wave propagation models for the characterization of radio channels in urban outdoor and indoor environments

A deterministic approach for the prediction of path loss and channel impulse response of UHF radio links in built-up areas, including building penetrating links, is presented. The wave propagation prediction is based on ray-tracing algorithms implemented in the URBAN-MICRO model. A brief description of this model is given and comparisons with path loss measurements are shown. Further an extension of the URBAN-MICRO model for in-building antenna locations, resulting in the new model URBAN-MICRO-I, is presented. Both models use vector oriented building data and raster based topography data. Arbitrary outdoor base station heights can be handled by the models, which is a very important feature from a practical point of view.

Fast determination of channel impulse responses by 3D wave propagation modeling

A new deterministic 3D wave propagation model is presented, which is as accurate as the original IHE-3D-RURAL wave propagation model [Lebherz et al., 1992, Kurner et al., 1994] but less time consuming. Therefore, the ray tracing is improved by using new and faster algorithms. As a consequence, now an area covering bit-error-rate prediction for digital communication systems such as GSM or digital audio broadcasting is possible.

Influence of the BER on the intelligibility of the received DAB signal

For Digital Audio Broadcasting networks new planning criterions apply: The bit error rate instead of fieldstrength is used to predict the coverage areas. Since several source and channel coding mechanisms have been developed for DAB, their influence on the intelligibility of the received signal is investigated in this paper. Hence, a value for the maximum allowed bit error rate of the unprotected channel is derived. This value guarantees very good signal quality and is used as planning criterion for coverage predictions.

Aperture-coupled microstrip patch phased arrays in C- and X-band : A contribution to future multi-polarization multi-frequency SAR systems

Future spaceborne SAR systems will use active phased array antennas with multi-polarization and multi-frequency capabilities. For high resolution SAR images of high quality the antennas have to provide a large bandwidth and an extreme polarization purity. These requirements can be met by aperture-coupled microstrip patch phased arrays based on low-permittivity, low-weight and low-cost foam substrates. The paper presents their design and their outstanding measured performance in C-band (5.3 GHz) and X-band (9.6 GHz). The constructed arrays show bandwidths of more than 150 MHz in C-band and more than 300 MHz in X-band. The polarization purity is typically in the range of 40 dB.