GNSS Receiver TIMU External Timescale Synchronization
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Solution Overview
Problem
Conventional GNSS receiver synchronization with external timescales is limited by the need for post-processing, which cannot address clock drift in real-time, leading to delayed availability of measurements.
Innovation Solution
Integration of a Time Interval Measurement Unit (TIMU) within the GNSS receiver allows for real-time correction of measurement processes, enabling synchronization with an external high-precision time reference and generation of Physical Pulse Signals (PPS) to align GNSS measurements with required time instants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If post-processing is used for synchronization, then measurement accuracy can be improved, but real-time availability is lost and measurement delays occur
Solution Approach 1:
The system performs preliminary synchronization by measuring time intervals between external PPS and internal PPS signals in advance, storing these measurements in a buffer, and using them proactively to correct measurement timestamps before output. This preliminary time interval measurement and buffering enables real-time correction without waiting for post-processing.
Solution Approach 2:
The system continuously measures time intervals between external and internal PPS signals, compares them against required time instants, and uses this feedback to dynamically adjust and correct measurement timestamps in real-time. The firmware monitors time interval measurements and automatically applies corrections to maintain synchronization with the external timescale.
2Measurement precision
If external high-precision time reference is integrated, then synchronization precision is improved, but device complexity increases
Solution Approach 1:
The system merges the external high-precision time reference (PPS signal) with the internal GNSS timing architecture by integrating a TIMU that measures time intervals between external and internal PPS signals. The firmware combines these time interval measurements with the existing time correction algorithm, unifying external and internal timing systems into a single synchronized operation without requiring separate independent systems.
Solution Approach 2:
The Time Interval Measurement Unit (TIMU) acts as an intermediary between the external PPS signal and the internal GNSS timing system. It measures time intervals between the two signals and provides this measurement data to the firmware, which then uses it to correct measurement timestamps. This intermediary approach enables precise synchronization without direct complex interaction between external and internal systems.
3Measurement precision
If time correction algorithm is enhanced for real-time correction, then measurement accuracy at required time instants is improved, but processing complexity increases
Solution Approach 1:
The firmware performs preliminary calculations by determining required time instants in advance based on external PPS signal characteristics, and proactively adjusts measurement timestamps using pre-calculated time corrections. This preliminary determination of required time instants and pre-computation of correction values simplifies real-time processing by avoiding complex runtime calculations.
Solution Approach 2:
The time correction algorithm dynamically adapts to varying time interval measurements between external and internal PPS signals. The firmware continuously monitors measured time intervals, compares them against required time instants, and dynamically adjusts correction values in real-time based on actual timing conditions, enabling flexible adaptation to different synchronization scenarios without fixed rigid processing.
Data Source
AI summary
GNSS timing receiver with synchronization of raw GNSS measurements to an external timescale. Synchronization is achieved by using a hardware Time Interval Measurement Unit (TIMU). The TIMU measures time intervals between two pulse signals and makes additional processing of these measurements. The first pulse signal is generated inside the GNSS receiver. The second pulse signal is the external pulse signal generated by an external time reference device. This time interval is used to control the time instant when the output GNSS measurement will be taken. In the first embodiment all actual GNSS measurements are physically taken at time instants indicated by external pulse signal. These measurements are used as output GNSS measurements. In another embodiment all actual GNSS measurements are taken at their default time instants indicated by internal pulse signal. But output GNSS measurements are calculated at the time instants indicated by the external pulse signal.