基于中心频率检测的应答机载波捕获技术

针对基于理想型积分环路滤波器的二阶锁相环在无信号输入时,环路中心频率会随热噪声发生漂移的问题,研究了卫星星载测控应答机的载波捕获技术.为解决无信号输入下的环路中心频率漂移问题,在基于正交欠采样技术及全数字载波恢复环的接收机结构基础上,通过一级中心频率检测器控制环路.当检测到上行信号时闭合环路,避免了接收机中心频率在无信号输入时随热噪声发生漂移.给出了中心频率检测器的设计方法,分析了检测器漏检概率和误判概率之间的关系,并在此基础上给出了检测器的具体参数选择依据.

Transponder carrier acquisition technique based on center frequency detection

In the condition of second order phase locked loop using perfect integrator loop filter, the loop center frequency drifts in response to thermal noise when no useful input signal presents. To avoid the problem of loop center frequency drift, the satellite on board transponder‘s carrier acquisition technique was studied. On the basis of all digital carrier recovery loop receiver architecture using I/Q sub-sampling technique, a center frequency detector was used to control the loop. This architectural solution allows to close the carrier recovery loop only when the uplink carrier signal is detected by the center frequency detector, thus avoiding the drift of center frequency in response to thermal noise at the receiver input. The design method of center frequency detector was given, and the relationship between the probability of missed detection and the probability of false alarm was analyzed. The detector parameter selection was given based on the result of analysis．