| US 7,522,100 B2 | ||
| Method and device for acquiring weak global navigation satellite system (GNSS) signals | ||
| Chun Yang, Harleysville, Pa. (US); and Hansheng Wang, San Jose, Calif. (US) | ||
| Assigned to SiRF Technology Holdings, Inc., San Jose, Calif. (US) | ||
| Filed on Jul. 01, 2005, as Appl. No. 11/173,894. | ||
| Prior Publication US 2007/0008217 A1, Jan. 11, 2007 | ||
| Int. Cl. G01S 1/00 (2006.01) | ||
| U.S. Cl. 342—357.12 | 20 Claims |
| 1. In a navigational system utilizing a plurality of satellites that transmit radio-frequency signals containing time and
orbit information of said satellites, a method of acquiring said satellite signals at a receiver, the method comprising:
receiving a satellite signal at the receiver;
performing short-length correlations between the received satellite signal and locally generated reference codes, wherein
each short-length correlation spans approximately 1 ms;
performing block accumulating coherent integration of said short-length correlations over a preset extended length, wherein
performing the block accumulating coherent integration includes:
reducing frequency error for a block of short-length correlations prior to
integrating said block with preceding blocks over said preset extended length;
adding said frequency error reduced block of short-length correlations to partial
sums of previous blocks of short-length correlations, thereby updating said partial sums, wherein each partial sum is added
for a different possible data bit edge and a corrected bit sign of said block; and
making a decision based upon said updated partial sums to ascertain the presence or absence of said satellite signal up to
this point.
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