MICROWAVE MODELING OF 2-D ACTIVE GRID ANTENNA-ARRAYS

We present a new measurement technique for determining the broadband d riving point impedance of large two-dimensional active grid arrays. Th e active array radiates a plane wave in the broadside direction when a ll elements are locked in phase. For analysis, the array is reduced to a single unit cell by exploiting the array symmetries. We determine t he driving point impedance of the unit cell by using the Dielectric Wa veguide Measurement method (DWM). The approximations of the method are discussed and the method is compared with other measurement technique s. We present results for four square arrays: dipole, bow-tie, double- Vee and slot array. We verify our measurement method by comparing it t o the full-wave theory in the whole range. We show that the results fo r the dipole and the bow-tie arrays agree very well with the quasistat ic theory and the results of others. We extend the quasistatic theory to the doube-Vee array with excellent agreement and present a modified quasistatic circuit for the slot array. Finally, we show that all fou r antenna arrays can be represented by very simple circuits that use o nly transmission lines as circuit elements. We find that the bow-tie a rray represents the best choice for broadband operation.