包络跟踪功率放大器(Envelope Tracking Power Amplifier,ETPA)具有高效率和高线性度等优势,已成为目前现代移动通信技术的研究热点。包络跟踪电源调制器是ETPA的关键模块之一,因为它能够提升PA在功率回退时的效率,从而提升整个通信系...包络跟踪功率放大器(Envelope Tracking Power Amplifier,ETPA)具有高效率和高线性度等优势,已成为目前现代移动通信技术的研究热点。包络跟踪电源调制器是ETPA的关键模块之一,因为它能够提升PA在功率回退时的效率,从而提升整个通信系统的效率。首先介绍包络跟踪技术(Envelope Tracking,ET)和包络消除与恢复技术(Envelope Elimination and Restoration,EER),对比两者的性能差异,重点介绍ET技术,分析其最常用的混合型包络放大器(Hybrid Envelope Tracking Amplifier,HETA)电路结构以及电路的关键的设计参数,然后对比和总结目前已有的HETA技术优化方案,接着列举ET技术在移动通信中的实际应用,最后考虑ET技术将要面临的挑战。展开更多
Background Assessment of the optic disc and retinal nerve fiber layer （RNFL） is essential for the diagnosis and monitoring of glaucoma.Knowledge of normal optic disc topography provides a benchmark for evaluating gl...Background Assessment of the optic disc and retinal nerve fiber layer （RNFL） is essential for the diagnosis and monitoring of glaucoma.Knowledge of normal optic disc topography provides a benchmark for evaluating glaucomatous pathologic changes,especially in its early stages.The purpose of this study was to evaluate the characteristics and correlation factors of the optic disc parameters using the Heidelberg Retina Tomograph Ⅱ （HRT Ⅱ） in a large sample of normal eyes of adult Chinese subjects.Methods Disc data were obtained from 6 830 subjects aged ＞30 years from the Handan Eye Study.All participants underwent comprehensive eye examinations and physical examinations.The associations of gender,age,body mass index,blood pressure,waist-to-hip ratio; refractive error,intraocular pressure,axial length,and disc area were assessed using simple and multiple regression analysis.The correlation between HRT Ⅱ parameters was evaluated.Results Of the 7 557 eligible subjects,6 830 took part in the study （90.4％ response rate） and 2 633 normal eyes with good-quality HRT Ⅱ images were selected.The mean disc area was 2.28 mm2 （standard deviation （SD） 0.43） and mean neural rim area was 1.80 mm2 （SD 0.29）.In multiple regression analysis,optic disc area significantly correlated with age,gender,and axial length （P ＜0.001）.All optic disc parameters showed a significant correlation with disc area （0.054 ＜r ＜0.736,P ＜0.01）.The association between mean RNFL thickness and rim area is statistically significant but not strong （regression linear equation：rim area =1.42 × mean RNFL thickness ＋ 1.32 mm2,P ＜0.001; R2=0.070）.The global RNFL cross-sectional area was significantly associated with global rim area （regression linear equation：rim area =1.14× RNFL cross-sectional area ＋ 0.44 mm2,P ＜0.001; R2 =0.271）.Conclusions The optic disc area in rural Chinese population is larger than reported in white and Japanese populations,similar to that of Indian population and urban Chinese population.Most optic disc measurements were moderately or weakly affected by disc area.In addition to the RNFL,there may be other factors affecting the rim area.The relationship between optic disc and axial length may suggest a link between larger disc area,thinning of the lamina cribrosa,and increased glaucoma susceptibility in myopic eyes.展开更多
文摘Background Assessment of the optic disc and retinal nerve fiber layer （RNFL） is essential for the diagnosis and monitoring of glaucoma.Knowledge of normal optic disc topography provides a benchmark for evaluating glaucomatous pathologic changes,especially in its early stages.The purpose of this study was to evaluate the characteristics and correlation factors of the optic disc parameters using the Heidelberg Retina Tomograph Ⅱ （HRT Ⅱ） in a large sample of normal eyes of adult Chinese subjects.Methods Disc data were obtained from 6 830 subjects aged ＞30 years from the Handan Eye Study.All participants underwent comprehensive eye examinations and physical examinations.The associations of gender,age,body mass index,blood pressure,waist-to-hip ratio; refractive error,intraocular pressure,axial length,and disc area were assessed using simple and multiple regression analysis.The correlation between HRT Ⅱ parameters was evaluated.Results Of the 7 557 eligible subjects,6 830 took part in the study （90.4％ response rate） and 2 633 normal eyes with good-quality HRT Ⅱ images were selected.The mean disc area was 2.28 mm2 （standard deviation （SD） 0.43） and mean neural rim area was 1.80 mm2 （SD 0.29）.In multiple regression analysis,optic disc area significantly correlated with age,gender,and axial length （P ＜0.001）.All optic disc parameters showed a significant correlation with disc area （0.054 ＜r ＜0.736,P ＜0.01）.The association between mean RNFL thickness and rim area is statistically significant but not strong （regression linear equation：rim area =1.42 × mean RNFL thickness ＋ 1.32 mm2,P ＜0.001; R2=0.070）.The global RNFL cross-sectional area was significantly associated with global rim area （regression linear equation：rim area =1.14× RNFL cross-sectional area ＋ 0.44 mm2,P ＜0.001; R2 =0.271）.Conclusions The optic disc area in rural Chinese population is larger than reported in white and Japanese populations,similar to that of Indian population and urban Chinese population.Most optic disc measurements were moderately or weakly affected by disc area.In addition to the RNFL,there may be other factors affecting the rim area.The relationship between optic disc and axial length may suggest a link between larger disc area,thinning of the lamina cribrosa,and increased glaucoma susceptibility in myopic eyes.
