Code Frequency Calculation for the GPS HDL Acquisition and Tracking Using C/A Code Example

Hope everyone is doing well,

On the GPS HDL Acquisition and Tracking Example, for the Tracking - DLL part, only the code phase of the C/A code is controlled. However, on a real scenario the code frequency of the modulated signal is different from 1.023 MHz. because of the Doppler Effect. Also on the Open-Source GPS Receiver projects, in addition to the code phaes, they control the code frequency in DLL Loop. However, this is not the case with the provided model. Is this due to the simplification on the RX Signal generation?

Answer 1

[Shashikanth Bonamonu]

Hi Kaan,

In the GPS HDL Acquisition and Tracking Example, the frequency offset due to the doppler effect is compensated by the Frequency Locked Loop (FLL). In every iteration of the loop, frequency offset is measured in the input signal and compensated. This compensation also applies to the C/A code in the input signal. So you do not have to separately compensate for the code frequency.