Design and Application of Multimode Substrate Integrated Waveguides in Parallel Multichannel Signaling Systems

Multimode signal transmission concept is employed in this paper to increase the channel capacity of a substrate integrated waveguide (SIW) interconnect. In order to generate two uncoupled channels without adding an additional physical link, ${rm TE}_{10}$ and ${rm TE}_{20}$ modes of an SIW interconnect are harnessed as signal carriers. To excite these two orthogonal modes simultaneously, a multimode double launcher is proposed and characterized. It is shown that the performance of the launcher is limited by the coupling between the two mode launchers (transitions). Therefore, a method for improving port isolation is suggested, which results in increasing the channel bandwidths. A balun structure based on an SIW is presented and included in the multimode waveguide in order to efficiently excite the ${rm TE}_{20}$ mode. Ultimately, the multimode waveguide with the optimized transitions is used in a parallel data transmission system demonstrating excellent transmission quality for the data rate of a 1-Gb/s/channel.