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Augmented Dual-Band Digital Predistorter for Reducing Cross-Band Intermodulation Distortion Using Predictive Injection Technique

In this paper, an augmented dual-band digital predistortion (DPD) technique for reducing the cross-band intermodulation distortion (IMD) using predictive injection technique is proposed to address some of the shortcomings of dual-band DPDs. The technique alleviates the need to observe the cross-band third-order IMD (IMD3) terms in the feedback loop by predicting the distortion terms and generating synthetic signals, which are then injected at the transmitter side. To highlight the issue, the wideband and dual-band DPD architectures and their respective limitations are briefly outlined. The theory behind the proposed concept is developed, and practical measurements performed using a Class AB power amplifier driven by a long-term evolution signal are provided to support the theory. The results obtained show that the proposed method achieves promising performance in mitigating the cross-band IMD3 issue faced by dual-band DPDs. This technique can be extended to mitigate higher order cross-band distortion as well.