Abstract: In a dynamic signal traffic scenario, a narrowband to wideband transition in a DPD system results in a tilt in the output spectrum until the next DPD adaptation cycle occurs. To address this problem, regularization term is applied with a weighing factor when performing DPD coefficient estimation and adaptation. The regularization term can be obtained from in a variety of ways: using pre-stored waveforms, through factory or in-situ calibration, or through an adaptive or opportunistic update by observing the system. Application of the regularization term improves the spectrum flatness for a narrow to wideband signal transition, and does not require transmitting additional calibration tones to correct the gain flatness.