- Thursday 21 January; 15:30: ELEC Seminar by Gaia Cavallo
Carrier aggregation intermodulation distortions in Advanced Systems
Achieving greater throughput in telecommunications requires increasing bandwidth. However, due to scarcity in carrier frequencies, the required bandwidth may not be available in a contiguous band. LTE Advanced uses multiple bands for one single user, which is known as carrier aggregation . However, power amplifier’s efficiency can only be achieved when operated in the nonlinear mode, in which multiple bands will lead to intermodulation distortions (IMD). The consequence can be a severe desensitization of the own receiver. Predistortion is one of the methods used for mitigating intermodulations.
Some of the predistortion methods perform the following steps:
- extract the IMD to be mitigated from the output;
- demodulate it;
- modulate it again at IMD carrie;
- add it (with opposite phase) to the main signal before amplification . Then be cancellation between IMDs generated in the power
- amplifier by the main signal and those reintroduced from output will be noticed. However, such cancellation will be possible only if the 2 IMDs have opposite phases.
In this project we analyse the consequences of carrier aggregation intermodulation distortions in LTE-Advanced and we design and hardware implement an IMD carrier generator, which will output a linear combination of used frequency carriers.
- Zukang Shen et al., Overview of 3GPP LTE-Advanced Carrier Aggregation for 4G Wireless Communications, in IEEE COMMUNICATION MAGAZINE, February 2012
- Mahmoud Abdelaziz et al., Low-Complexity Subband Digital Predistortion for Spurious Emission Suppression in Noncontiguous Spectrum Access, in IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 64, NO. 11, november 2016