机载设备IRIG-B(AC)码的滤波及其数字相位补偿

Filtering and digital phase compensation of IRIG-B(AC) code in airborne equipment

为了解决机载环境下交流B码信号中的噪声和畸变问题,提高解码的精度和稳定性,设计了中心频率在1 kHz的带通滤波器对IRIG-B码信号进行滤波;然后,针对滤波后所引入的相位差设计了一个数字补偿电路,对1 PPS信号进行相位校准,消除相位误差。实验结果表明:滤波有效地抑制了信号中的噪声,还将失真的信号还原成真实的信号,无用的频率信号以-34 dB/十倍频率的水平得到抑制;经过数字相位补偿后,不仅消除了由于滤波所引入的相位差,而且消除了由于过零器的过零精度等所引入的相位差,1 PPS准时点的精度由文献[1]的优于10μs提高到了优于3μs。该设计满足机载环境下交流时间码的解码要求,消除了噪声的干扰和信号的失真,提高了解码的精度和稳定性。

In order to eliminate the interference of airborne environment and to improve the precision of decode and the EMC ability, the filtering of IRIG-B （AC） and the compensation of phase hysteresis caused by the filter are studied. A band pass filter with a 1 kHz center frequency is designed, then the digital compensation is used for the phase hysteresis caused by filter. The results show that the ability of anti-jamming, anti-distortion and the decoding stability of the decoder are improved,and the useless frequency signals are depressed by -34 dB/10 octave. The digital compensation strategy can eliminate not only the phase hysteresis, but also the error caused by zero crossing detector. The timing precision of 1 PPS is enhanced from better than 10us to better than 3 us. The airborne system satisfies the decoding requirement of IRIG-B （AC）, eliminates the noise interference and signal distortion,and enhances the decoding precision and stability.