A Baseband Wireless VNA for the Characterization of Multiport Distributed Systems

Frequency characterization of spatially large structures has become increasingly required, mostly in the fields of structural health monitoring (SHM) and communication systems based on nonconventional media. When the ports of the system under measurement are far apart, methods based on traditional wired instruments become unattractive for field applications, due to the increased complexity, cost, and signal integrity-related issues. Aiming toward removing the wired connection from the ports of the system under test and the elaboration unit (EU), the main issue to be dealt with is the time synchronization of measurements at the ports. This contribution proposes a solution to such an issue by presenting a Wireless Vector Network Analyzer (WVNA), suitable for the characterization of distributed systems. For this purpose, a wireless synchronization scheme is proposed, which is based on the disciplining of the signal sampling clock from the 1-pulse/s reference signal. The proposed synchronization method reduces clock jitter at different ports at 1.13
$\mu \text{s}$
over a 300-s observation interval. The hardware and software implementation of the system are detailed and experimental results proving its operation are provided.