A mm-Wave 3-Way Linear Doherty Radiator with Multi Antenna Coupling and On-Antenna Current-Scaling Series Combiner for Deep Power Back-Off Efficiency Enhancement

Abstract

There is a growing interest in exploring antenna-electronic co-designs that leverage antennas (including their low-loss metal structures, design versatility, multi-feed driving capabilities) as a new design paradigm to radically advance mm-wave front-end performance. In particular, enhancing the peak/back-off transmitting efficiency is essential for future mm-wave wireless communications, such as 5G, which will predominantly use complex modulations with large peak-to-average-power ratio (PAPR) and extra power back-off (PBO) for linearity and reliability. Consequently, mm-wave transmitters often operate at deep PBO (9 to 12dB) with poor average efficiency. Although mm-wave Doherty/Outphasing PAs have been widely explored, there is limited success in high-order active load modulation for deep-PBO efficiency enhancement with high PA linearity, mainly due to the complexity and prohibitive loss of on-chip passive networks. On the other hand, most existing antenna-electronic radiators only follow basic Class-AB/B efficiency roll-off with rapidly degraded PBO efficiency [1,2]. Some use active load modulation on a single multi-feed antenna, whose simple structures support only 6dB PBO efficiency enhancement and limited PBO extension [3].