An Experimental Study on Multibeam Digital Predistorter with Intercarrier Interference Suppression

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.