Harmonically Related Concurrent Tri-Band Behavioral Modeling and Digital Predistortion

Jaraut, Praveen; Rawat, Meenakshi; Ghannouchi, Fadhel M.

doi:10.1109/tcsii.2018.2873251

Cited by 12 publications

(10 citation statements)

References 16 publications

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“…In the literature, [9]- [15] explore the cases related to harmonic interference. The works reported in [9]- [11] use a feed-forward harmonic cancellation technique for harmonic suppression.…”

Section: B Comparision Of Nn Model With the Exiting Harmonic Related Solutionsmentioning

confidence: 99%

“…This digitally controlled harmonic cancellation techniques can omit the switched filter bank, as shown in Fig. 1, and result into filter-less multi-octave transmitter architecture [9]- [15]. This filter-less multi-octave transmitter architecture can present frequency agile and miniaturized solution in VHF/UHF bands particularly suitable for SDR application.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, most of these works are validated up to 2 nd harmonic cancellation. The models reported in [12]- [15] claims that they do not require the injection of the reference signals at the input of PA for harmonic modeling. This is because of their special and rare scenario where the concurrent multi-band transmission happens at harmonically related frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Singhal

Rawat

2020

IEEE Access

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This paper presents and demonstrates the design of a filter-less transmitter architecture with digitally assisted harmonic cancellation. A neural network is used to model the harmonics as well as IMD for digital predistortion applications. This neural network-based harmonic modeling does not require any reference signal to be injected at the input of PA, thereby reducing the complexity in characterizing the harmonics. An in-house 10 W PA operating from VHF to L-band has been designed and characterized for its harmonic suppression. This PA is used along with agile RF transceiver AD9361 from Analog Device and Xilinx embedding platform using Zynq ZC-706 system-on-chip for implementing the entire transmitter. The receiver of AD9361 captures the nonlinearity of the PA in terms of harmonics as well as intermodulation distortion (IMD) components for modeling and predistortion. The proposed architecture can handle all types of distortions due to hardware as well as PA nonlinearity. Besides, it is also able to cancel the harmonics using a harmonic injection in the feed-forward configuration. This transmitter architecture has the advantages of being low cost, filter-less, wideband, frequency agile, reconfigurable and less bulky compared to the conventional scheme. The proposed scheme is demonstrated to transmit 5 MHz LTE signal at different frequencies over the range of 100 MHz to 400 MHz. In such a case, the second and third harmonics appear over the frequency range from 200 MHz to 1.2 GHz, which are within the amplification range of PA, yet they are suppressed without using any filter at the output. More than −40 dBc harmonic rejection is achieved over the entire operating range of this filter-less transmitter. The adjacent channel leakage ratio (ACLR) is always better than −45 dBc after applying digital predistortion.

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Section: B Comparision Of Nn Model With the Exiting Harmonic Related Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Singhal

Rawat

2020

IEEE Access

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“…Power back-off can be used to linearize the behavior of the HPA, but it reduces energy efficiency. Digital predistortion (DPD) of the input signal can help linearize the behavior of PA in the saturation region [8], [9]. DPD systems, however, cannot be directly applied to the 5G systems, as using dedicated DPD circuitry at each element of a massive MIMO transmitter would result in an infeasible amount of power consumption as number of antennas becomes large.…”

Section: Introductionmentioning

confidence: 99%

Linear CE and 1-bit Quantized Precoding With Optimized Dithering

Saxena

Mezghani

Heath

2020

IEEE Open J. Signal Process.

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High power amplifiers (HPA), used at transmission, add nonlinear impairments to the output signals. Through Constant envelope (CE) transmission, distortion in the signal can be avoided without wasting power on PA linearization. A more restricted form of CE transmission, 1-bit quantized transmission, further simplifies the RF chain and reduces the DAC power consumption. In this paper, for CE transmission and 1-bit quantized transmission at the BS antennas, we analyze downlink transmission for low complexity linear precoding. We observe that for small numbers of users in the downlink, correlation among the quantization error components across BS antennas is high, deteriorating the performance rapidly as number of users become smaller. To improve performance for smaller numbers of downlink users, we propose the addition of correlated Gaussian dither to the precoded signal before quantization and subsequent transmission. We observe that the receive SQINR peaks for finite non-trivial dither power. For given value of transmit power, number of BS antennas and number of users, SQINR is maximized analytically by the transmitter, to find the optimum dither power, using the Bussgang decomposition. We observe that with the implementation of optimized dithering, the error floor in the coded BER at high transmit power, for CE and 1-bit quantized transmissions, is pushed down significantly. We also observe that optimum dither power increases monotonically with transmit power, with rate of increase decreasing with increasing transmit power. Further, the optimum dither power strictly increases with number of BS antennas.

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“…The use of 5G spectrally efficient waveforms featuring high peak-to-average power ratio (PAPR) and occupying wider bandwidths in multiple antenna transmitters [1] only aggravates such compromise. When considering wide bandwidth signals, carrier aggregation or multi-band configurations [2] in high efficient transmitter architectures, such as Doherty PAs, envelope tracking PAs or outphasing transmitters, the number of parameters required in the DPD model to compensate for both static nonlinearities and dynamic memory effects can be unacceptably high. This has a negative impact in the DPD model extraction/adaptation process, because it increases the computational complexity which may provoke over-fitting and uncertainty in the DPD estimation stages [3].…”

Section: Introductionmentioning

confidence: 99%

Spectral Weighting Orthogonal Matching Pursuit Algorithm for Enhanced Out-of-Band Digital Predistortion Linearization

Gilabert

López‐Bueno

Montoro

2019

IEEE Trans. Circuits Syst. II

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This paper presents a new variant of the orthogonal matching pursuit (OMP) algorithm for reducing the computational complexity of the digital predistortion (DPD) behavioral model in the forward path. The proposed spectral weighting OMP (SW-OMP) algorithm focuses on selecting the most relevant basis functions to compensate for the out-of-band residual distortion which may eventually be masked by the dominant in-band residual error. This basis selection is carried out in an off-line process that does not affect the computational complexity of the real-time closed-loop DPD but, on the contrary, reduces its complexity while enhancing the robustness. Experimental results show that by selecting the DPD coefficients with the SW-OMP, the inherent ACLR and NMSE degradation suffered when reducing the number of coefficients is mitigated under strong nonlinear operation, when compared to using the basis functions selected by the classical OMP algorithm.

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Harmonically Related Concurrent Tri-Band Behavioral Modeling and Digital Predistortion

Cited by 12 publications

References 16 publications

Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Linear CE and 1-bit Quantized Precoding With Optimized Dithering

Spectral Weighting Orthogonal Matching Pursuit Algorithm for Enhanced Out-of-Band Digital Predistortion Linearization

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