Diversity techniques for rotorcraft wireless communications

Transmitted and received signals involving rotorcrafts are subject to inter-modulations caused by the rotor blades. The statistical characteristics of the wireless communication link between a rotorcraft transmitter and a receiver on the ground are developed. Both the scattering and Doppler effects of the rotating blades on the impairment of frequency modulated frequency hopping signals are considered. The channel model includes the near-field wave propagation between the transmitter antenna and the scattering blades. The channel model is used to examine the performance of different diversity techniques, namely, the transmitter diversity, multicarrier frequency hopping (MCFH) and the fast frequency hopping (FFH), in view of the antenna polarization and relative strength of the direct path and the scattering component from the rotating blades.