Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Modified Polar Sigma-Delta Transmitter for Multiradio Applications | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2010 Article ID 979120 9 pages doi 2010 979120 Research Article Modified Polar Sigma-Delta Transmitter for Multiradio Applications Martha Liliana Suarez Penaloza 1 Vaclav Valenta 1 2 Genevieve Baudoin 1 Martine Villegas 1 and Roman Marăálek2 1 Universite Paris-Est ESYCOM ESIEE Paris 93160 Noisy-le-Grand France 2 Department of Radio Electronics Brno University of Technology 61200 Brno Czech Republic Correspondence should be addressed to Vaclav Valenta Received 7 June 2010 Revised 20 August 2010 Accepted 16 September 2010 Academic Editor George Tombras Copyright 2010 Martha Liliana Suarez Penaloza et al. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Radio transmitters capable of transforming variable envelope signals into constant envelope signals can be associated with high-efficiency switched mode power amplifiers. One ofthe techniques providing this conversion is Polar Sigma-Delta SA architecture. This approach provides efficient solution for high-dynamic signals and moreover it offers flexibility in a multiradio environment. The overall concept of the polar SA transmitter is presented here along with novel modifications and improvements. Namely when recombining the envelope and the phase signals it is suggested to replace the analog mixing by a digital mixing. The impact of a frequency synthesizer with a switched loop bandwidth and its imperfections on the overall polar SA architecture is investigated as well. The Mobile WiMAX standard has been chosen for validation due to very high requirements in terms of power dynamics and the variable channel bandwidth. Simulation results are presented in this paper and advantages and drawbacks of this novel approach are pointed here as .
