Date Added: Dec 2012
Autonomous Navigation Systems (ANS) used in ballistic missiles and other high dynamic platforms are mostly dependent on the Global Positioning System (GPS). GPS users face limitations in terms of missile high dynamics and signal interference. Receiver's requirements to avoid these problems are conflicting. The Phase Lock Loops (PLLs) for tracking GPS signals are required to have a bandwidth as narrow as possible to reduce the impact of signal interference. However, the loop bandwidth has to be as wide as possible to accommodate high signal dynamics. The approach usually adopted is to start tracking using a Frequency Lock Loop (FLL) to reduce frequency acquisition/reacquisition times before switching to a PLL or FLL-assisted-PLL. However this approach does not prevent frequent loss of lock, compromising receiver performance.