Helicopter rotor-blade modulation of antenna radiation characteristics

Author

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

Author_Institution

Dept. of Electr. Eng., Arizona State Univ., Tempe, AZ, USA

Volume

49

Issue

5

fYear

2001

fDate

5/1/2001 12:00:00 AM

Firstpage

688

Lastpage

696

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 HF and VHF bands. Specifically, the Doppler spectrum of the magnitude and phase of the radiated field from 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

Keywords

Doppler effect; HF antennas; VHF antennas; aircraft antennas; aircraft communication; antenna radiation patterns; dipole antennas; electric impedance; error statistics; helicopters; loop antennas; quadrature phase shift keying; receiving antennas; wire antennas; 10 to 300 MHz; BER; Doppler spectrum; HF; QPSK; VHF; angle; antenna gain; antenna radiation characteristics; bit error rate; circularly polarized receiving antennas; communication links; frequency; fuselage mounted antenna; gain; helicopter rotor-blade modulation; horizontal short dipole; input impedance; linearly polarized receiving antennas; magnitude; phase; quadrature phase-shift keying; radiated field; rotor angle; rotor modulation; scaled helicopter model; tail boom; towel-bar antenna; vertical short dipole; wire antennas; Angular velocity; Bit error rate; Blades; Dipole antennas; Frequency; Helicopters; Impedance; Tail; Transmitting antennas; Wire;

fLanguage

English

Journal_Title

Antennas and Propagation, IEEE Transactions on

Publisher

ieee

ISSN

0018-926X

Type

jour

DOI

10.1109/8.929622

Filename

929622