A vector network analyzer is an instrument that measures the frequency response of a component or a network composed of many components, which can be both passive and active. A VNA measures the power of a high-speed signal going into and coming back from a component or a network, because power, in contrast to voltage and current, can be measured accurately at high frequencies. The built-in computer in the VNA calculates key parameters such as return loss and insertion loss of the network under test. It is also capable of visualizing the results in different formats—for example, real/imaginary, magnitude/phase, Smith chart, etc. In high-speed system tests, VNA is often used to characterize multi-port networks consisting of components such as connectors, filters, amplifiers, and transmission line/coaxial channels. A vector network analyzer is used to measure the performance of circuits or networks such as amplifiers, filters, attenuators, cables and antennas.