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The necessity of the rapid evolution of wireless communications, with continuously increasing demands for higher data rates and capacity Zheng (Big datadriven optimization for mobile networks toward 5g 30:44–51, 2016), is constantly augmenting the complexity of radio frequency (RF) transceiver architecture. A significant component in the configuration of such complex radio transceivers is the power amplifier(PA). Multiple distributed PAs are now common in proposed RF architectures. PAs exhibit non linear behaviour, causing signal distortion in transmission. Behavioural models offer a concise representation of a PAs characteristic performance which is extremely useful in simulating performance of multiple nonlinear power amplifiers. A considerable drawback with using the Recursive Least Squares (RLS) technique is that the instability of the coefficients during the training of the model. This manuscript provides a computationally efficient technique to detect the onset of instability during adaptive RLS training and subsequently to inform the decision to cease training of dynamic memory polynomial based behavioural models, to avoid the onset of instability. The proposed technique does not require modification of the RLS algorithm, merely an observation of the pre-exsisting autocorrelation function based update. This technique is experimentally validated using four different signal modulation schemes, LTE OFDM, 5G-NR, DVBS2X and WCDMA. [ABSTRACT FROM AUTHOR]

This paper proposes a new crest factor reduction scheme to reduce instantaneous-to-average power ratio (IAR) resulting decent peak reduction, and adjacent channel leakage ratio (ACLR) reduction, though the error vector magnitude (EVM) is significantly enhanced. In the conventional peak cancellation (CPC) technique, peak regrowth occurs as a result of finite impulse response (FIR) filter windows overlapping. The peak regrowth problem in CPC technique can be compensated, though this will lead to increased computational complexity and degradation in EVM. The proposed algorithm allocates spacing to contiguous peaks to avoid FIR filter windows overlapping. Two types of overlapping are discussed, incremental and decremental. The optimum spacing can be determined from the FIR filter impulse response characteristic. Simulations are carried out with different intra-band non-contiguous carrier aggregated OFDM signals. The results of simulations show between 3 and 10% improvement in EVM performance while maintaining equivalent IAR and ACLR performance. Applying the proposed optimum spacing peak cancellation scheme compared to the conventional peak cancellation technique. [ABSTRACT FROM AUTHOR]

Modern wireless network operators are consistently looking for improvements in the wireless access infrastructure that minimize size, weight, and power. Therefore, compact multiband RF and wideband RF solutions offer an attractive role in forthcoming fifth generation networks. This paper presents a novel compact wideband RF transmitter architecture that is based upon an undersampled digital predistortion (DPD) methodology. The proposed architecture minimizes the required number of RF/analog components in the system by using RF-DAC-based direct RF sampling at the forward transmitter data path and one undersampled analog-to-digital conversion (ADC) with certain bandpass filters at the DPD sampling receiver path. Extensive experimental results validate that the DPD-enabled RF transmitter bandwidth can be significantly increased using the proposed multirate track-and-hold amplifiers architecture. Experimental tests achieved multiple GHz DPD bandwidths with satisfactory linearization performance via very compact sampling receiver that has one undersampled ADC. Particularly, we evaluated three application scenarios: 1) three-band carrier aggregated LTE signals (each one occupying 20-MHz instantaneous bandwidth), the linearization performance achieved 50-dBc adjacent channel power ratio (ACPR) with more than 1-GHz bandwidth using ADC running at 76.8 and 61.44 MSPS; 2) single-band LTE signal with continuous 100-MHz instantaneous bandwidth, the linearization performance achieved −48-dBc ACPR using 61.44-MSPS ADC; and 3) single-band LTE signal with continuous 20-MHz bandwidth at 4 GHz, the linearization performance achieved −54-dBc ACPR using 61.44-MSPS ADC. [ABSTRACT FROM PUBLISHER]

In this paper, a nonlinear autoregressive with exogenous inputs (NARX) digital pre-distortion scheme to linearize power amplifiers is proposed. The proposed NARX digital pre-distortion gives better accuracy and spectral leakage suppression compared with other commonly used Volterra-based techniques. The stability criterion of the NARX digital pre-distortion is derived from the frequency domain analysis. Simulation is carried out with a 20 MHz single carrier long-term evolution signal and two-carrier long-term evolution signal and instantaneous to average ratio of 6.2 dB at 0.01% complementary cumulative distribution function (CCDF). The results of simulation analysis show a slight improvement in adjacent channel leakage ratio performance with 30% reduction in the number of floating point operations compared with conventional pre-distortion techniques. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A low-complexity peak-to-average power ratio (PAPR) reduction scheme in an orthogonal frequency division multiplexing system is proposed. The proposed scheme utilizes a new phase sequence based on a gray code structure and a similarity measurement block. Due to the ordered phase sequences, a noteworthy reduction capacity is obtained in terms of the number of multiplication and addition operations and the side information. Simulations are performed with quadrature phase shift keying modulation and a Saleh model power amplifier. The proposed scheme offers a significant PAPR reduction and bit error rate performance at approximately the same total complexity compared to the conventional partial transmit sequence and the enhanced partial transmit sequence (EPTS) techniques. The results show that at the same PAPR reduction, this scheme provides a complexity reduction of at least 42.3 % over that of the EPTS technique. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of existing and novel behavioral models targeted at the outphasing power amplifier (PA) architecture. A comprehensive comparison of ten modeling strategies is presented in the results. Novel techniques for outphasing PAs, such as vector switched and dual path time series, are also presented for the first time. Investigation of such techniques was driven by the analysis of outphasing operation at minimum output powers, demonstrating the generation of frequency-dependent amplitude and phase deviations, which can be difficult to characterize. The increased robustness was achieved at the cost of additional complexity; for practical implementation, time series coefficient reduction techniques were also evaluated. The results of all modeling approaches are experimentally validated for the wideband operation of an NXP 19-W GaN digital outphasing amplifier module. Considering computational complexity and accuracy for system-level modeling across all presented options, a subset of existing and new models is identified as best suited for modeling outphasing PAs. [ABSTRACT FROM PUBLISHER]