Receiver having a memory based search for fast acquisition of a spread spectrum signal

DETAILED DESCRIPTION OF THE INVENTION FIG.
1 is a block diagram of a (global positioning system) GPS receiver of the present invention referred to by the general reference number 10.
The GPS receiver 10 receives a GPS signal through an antenna 12 capable of operating at a GPS frequency of 1575.
42 GHz.
The GPS signal has a carrier frequency and a code having a reference time.
The antenna 12 passes the GPS signal to a filter/LNA 14 for bandpass filtering about the GPS frequency and amplification.
The filtered, amplified GPS signal, shown as L1 in FIG.
1, is then frequency translated in a downconverter 16 using a first local oscillator signal (LO.
sub.
1) to an intermediate frequency (IF) GPS signal, shown as L1.
sub.
-- IF.
An IF processor 18 uses a second local oscillator signal (LO.
sub.
2) for a second frequency translation to a lower frequency (LF) GPS signal and a sampling clock signal (SCLK) for digitizing the LF GPS signal and issuing a digitized GPS signal (SIG).
The LO.
sub.
1, LO.
sub.
2, and SCLK signals; and a local time signal (T.
sub.
L) and a high frequency sampling signal (F.
sub.
HS) are generated by a frequency synthesizer 20 using a single reference frequency.
The IF processor 18 passes the digitized GPS signal SIG to one or more C/A code tracking modules collectively shown as 22 and a memory-based search engine 30.
The C/A code tracking modules 22 use the sampling clock SCLK and T.
sub.
L signals in traditional methods of tracking the GPS signal from one or more GPS satellites once the GPS signal has been acquired by the memory-based search engine 30.
The memory-based search engine 30 uses the sampling clock SCLK and the high frequency clock F.
sub.
HS signals in methods of the present invention described herein to rapidly acquire the GPS signal to achieve a faster time to first fix.
The C/A code tracking modules 22 and the memory-based search engine 30 communicate with a microprocessor system (.
mu.
P) 32.
The microprocessor system 32 operates in a conventional manner to process information and to control and receive data from the elements of the GPS receiver 10 with control/data signals