Bandpass predistortion method and apparatus for radio transmission

k kk kk k kAn apparatus and method for generating an envelope predistorted radio frequency signal which avoids undesirable spurious emissions. A complex baseband signal, having an in-phase component I and a quadrature component Q, is sampled and filtered in a sampling circuit and filter circuit to obtain samples Iof the in-phase component and samples Q, the quadrature component. The magnitude xof each sample pair is determined in a first calculation circuit. An amplitude and phase distortion factor D, based on scaled values of the archyperbolic tangent and the hyperbolic tangent of the baseband sample magnitude is determined in further calculation circuit and a multiplier. Each sample Iof the in-phase component and Qof the quadrature component is multiplied by the corresponding distortion factor D, and the resulting predistorted components combined and upconverted to provide a predistorted baseband signal which is amplified in a power amplifier having hyperbolic tangent distortion.