The Formation of a Chip Scale Atomic Clock Ensemble Using Software Defined Radios

Low size, weight, and power (SWaP) clocks are expected to play a key role in new positioning, navigation, and timing (PNT) systems, providing augmentations or alternatives to conventional global navigation satellite systems (GNSS). Distributing high-quality PNT services from payloads with more limited resources than GNSS satellites requires signal generation from low SWaP hardware. This paper describes stable signal synthesis based on a low cost clock ensemble using software defined radio (SDR) metrology techniques and clock ensemble algorithms. First, the capacity to accurately characterize the stability of different clocks using the SDR is demonstrated. Experimental results then establish the ability to steer an oven controlled crystal oscillator (OCXO), initially to a single reference clock signal, and then to the implicit ensemble mean (IEM) of three chip scale atomic clocks (CSACs). This steered output signal has noise comparable to the short term stability of the OCXO and long term stability similar to the best clock in the ensemble.