一种低复杂度的数字鉴频器

A Low-Complexity Digital Frequency Detector

在数字通信系统中,发送端和接收端的载波往往存在一定的频差。当频差较大时,接收端用于载波恢复的锁相环路无法锁定,导致系统不能正常工作。此时可以借助锁频环路来扩大频率捕捉范围,而锁频环路的核心部件则是鉴频器。本文提出了一种低复杂度的数字鉴频器,它能够从解调数据星座点的旋转中提取频差信息,可用于QAM和PSK调制方式的频率捕捉。结果表明,这种鉴频器不但具有较大的频率捕捉范围,而且非常易于实现。

In a digital communication system, usually there exist carrier frequency offset between the sender and the receiver. If the frequency offset is large enough, the traditional PLL cannot be locked. Such situation would lead to the system corruption. To expand the scope of frequency capturing, an additional FLL is used. Essentially it is a frequency detector. In this paper, a low-complexity digital frequency detector is proposed. Information concerning the frequency offset is extracted from the rotation of the constellation points of the demodulated data and could be applied to capturing the frequency of QAM or PSK modulated signals. As the result shows, using the proposed detector, not only the range of frequency being captured can be widen, but it is easy to be implemented.