M.Sc Thesis

M.Sc StudentGinzberg Nimrod
SubjectLinearization Technique of a Diplexer-Free Transmitter
for Carrier Aggregation Signals
DepartmentDepartment of Electrical and Computer Engineering
Supervisor ASSOCIATE PROF. Emmanuel Cohen
Full Thesis textFull thesis text - English Version


In this work we introduce a transmitter architecture and a linearization technique for a concurrent transmission of two intra-band non-contiguous carrier aggregation signals at the 5 GHz UNII frequency band. The technique is based on low power and narrowband analog signal injection to compensate for out-band third-order intermodulation distortions (IMD3). Inband intermodulation and crossmodulation distortions are addressed using a 2D-DPD algorithm. The combination of digital predistortion to account for inband nonlinearities, and analog cancellation of out-of-band IMD3, enables to achieve wideband linearization over the entire third-order distortion bandwidth of the transmitter using practical sampling rates of narrowband DACs and ADCs. The proposed transmitter comprises two power amplifiers (PA), which are connected in parallel to a single antenna. Mutual PA loading is mitigated by designing the PAs to introduce high output impedance. The high output impedance characteristic, together with inband and out-of-band linearization, enable a diplexer-free transmission of two carriers along the aggregated transmission band. The system is studied theoretically and experimentally using widely spaced CW and OFDM signals. In the CW test we achieve -52 dBc spur level in the compensated system, and 30 dB improvement in total spurious level compared to a single two-tone PA. In the OFDM test we demonstrate 7-12 dB suppression in the power level of the out-of-band third- order intermodes, and 6-9 dB improvement in EVM achieved by the 2D-DPD algorithm. We also show that the linearization technique is independent of the signals' power and on the frequency separation between the channels.