单工无线呼叫系统分发射和接收两大部分。发射部分采用锁相环式频率合成器技术， MC145152和MC12022芯片组成锁相环，将载波频率精确锁定在35MHz，输出载波的稳定度达到4×10-5，准确度达到3×10-5，由变容二极管V149和集成压控振荡器芯片MC1648实现对载波的调频调制；末级功放选用三极管2SC1970，使其工作在丙类放大状态，提高了放大器的效率，输出功率达到设计要求。接收部分以超大规模AM/FM立体声收音集成芯片CXA1238S为主体，灵敏度、镜像抑制、信噪比等各项性能指标均达

电子爱好者们经常希望测试自己的音频设备如声卡、碟机、功放、音箱等的性能指标，却苦于没有价格高昂的专业测试设备而无从下手，设计制作时也无法进行必要的测试指导。有些CD碟提供了测试信号，如著名的“雨果发烧碟（一）”、“My Disk”等，《无线电》也曾推出音频测试CD。但CD信号的精度有限，而且没有操作系统的配合，测量、记录和分析都很不方便。-Electronic fans often want to test their audio devices such as sound cards, CD,

This book is about the world’s dominant 4G mobile telecommunication system, LTE. In writing the book, my aim has been to give the reader a concise, system level introduction to the technology that LTE uses. The book covers the whole of the system

Radio is the use of radio waves to carry information, such as sound, by systematically modulating some property of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width.[n 1] When radio wave