A Vector Network Analyzer (VNA) measures the magnitude and phase characteristics of networks, amplifiers, components, cables, and antennas. A VNA also compares the incident signal leaving the analyzer with either the signal that is transmitted through the test device or the signal rejected from its input. This application note will introduce the basic fundamentals of the VNA and cover specific topics including phase and amplitude measurements, scattering parameters (S-parameters), and the polar and Smith chart displays.