A linear high-efficiency millimeter-wave CMOS Doherty radiator leveraging on-antenna active load-modulation

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Nguyen, Huy Thong
Wang, Hua
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This thesis presents a Doherty Radiator architecture that explores multi-feed antennas to achieve an on-antenna Doherty load modulation network and demonstrate high-speed high-efficiency transmission of wideband modulated signals. On the passive circuits, we exploit the multi-feed antenna concept to realize compact and high-efficiency on-antenna active load modulation for close-to-ideal Doherty operation, on-antenna power combining, and mm-Wave signal radiation. Moreover, we analyze the far-field transmission of the proposed Doherty Radiator and demonstrate its wide Field-of-View (FoV). On the active circuits, we employ a GHz-bandwidth adaptive biasing at the Doherty Auxiliary power amplifier (PA) path to enhance the Main/Auxiliary Doherty cooperation and appropriate turning-on/-off of the Auxiliary path. A proof-of-concept Doherty Radiator implemented in a 45nm CMOS SOI process over 62-68GHz exhibits a consistent 1.45-1.53× PAE enhancement at 6dB PBO over an idealistic class-B PA with the same PAE at P1dB. The measured Continuous-Wave (CW) performance at 65GHz demonstrates 19.4/19.2dBm PSAT/P1dB and achieves 27.5%/20.1% PAE at peak/6dB PBO, respectively. For single-carrier 1Gsym/s 64-QAM modulation, the Doherty Radiator shows average output power of 14.2dBm with an average 20.2% PAE and -26.7dB EVM without digital predistortion. Consistent EVMs are observed over the entire antenna FoV, demonstrating spatially undistorted transmission and constant Doherty PBO efficiency enhancement.
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