Global Positioning System Reference
In-Depth Information
605
Received
code
Frame 71
0
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700
Time [samples]
FIGURE 7.22. Close-up of frame 71 from Figure 7.21. In this case, the beginning of the
C/A code is at sample 605 of the total of 38,192.
Since the prompt code is precisely aligned with the incoming signal to the nearest
sample, the maximum error as a result of the discrete samples will be half that or
<
5 m, which is sufficient for C/A code-type signals. If the sampling frequency is
lower, a higher precision is required. Then it is possible to use the residual code
phase at the end of each ms period to further refine that accuracy.
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