Fast acquisition of gps signal corrupted by doppler or time delay effects

Abstract

An RF translator is placed on an artillery shell. The RF translator receives a GPS signal, converts the GPS signal to an S band signal, and then transmits the S band signal. The S band signal is received by a ground antenna and it is converted back to an L1 GPS signal. The transmission of the S band signal to a ground antenna induces two effects which make fast direct P(Y) acquisitions difficult. First, since the artillery shell is moving, a carrier Doppler is induced on the S band signal. Second, the time delay caused by the transmission of the S band signal affects the nominal code phase for acquisition. Acquisition of GPS signals corrupted by second frequency data effects require special compensation if fast direct P(Y) code acquisition is desired. A carrier Doppler and a code phase compensation term allow the GPS ground receiver software to focus its search window for the carrier frequency (code rate) and the code phase (time delay). By adding in these new compensation terms, small centered searches can be used and fast direct P(Y) code acquisition is possible.