The Agilent Technologies 8509B network analyzer is an instrument which measures the complex transmission and reflection characteristics of two-port devices in the frequency domain. It does this by sampling the incident signal, separating the transmitted and reflected waves, and then performing ratios that are directly related to the reflection and transmission coefficients of the two-port. Frequency is swept to rapidly obtain amplitude and phase information over a band of frequencies of interest.

Agilent Technologies 8509B network analyzers utilize synthesized-frequency sources to provide a known test stimulus that can sweep across a range of frequencies or power levels. Agilent Technologies 8509B network analyzers also can perform ratioed measurements (including phase), which require multiple receivers. The Agilent Technologies 8509B can provide a wealth of knowledge about a device under test (DUT), including its magnitude, phase, and group-delay response.