TY - JOUR
T1 - Multi-port Active Load Pulling for mm-Wave 5G Power Amplifiers
T2 - Bandwidth, Back-Off Efficiency, and VSWR Tolerance
AU - Chappidi, Chandrakanth Reddy
AU - Sharma, Tushar
AU - Sengupta, Kaushik
N1 - Funding Information:
Manuscript received August 10, 2019; revised November 15, 2019; accepted December 30, 2019. Date of publication April 10, 2020; date of current version July 1, 2020. This work was supported by the SRC Global Research Collaboration (GRC), in part by the Texas Analog Center of Excellence (TxAce), Office of Naval Research, Defense Advanced Research Projects Agency (DARPA), and in part by the Qualcomm Innovation Funding (QinF). (Corresponding author: Tushar Sharma.) The authors are with the Department of Electrical Engineering, Princeton University, Princeton, NJ 08544 USA (e-mail: sharma.tushar17@ieee.org; kaushiks@princeton.edu).
Publisher Copyright:
© 1963-2012 IEEE.
PY - 2020/7
Y1 - 2020/7
N2 - The opening of spectral bands in the millimeter-wave (mm-Wave) spectrum from 26 GHz and extending up to the E-band poses new challenges to the power amplifier (PA) design for spectrally agile radios. They are expected to operate with high energy efficiency at peak and back-off levels to process signals with high peak-to-average power ratio (10 dB), while being able to maintain their performance across a wide range of 5G bands. In addition, the PAs can experience strong load impedance mismatch conditions in a user equipment (UE) that pose additional challenges in handling strong voltage-standing-wave-ratio (VSWR) events. In this article, we present a systematic approach to exploit active load pulling in a multi-port network that synthesizes optimal impedance conditions for 1) broadband peak and back-off operation and 2) mitigating VSWR events at peak power. As proofs of concept, we present two PAs in 65-nm bulk CMOS process. The first chip demonstrates Psat between 16.3 and 19.3 dBm across 37-73 GHz, with an improvement in the output drain efficiency (ηout) of up to 3.2× 5.8× at 6-/9.6-dB power back-off (PBO) across the frequency range compared to class-A operation. The second chip achieves 26-42-GHz Psat-dB bandwidth with Psat> 19 dBm and PAEpeak> 20 % across all 28-40-GHz bands and with up to 3.35× and 4.84× enhancement in PAE at the PBO levels of 6 and 9.6 dB over class-A operation, respectively. The PA also demonstrates strong tolerance to VSWR events with only 2 dB degradation over a VSWR 4:1 load circle at a frequency of 33 GHz.
AB - The opening of spectral bands in the millimeter-wave (mm-Wave) spectrum from 26 GHz and extending up to the E-band poses new challenges to the power amplifier (PA) design for spectrally agile radios. They are expected to operate with high energy efficiency at peak and back-off levels to process signals with high peak-to-average power ratio (10 dB), while being able to maintain their performance across a wide range of 5G bands. In addition, the PAs can experience strong load impedance mismatch conditions in a user equipment (UE) that pose additional challenges in handling strong voltage-standing-wave-ratio (VSWR) events. In this article, we present a systematic approach to exploit active load pulling in a multi-port network that synthesizes optimal impedance conditions for 1) broadband peak and back-off operation and 2) mitigating VSWR events at peak power. As proofs of concept, we present two PAs in 65-nm bulk CMOS process. The first chip demonstrates Psat between 16.3 and 19.3 dBm across 37-73 GHz, with an improvement in the output drain efficiency (ηout) of up to 3.2× 5.8× at 6-/9.6-dB power back-off (PBO) across the frequency range compared to class-A operation. The second chip achieves 26-42-GHz Psat-dB bandwidth with Psat> 19 dBm and PAEpeak> 20 % across all 28-40-GHz bands and with up to 3.35× and 4.84× enhancement in PAE at the PBO levels of 6 and 9.6 dB over class-A operation, respectively. The PA also demonstrates strong tolerance to VSWR events with only 2 dB degradation over a VSWR 4:1 load circle at a frequency of 33 GHz.
KW - 5G
KW - Back-off
KW - DAC
KW - broadband
KW - load impedance mismatch
KW - load-pull
KW - millimeter wave (mm-Wave)
KW - power amplifier (PA)
KW - power combining
KW - voltage-standing-wave-ratio (VSWR)
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U2 - 10.1109/TMTT.2020.2977342
DO - 10.1109/TMTT.2020.2977342
M3 - Article
AN - SCOPUS:85087795403
SN - 0018-9480
VL - 68
SP - 2998
EP - 3016
JO - IEEE Transactions on Microwave Theory and Techniques
JF - IEEE Transactions on Microwave Theory and Techniques
IS - 7
M1 - 9063676
ER -