Microwave modeling of 2-D active grid antenna arrays

A new measurement technique for determining the broadband driving point impedance of large two-dimensional active grid arrays is presented. The active array radiates a plane wave in the broadside direction when all elements are locked in phase. For analysis, the array is reduced to a single unit cell by exploiting the array symmetries. The driving point impedance of the unit cell is determined by using the dielectric waveguide measurement method (DWM). The approximations of the method are discussed, and the method is compared with other measurement techniques. Results are presented for four square arrays: dipole, bow-tie, double-vee and slot array. The measurement method is verified by comparing it to the full-wave theory in the whole range. It is shown that all four antenna arrays can be represented by very simple circuits that use only transmission lines as circuit elements. The bow-tie array is found to represent the best choice for broadband operation.>