非合作情况下长码直扩卫星信号载频检测和功率估计方法

摘要

Considering the characteristics of long-code Direct Sequence Spread Spectrum ( DSSS) satellite signal,such as low signal-to-noise ratio,obvious Doppler frequency impact and long pseudo-random code cycle,a long-code DSSS satellite signal carrier frequency detection and power estimation scheme in non-cooperative case is proposed .In this scheme,the Doppler frequency impact is restrained by adding its first-order derivative information in the local NCO .A “Lead-Lag” structure is used in the detection circuits to prevent the measurement excursion along the peak line on the two-dimensional plane formed by frequency and its first-order derivative .Then,Least Square prediction is employed to cut down the NCO searching range.The simulation results indicate that the proposed scheme can effectively reduce the estimation error caused by the Doppler frequency impact,and the signal-to-noise ratio reaches -21 dB.%针对长码直接序列扩频卫星信号信噪比低、多普勒频率影响明显、码周期长等特点，提出了一种非合作情况下长码直扩卫星信号载频检测和功率估计的方法。该方法通过在本地NCO中加入多普勒频率一阶导数信息来抑制多普勒频率的影响；在检测电路中加入“超前-滞后”结构，以防止频率测量值在频率及其一阶导数构成的二维平面上沿脊线发生偏移，并利用最小二乘方法对频率进行预测，以减小搜索范围。仿真结果表明，所提方法能够较好地减小多普勒频率引起的估计偏差，检测信噪比达到-21 dB。