A fast acquisition AFC for helicopter satellite communications

In helicopter satellite communications, removal of time-varying Doppler shift due to helicopter maneuver is one of the most important issues. The conventional automatic frequency control (AFC) scheme for helicopter satellite communications removes Doppler shift exactly. However, its acquisition time is extremely long. This is caused by a delay element in the feed-back loop. In this paper, we propose a novel AFC scheme for helicopter satellite communications to reduce the acquisition time. The proposed AFC scheme consists of a feed-back loop and a feed-forward loop. This configuration excludes the delay element from the feed-back loop. Results of computer simulation show that the proposed AFC scheme significantly reduces its acquisition time.