Accession Number : AD0432047


Title :   THE DOUBLE-HELIX ANTENNA AND ITS VARIANTS: A NEW CLASS OF TUNABLE ENDFIRE ANTENNAS,


Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS


Personal Author(s) : Ehrenspeck,H W


Report Date : Dec 1963


Pagination or Media Count : 14


Abstract : Endfire antennas develop their maximum gain when the phase velocity of the surface wave traveling along the structure is adjusted to its optimum value determined as a function of antenna length and operating frequency. These antennas usually have a relatively small pattern bandwidth and, if maximum gain is desired, can be used over only a small frequency range. The antennas described in this paper inaugurate a new class of antennas that are tunable for maximum gain in the endfire direction over a wide frequency range; tuning is accomplished by changing the phase velocity continuously or in prescribed steps. Such antennas include certain spatial configurations of the double helix (a novel type of endfire antenna) and its artificical and natural dielectric variants. Useful structures are obtained through parallel displacement of two juxtaposed elements or angular displacement of a scissors arrangement. Model measurements show that maximum gain can be obtained over a frequency range of more than 2:1. Tuning effects are illustrated in detail by means of nearfield plots of a tuned dielectric antenna. (Author)


Descriptors :   *HELICAL ANTENNAS , GAIN , BANDWIDTH , BROADBAND , PHASE CONTROL , FREQUENCY


Distribution Statement : APPROVED FOR PUBLIC RELEASE