Generalized multimode scattering parameters and the applications in antenna and radio frequency component designs

This article applies the generalized multimode S-parameters to multiport antennas and radio frequency (RF) components for CAD applications. Consider the special case of impedance matching which could significantly simplify the multimode representation on port and remove the requirement on calculating port impedance. N single-ended ports of a network are regarded as one generalized multimode port, supporting N orthonormal modes represented by N orthonormal basis vectors, respectively. By doing this, in antenna and RF component designs, one can only focus on specific modes interested, while ignore others. A multiport network's characteristics could be represented and understood in a much simpler manner because fewer but more intuitive physical quantities are considered. Therefore, this can significantly simplify the analysis, design, and optimization of multiport networks. For better illustration, several examples, including branch-line coupler, mixed-mode case, sequential rotation feeding antenna, and monopulse feed are analyzed and designed. Complicated analyses in network design using the single-ended S-parameters, including matching, amplitude and phase unbalance, could be converted into much simpler ones from the generalized multimode perspective.