随着现代科技的进步，各行业涌现出大量以电话授时为基础的多种应用。通过公共电话交换网（PSTN，Public Switched Telephone Network）进行电话授时服务已广泛应用于通信、电力、交通与金融等部门。在电话授时技术中，关键问题是解决时延的精确测量，现有电话授时技术的信道时延测量误差较大。本论文研究的目的是提高电话信道时延的测量精度，以满足电话授时的需求。 首先，论文阐述了公共电话网的一般组成结构，重点研究了电话交换网中交换设备的时延特性。论文对比了不同的时延测量方法，通过对时延测量方法的研究和分析，在现有电话信道时延测量的基础上，提出一种在PSTN信道中利用伪随机码（PN码）相关特性（即通过检测相关函数峰值）来测量信道时延的新方法。 其次，在分析PSTN信道时延测量原理的基础上提出了基于PN码的时延测量系统的总体方案，包括系统实现方案的设计、信号体制的设计和信号处理方案的设计；针对本系统时延测量信号的特性，设计出了基于匹配滤波器捕获方案、基于科斯塔斯环的载波跟踪环路和基于延迟锁定环的码跟踪环路。 最后，搭建了FPGA＋DSP的数字化电话信道时延测量系统实验平台，完成了时延测量系统整体功能验证，并且在PSTN端局内进行了实际测试。测试结果表明，该电话信道时延测量系统在端局内线路时延波动测值优于6.67 ，测量精度高于传统的电话信道时延测量方法，达到预期目标。

With the development of technology, diversified applications based on telephone time service emerge in national various professions. Time service based on Public Switched Telephone Network (PSTN) has already been widely used in telecommunications, electricity, transportation and financial sectors. The heart of the matter in telephone time service is how to measure the delay of transmission time exactly, since the measurement error of time delay in current telephone time service is a bit large. This thesis aims to improve the measurement accuracy of telephone channel delay in order to meet the needs of telephone time service. Firstly, this paper gives us a brief introduction about the general structure of public telephone network; this part focuses more on the characteristics of the time delay in switching equipments. Then the paper compares different methods of time delay measurement, and after researching and analyzing those methods, the author put forward a new way to measure time delay based on those existing telephone channel delay measurements, which is measuring the time delay by using correlation properties(through inspect related function peak) of pseudo-random (PN) code. Next, the paper design out the overall program about time delay measurement system based on PN code on the basis of the analysis of PSTN principle, including designations about signal system, signal management alternative and how to achieve the project. Then，according to those features in the measurement signal of time delay system, the author design out the capture scheme based on DMF, the carrier tracking loop based on the Costas loop and PN Code tracking loop based on DLL. Finally, the digitalized telephone channel time delay measurement experimental board based on FPGA and DSP is developed, and also finished the text of its function in the whole delay measurement system, for example, in PSTN. From the test result, we can conclude that in this area, the fluctuation is less than 6.67 microseconds with the new method in telephone channel, much more accurate than traditional method, which just meet the expected goal.