This paper proposes an integrable analog domain linearization architecture for power amplifiers (PAs) in multi-input multi-output (MIMO) systems, using a spectrum shaping circuit with nonlinear feedback. This architecture consists of a nonlinear distortion extracting loop and an N-order spectrum shaping circuit. The extracting loop aligns the PA input and output signals in amplitude with a 180-degree phase difference and then adds them together to extract the nonlinear distortion signal. The spectrum shaping circuit reshapes the spectrum of the extracted nonlinear distortion signal using N identical analog chains but with different group delays and attenuation parameters, and finally injects it back to the PA input to suppress the nonlinear distortion of the target frequency. Moreover, the delay in the remaining spectrum shaping channels has multiple relationships to the first channel, which can be easily integrated into the PA design stage with low complexity. Particularly, the center frequency of the nonlinearity suppression can be easily shifted by modifying the attenuation parameters in the N-order spectrum shaping circuit. We designed the proposed architecture using off-the-shelf discrete components and demonstrated its nonlinear distortion suppression performance at different target frequencies for the PA chip CMPA006002F.

Significant intermodulation signals (IMD) are generated by power amplifiers in fully connected hybrid beamforming (FCHBF) networks. These IMD signals form beams that radiate in different directions and some high power beams generated by IMD signals can deviate from the linear beam direction. These beams can result in reduced energy efficiency, and interference to other users’ communications. This paper proposes a novel auxiliary channel architecture for linearizing FC HBF transmitters. The architecture addresses the problem of high power non-main beams in FC HBF arrays by compensating for nonlinearity using auxiliary channels. Furthermore, the full angle method, which combines beam-level DPD and auxiliary channel architecture, is introduced to linearize the main beams and improve the model identification accuracy by removing uncorrelated terms. For a two beam 512 element FC HBF uniform linear array, the simulation results show that the proposed DPD technique achieves an improvement of over 6 dB in the normalized mean square error (NMSE) in up to 90% of the directions, and 10 dB of NMSE improvement in 60% of directions.

In this paper, an asynchronous layered space-time architecture is proposed to realize the spatial multiplexing over the Ricean multiple-input multiple-output (MIMO) channels. Based on reducing the correlation of spatial shaping pulses between the multiplexed streams, this approach can be used to solve the problem of detection in the ill-conditioned channel matrix. It is shown that at the receiver, the reduction of the correlation enables the requirement on the number of the receive antennas to be removed by the zero forcing (ZF) detector compared with the conventional synchronous layered space-time architecture. First, this paper presents how to exploit the correlation of spatial shaping pulses between the multiplexed streams. Then deriving the exact closed-form expression of error rate for the proposed scheme, this paper finds that the maximum possible diversity gain can be achieved based on the independent layered architecture by the ZF detector at the cost of limited multiplexing gain.

In this paper, an asynchronous layered space-time architecture is proposed to realize the spatial multiplexing over the Ricean multiple-input multiple-output (MIMO) channels. Based on reducing the correlation of spatial shaping pulses between the multiplexed streams, this approach can be used to solve the problem of detection in the ill-conditioned channel matrix. It is shown that at the receiver, the reduction of the correlation enables the requirement on the number of the receive antennas to be removed by the zero forcing (ZF) detector compared with the conventional synchronous layered space-time architecture. First, this paper presents how to exploit the correlation of spatial shaping pulses between the multiplexed streams. Then deriving the exact closed-form expression of error rate for the proposed scheme, this paper finds that the maximum possible diversity gain can be achieved based on the independent layered architecture by the ZF detector at the cost of limited multiplexing gain.