X-parameters: The new tendency in the characterization of nonlinear RF devices

The X parameters allow characterize, analyze and model nonlinear devices and systems under a wide range of frequencies from 10 MHz to 50 GHz. These parameter are the evolution of the small signal S parameters, since it can work both in the linear region as in the nonlinear region of the device under test (DUT). Its application is centered in the field of power amplifiers, because they describe with great accuracy of nonlinear intrinsic behavior of any active DUT without an electrical equivalent circuit. This paper analyzes clearly the theory of X parameters, by means of a design example of a RF amplifier at 5 GHz with a power gain of 10 dB using S and X parameters.