Characterization of GPS Disciplined Oscillators Using a Laboratory GNSS Simulation Testbed

This paper introduces a testbed to characterize the performance of GPS disciplined oscillators using a GNSS signal simulator and a measurement system based on software-defined radios and digital signal processing that allows to examine the stability of up to four devices with sub-nanosecond precision, time-coherently for 1 PPS and 10 MHz signals, in a controllable laboratory environment with reproducible and adjustable GNSS signal settings over a long-term observation period. To demonstrate the effectiveness of this method, four devices of one specific low-cost GPSDO type available to the authors are characterized and compared in terms of their positional accuracy and their time and frequency stability in steady state and during stabilization.