基于FPGA的自适应解调器设计

Design of Adaptive Demodulator for IRIG-B(AC) Code Based on FPGA

IRIG-B(AC)码广泛应用于航天测控系统的远距离时间同步,由于在传输过程中信号易受干扰且存在路径传输时延,因此采用IRIG-B(AC)码实现时间同步其精度往往较差。为满足远距离高精度时间同步要求,针对IRIG-B(AC)码同步误差较大问题,提出一种基于FPGA的数字化解调方法。该方法采用全数字化软件设计,具备相位自动判别功能,针对不同调制比和不同输入幅值的IRIG-B(AC)码,能够实现快速自适应解调译码。测试结果表明,该方法抗干扰能力强,工作稳定可靠,使IRIG-B(AC)码的时间同步精度得到极大提升,甚至优于1μs。

IRIG-B （AC） code is widely used in aerospace measurement and control systems for long-distance time synchronization. However, due to the signal interference and transmission delay during the process of transmission, the accuracy of time synchronization realized by IRIG-B（AC） code is quite low.In order to meet the requirement for long-distance high accuracy time synchronization, and considering the synchronization error of IRIG-B（AC） code, a novel digital demodulation method based on FPGA software is proposed. This method adopts an all-digital software design with an automatic phase discrimination function.According to the different modulation ratios and input amplitudes of IRIG-B （AC）codes, the method can realize fast adaptive demodulation and decoding.The test results show that this method has a strong anti-interference capability and operates stably and reliably. With the function of this method, the time synchronization accuracy of IRIG-B （AC）code is greatly improved, even better than 1 p,s.