A network analyzer is an instrument used to analyze the properties of electrical networks, especially those properties associated with the reflection and transmission of electrical signals known as scattering parameters (S-parameters). Network analyzers are used mostly at high frequencies; operating frequencies can range from 9 kHz to 110 GHz.
Special types of network analyzers can also cover lower frequency ranges down to 10 Hz. These network analyzers can be used for example for the stability analysis of open loops or for the measurement of audio and ultra sonic components.

The two main categories of Network Analyzers are

Scalar Network Analyzer (SNA) - Measures amplitude properties only

Vector Network Analyzer (VNA) - Measures both amplitude and phase properties
A VNA may also be called a gain-phase meter or an Automatic Network Analyzer. An SNA is functionally identical to a spectrum analyzer in combination with a tracking generator. As of 2007, VNAs are the most common type of network analyzer, and so references to an unqualified 'network analyzer' most often mean a VNA. The three biggest VNA manufacturers are Agilent, Anritsu, and Rohde & Schwarz.

A new category of network analyzer is the Microwave Transition Analyzer (MTA) or Large Signal Network Analyzer (LSNA), which measure both amplitude and phase of the fundamental and harmonics. The MTA was commercialized before the LSNA, but was lacking some of the user-friendly calibration features now available with the LSNA.