arctan

A study of Arctan and PLL digital RDC algorithm is carried on.

对反正切法和锁相环法这两种传统的数字RDC算法进行了研究。

LFM can be demodulated by the same arithmetic as for FM, and the demodulated signal takes on the shape of saw-tooth-wave and the period of LFM can be estimated while modulation slope can't because of arctan operation.

LFM信号可以用实现FM的方法来进行解调，解调信号呈锯齿状，可以从中获得调制信号周期，但是因算法中存在反正切运算，致使无法从中获得LFM的调制斜率。

In phase calculate of phase-shifting interference technique, Because of the periodicity of function arctan, all the phase values are ranged over-π to π. The transitions of phase values form wrapped wavefront.

在移相干涉技术的相位计算中，周期函数arctan的相位值分布在[-π，π]之间，相位值分布的跃变形成了被压包后的波面。

Because the CORDIC algorithm can change the arctan function and round of angle to addition and shift operation, the novel model presented in the paper can complete frequency offset estimation and correction in digital field in the same time.

由于CORDIC算法能把复杂的反正切函数求解和角度旋转操作转化为简单的移位和加法操作，文中所给出的同步模型可在数字域同时完成频率偏移估计和频率偏移校正。