A RF predistorter using a delay mismatch for an additional IM3 path

We describe a RF predistorter (RFPD) which has multiple intermodulation (IM) paths for individual cancellation of IM3 and IM5 components. To compensate for the memory effect of the power amplifier and improve the linearization ability of the predistorter, we attached an additional IM3 path to the predistorter which had a delay mismatch against the original IM3 path. The optimized delay mismatch, phase, and magnitude of the additional IM3 components enabled the RFPD to moderately compensate for the memory effect of the IM3 components which were generated by the main amplifier. The proposed RFPD was experimentally verified at the 2.14 GHz band. Using a two-tone signal with a tone spacing of 20 MHz, the lower and upper IM3 components were cancelled by 26.21 and 22.84 dB, respectively. Without an additional IM3 path, the lower and upper IM3 components were only cancelled by 17.11 and 12.68 dB, respectively.