Nonlinear/electromagnetic co-design of MIMO and UWB radio links

The purpose of the paper is to demonstrate a general and rigorous computer-aided design (CAD) procedure that can potentially provide a systematic answer to the needs of modern circuit-level microwave system simulation/design by combining nonlinear, electromagnetic (EM), and propagation analysis tools. As examples of application, a systematic approach to a full CAD-based treatment of multi-input multi-output (MIMO) and ultra wide band (UWB) links is presented. The EM theory allows to evaluate a set of Norton equivalent generators to derive a circuit description of the receiver excitation: in the MIMO case one generator for each ray coming from each transmitting antenna; in the UWB case one generator for each harmonic frequency used to describe the spectrum of the impulse-radio (IR)-UWB signal. For the first time, highly-complex radio frequency (RF) links can be optimized by means of the rigorous circuit-level CAD tool here presented: the selection of both the optimum distance between the receiving antennas and the optimum transmitted pulse shape is numerically performed in the MIMO and UWB case, respectively.