摘要
提出一种新的锁频环(FLL)鉴别器设计思路.在回波信号多普勒变化率较小的前提下,将正交解调后的差信号视为线性调频(LFM)信号,同时提取其起始频率和频率变化率作为FLL误差控制量,增强了FLL容忍高动态信号的能力.FFT鉴别算法和点积叉积鉴频算法在频率跟踪的不同阶段相互配合构成鉴别器,既获得了宽的鉴别范围又获得了高的鉴别精度.针对极低信噪比情况下偶发鉴别野值的问题,提出了行之有效且实现简单的野值识别与剔除算法.仿真结果表明上述思路可行,采用该鉴别器的FLL在信噪比低至-40 dB时能够容忍较高动态变化,且频率跟踪精度达0.2 Hz.
A novel design idea for frequency-locked-loop（FLL） discriminator is proposed,under the premise of changing rate of frequency-rate in returned signal is rather small,the signal after quadrature-demodulation can be regarded as a linear frequency-modulated（LFM） signal,by using estimations of its initial frequency and frequency rate as error control quantities of FLL,FLL＇s toleration ability to high dynamic signals is greatly enhanced.FFT discriminator and dot-product cross-product discriminator are exploited by FLL discriminator at different phase of frequency-tracking,thus wide discriminate range and high discriminate precision are acquired.An effective and simple abnormal value elimination method is presented especially for the abnormal discriminate value under extremely-low-SNR.Simulation results applying the discriminator to a FLL showed that FLL can tolerate rather high dynamics and tracking accuracy of frequency achieved 0.2Hz even under a SNR as low as-40dB,which verified the validity of above ideas.
出处
《北京理工大学学报》
EI
CAS
CSCD
北大核心
2009年第3期245-249,共5页
Transactions of Beijing Institute of Technology
关键词
鉴别器
载波频率跟踪
极低信噪比
高动态
discriminator
tracking of carrier frequency
extremely-low-SNR
high-dynamic
