Outspacing Planar Phased Arrays for Wireless Communications Infrastructure

Abstract

The future mobile-data demand, driven by 5G and 6G wireless communications, puts enormous pressure on the required infrastructure. Especially the need for higher data rates and corresponding higher operating frequencies calls for new transmitter concepts with improved power-added efficiencies. Outspacing, which combines outphasing, also known as linear amplification with nonlinear components (LINC), a phased array, and spatial power combining, could be a promising solution for these challenging performance requirements. In this paper, an extended array-level analysis is performed on the efficiency, mutual coupling, and transmit performance of outspacing arrays supported by new performance metrics, since conventional metrics show to be insufficient for analyzing the outspacing concept. The analysis of the concept is performed on two different planar outspacing configurations. The presented outspacing concept with an element spacing of ${\lambda }_0/2$ appears to be very suited for applications that require a limited scan range, typically smaller than ±20°. A prototype is realized and characterized for a limited-scan scenario at 2.4 GHz to limit technology-related risks in the verification of the outspacing concept. The outspacing planar array is tested using an over-the-air (OTA) test concept applied in an anechoic test facility. An error vector magnitude below 3%, when transmitting a QAM16 signal, is realized in the main beam of the antenna without the use of calibration. Furthermore, an analysis is done on additional efficiency improvements. The active reflection coefficient, which is strongly related to the mutual coupling between the array elements, appears to have very interesting properties for improving amplifier drain efficiency by active load modulation.