Most design engineers are familiar with tools of the trade such as voltmeters, oscilloscopes, signal generators, and spectrum analyzers. Some may not have had the opportunity to use a vector network analyzer (VNA). It’s the intent of this article to introduce VNA measurement and present a few typical applications.
Why is a VNA Useful?
Transmission lines can support RF propagation in either direction. Signals traveling along a transmission line may encounter localized impairments that aren’t precisely 50 Ω, such as connectors or transitions from coaxial to planar media (other impedances such as 75 Ω are common, but for the purposes of this explanation we will use 50 Ω). Each impairment generates a reflection that travels back toward the source along the transmission line.