Network analyzer (electrical)

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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.^[1]

1 Overview
2 AC power systems
3 See also
4 References
5 External links

[edit] Overview

A network analyzer (HP 8720A) showing a Smith chart.

Special types of network analyzers can also cover lower frequency ranges down to 1 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.^[2]

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 analyzers, 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.

[edit] AC power systems

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From about 1929 to the late 1960s, large alternating current power systems were modelled and studied on AC network analyzers. These were an outgrowth of the DC calculating boards used in the very earliest power system analysis. These systems were essentially models of the power system, with generators, transmission lines, and loads represented by miniature electrical components with scale values in proportion to the modeled system. Model components were interconnected with flexible cords to represent the schematic of the modelled system. To reduce the size of the model components, the network analzyer was energized at a higher frequency than the 50 Hz or 60 Hz utility frequency, and model circuits were energized at relatively low voltages to allow for safe measurement with adequate precision. AC network analyzers were much used for power flow studies, short circuit calculations and studying system stability but were ultimately replaced by numerical solutions running on digital computers. Since the multiple elements of the AC network analyzer formed a powerful analog computer, occasionally problems in physics and chemistry were modelled (by such researchers as Gabriel Kron of General Electric), during the period up to the late 1940s prior to the ready availability of general-purpose digital computers ^[3].