Title :
Frequency-domain Green´s function for a planar periodic semi-infinite phased array. II. Diffracted wave phenomenology
Author :
Capolino, F. ; Albani, M. ; Maci, S. ; Felsen, L.B.
Author_Institution :
Dept. of Inf. Eng., Siena Univ., Italy
fDate :
1/1/2000 12:00:00 AM
Abstract :
For pt.I see ibid., vol.48, no.1, p.67-74, 2000. This second part of a two-paper sequence deals with the physical interpretation of the rigorously derived high-frequency asymptotic wave-field solution in part I, pertaining to a semi-infinite phased array of parallel dipole radiators. The asymptotic solution contains two parts that represent contributions due to truncated Floquet waves (FWs) and to the corresponding edge diffractions, respectively. The phenomenology of the FW-excited diffracted fields is discussed in detail. All possible combinations of propagating (radiating) and evanescent (nonradiating) FW and diffracted contributions are considered. The format is a generalization of the conventional geometrical theory of diffraction (GTD) for smooth truncated aperture distributions to the truncated periodicity-induced FW distributions with their corresponding FW-modulated edge diffractions. Ray paths for propagating diffracted waves are defined according to a generalized Fermat principle, which is also valid by analytic continuation for evanescent diffracted ray fields. The mechanism of uniform compensation for the FW-field discontinuities (across their truncation shadow boundaries) by the diffracted waves is explored for propagating ad evanescent FWs, including the cutoff transition from the propagating to the evanescent regime for both the FW and diffracted constituents. Illustrative examples demonstrate: (1) the accuracy and efficiency of the high-frequency algorithm under conditions that involve the various wave processes outlined above and (2) the cogent interpretation of the results in terms of the uniform FW-modulated GTD
Keywords :
Green´s function methods; antenna phased arrays; antenna radiation patterns; dipole antenna arrays; electromagnetic wave propagation; frequency-domain analysis; geometrical theory of diffraction; planar antenna arrays; FW-excited diffracted fields; FW-field discontinuities; FW-modulated edge diffractions; GTD; HF algorithm accuracy; HF algorithm efficiency; cutoff transition; diffracted wave phenomenology; edge diffraction; evanescent Floquet waves; evanescent diffracted ray fields; frequency-domain Green´s function; generalized Fermat principle; geometrical theory of diffraction; high-frequency algorithm; high-frequency asymptotic wave-field solution; parallel dipole radiators; planar periodic semi-infinite phased array; propagating Floquet waves; propagating diffracted waves; ray paths; smooth truncated aperture distributions; truncated Floquet waves; truncated periodicity-induced FW distributions; truncation shadow boundaries; uniform compensation; Aerospace engineering; Apertures; Dipole antennas; Green´s function methods; Linear antenna arrays; Mechanical engineering; Phased arrays; Physical theory of diffraction; Propagation constant;
Journal_Title :
Antennas and Propagation, IEEE Transactions on