X-parameters represent a new category of nonlinear network parameters for high-frequency design and are used for characterizing the amplitudes and relative phase of harmonics generated by the nonlinear behavior of components. Developed and introduced by Agilent Technologies, X-parameters are applicable to both large-signal and small-signal conditions, and for linear and nonlinear components. They correctly characterize impedance mismatches and frequency mixing behavior to allow accurate simulation of cascaded nonlinear X-parameter blocks (e.g., amplifiers and mixers), in wireless design. X-parameters play a key role in the development of active devices like the power amplifier (PA) and mixers—critical components in today’s wireless designs.