New planar microwave devices and antennas by practical surface-wave launching

Classic feeding techniques and dielectric slab selection for planar circuit 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. 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 by the authors suggest 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 surface-wave launchers, as described in this review article include, new quasi-optical planar circuits, leaky-wave antennas, and other guiding structures for power combining at microwave and millimeter-wave frequencies.