There are more than twenty Vector Network Analyzer (VNA) manufacturers in the world. Most of them are listed below:
AEA Technology
Anritsu
Bird
Ceyear
Copper Mountain Technologies
Elmika
Farran
GSI Protek
Keysight Technologies
MegiQ BV
Mini-Circuits
National Instruments Corporation
OML
Pico Technology
PocketVNA
Rohde & Schwarz
Sanko Technologies
Siglent
Tektronix
Teledyne LeCroy
Transcom Instruments