数控振荡器相位截断对频域抗干扰性能影响分析

Numerically controlled oscillator phase truncation effect on performance of frequency domain anti-jamming

全球导航卫星系统频域抗干扰接收机中,普遍采用数控振荡器生成本振信号。由于硬件约束,通常需要对数控振荡器进行相位截断。而数控振荡器相位截断是否合理对抗干扰性能影响较大。针对该问题,从数控振荡器相位截断导致的本振杂散着手,从理论上分析其对混频和频域抗干扰环节的影响。在此基础上,给出一种数控振荡器查找表地址位宽的理论计算模型,使得接收机的载噪比损耗接近无数控振荡器相位截断的频域抗干扰接收机。仿真结果表明,抑制带宽大于100k Hz、干信比小于80d Bc的窄带干扰时,计算的数控振荡器查找表地址位宽不超过10bit。与无数控振荡器相位截断的频域抗干扰接收机相比,采用数控振荡器混频的抗干扰接收机的载噪比损耗最多增加0.6d B。

Numerically controlled oscillator is usually adopted in current GNSS （ Global Navigation Satellite System） frequency domain anti- jamming receiver. Constrained by hardware, numerically controlled oscillator phase truncation is needed. But, whether numerically controlled oscillator phase is truncated reasonably influences anti-jamming performance greatly. Aiming at the problem, its effect on mixing and frequency domain anti-jamming was analyzed theoretically based on local oscillator spur caused by numerically controlled oscillator phase truncation. A theoretical computing module of numerically controlled oscillator lock-up table width was brought forward. Thus, carrier noise loss approximated that of receiver with non-truncated phase numerically controlled oscillator. Simulations show that numerically controlled oscillator look-up table width computed by that module is no more than 10bit, when suppressing nan^w band interference whose band is above 100kHz and jam-signal-ratio is below 80dBc. When adopting that width, carrier noise loss of receiver with numerically controlled oscillator phase truncation increases 0.6dB at most, compared to that of receiver with non-truncated numerically controlled oscillator phase.