Three-State Kalman Filter Algorithm

1pps-Locking-Modules

Quartzlock (UK) Ltd.

This is a module to control an OCXO or Rubidium oscillator with 1PPS from a GPS receiver. The Quartzlock A6-1PPS uses a 3 state Kalman filter algorithm to measure & correct the frequency offset of the oscillator with respect to the 1PPS input. Time-tagged input 1PPS to 200ps resolution & <1ns jitter. Analog interpolator is self calibrating. Interface to GPS decodes messages & extracts relevant info. i.e. time correction data for 1PPS output, this has AVAR of the Rb or OCXO i.e. 5 x 10-12/s & <100ps RMS jitter. The output is steered to time coincidence with GPS time/UTC to 1ns resolution. Holdover initiated by 1PPS fail or data from GPS RX that 1PPS is inaccurate. During holdover, measured frequency offset & drift steer the oscillator & 1PPS is still available.