A vector network analyzer (VNA) measures a performance of a radio frequency (RF) and/or microwave/millimeter wave device under test (DUT) and produces measured results in terms of network scattering parameters. Vector network analyzers include a signal source to stimulate a device under test (DUT) and one or more tuned receivers to measure responses of the DUT to the stimuli provided by the source. In many situations, a DUT is a relatively small component designed to interface with a trace contact point on a printed circuit board (PCB). Different DUTs can have different types of connection configurations at their ports. For example, a two-port DUT can have one of many of possible configurations of connectors at its two ports. Many network analyzers typically utilize an interface adapted to receive a coaxial coupling. Network analyzers typically operate by sweeping a stimulus signal across a range of frequencies and applying the stimulus signal to a DUT and measuring the response of the DUT. The measurements generated by network analyzers typically possess inaccuracies due to a number of issues. For example, impedance mismatches associated with the network analyzer and/or a test set-up create errors in the measurements. A VNA can be used to test for component malfunctions at cell sites. VNAs transmit a microwave signal to a test device and receive a return signal to enable characterization of the test device. With a VNA, a user can easily identify a fault in a test device, such as a transmission line, and measure the distance from the VNA to the fault or discontinuity. VNAs enable a user to easily identify a fault in a cell site component and to measure the distance from the test device to a fault or discontinuity. A VNA also enables calibration to extend the test port connection to the end of a cable connected to the test port by accounting for any phase and amplitude differences.

Vector network analyzers incorporate high frequency transmission/reflection (T/R) test sets to determine the transmission and reflection characteristics of various devices under test (DUTs). The measurement accuracy of a VNA generally improves as the impedances of a source port and a load port of the T/R test set more closely match a predetermined characteristic impedance. A typical network analyzer includes an output port and an input port, each of which includes a coaxial transmission line connector. The network analyzer transmits broadband signals through the DUT to determine its power transmission and reflection characteristics, commonly referred to as S-parameters. S-parameters are transmission and reflection (T/R) coefficients for the DUT computed from measurements of voltage waves traveling toward and away from a port or ports of the DUT. In general, an S-parameter is expressed either in terms of a magnitude and phase or in an equivalent form as a complex number, the complex number having a real part and an imaginary part. Network analyzers for measuring the transmission and reflection parameters of any object under test disposed between two test ports must be calibrated with the help of so-called calibration standards in order to correct for system errors. Network analyzers for the measurement and representation of frequency-dependent measurement parameters of an object under measurement have a locked oscillator switchable in steps between successive measurement points in the frequency within a predetermined overall frequency band, and have a frequency-selective measurement device synchronously tunable with the locked oscillator. Network analyzers measure the antenna return loss of a cellular base station antenna by injecting a swept signal covering the antenna transmit and/or receive frequencies into the device under test and measuring the magnitude and phase of the signal that is reflected back.

The measurement accuracy of network analyzers may be considerably improved by system error correction which can be obtained by calibration measurements which are realized in such a way that several calibration standards are successively connected between the two externally accessible test ports of the network analyzer where the transmission and reflection parameters will then be measured. In general, network analyzer calibration occurs by applying a stimulus signal to "standards" and estimating the systematic errors from the measurements. Measurement calibration is a process that improves measurement accuracy by using error correction arrays during signal processing to compensate for systematic measurement errors. Measurement errors are classified as random and systematic errors. Random errors, such as noise and connector repeatability are non-repeatable and not correctable by measurement calibration. Systematic errors, such as tracking and crosstalk, are the most significant errors in most RF measurements. Systematic errors include all static (repeatable) errors, and non-systematic errors include noise, drift, and other time variant errors. Systematic errors are due to system frequency response, isolation between the signal paths, and mismatch in the test setup. Frequency response errors are gain errors that are a function of frequency. Isolation errors result from energy leakage between signal paths in transmission measurements. The calibration process involves measuring certain well known devices, called standards, with the non-ideal network analyzer. With proper application, these raw measurements can be used to solve for all systematic errors. After calibration, the systematic network analyzer errors can be removed from the measurements of any unknown device; this is called error correction.

Network analyzers are devices utilized to connect to communications networks, particularly packet networks, which monitor the signaling state and traffic flow of communications on the network. Communication networks are in wide use in many technological fields including distributed computing, data exchange and telecommunication applications. Communication networks generally include many nodes, such as bridges, LAN switches, routers, cross-connections and telephone switches. The networks further include communication links, such as cables, point-to-point radio connections and optical fibers, which connect the nodes. In a packet-based network, such as an Ethernet network, the computing devices communicate data by dividing the data into small blocks called packets, which are individually routed across the network from a source device to a destination device. In a packet network such as a local area network multiple computers exchange messages via a common network medium such as a fiber optic cable. A wide variety of formats and protocols are used to ensure that messages or packets sent by a sending computer are received by the intended receiving computer. A protocol analyzer is a tool that captures data from a network and displays the data to the user. The protocol analyzer typically allows the user to browse the captured data, and view summary and detail information for each packet. A network router reads every packet of data passed to it, determining whether it is intended for a destination within the router's network or whether it should be passed further along the Internet.