Showing papers by "Hiroyoshi Ishikawa published in 2022"
01 Sep 2022
TL;DR: In this article , the authors presented the experimental verification of a digital predistorter with an intercarrier interference suppression ability for a multibeam array antenna transmitter, which can reduce power consumption by allowing the final power amplifiers (PAs) of the antenna transmitter to operate in a highly efficient nonlinear mode and by compensating for the nonlinear distortions of the PAs with a unified dedicated DPD per subarray.
Abstract: This paper presents the experimental verification of a digital predistorter (DPD) with an intercarrier interference suppression ability for a multibeam array antenna transmitter. The proposed DPD reduces power consumption by allowing the final power amplifiers (PAs) of the array antenna transmitter to operate in a highly efficient nonlinear mode and by compensating for the nonlinear distortions of the PAs with a unified dedicated DPD per subarray. In addition, it provides the required high quality of transmitting signals for a high throughput, such as realizing a 256-quadrature amplitude modulation (QAM) transmission instead of a 64-QAM transmission. However, error vector magnitude (EVM) degradation in the beam direction occurs due to imperfections of the analog circuits. Accordingly, this paper proposes a modified version of the proposed multibeam DPD to solve the abovementioned problem. Some experimental results obtained for two beams at 28.0 and 28.4 GHz demonstrate that the modified multibeam DPD can improve the EVM and achieve a value of less than 3%, which completely satisfies the 3GPP requirements for a 256-QAM transmission.
01 Sep 2022
TL;DR: In this paper , the authors proposed a band-oriented DPD architecture for fully connected antenna arrays (FC-HA) with a unified digital core for all power amplifiers (PAs) in the array, which can be linearized with a single, multi-core DPD.
Abstract: Fully connected hybrid antenna arrays (FC-HA) are attractive, low-complexity alternatives to the fully digital array architecture. However, the sub-array architecture performance is limited by reduced beamforming gain because of array partitioning. In this study, we provide a theoretical analysis of the connection between a wideband digital predistorter (DPD) and its equivalent for a fully connected antenna array (AA). Then, we propose new hardware-efficient band-oriented architecture by moving all AA-specific DPD calculations into the analog radio frequency site. To our knowledge, this is the first band-oriented DPD architecture for FC-HA. In the proposed DPD, the unified digital cores are common for all power amplifiers (PAs) in the array. This enables a set of PAs to be linearized with a single, multi-core DPD. The performances of the proposed band-oriented DPD were evaluated with the help of computer simulation. The simulation results demonstrate that both the in-band and the out-of-band intermodulation distortion for all PAs in the array can be successively suppressed with a single multi-core DPD regardless of the individual beam’s directions. Unlike current all-digital state-of-the-art solutions, the proposed band-oriented DPD has a significantly low digital hardware complexity because of the digital core unification, thus reducing its power consumption requirement.