GPS disciplined rubidium oscillator

The proposed product uses a rubidium oscillator as its main frequency standard. A rubidium oscillator has very good short and medium term stability. The maximum drift rate is expected to be less than 4 parts in 10¹¹ per month. There may be a frequency offset of up to 1 part in 10¹⁰ after initial calibration. By comparing the phase difference between the GPS 10 MHz output, and the 10 MHz output from the rubidium oscillator, it is possible to correct the initial frequency offset and remove the drift. By using sufficiently long time constants in the control loop, it is possible to remove the effects of SA (selective availability) completely, and frequency accuracies equivalent to GPS time, which is itself locked to UTC within ±100 ns, may be obtained. It is vital that the system is tolerant of GPS signal failures. The rubidium is sufficiently stable to free run for hours or days provided that the control voltage is held at the point where the GPS control was interrupted. This report will consider the design of the hardware down to block diagram level. The control algorithm will be considered in detail and performance analysis of the selected method will be carried out on simulated data