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Direct measurement of the radiation resistance of a dipole antenna in the whistler/lower hybrid wave regime
Author(s) -
Pribyl Patrick,
Gekelman Walter,
Gigliotti Alex
Publication year - 2010
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 - 10.1029/2009rs004266
Subject(s) - whistler , antenna (radio) , dipole antenna , radiation , physics , radiation pattern , dipole , radiation resistance , optics , computational physics , telecommunications , computer science , plasma , nuclear physics , quantum mechanics
An electrically short dipole antenna radiating high‐frequency waves is instrumented in such a way as to directly measure its radiation impedance when immersed in a laboratory plasma. By measuring both current and voltage at the radiating end, transmission line effects are largely eliminated, and extremely accurate results can be obtained. Initial results are presented for wave frequencies ranging from lower‐hybrid to whistler, for density varying from 2 × 10 18 m −3 down to 2 × 10 15 m −3 . The initial experiments are performed for ω / ω ce ≪ 1. At the highest density, the impedance is approximately real, varying from 400 Ω at 30 MHz down to 100 Ω at 180 MHz, while at the lowest density, the impedance is almost entirely capacitive, at roughly 1.6 pF.