A 28-GHz Flip-Chip Packaged Chireix Transmitter With On-Antenna Outphasing Active

Abstract

This paper presents a packaged 28-GHz Chireix outphasing transmitter (TX) for power amplifier (PA) efficiency enhancement at both peak and back-off output power (PBO). The main objective is to investigate the possibility of employing a multi-feed antenna as a multi-port passive network to perform outphasing active load modulation. As a proof of concept, an outphasing TX architecture is proposed by leveraging a dual-feed loop antenna (DLA) to achieve high efficiency trans- mission of wideband complex modulated signals. Theoretical analysis and simulation results prove that the proposed DLA is electrically equivalent to an ideal differential series non-isolating power combiner, enabling superior on-antenna outphasing oper- ation. Multi-functional signal processing is therefore achieved in a single loop-antenna footprint, including high-efficiency on-antenna power combining, outphasing active load modulation, and millimeter-wave (mm-Wave) signal radiation. Moreover, unlike conventional spatial vectorial combining techniques (e.g., spatial IQ or spatial outphasing), the antenna-level signal process- ing preserves the wide antenna unit field of view (FoV) and is particularly suitable for array or multiple-input-multiple-output (MIMO) applications. The proposed Chireix TX contains two phase-shifted sub-TXs simultaneously driving a DLA on package. The measurements demonstrate a 53%/43% PA drain/power- added efficiency (DE/PAE) at 17.1-dBm saturated output power (P sat) and 36%/23% DE/PAE