Jo Verhaevert

Direction of a arrival (DOA) parameter estimation with the SAGE algorithm

In this study, we investigate the estimation of the relative delay, the azimuth and elevation angle and the complex amplitude of a known received signal with the space alternating generalised expectation (SAGE) maximisation algorithm. This optimisation algorithm is used to replace the high-dimensional optimisation procedure, necessary to compute the joint maximum likelihood estimate of the parameters using several separate maximisation processes, which can be performed sequentially. Spherical arrays provide wide scan coverage with low grating lobe levels. Because a uniform antenna element distribution on this spherical surface gives rise to the smallest variations in received signal levels over the whole angular space, a uniform distribution of antennas on a sphere is used. For this completely general three-dimensional array, we have for the fitst time investigated the resolution of the SAGE algorithm, the convergence and the bit error rate as a function of the signal to noise ratio. We will show that this algorithm is a powerful tool that can be applied successfully for high-resolution parameter extraction.

Uniform spherical distributions for adaptive array applications

This study investigates optimal three dimensional antennas for adaptive applications. The choice of the antenna element distribution on the spherical surface is governed by the desire to maintain a nearby constant pattern. Spherical arrays provide wide scan coverage with low grating lobe levels. We calculate the uniform distribution of a set of antennas on a sphere. Based on formulas of the spherical trigonometry, we show all the possible exact uniform distributions. It is astonishing, that only five possible solutions can be found. In this paper, the co-ordinates and the figures of these regular polyhedrons are shown. Because the number of possible uniform spherical distributions is limited, the number of elements that can be placed uniformly without approximation on a spherical surface is also limited to 20.

Analysis of the SAGE DOA parameter extraction sensitivity with 1.8 GHz indoor measurements

A channel measurement campaign, done with a system from the University of Kassel, is reported. With very high bandwidth (600 MHz), a large room has been measured at 1.8 GHz with a moving antenna, forming a synthetic aperture. The transformation from the transfer function in the frequency-domain to the time-domain received signal, with the training sequence included, is explained. On these data, the space alternating generalised expectation maximisation (SAGE) algorithm is applied to extract with high resolution the direction of arrival (DOA) parameters, in this case the time delay, the azimuth angle and the complex amplitude for every significant path. The extraction results are evaluated and visually interpreted.