A Touchstone file was originally a proprietary file format for the eponymous frequency-domain linear circuit simulator [1] from EEsof, launched in 1984 and acquired by HP. The simulator has been called HP/EEsof, then its engine has been successively included in the jOmega and ADS software suites and it is now owned by Keysight.
EEsof, today known as Keysight EEsof EDA, is a provider of electronic design automation (EDA) software that helps engineers design products such as cellular phones, wireless networks, radar, satellite communications systems, and high-speed digital wireline infrastructure. Applications include electronic system level (ESL), high-speed digital, RF-Mixed signal, device modeling, RF and Microwave design for commercial wireless, aerospace, and defense markets.
The Touchstone simulator has long since been superseded, [2] but its file format lives on.
A Touchstone file (also known as an SnP file after its set of file extensions [3] ) is an ASCII text file used for documenting the n-port network parameter data and noise data of linear active devices, passive filters, passive devices, or interconnect networks. An example of the format of the S-parameter section is given in the article about S-parameters. In addition to S-parameters, other representations such as Y-parameters and Z-parameters can be recorded.
ASCII, abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.
Scattering parameters or S-parameters describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals.
It later became a de facto industry-standard file format not only for circuit simulators but also for measurement equipment (e.g. vector network analyzers, or VNAs), then later still an EIA standard as part of the Input/output Buffer Information Specification (IBIS) project. [4] On April 24, 2009, the IBIS Open Forum ratified version 2.0, [5] superseding Version 1.1. [6] Version 2.0 adds IBIS-style keywords such as [Reference], which permits per-port definition of the reference environment.
A de facto standard is a custom or convention that has achieved a dominant position by public acceptance or market forces. De facto is a Latin phrase that means in fact in the sense of "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established", as opposed to de jure.
A network analyzer is an instrument that measures the network parameters of electrical networks. Today, network analyzers commonly measure s–parameters because reflection and transmission of electrical networks are easy to measure at high frequencies, but there are other network parameter sets such as y-parameters, z-parameters, and h-parameters. Network analyzers are often used to characterize two-port networks such as amplifiers and filters, but they can be used on networks with an arbitrary number of ports.
The Electronic Industries Alliance was a standards and trade organization composed as an alliance of trade associations for electronics manufacturers in the United States. They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable. The EIA ceased operations on February 11, 2011, but the former sectors continue to serve the constituencies of EIA.
Several further enhancements to the file format that allow description of the non-linear behavior of the component have been developed under the P2D and S2D pair of formats, [7] but these two have been superseded by the X-parameters functionality.
X-parameters are a generalization of S-parameters and are used for characterizing the amplitudes and relative phase of harmonics generated by nonlinear components under large input power levels. X-parameters are also referred to as the parameters of the Poly-Harmonic Distortion (PHD) nonlinear behavioral model.
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