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Surface Waves and Mode Selection on Multielement Spiral Antennas
Author(s) -
RuShao Cheo B.,
Rumsey V. H.
Publication year - 1968
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1002/rds196833267
Subject(s) - spiral (railway) , excitation , physics , mode (computer interface) , surface wave , surface (topology) , power (physics) , electromagnetic radiation , radiation , optics , acoustics , mathematics , mathematical analysis , geometry , quantum mechanics , computer science , operating system
The solution of Maxwell's equations for the idealized sheet of spiral antennas has been extended to a cos nφ input excitation. At large distances the current density is the combination of a circularly polarized surface wave that vanes as exp (− jnφ ) and the frequency independent current distribution previouslr worked out. The frequency independent component is almost entirely in the exp ( jnφ ) mode. Half the input power goes into the exp ( jnφ ) radiation pattern, and almost half goes into the surface wave. This explains the remarkable mode selection properties of multielement spiral antennas that were observed a few years ago.