An “Add-On” Method for the Analysis of Scattering from Large Planar Structures

The problem of the analysis of large planar structures, of the order of a few thousands unknowns, is addressed by a new “add-on” procedure, where the computation is done in a gradual manner by building up the body from small patches which are added sequentially. At each stage, the problem solved reflects the size of the small addition only, and the solution to an actual partial body is obtained. An important feature of this method is its ability to utilize a priori known information on a portion of the scatterer as an initial stage for the economic analysis of the entire structure. The process takes into account the interactions between all segments of the body. “Pulse response” amplitudes are chosen as convenient unknowns for this procedure. These are the amplitudes of subsectional basis functions under an excitation that comes from unit pulse current sources. They help make the interaction relationships simple algebraic and very economical. The response to any incident wave is recovered at the end of the process by a superposition of the responses to individual pulses that constitute the expansion of the equivalent current describing the incident wave. The process proves to be very efficient both in terms of computation time and storage requirements as seen in the computed examples of the order of 1000 to 6000 unknowns presented below.