Design Technologies for Silicon-Based High-Efficiency RF Power Amplifiers:A Brief Overview

This paper presents a brief overview of several promising design technologies for high efficiency silicon-based radio frequency （RF） power amplifiers （PAs） as well as the use of these technologies in mobile broadband wireless communications. Four important aspects of PA design are addressed in this paper. First, we look at class-E PA design equations and provide an example of a class-E PA that achieves efficiency of 65-70% at 2.4 GHz. Then, we discuss state-of-the-art envelope tracking （ET） design for monolithic wideband RF mobile transmitter applications. A brief overview of Doherty PA design for the next-generation wireless handset applications is then given. Towards the end of the paper, we discuss an inherently broadband and highly efficient class-J PA design targeting future multi-band multi-standard wireless communication protocols.

Air pollution health burden embodied in China's supply chains

Product trade plays an increasing role in relocating production and the associated air pollution impact among sectors and regions.While a comprehensive depiction of atmospheric pollution redistribution through trade chains is missing,which may hinder targeted clean air cooperation among sectors and regions.Here,we combined five state-of-the-art models from physics,economy,and epidemiology to track the anthropogenic fine particle matters(PM_(2.5))related premature mortality along the supply chains within China in 2017.Our results highlight the key sectors that affect PM_(2.5)-related mortality from both production and consumption perspectives.The consumption-based effects from food,light industry,equipment,construction,and services sectors,caused 2e22 times higher deaths than those from a production perspective and totally contributed 63%of the national total.From a cross-boundary perspective,25.7%of China's PM_(2.5)-related deaths were caused by interprovincial trade,with the largest transfer occurring from the central and northern regions to well-developed east coast provinces.Capital investment dominated the cross-boundary effect(56%of the total)by involving substantial equipment and construction products,which greatly rely on product exports from regions with specific resources.This supply chain-based analysis provides a comprehensive quantification and may inform more effective joint-control efforts among associated regions and sectors from a health risk perspective.