Full-wave analysis of planar surface-wave launchers offering efficient surface-wave excitation and guiding structure feeding

Classic feeding techniques and dielectric slab selection for planar circuits and antenna designs can be challenging at microwave and millimeter-wave frequencies. Substrates can become electrically thick and unwanted surface-wave (SW) field distributions may be excited potentially spoiling device performance. Thus SWs are typically looked upon as an adverse effect causing parasitic radiation and power losses. However, by using an alternative design approach, SWs can actually be utilized to the advantage as a simple an efficient feeding scheme. In particular, by selecting electrically thick substrates with relatively high dielectric constant values, and with the appropriate arrangement of slots within the ground plane, SWs can be efficiently excited. In this work a full-wave analysis is provided in the spectral domain by examining the fields generated by the main slot connected to the feeding transmission line. Numerical results show that there is a broad frequency range which can offer increased TM SW power levels when compared to the radiated space wave power. Applications for these printed SWLs include new quasi-optical planar circuits, leaky-wave antennas, and other guiding structures for operation at microwave and millimeter-wave frequencies.