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To reduce the demand for frequently adjusting phase shifts in the fifth-generation (5G) multiple-input multiple-output (MIMO) beamforming transmitters, in this article, a novel digital predistortion (DPD) technique is proposed, which employs multiple predistortion boxes to shape the pattern of nonlinear distortions in space in order to linearize multiple targets simultaneously. By using this approach, the linearization angle is widened and thus the communication quality can be kept when the user moves off the main beam direction. As a proof of concept, two DPD boxes, namely main and auxiliary boxes, are used to realize the 2-target linearization. A new model extraction method is also proposed with a dedicated over-the-air (OTA) feedback post-processing stage. Simulation and experiment are demonstrated on a 4-path beamforming transmitter. The results show that the proposed DPD method can effectively widen the linearization angle with reasonable additional complexity.

This paper presents a dual-band and wideband switchable Doherty power amplifier (DPA) with back-off efficiency reconfiguration. It can be operated in wideband mode and dual-band mode with higher back-off efficiency through switching the carrier and peaking amplifier roles directly. The phase relationship required for dual-mode operation is first given. Meanwhile, the efficiency reconfigurable feature is realized by utilizing the integrated compensating reactance (ICR) technology. To verify the proposed circuits, a back-off efficiency reconfigurable dual-mode Doherty power amplifier (DM-DPA) which can be operated in wideband mode from 3 GHz to 3.8 GHz and dual-band mode at 2.4 GHz and 4.4 GHz was designed and fabricated. The implemented efficiency reaches 35% and 40% for wideband mode and dual-band mode respectively at 6-dB back-off power. When excited by a 100-MHz long-term evolution-advanced modulated signal with 6.5-dB peak-to-average power ratio, the DM-DPA can achieve an average efficiency of more than 37.3% in both wideband and dual-band modes. To the best of authors’ knowledge, this is the first kind of operation mode switchable DPA with back-off efficiency reconfiguration.

This paper proposes a novel dual-input decomposed vector rotation model (DI-DVR) for multi-antenna transmitters by borrowing the concept of the decomposed vector rotation (DVR) into the dual-input model. Experimental results of a two-antenna transmitter show that the proposed model can obtain better normalized mean square error (NMSE) and adjacent channel power ratio (ACPR) compared with dual-input canonical piecewise-linear (DI-CPWL) function. In addition, the model requires fewer coefficients, providing a promising method for multi-antenna transmitters in 5G wireless systems.

This paper proposes a hybrid dual-input model (HDI) to linearize multi-antenna transmitters with antenna crosstalk. Proposed model reduces model complexity by decomposing the overall nonlinearity of the system into the PA part, the crosstalk part and modeling them separately. Based on the dual-input (DI) model, it selects some terms of DI model appropriately to model more accurately. The performance of proposed model is better than the DI model and can compare with the dual-input canonical piecewise-linear (DI-CPWL) model. Measurement results of a two-antenna transmitter show that the HDI model requires fewer coefficients than the dual-input model and DI-CPWL model.

In order to evaluate the pollution degree of the dust in Hangzhou City, the indoor dust samples of 19 offices, families and students' dormitories were collected from August to March in 2013 at Hangzhou for evaluating the pollution level of polybrominated diphenyl ethers (PBDEs), to analyze concentrations of 14 PBDEs congeners and congener distribution as well as the possible influencing factors, and to estimate the PBDEs exposure levels of adults and children through the dust intake. The results showed that the average ∑