Simulations of Antennas Mounted on Rotorcrafts

Inder J. Gupta, Khadir A. Griffith

Abstract:	Blade rotation affects the performance of a GNSS receiver mounted on a rotorcraft. This is true for receivers equipped with fixed pattern antennas or adaptive pattern antennas. To evaluate the performance of a GNSS receiver mounted on a platform using computer simulations or wave front simulators, one needs to include the in situ response of the receiver antenna in the simulation/simulator. For fixed wing platforms, this can be easily accomplished. One can measure or analyze the response of the individual elements of the antenna over the GNSS frequency band along the aspect angle of interest. The incoming signals from that aspect angle are then convolved with the antenna element response to include the platform and antenna effects. The convolution can be carried out in the frequency domain or in the time domain. For GNSS receivers mounted on a rotorcraft, the above approach does not work. The antenna response varies with frequency as well as with time, and for a given frequency is periodic in nature. The repetition rate depends on the blade speed and the number of blades. In this paper, we present a simple approach to include the blade modulation effects in computer simulations/wavefront simulators. The approach exploits the periodic nature of the antenna response in that the time varying response of the antenna is represented by a Fourier series. The approach can be implemented using a FIR filter and modulator. Some numerical results obtained using the suggested approach are also presented. The numerical results demonstrate how the incident signals are affected by the blade modulation.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2766 - 2771
Cite this article:	Gupta, Inder J., Griffith, Khadir A., "Simulations of Antennas Mounted on Rotorcrafts," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2766-2771.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In