ST2276
Scientech Technologies Pvt. Ltd.
12
Experiment 2
Objectives :
1.
Understanding the principle of GPS Satellite.
2.
Understanding the generation of L1 carrier frequency.
3.
Understanding the operation of GPS Receiver.
4.
Establishing the link between the GPS Satellite and GPS Trainer.
Theory :
GPS Satellite Block diagram :
On board the Satellite have four atomic clocks. The following time pulses and
frequencies required for day-to-day operation are derived from the resonant frequency
of one of the atomic clocks shown in figure :
1.
The 50Hz data pulse.
2.
The C/A code pulse (Coarse/Acquisition code, PRN-Code, coarse reception
code at a frequency of 1023 MHz), which modulates the data using an exclusive
or operation (this spreads the data over a 1 MHz bandwidth).
3.
The frequency of the civil L1 carrier (1575.42MHz)
The data modulated by the C/A code modulates the L1 carrier in turn by using
Bi-Phase-Shift-Keying (BPSK). With every change in the modulated data there is a
180 deg change in the L1 carrier phase.
Figure 7
HiK-Consulting