Timing Offset and Timing Stability for a Dual-Clock Channel Sounder

We describe a mathematical framework for evaluating timing offset and timing noise in channel sounders based on a second-order deterministic model and a stochastic metric based on the Allan deviation. Using this framework, we analyze the timing offset and noise for a 1–6-GHz correlation-based channel sounder that uses rubidium (Rb) clocks to provide a common timebase between the transmitter (Tx) and receiver (Rx). We study timing behavior in three clock-distribution configurations. In the “untethered” configuration, the Tx and Rx each have an Rb clock, and no physical timing cable is connected between the clocks. In the “tethered” configuration, a coaxial cable synchronizes timing between the two separate clocks. Finally, a benchmark “single-clock” configuration is used where a single Rb clock drives the Tx and Rx.