Limitations for pilot-component accumulation time due to reference oscillator instability. Experiment technique and results

Increasing accumulation time for the pilot component of navigation signal allows improvement of the receiver-s sensitivity and antijam capability in fine acquisition and non-coherent tracking modes. For static user position, the reference oscillator-s drift is the only limiting factor for the correlator accumulation time. The scope of this article is the experimental exploration of oscillator-s drift impact on the SNR and accumulation time problem. The experiment technique and results are presented for a number of popular TCXOs: GK-99TK, GK-206TK, GTXO-83. OCXO was also considered. It is shown for TXCOs that the pilot component correlator accumulation time should be not more than 0.1-0.3 s. Experiment revealed that maximum reasonable accumulation time for a given oscillator is inverse to its Allan deviation at τ = 0.1 s. Also experiment has shown that the considered TCXOs allow tightening of the 3-rd order PLL bandwidth down to 1.3-6 Hz. Generally, minimal working PLL bandwidth is proportional to Allan deviation at τ = 1 s.