L. Lukama

Performance of a three-branch orthogonal polarization diversity scheme

The performance of a three-branch orthogonal polarization scheme consisting of one vertically polarized and two orthogonal horizontally polarized antennas at the receiver with a horizontally and vertically polarized transmitter is investigated. The paper shows that such a scheme provides diversity improvement of about 2dB more than the dual-branch system. Also the signals received at the three branches are highly uncorrelated. This scheme can make significant improvements in the link budget of a mobile network.

Spatial diversity analysis for digital TV systems

Spatial diversity for digital TV systems has been studied using the results of a measurement campaign of the radio channel complex frequency response for two different situations: an outdoor-indoor channel and an indoor-indoor channel. It is shown that the actual improvement of spatial diversity is not only the mean level increase, but the reduction of both the level crossing rate (LCR) and the average fade duration (AFD). The mean level gain is in the range 1.2-3 dB for the indoor-indoor channel and within 1.4-2.9 dB for the outdoor-indoor channel and the LCR/AFD improvement is between 9.5 and 15 dB for both environments. To explain the behavior of the diversity system, high resolution angle of arrival and delay information was obtained. It is concluded that it is the interference of the direct propagation path with the main reflections that causes the received field to follow a standing wave pattern and shapes the spatial diversity gain behavior.

Comparison of measured and theoretical diffracted fields around building corners at 2.4 GHz

Several channel sounding measurements in around-the-corner propagation scenarios have been performed with a vector network analyzer and a synthetic volume aperture receiving array at 2.44-2.45 GHz. A radio imaging technique applied to such measurement data yields time delay, direction of arrival and path loss corresponding to individual field components arising due to multipath propagation. This allows the identification of the diffracted components of the received geometrical optics by incorporating diffraction phenomena in the limit of field and the determination of the corresponding diffraction coefficients experimentally. The measured values were compared to various theoretical diffraction coefficients and conclusions have been drawn from the comparison. In addition, a review of the existing models for diffraction is given.