GPS Satellite Signal Simulation

Application Background

This program serves to generate GPS simulation signals by providing a comprehensive solution that includes C/A code generation algorithms, navigation data creation, and spread spectrum implementation. It is particularly suitable for undergraduate and graduate students beginning their GPS studies, as well as professionals requiring GPS signal simulation capabilities.

Key Technologies

1. Generation of C/A Code Baseband/IF Signals

The process of generating a complete signal modulated on the L1 carrier involves the following operations:

1) PRN Code Selection: The program implements Gold code generation algorithms specifically for satellite PRN number "5", using shift register implementations to create the characteristic C/A code sequences with proper code phase initialization.

2) Navigation Data Insertion: The navigation data operates at 50bps rate and undergoes spread spectrum modulation with C/A codes to generate baseband signals. The data structure follows the GPS specification: 30-bit navigation data words form a word, 10 words constitute a subframe, 5 subframes make up a page, and 25 pages complete one cycle. The program encodes GPS time information including week number and Time of Week (TOW). The week number updates once per page, occupying the first 10 bits of the third word in the first subframe. TOW updates every subframe, located in the first 17 bits of the second word. Remaining navigation data positions can be populated with random values. The algorithm implements cyclic generation of 25 pages of navigation data through structured data framing techniques.

3) Signal Format Requirements: The baseband signal utilizes square wave modulation with binary levels (0 and 1), 50% duty cycle, without added noise components. The implementation uses digital waveform generation techniques with precise timing control for signal synchronization.

After completing these operations, the program generates a complete baseband/IF signal suitable for GPS simulation applications.

Additionally, the program includes comprehensive documentation containing detailed operational procedures and technical explanations of the underlying algorithms, facilitating user understanding and implementation.