Planar leaky-wave antenna designs for directive beam scanning

Various high gain LW antenna designs have been investigated for satellite and radar applications at millimeter frequencies. By using cylindrical surface-wave (SWs) on a grounded dielectric slab (GDS) and by the addition of appropriate metallic grating or strips, leaky-waves (LWs) can be excited. Four continuous strip gratings are measured and theoretically investigated achieving backward and forward beam scanning as a function of frequency. These designs display a LW stopband at broadside. Conversely, directive broadside radiation is achieved with a segmented circular strip grating.;In addition, an arrayed configuration of SWLs is also investigated for SW beam scanning. By variation of the relative phase difference between SWL elements the SW fields can be steered into different regions on the GDS. A two element array of SWLs is developed and the results are extended to a six element design with non-uniform weighting. This controlled SW excitation can also dictate the region of LW field generation on the guiding surface, steering directive beam patterns at a single frequency in the far field. Three specific grating configurations are presented: an elliptical and asymmetrical grating followed by a segmented strip design.;Yagi-Uda like surface-wave launchers (SWLs) are utilized as the antenna feed which generate a bound cylindrical T M0 SW mode on the GDS. Essentially, ground plane slots define these SWLs and the configurations act as magnetic dipole sources for the investigated LWA designs. Such guided SWs on planar substrates are generally an adverse effect that can degrade the performance of monolithic integrated circuits and antenna arrays at millimeter wave frequencies. However, with appropriate boundary conditions and substrate characteristics, the T M0 SW mode can be harnessed as an efficient means of power transport and thus a novel planar antenna feeding technique. Specifically, two types of SWL antennas are examined for unidirectional and bidirectional SW beam patterns on the guiding surface; unidirectional SWs are produced by directive SWLs and bidirectional SWs are driven by non-directive SWLs.