GPS L1 Signal can be represented from the following components
is a C/A signal component. The C/A component is a repeating Gold Code 1023 units long with at a frequency of 1.023 MHz. These units are called chirps rather than bits to emphasize that no data is transmitted through them.
is the information carrying part of the signal. It is transmitted at 50 Hz. The C/A code is repeated 20 times in one Data bit.
is the L1 frequency. This is transmitted at a rate of of 1575.42 Mhz. This signal is affected by the doppler effect from movement by both the transmitting satellite. For almost all receivers this signal is brought down to an intermediate frequency before it is processed. The GN3S receiver supplied by the department sets the IF frequency to 4.1304 Mhz and a sampling frequency of 16.368 Mhz.
Doppler effect of signal
is the maximum frequency of the Doppler shift.
is the velocity of the satellite. This is approximately 929(m/s) (2078 miles/hour).
is the speed of light.
Thus the maximum frequency range is pluss or minus 4.9kHz or roughly a total range of 10kHz.
For the C/A code this is pluss or minus 3.2 Hz or total range of 6.4 kHz.
For a receiver in an airplane these ranges should be doubled.
