The present disclosure generally relates to predistortion that compensates for non-linearity of a power amplifier as well as short-term and long-term memory effects of the power amplifier. The apparatus also has a chassis that accommodates an impedance matching circuit, provided in the middle of a supply path for feeding RF power from an RF generator to the plasma excitation electrode, for matching the impedance between the RF generator and the plasma processing chamber. The at least one finger receptacle includes side wall portions and an open insert end. The cannula has at least first, second and third flow paths which can be connected with a desired supply, monitoring or detection device. The measurement data produced includes values for grating spacing, tilt angle, and diffraction efficiency with a high spatial resolution. The system implements a communication protocol in which the external communication device interrogates any implantable medical devices within range to establish one-to-one communication links for purposes of exchanging data andor programming the medical devices.