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2024

Beidou timing terminal 1PPS signal output

The 1PPS signal from a Beidou timing terminal stands for “1 pulse per second.” Nowadays, most satellite navigation timing terminals are required to provide this output.

The 1PPS signal of a Beidou timing terminal stands for “1 pulse per second.” Today, most satellite‑navigation timing terminals are required to output this signal. Its purpose is to mark the exact second, typically using the rising edge of the 1PPS pulse. Because the navigation signals transmitted by the Beidou Satellite Navigation System—containing both BDT and UTC time—experience a propagation delay when they reach the timing terminal’s antenna, employing the 1PPS rising edge to timestamp BDT and UTC at the start of each second achieves very high precision, on the order of nanoseconds, with no accumulated error. The 1PPS rise time should generally be less than 50 nanoseconds, with a pulse width ranging from 20 to 200 nanoseconds. The 1PPS signal provides only a second‑level pulse reference and does not convey time information on its own; it must be used in conjunction with TOD data. Typically, a timing terminal begins transmitting TOD information one millisecond after the 1PPS rising edge and completes transmission within 500 milliseconds. This TOD information indicates the precise moment corresponding to the current 1PPS rising edge, and the TOD protocol is transmitted at a rate of once per second. Transmission of 1PPS and TOD data is usually carried out using an RS‑422 level interface, with either an RJ45 or a DB9 serial connector as the physical interface.

Timekeeping Characteristics of Atomic Clocks in Timing Systems

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Timekeeping Characteristics of Atomic Clocks in Timing Systems

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