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Unformatted text preview: CA code and P code are broadcast 90 degrees out of phase Received signals will differ in frequency due to Doppler shift in frequency since both satellite and receiver are moving relative to each other. CA code is a fixed 1023 chips (fixed pattern of bits) Each satellite has its own CA code 1 chip = 1540 cycles of carrier signal 20 x 1023 PRN chips = 1 data bit CA code is 1 ms long, and thus repeats 1000 per second Subframes 1-3 contains all necessary information = ephemerides, GPS time, sat clock corrections Subframes 4-5 contain almanacs older or less accurate ephemerides 25 frames = 12.5 minutes are needed to transmit the full almanacs Data is modulated at 50 bps for the navigation message on L1...
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- Fall '08