GPS Signal Fundamental 10.23MHZ L, carrier phase C/A code P code Navigation 157542MHz103MH|10.23MH S0BPS Ly carrier phase P code 1201260Nz 10.23MHZ OBPS 電 Principles of the Global Positioning System 20053-181(1 Two codes are used for the satellite clock readings both characterized by a pseudorandom noise (PRN) sequence Code Type frequency Repeated time coarse/acquisition f10 everv millisecond lear/access(C/A) precision(or protected) once every 266.4 code (p-code) W-code encrypt the P-code to transmitted in 30 the Y-code, f 20 seconds Y-code Encrypted by W-code Principles of the Global Positioning System 2005-3-186 Principles of the Global Positioning System 2005-3-18 11 11 GPS Signal Fundamental frequency 10.23MHz L1 carrier phase 1575.42MHz L2 carrier phase 1227.60MHz C/A code 1.023MHz P code 10.23MHz P code 10.23MHz Navigation message 50BPS Navigation message 50BPS ×154 ×120 ÷10 ÷204600 Principles of the Global Positioning System 2005-3-18 12 Two codes are used for the satellite clock readings, both characterized by a pseudorandom noise (PRN) sequence