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Energy-efficient Transmitter Designs for 6G Involving Multiple Antenna Systems
Publication . Diacu, Marius-Gabriel; Guerreiro, João; Oliveira, João
Transmitter architectures which can more efficiently amplify high-Peak-to-Average
Power Ratio (PAPR) signals need to be developed, since the Radio Access Network
(RAN) represents the vast majority of modern cellular network energy consumption.
This stems from the use of modulations such as Orthogonal Frequency-Division
Multiplexing (OFDM) for Spectral Efficiency (SE) optimization. Energy costs are a major
factor for operators, and cellular network energy demands are only predicted to
increase, due to the increasing data-rate and better connectivity goals. The Radio
Frequency (RF) Power Amplifier (PA) is the limiting block in transmitter efficiency,
followed by the power combiner, which prioritizes their optimization. The QDA with
Combination Over-the-Air (QDA-CoA) architecture was deemed as the most promising
starting point, using parallel class E PAs, which are highly efficiency, and simultaneously
removing the circuit-based power combiners, avoiding their insertion losses. With the
goal of further enhancing it, the QDA-Power Combination OTA (PCOA) architecture was
established, which considers a Rectangular Array (RA) with beamforming, allocating an
Uniform Planar Array (UPA) subarray to transmit each component, after being
individually amplified by class E PAs. Theoretical frameworks were developed to
describe the input signal processing, the class E PAs and the RA, were shown to offer
strong starting points for the simulation-based sizings, and led to key architecture-level
optimizations. However, a distortion issue in the PCOA architecture was also
uncovered. In simulation, the RA was sized considering rectangular Microstrip Patch
Antennas (MPAs), achieving radiation efficiencies as high as 81.83% for a 3.5 GHz
carrier frequency. Mutual coupling was shown to have a significant impact on the array
impedances and S-parameters. High-level simulation results show that PCOA is
performed as intended, however, there is distortion due to the varying array gain, not
allowing QDA-PCOA results to be obtained. An UPA subarray prototype was also
elaborated, based on more detailed, layer-by-layer models, serving as an example for
the complete array design methodology.
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Fundação para a Ciência e a Tecnologia
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Avaliação UID 2023/2024
Número da atribuição
UID/50008/2025