X-parameters
Encyclopedia
Description
X-parameters represent a new category of nonlinear network parametersNetwork analysis (electrical circuits)
A network, in the context of electronics, is a collection of interconnected components. Network analysis is the process of finding the voltages across, and the currents through, every component in the network. There are a number of different techniques for achieving this...
for high-frequency design and were developed and introduced by Agilent Technologies
Agilent Technologies
Agilent Technologies , or Agilent, is a company that designs and manufactures electronic and bio-analytical measurement instruments and equipment for measurement and evaluation...
as functionality included in N5242 Nonlinear Vector Network Analyzer
Network analyzer (electrical)
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...
, and the W2200 Advanced Design System
Advanced Design System
Advanced Design System is an electronic design automation software system produced by Agilent EEsof EDA , a unit of Agilent Technologies. It provides an integrated design environment to designers of RF electronic products such as mobile phones, pagers, wireless networks, satellite communications,...
in 2008. (Nonlinear vector network analyzers are sometimes called large signal network analyzers.)
X-parameters are applicable to both large-signal
Large-signal model
Large-signal modeling is a common analysis method used in electrical engineering to describe nonlinear devices in terms of the underlying nonlinear equations....
and small-signal conditions, for linear and nonlinear components. They are a mathematical superset of S-parameters
Scattering parameters
Scattering parameters or S-parameters describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals....
meaning that, in the limit of a small signal, Agilent’s X-parameters reduce to S-parameters.
They help overcome a key challenge in RF engineering
RF engineering
Radio frequency engineering is a subset of electrical engineering that deals with devices that are designed to operate in the Radio Frequency spectrum...
, namely that nonlinear impedance
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
differences, harmonic mixing
Frequency mixer
In electronics a mixer or frequency mixer is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals at frequencies f1 and f2 are applied to a mixer, and it produces new signals at the sum f1 + f2 and difference f1 -...
, and nonlinear reflection effects occur when components are cascaded under large signal operating conditions. This means that there is a nonlinear and as such non-trivial relationship between the properties of the individual cascaded components and the composite properties of the resulting cascade. This situation is unlike that at DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
, where one can, for example, simply add the values of resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s connected in series. X-parameters help solve this cascading problem: if you measure the X-parameters of a set of components individually, you can calculate the X-parameters (and hence the non-linear transfer function) of any cascade made from them. Calculations based on X-parameters are usually performed within a harmonic balance simulator environment.
X-parameters are based on the polyharmonic distortion modeling work of Dr. Jan Verspecht and Dr. David E. Root.
While the X-parameter format and underlying equations are open and documented in several IEEE papers, the trademark owner Agilent also states that Given the rapidly developing state of the technology, as well as finite resources, Agilent currently can provide additional support only to key customers and strategic partners whose efforts are focused on improving the technology.
External links
- Fundamentally Changing Nonlinear Microwave Design by David Vye Editor, Microwave Journal Vol. 53 No. 3 March 2010 Page 22