In this paper, the high potential of varactor-based dynamic load modulation (DLM) techniques for wideband cellular applications is demonstrated. A systematic design procedure is proposed to ensure high-efficiency wideband performance. It incorporates harmonically tuned power amplifier (PA) concepts and tunable matching techniques in an integrated design. A DLM transmitter at 2.65 GHz with a peak output power of 6 W is designed using the proposed procedure. In order to investigate the wideband performance of the implemented demonstrator, WCDMA signals with scaled bandwidths are employed. The signal peak-to-average ratio is 7 dB and the same for all the experiments. For the 38.4-MHz signal, which has a corresponding channel bandwidth of > 40 MHz, an average power added-efficiency (PAE) of 44%, normalized mean square error (NMSE) of -35 dB, and adjacent channel leakage ratio (ACLR) of -43 dBc are measured.