Energy-Efficient Array Transmitters Through Outphasing and Over-the-Air Combining

Lampu, Vesa; Xu, Guixian; Anttila, Lauri; Brihuega, Alberto; Kosunen, Marko; Unnikrishnan, Vishnu; Ryynänen, Jussi; Valkama, Mikko

doi:10.1109/ieeeconf53345.2021.9723289

Cited by 1 publication

(4 citation statements)

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“…Again, increasing the number of amplitude levels improves the performance of the OP-based systems. The alternating beamforming scheme is able to meet the 28 dBc limit even with a single amplitude level, if sufficiently many antennas are employed, as was also shown in [49]. A more moderate number of antennas is required to meet the limit if the system has more amplitude levels.…”

Section: A Beampatterns and Trp-sdrmentioning

confidence: 58%

“…Additionally, in order to avoid generating grating lobes in the beampattern, antenna elements transmitting similar signals need to have separation less than λ/2. Therefore, to meet this criteria also in the alternating beamforming case, the antenna separation to wavelength ratio ρ is set to 0.25 [48], [49]. In the simulations, in order to avoid spatial aliasing, we consider an angle range between −90 • and 90 • , with an increment of 0.25 • .…”

Section: Numerical Results and Analysismentioning

confidence: 99%

“…While some research on the combinerless OP exists, as reviewed above, a comprehensive analysis of its characteristics and feasibility in the large array context, in terms of transmitted signal quality and integrity in the spatial domain, is missing. In this article, building on our early work in [49] on singlelevel OP, we aim to fill this gap. Unlike prior art, this work analytically considers the spatial domain, i.e., emissions not just towards the intended user but to all spatial directions.…”

Section: B Contributionsmentioning

confidence: 99%

“…depending on the adopted beamforming scheme. In this paper, we consider two distinct beamforming schemes: alternating and block, similar to [42] and our early work in [49]. In the former, the component signals alternate in the antennas, such that even indexed antennas transmit S 1 [n] and odd indexed antennas transmit S 2 [n], while in the latter the signals are grouped in equally sized blocks, such that the first M/2 antennas transmit S 1 [n] and the latter M/2 antennas transmit S 2 [n].…”

Section: B Beamforming Schemesmentioning

confidence: 99%

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Multilevel Outphasing With Over-the-Air Combining in Large Antenna Arrays

Lampu,

Xu,

Brihuega

et al. 2023

IEEE Trans. Commun.

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This article investigates the feasibility of combinerless multilevel outphasing transmitter as a potential architecture for large millimeter-wave (mmWave) phased arrays. We consider two distinct ways of distributing the component signals to the antennas and develop a model for the received signal at each radiated spatial direction from a phased array. Based on the received signal model, we derive expressions for the signal-to-distortion ratio as well as total power experienced at each spatial direction. Furthermore, antenna branch mismatches, overload distortion and quantization are considered, and an analytical model for the signal-to-distortion ratio at the intended receiver is derived. We additionally establish a model for comparing the achievable energy efficiency to those of the relevant reference methods. Extensive numerical experiments are carried out to verify the analytical works, and to assess the commonly used metrics of error vector magnitude (EVM) and total radiated power adjacent channel leakage ratio (TRP-ACLR). It is shown that the combinerless architecture is a valid option for mmWave phased arrays, demonstrating favorable EVM results and TRP-ACLR beyond the 28 dBc limit imposed by the 3GPP, even in the presence of the considered distortions. The conducted energy efficiency assessment shows that efficiency of the reference methods can be exceeded with sufficient amount of outphasing levels. The considered architecture is thus an interesting alternative for addressing the linearity vs. energy-efficiency challenge in mmWave phased-array systems.

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Section: A Beampatterns and Trp-sdrmentioning

confidence: 58%

Section: Numerical Results and Analysismentioning

confidence: 99%

Section: B Contributionsmentioning

confidence: 99%

Section: B Beamforming Schemesmentioning

confidence: 99%

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