CODE-FREE DUAL-FREQUENCY CPS RECEIVER DESIGN

THE GLOBAL POSITIONING SYSTEM (GPS) SATELLITES TRANSMIT INFORMATION ON TWO FREQUENCIES IN THE L-BAND: L(1) AT 1575.42 MHZ AND L(2) AT 1227.6 MHZ. THESE TWO TRANSMISSIONS ARE PHASE-COHERENT SINCE THEY ARE DERIVED FROM A COMMON OSCILLATOR. BOTH OF THESE FREQUENCIES ARE MODULATED BY A P-CODE CONSISTING OF PSEUDO-RADOM ONE'S AND ZERO'S. THE TRANSMISSION RATE IS 10.23 MHZ AND THE CODE ON BOTH THE TRANSMISSIONS IS COHERENT. THE IMPORTANCE OF GPC SATELLITES FOR IONOSPHERIC RESEARCH IS IN THE DUAL COHERENTLY TRANSMITTED FREQUENCIES DESIGNED FOR THE NAVIGATION USER TO CORRECT FOR IONOSPHERIC ERRORS. SINCE THE P-CODE HAS LIMITED ACCESSIBILITY, IT IS PROPOSED TO ANALYZE AND OPTIMIZE TWO SIMPLER RECEIVER DESIGNS WHICH DO NOT REQUIRE THE KNOWLEDGE OF THE P-CODE. ONE SYSTEM IS MORE ACCURATE BUT REQUIRES SOMEWHAT COMPLEX CIRCUITRY TO DETERMINE THE DIFFERENTIAL GROUP DELAY. THE SECOND SYSTEM PROPOSED IS MUCH SIMPLER AND CHEAPER TO IMPLEMENT BUT OF ADEQUATE ACCURACY TO DETERMINE THE DIFFERENTIAL GROUP DELAY TO CALIBRATE THE DIFFERENTIAL CARRIER PHASE FOR ABSOLUTE VALUE OF ELECTRON CONTENT. IN BOTH SYSTEMS, THE DIFFERENTIAL CARRIER PHASE AND SIGNAL AMPLITUDES ARE ALSO MEASURED. THE PARAMETERS PROVIDE NECESSARY INFORMATION ON IONOSPHERIC IRREGULARITIES AND DISTURBANCES.