ABSTRACT
This chapter focuses on the one-dimensional formulation and describes Electronically Scanned Arrays (ESA) pattern behavior for ESA architectures. There are multiple ESA architecture topologies that can be used for implementing subarray beamforming. These involve using one or multiple combinations of phase shifter, time delay, and digital beamforming. The two-dimensional formulation for subarrays is left as an exercise for the reader, but can be readily derived as outlined by the formulation for nonsubarrayed ESAs. Phase shifter delay or time delay can be employed on the element level. Elemental time delay adds undesired complexity especially for large ESA. Implementing phase delay at the element level and time delay at the subarray level provides robust scan performance with limitations on instantaneous bandwidth. These limitations provide an advantage over a nonsubarrayed ESA of the same size that has phase-only steering. An alternative to time delay steering at the subarray level is to place a receiver channel at each subarray and combine the subarrays digitally.
