Time domain UTD for pulsed scattering from finite periodic and nonperiodic flat strip arrays

Abstract

Several recent studies have dealt with frequency domain (FD) and time domain (TD) scattering by truncated periodic or quasiperiodic arrays of perfectly conducting thin flat strips. Various asymptotic algorithms have been developed, and their validity has been assessed from comparisons with numerically generated data. For short-pulsed (SP) plane wave excitation of large arrays with wide strips compared to the pulse width and with correspondingly large interelement spacing, previously employed numerical methods (like FDTD, FFT of FD method of moments) become intractable for monitoring the early-to-late time response. It is shown here that Fourier inversion (FT) of FD uniform asymptotic theory of diffraction (UTD) applied to each strip, neglecting interaction between strips, yields excellent results when compared with a reference solution for an infinite array obtained by FT of FD Floquet modes (FM). Based on this comparison, the TD-UTD algorithm is used to synthesize SP plane wave scattering from arbitrarily spaced coplanar strips, which could have unequal widths. It is shown how superposition of individual strip scatterings synthesizes collective responses that are interpretable under quasiperiodic conditions as superpositions of TD-FM. Short-time Fourier transforms extract the time-frequency distributions corresponding to various scenarios. >