Time-Domain Evaluation Method for Clock Frequency Stability Based on Precise Point Positioning

The Global Navigation Satellite System (GNSS) and GNSS receivers can be used to measure the time-frequency errors of receiver clocks so as to evaluate their frequency stability. The calculation of receiver clock error by single point positioning (SPP) is not highly accurate, resulting in the limited evaluation of clock frequency stability. Therefore, this study proposes a precision point positioning (PPP) evaluation method. In this method, the receiver is driven by an external clock to be evaluated, and the receiver clock error calculated by PPP is used as the measured clock phase error to calculate the Allan variance. The frequency stability of three clocks with different grades (temperature compensated crystal oscillator [TCXO], oven controlled crystal oscillator [OCXO], and rubidium clock) are evaluated with the PPP evaluation method. The PPP evaluation method can evaluate the frequency stabilities of TCXO and OCXO for an average interval of more than 1 s, and the evaluation error of OCXO is less than 1.3 × 10
^-11
. As for the rubidium clock, its frequency stability can be evaluated by the PPP evaluation method for an average interval of more than 66 s, and the error is less than 2 × 10
^-13
. In general, the PPP evaluation method involves simple operations, achieves high accuracy, and is easily popularized.