Measuring networks with two ports separated by more than several feet, or in situations where it is hard to place a vector network analyzer (VNA) in close proximity to the ports of a device-under-test (DUT) has always been a challenge. The typical solution to this challenge is to sacrifice measurement completeness and use only a single port network analyzer, use a remote power sensor with a VNA, or to vastly increase the cost of test and use a high-performance 2-port VNA and long lengths of low loss VNA coaxial cables. Any of these methods require measurement quality sacrifices and ultimately degrade the dynamic range of the measurement. Fortunately, there is a new solution that leverages high precision timing synchronization between two 1 port VNAs to create a distributed 2-port VNA. This modular instrument directly connects through standard coaxial connectors to the DUT’s ports, which may be separated by over 100 meters.
This paper discusses the historical challenges associated with network measurements over distance, applications where this is a challenge, the unique considerations for these applications, and how this new modular solution addresses these challenges and opens the doors to a new realm of 2-port VNA measurements that are port separation distance agnostic to 100 meters.