Optimal delta-sigma modulation based noise shaping for truly aliasing-free digital PWM

In recent years, carrier based pulse-width modulation (PWM) has been extensively used for reducing input signal resolution in all-digital transmitters, and is known to provide better coding efficiency than other power encoding methods, e.g. delta-sigma modulation (DSM). Unfortunately, high levels of in-band distortion introduced by fully digitally implemented PWM, limit its usage in transceivers realized for software defined radio. In this paper, we exploit time-domain characterization of digital PWM in-band distortion, and propose a multilevel power encoding scheme based on DSM-PWM hybrid architecture with carefully selected design parameters, which enable optimal in-band distortion cancellation with low hardware complexity. Experiments with an arbitrary waveform generator are used to demonstrate effectiveness of the proposed novel power encoding scheme, and are compared with a standard multilevel PWM. The novel power encoding scheme offers −20dB improvement in SNR, while maintaining similar coding efficiency of roughly 73%.

[1]  Wim Dehaene,et al.  Continuous-Time Digital Front-Ends for Multistandard Wireless Transmission , 2013 .

[2]  Shintaro Shinjo,et al.  Concurrent Multiband Digital Outphasing Transmitter Architecture Using Multidimensional Power Coding , 2015, IEEE Transactions on Microwave Theory and Techniques.

[3]  F M Ghannouchi,et al.  Power amplifier and transmitter architectures for software defined radio systems , 2010, IEEE Circuits and Systems Magazine.

[4]  Peter Singerl,et al.  Aliasing-Free Digital Pulse-Width Modulation for Burst-Mode RF Transmitters , 2013, IEEE Transactions on Circuits and Systems I: Regular Papers.

[5]  Baher Haroun,et al.  A PWM Based Fully Integrated Digital Transmitter/PA for WLAN and LTE Applications , 2015, IEEE Journal of Solid-State Circuits.

[6]  A. Amin,et al.  Exploring aliasing distortion effects on regularly-sampled PWM signals , 2008, 2008 3rd IEEE Conference on Industrial Electronics and Applications.

[7]  Harald Enzinger,et al.  Analytical description of multilevel carrier-based PWM of arbitrary bounded input signals , 2014, 2014 IEEE International Symposium on Circuits and Systems (ISCAS).

[8]  Riccardo Rovatti,et al.  Spectral aliasing effects of PWM signals with time-quantized switching instants , 2004, 2004 IEEE International Symposium on Circuits and Systems (IEEE Cat. No.04CH37512).

[9]  Peter M. Asbeck,et al.  An improved algorithm for waveform generation for digitally-driven switching-mode power amplifiers , 2016, 2016 IEEE Radio and Wireless Symposium (RWS).

[10]  F. Raab.  Class-D power amplifier with RF pulse-width modulation , 2010, 2010 IEEE MTT-S International Microwave Symposium.

[11]  Rui Ma.  A review of recent development on digital transmitters with integrated GaN switch-mode amplifiers , 2015, 2015 IEEE International Symposium on Radio-Frequency Integration Technology (RFIT).

[12]  David Seebacher,et al.  Reduction of Aliasing Effects of RF PWM Modulated Signals by Cross Point Estimation , 2014, IEEE Transactions on Circuits and Systems I: Regular Papers.