Helicopter rotor-blade modulation of antenna radiation characteristics

Anastasis C. Polycarpou, Constantine A. Balanis, Andrej Stefanov

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

This paper investigates rotor modulation on the gain and input impedance of an antenna mounted on a helicopter's fuselage. The rotor blades, which are rotating about an axis with a given angular velocity, continuously modulate the signal transmitted by the antenna and adversely affect the established communication links. In this study, particular emphasis is placed on wire antennas operating within the high frequency (HF) and very high frequency (VHF) bands. Specifically, the Doppler spectrum of the magnitude and phase of the radiated field by a vertical and a horizontal short dipole underneath the rotors is computed and analyzed. The variation of the corresponding antenna gain as a function of rotor angle and frequency is also investigated. The same type of analysis is then extended to a 14-ft towel-bar antenna mounted on the tail boom of a 10:1 scaled helicopter model. In addition to gain, the variation of input impedance versus angle and frequency is computed within the HF band. Finally, the bit error rate (BER) assuming a quadrature phase-shift keying (QPSK) modulation is evaluated assuming linearly and circularly polarized receiving antennas.

Original languageEnglish
Pages (from-to)688-696
Number of pages9
JournalIEEE Transactions on Antennas and Propagation
Volume49
Issue number5
DOIs
Publication statusPublished - May 2001

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