Inventors:
Paul V. Broekhoven - Needham MA
Daniel Fitzmartin - Newton MA
Paul Blasche - Arlington MA
Duncan B. Cox - Manchester MA
Triveni Upadhyay - Burlington MA
Assignee:
The Charles Stark Draper Laboratory, Inc. - Boston MA
International Classification:
H04K 102
Abstract:
A precorrelation digital spread spectrum receiver includes a signal converter for amplifying and directly converting RF band spread spectrum signals received by an antenna to a digitized baseband signal comprising a sequence of N-bit quantized baseband values. The baseband signal is a linear composite signal containing signals from all satellite channels as well as noise and jamming. An N-bit digital correlator correlates successive N-bit baseband signal values with successive local code values to produce plural correlation signals. A vector processor processes the correlation signals to derive early, late and on-time code correlation signals. The processed correlation signals are accumulated to provide process gain and are used to form error signals for carrier and code tracking, and measurement purposes. A sequential-tracking multi-channel embodiment time shares a common set of circuit elements and digital processing instructions to successively track different channels. In a preferred embodiment, the vector processor uses micro-code instructions to remove the carrier Dopler shift by multiplying the correlation value with a stored complex constant corresponding to the Doppler contribution.