资料介绍
GPS Tutorial 2GPS Tutorial #2
Signals and Messages
Darren Sessions
GPS Tutorial #2
PRN Codes Signal Structure Navigation message Error Sources
PRN Codes
PRN = Pseudo Random Noise
Codes have random noise characteristics but are precisely defined.
A sequence of zeros and ones, each zero or one referred to as a “chip”.
Called a chip because they carry no data. Gold codes use 2 generator polynomials. C/A, P and Y
Selected from a set of Gold Codes.
Three types are used by GPS
PRN Code Generation
+
Tapped feedback Shift register Polynomial = 1 + x3 + x10
1 0 0 3 1 0 2 0 3 1 4 0 5 0 6 0 7 1 8 1 9 1 10 0 10
Output
nth
+
1 0 0 0 1 1 1 0
(n+1)th
G1 = 1 + x3 + x10
PRN Code Generator
1
G2 = 1 + x2 + x3 + x6 + x8 + x9 + x10 2 3 4 5 6 7 8 9 10
PRN Code 1 2
Taps 2
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