高灵敏度自动增益控制接收机群时延波动畸变的预判分析

Prejudgment and Analysis of the Distortion of Group Delay Ripple for High-Sensitivity Automatic Gain Control Receiver

随着高性能卫星测控技术、导航技术、深空探测技术的发展以及宽带扩频等技术的大量应用,对星载高灵敏度自动增益控制接收机群时延波动指标的要求也越来越严格.而在工程实践中,高灵敏度接收机的某些微波特性会导致群时延波动的畸变.本文通过分析微波高灵敏度接收机自动增益控制环路的变化及干扰、反射、微波泄露等实际的工况,对群时延波动进行了估算,推导出了其畸变的预判公式,得出了自动增益控制接收机群时延波动畸变的预判依据.最终,本文通过对星载L频段高灵敏度导航接收机实例分析和设计,将其自动增益控制环路中可调衰减器群时延调整为8.7 ps,小于18.6 ps的指标;内部电磁泄露空间隔离度为-60 dB,优于-46 dB的指标;驻波比为1.5,优于2.2的指标;镜频抑制为25 dBc,大于所需的20.8 dBc的指标.经系统联试验证,群时延波动畸变小于1 ns,说明针对高灵敏度自动增益控制接收机群时延波动畸变的预判分析方法及结果正确,对其工程设计、器件选取具有重要的指导意义.

With the development of high-performance satellite measurement and control technology,navigation tech⁃nology,deep space exploration and wide applications of broadband spread-spectrum technology,strict requirements are put forward for the distortion of group delay ripple for the spaceborne high-sensitivity automatic gain control receiver.But in engineering practice,due to some microwave characteristics of the high-sensitivity receiver,there may be distortion in group delay ripple.By analyzing the distortion caused by the variation of automatic gain control loop and its microwave leakage,reflection and mirror frequency interference,the approximate analysis formula in the worst case is deduced,and the prediction basis of group delay distortion is given.Through the analysis and design of spaceborne L-band high-sensitivity navigation receiver,the group delay change of adjustable attenuator in the automatic gain control loop is 8.7 ps,less than the index 18.6 ps;the spatial isolation of internal electromagnetic leakage−60 dB is better than the index−46 dB;the stand⁃ing wave ratio of 1.5 is better than the index 2.2,and the mirror frequency suppression of 25 dBc is greater than the required 20.8 dBc.Finally,the system test shows that the group delay ripple distortion is less than 1 ns,which proves that the pre⁃judgment method and results for the group delay ripple distortion of high-sensitivity automatic gain control receiver are cor⁃rect,which has important guiding significance for its engineering design and device selection.