arXiv subjects

M. P. Fitz

Publications and source records attributed to M. P. Fitz.

2 recordsLinked to original sources

arXiv2006

Experiments with Compact Antenna Arrays for MIMO Radio Communications

The problem addressed in this study is how to design and test compact antenna arrays for portable Mulitple-Input Multiple-Output (MIMO) transceivers. Mutual coupling in an antenna array affects signal correlation and array radiation efficiency - both of which have dramatic consequences for MIMO channel capacity. Mutual coupling becomes more pronounced as array aperture shrinks and is therefore a critical issue in compact array design. Two novel compact arrays are designed and fabricated for use in MIMO enabled mobile devices. These arrays are extremely compact yet demonstrate acceptable mutual coupling and radiation efficiency because of the MIMO-specific criteria used during their design. An experimental methodology is presented for fair and meaningful characterization of MIMO arrays by field trial. This methodology addresses the issue of capacity normalization and quantifies how well an antenna array's radiation pattern interfaces with multipath propagation. Results are presented from an extensive measurement campaign in which a true MIMO transceiver testbed is outfitted with compact arrays and dipole arrays of various sizes. A comprehensive and fair comparison is made between the compact arrays and dipole arrays in a variety of indoor propagation scenarios. Design recommendations for compact MIMO arrays are given.

physics.ins-det↗

arXiv2006

Untangling the SVD's of Random Matrix Sample Paths

Singular Value Decomposition (SVD) is a powerful tool for multivariate analysis. However, independent computation of the SVD for each sample taken from a bandlimited matrix random process will result in singular value sample paths whose tangled evolution is not consistent with the structure of the underlying random process. The solution to this problem is developed as follows: (i) a SVD with relaxed identification conditions is proposed, (ii) an approach is formulated for computing the SVD's of two adjacent matrices in the sample path with the objective of maximizing the correlation between corresponding singular vectors of the two matrices, and (iii) an efficient algorithm is given for untangling the singular value sample paths. The algorithm gives a unique solution conditioned on the seed matrix's SVD. Its effectiveness is demonstrated on bandlimited Gaussian random-matrix sample paths. Results are shown to be consistent with those predicted by random-matrix theory. A primary application of the algorithm is in multiple-antenna radio systems. The benefit promised by using SVD untangling in these systems is that the fading rate of the channel's SVD factors is greatly reduced so that the performance of channel estimation, channel feedback and channel prediction can be increased.

math.ST↗