Electromagnetic channel modeling and measurement using MIMO FMCW radar

Abstract

Multiple input multiple output (MIMO) systems have the potential to dramatically increase data speed of wireless systems. Implementation and evaluation of MIMO systems need a comprehensive understanding of MIMO channels. This dissertation deals with electromagnetic channel modeling and measurement for MIMO systems, important issues for the practical deployment of multiple antenna systems. One of the focuses of this research has been on modeling MIMO channels with the use of polarized antennas in three dimensional (3D) propagation environments. In this regard, the proposed model can be used to evaluate any kind MIMO array antennas including 3D array or polarized array in a given propagation environment. The channel measurement in a practical environment is important as it provides statistic results, such as delay profiles or cross-polarization discrimination (XPD) for realistic channel modeling. Channel measurements can be carried out by using a pseudorandom noise (PN) code radar system or by sweeping a vector network analyzer (VNA). However, this system is expensive, especially for high frequency bands like X band or Ku band. Much of the work in this thesis is to develop a Ku-band frequency modulated continuous wave (FMCW) radar system, worked as a channel sounder, to capture channel coefficients. High performance of FMCW signals in terms of linearity and phase noise is achieved through the proposed signal generation scheme based on a two sweeping voltage-controlled oscillator (VCO) source, eventuating to an accurate ranging ability, 0.2% range error with a fast sweeping rate of 100μs. The proposed FMCW radar system is then used as a channel sounder to investigate the delay profile and XPD in reverberation chamber. The measurement results can be used as references for transmission in Ku band.