A method, corresponding apparatus, and corresponding system for acquiring a received
spread spectrum signal, the received signal having a carrier component at a carrier
frequency, a code component having a code period, and a data component, the acquiring
including matching the phase of a replica of the code component to the phase of
the received code component and also determining any shift in the carrier frequency
away from a transmitted carrier frequency, the method including the steps of: performing
a first acquisition of the received signal so as to provide an approximately estimated
carrier frequency and a phase of the replica and also so as to provide a code-wiped
and an approximately carrier-wiped signal; and performing a second acquisition
of the approximately carrier-wiped signal, the second acquisition including a substep
of data wipe-off involving a squaring or similar operation on a signal derived
from the approximately carrier-wiped signal; thereby providing a correction to
the approximately estimated carrier frequency, a correction that accounts for the
carrier frequency shift remaining after the first acquisition. The invention also
comprehends a method including only a single acquisition, an acquisition including
a data wipe-off involving a squaring or similar operation on a signal having a
data component and a frequency component, i.e. the invention is of use in acquiring
any kind of signal having a carrier component and a data component, regardless
of whether a first, typically relatively coarse acquisition is performed.
