Abstract: A precision vector network analyzer which is suitable for a wide range of applications including both laboratory and automated production measurements and testing is disclosed. New measurement capabilities, greater ease of use, and nearly complete automation are provided. Contributions include fully corrdinated communications between subsystem modules; real time, two channel, precision vector measurements with complete, internal error correction; wide frequency capability from RF to millimeter bands; combined time and frequency domain analysis and display; measurements either in the swept or step frequency modes; and user definable test functions and calibration device sets.