Average Linearization of Phased Array Transmitters Under Random Amplitude and Phase Variations

Abstract

We study the impact of amplitude and phase differences between the parallel power amplifier (PA) branches in a phased array and their impact on the performance of the digital predistortion (DPD). The DPD coefficients are estimated from the array response in the far-field. The DPD coefficients need to be updated for changes in the nonlinear behavior of the PAs due to amplitude and phase variations. We present a training mechanism which makes the DPD robust to branch specific amplitude and phase weights and can tolerate these variations without the need of adapting to individual changes in the nonlinear behavior of the PA branches. The DPD is trained for a set of random amplitude and phase weights following normal distribution and the resultant mean DPD coefficients are used for predistortion. The simulation results show that the mean DPD can achieve the same average linearity performance as the continuously trained reference DPD for 32 elements uniform array.

A Cross-Mode Universal Digital Pre-Distortion Technology for Low-Sidelobe Active Antenna Arrays in 5G and Satellite Communications

“…Additionally, nowadays, active arrays tend to be more integrated and compact [9], making one-to-one pre-distortion of PAs infeasible. [5], (b) average DPD [10], and (c) the proposed cross-mode universal digital pre-distortion (CMUDPD).…”

“…To reduce the feedback-path quantity, the average DPD system with one feedback path was proposed to linearize the active array, as shown in Figure 1b [10]. Only one ADC component remains in the average DPD system, which reduce sits ADC power consumption compared with Figure 1a.…”

“…In Table 1, the proposed CMUDPD is compared with several representative state-ofthe-art DPD methods. Several DPD technologies studied in [5,10,12,24] consider uniform arrays. Although parametric variations in P in are involved in [10,12], their amplitudes are relatively small compared to those in low-sidelobe arrays.…”

“…Several DPD technologies studied in [5,10,12,24] consider uniform arrays. Although parametric variations in P in are involved in [10,12], their amplitudes are relatively small compared to those in low-sidelobe arrays. In [10], the resultant average DPD coefficients were obtained by training a set of random amplitude and phase data following the normal distribution.…”

“…Although parametric variations in P in are involved in [10,12], their amplitudes are relatively small compared to those in low-sidelobe arrays. In [10], the resultant average DPD coefficients were obtained by training a set of random amplitude and phase data following the normal distribution. For the array DPD method studied in [20] for lowsidelobe arrays, it is mandatory to synthesize all PAs' outputs by two steps, i.e., linearizing the higher driven PAs, followed by cancelling compression by the lower driven PAs, to form a single feedback signal.…”