Scan impedance of RSW microstrip antennas in a finite array

Scan impedances of finite reduced surface wave (RSW) arrays are studied. Center element scan impedances of linear arrays and two-dimensional (2-D) square lattice arrays are calculated and compared with those of conventional microstrip arrays. Results show that compared with conventional microstrip arrays, broadside scan impedance of RSW arrays has less variation and converges much faster when the array size increases. Scan performance of the linear and 2-D square lattice RSW arrays are also studied. Results show that the RSW array can avoid the scan blindness (when the array spacing is greater than 0.5[[lambda].sub.0]) and the scan impedance has much less variation than that of conventional microstrip array with the same array spacing. However, due to the size limitation of RSW elements, the grating lobes cannot be avoided. Hence, the scan region is limited to about 20[degrees] (with 0.75[[lambda].sub.0] array spacing). Compared with conventional microstrip arrays with 0.5[[lambda].sub.0] array spacing, the results show no favor to RSW arrays. Index Terms--Mutual coupling, reduced-surface-wave (RSW) antenna, scan blindness, scan impedance.