A 40-GHz Load Modulated Balanced Power Amplifier Using Unequal Power Splitter and Phase Compensation Network in 45-nm SOI CMOS

Abstract

In this work, a ten-way power-combined power amplifier is designed using a load modulated balanced amplifier (LMBA)-based architecture. To provide the required magnitude and phase controls between the main and control-signal paths of the LMBA, an unequal power splitter and a phase compensation network are proposed. As proof of concept, the designed power amplifier is implemented in a 45-nm SOI CMOS process. At 40 GHz, it delivers a 25.1 dBm Psat with a peak power-added efficiency (PAE) of 27.9%. At 6-dB power back-off level, it achieves 1.39 times drain efficiency enhancement over an ideal Class-B power amplifier. Using a 200-MHz single-carrier 64-QAM signal, the designed amplifier delivers an average output power of 16.5 dBm with a PAE of 13.1% at an EVMrms of -23.9 dB and ACPR of -25.3 dBc. The die size, including all testing pads, is only 1.92 mm 2 . To the best of the authors' knowledge, compared with the other recently published silicon-based LMBAs, this design achieves the highest Psat.Index Terms -Doherty amplifier, load-modulated balanced amplifier (LMBA), millimeter-wave (mm-wave) power amplifier, power back-off capability, radio-frequency integrated circuits (RFIC), silicon-on-insulator (SOI).

A 39 GHz Doherty-Like Power Amplifier With 22dBm Output Power and 21% Power-Added Efficiency at 6dB Power Back-Off

“…Moreover, from the viewpoint of architectural comparison, both linear and Doherty like designs are included in the table. The concepts of LMBAs have been discussed in several literature [21]- [23], but only a few works related to on-chip implementation [18]- [20]. Compared with the abovementioned literature as well as the other works published, the presented work achieves the highest efficiency enhancement ratio with excellent power-added efficiency at both saturated and power back-off levels (6 dB).…”

“…Multiple options can be used to apply a 90° delay line at 39 GHz. In contrast to other structures, the transmission-like structure is quite long [18]- [20]. Therefore, a phase compensation network based on the lumped-element structure is used in this design [32]- [35].…”

“…However, it is still unclear if there is any alternative design solution for the magnitude and phase compensation networks. Moreover, in our recently published work in [20], although a relatively high output power is achieved, the efficiency enhancement at 6 dB PBO level is still limited.…”

“…Recently, a novel concept called load-modulated balanced amplifier (LMBA) has been proposed and feasibility studies of introducing this for CMOS based power amplifier design have been carried out in [18]- [20]. The simplified conceptual schematic of the LMBA principle is shown in Fig.…”

“…However, based on our reviews of recent relevant literature in the past few years, it can be found that most existing designs are implemented on printed-circuit-board (PCB) technology with discrete transistors. The implementation of this ideas in silicon based technologies, such as SiGe, SOI, and CMOS, has not been extensively verified [18]- [20]. Therefore, the research on silicon based LMBA designs can be considered today in its infancy and, hence, it still faces some major design challenges.…”