Transmitter Linearization for mm-Wave Communications Systems
In the first line of work, we have focused on a mm-wave PA. A PA has high efficiency at high input power at the expense of linearity, whereas it operates linearly for lower input power levels while sacrificing efficiency. To attain both linearity and efficiency, predistortion is often used to compensate for the PA nonlinearity. Yet, the trade-offs related to predistortion complexities are not fully understood. To address this challenge, we have used our proposed framework for evaluation of predistorters using modulated test signals and implemented it using digital predistortion and a mm-wave PA. This set-up enabled us to investigate the trade-offs between linearity, efficiency and predistorter complexity in a systematic manner. We have shown that to achieve similar linearity levels for different PA classes, predistorters with different complexities are needed and provided guidelines on the achievable limits in term linearity for a given predistorter complexity for different PA classes.
In the second line of work, we have focused on linearization of an E-band transmitter using a baseband analog predistorter (APD) and under constraints given by a spectrum emission standard. In order to use the above proposed framework with these components, characterizations of the E-band transmitter and the APD are performed. In contrast to typical approaches in the literature, here joint mitigation of the PA and I/Q modulator impairments is used to model the transmitter. Using the developed models, optimal model parameters in terms of output power at the mask limit are determined. Using these as a starting point, we have iteratively optimized operating point of the APD and linearized the E-band transmitter. The experiments demonstrated that the analog predistorter can successfully increase the output power by 35% (1.3 dB) improvement while satisfying the spectrum emission mask.
mm-wave power amplier
Halil Volkan Hünerli
Chalmers, Mikroteknologi och nanovetenskap (MC2), Mikrovågselektronik
A Methodology for Analysis of mm-Wave Transmitter Linearization Trade-offs Under Spectrum Constraints
Konferensbidrag (offentliggjort, men ej förlagsutgivet)
Hünerli, H. V, Özen M, Gavell M, Fager C. E-band Transmitter Linearization Using Analog Predistortion
Smarta radiosändare för framtidens millimetervågssystem
Stiftelsen för Strategisk forskning (SSF), 2017-01-01 -- 2021-12-31.
Informations- och kommunikationsteknik
Annan elektroteknik och elektronik
Technical report MC2 - Department of Microtechnology and Nanoscience, Chalmers University of Technology: MC2-440
Chalmers tekniska högskola
Opponent: Rui Hao, Ericsson AB, Sweden