A Chain-Weaver Balanced Power Amplifier With an Embedded Impedance/Power Sensor

Abstract

This article introduces an N-way chain-weaver balanced power amplifier (PA) for millimeter-wave (mm-wave) phased-array transmitters (TXs). Taking advantage of the pro- posed combining network, an embedded impedance/power sensor is implemented, which can be utilized for output power regula- tion, built-in self-test, and load-based performance optimization. The proposed PA architecture offers linearity and gain robustness under the antenna’s frequency/time-dependent voltage standing wave ratio (VSWR). In the event of impedance mismatch, the proposed PA provides N different loads equally distributed on the VSWR circle. Consequently, the performance of the PAs is the average of N PAs with N different loads, which makes this structure VSWR resilient. As a proof of concept, an eight-way chain-weaver balanced PA (BPA) is realized in 40-nm bulk CMOS technology, and it delivers 25.19-dBm PSAT with 16.19% PAE. The proposed PA supports a 2-GHz 64-QAM OFDM signal with 16-dBm average power, achieving −25-dB error vector magnitude (EVM). The average EVM is better than −30.3 dB without digital pre-distortion (DPD) for an “800-MHz 256-QAM OFDM” signal while generating an average output power of 12.17 dBm. The performance of the PA is also evaluated under 1.5:1–3:1 VSWR conditions. The measured small-signal gain variation under VSWR 3:1 is ±0.7 dB. Moreover, assum- ing any frequency/time-dependent loading condition within the VSWR 3:1 circle, the proposed chain-weaver BPA achieves <2.8◦ ampli