Intermodulation Mitigation in Concurrent Multi-band PAs using Multi-band Predistortion Techniques
5G and beyond RF transmitters utilize multi-band carrier aggregation to increase data throughput. Typically, these bands are far apart in frequency and require parallel transmit paths to transmit signals in each band concurrently. An effective way to reduce cost and design space is to combine the low power RF signals, and amplify all the signals together using one multi- band enabled PA. However, multi-band signals passed through a nonlinear device introduce more complex challenges, such as producing intermodulation distortion (IMD) products at frequencies other than the main transmitted channels.
As the number of bands increase at the input of the PA, numerous amounts of IMD products will be generated at the output of the PA. Suppression of these IMD components without capturing these signals is desired and will reduce the count of feedback receivers required. This contribution to the workshop will discuss the different approaches to mitigate the problem of in-band, out-of-band and inter-band IMD in concurrent multiband PAs. Multiband DPD architectures using (i) a multi-stage predistortion based technique, (ii) distortion injection based technique and (iii) distortion prediction based technique will be presented and compared from performance and implementation perspective.