Sponsor: Coastal Los Angeles Chapter, MTT17
Speaker: Paul Draxler from MaXentric Technologies will present a talk on Digital Predistortion

Meeting Date: 12 Apr 2023
Time: 06:00 PM to 08:00 PM
Cost:
Location: Torrance, California
Reservations: IEEE
Summary:
This talk will open with DPD techniques for Class AB power amplifiers, then we will migrate to traditional envelope tracking PAs, where the supply is modulated with the RF envelope such that the PA is operating rail-to-rail the majority of the time. DPD for narrow band ETPA’s is very similar to that used for Class AB PAs in that there is a one-to-one mapping of the instantaneous output power and the supply voltage. Efficient Sparse Signal Processing techniques are introduced, followed by an efficient, model for wideband ETPA operation for carrier aggregated signals with up to 450 MHz of carrier separation and high peak to average ratio. This algorithm has been implemented for open loop and a batch mode closed loop operation. This model and these techniques reduce the number of inverse model terms significantly, using 40 terms of >700, while achieving reduced spectral emissions, improved computational efficiency, linearity and power efficiency. These improvements are achieved by calculating the covariance matrix within the Doubly Orthogonal Matching Pursuit (DOMP) algorithm to assist with parametric estimation through Reduced Computation-DOMP (RC-DOMP) to replace the Moore-Penrose inverse. With all these techniques, we can perform parameter estimation updates within 1 second on a Xilinx ZCU208 RFSOC achieving specification compliant performance, enabling future efficient real time closed loop operation. Measurements of a 4 CA signal with 500MHz signal bandwidth, around 3.7 GHz is presented, with peak to average ratio of 6dB after crest factor reduction, Po>38.9dBm, EMV <4%, and <-35dBc spectral regrowth with DPD.

Bio: Dr. Paul Draxler received his BSEE and MSEE at the University of Wisconsin – Madison and his PhD at UCSD. He is currently working with MaXentric Technologies in LaJolla leading the DSP team on a number of wideband envelope tracking PA programs. He has over 15 years of power amplifier design experience including wideband PAs (>3:1 bandwidths), handset and basestation envelope tracking PAs, Doherty, and sub 6GHz, 5G-NR design strategies using GaAs, CMOS, and GaN device technology. To achieve better transmitter performance he performed electromagnetic simulations and folded in digital signal processing (improving Tx and Rx chain performance) for digital predistortion and receiver interference cancellation. He has had a second career (>10 years) focused on computer aided engineering (EEsof and HP-EEsof) and RF Tools (Qualcomm). At EEsof he addressed nonlinear modeling, custom MMIC environments, and architected electromagnetic simulation products At Qualcomm, he helped engineers across the company with RF Tools and System tools (Mathworks) to debug project issues via simulation. Paul was on the organization committee of the UCSD PA Symposium from 2004-2014 and IMS TPRC from 1998-present. Paul has published over 50 technical papers and has over 15 patents.