航空通信导航雷达叠加导频信道串扰抑制系统设计

Design of Interference Suppression System for Airborne Communication and Navigation Radar Overlay Pilot Channel

摘要:

航空通信导航雷达系统叠加导频通过共享时频资源，可避免独立导频信道对频谱的额外占用，使得导频串扰信号频率呈现随机游走特性，从而容易忽略叠加导频信道串扰信号的频域特性，导致频段串扰均值较高。为此，设计航空通信导航雷达叠加导频信道串扰抑制系统。该硬件设计采用FPGA+DSP异构架构，AD模块设计结合精确的终端匹配方案，在保障AD转换精度的同时，使系统在复杂电磁环境下仍能维高速数据传输性能。在软件部分，基于EMD分解算法与KL散度在采集的航空通信导航雷达与导频信道叠加信号中分离出串扰信号，作为串扰抑制的基础信号。将基于串扰观测的控制器作为串扰抑制控制器，获取叠加导频信道分离出来串扰信号的频域特性，利用具有频域选择性的前馈控制器，根据串扰信号的动态频域分布特性实现精准抑制。实验测试结果表明，设计系统的航空通信导航雷达叠加导频信道串扰抑制实际表现效果较好，叠加信号在串扰抑制后变得平滑。设计系统在各频段的残余近端串扰均值均低于10dB，说明系统未能完全抑制的串扰量较低。设计系统的航空通信导航雷达叠加导频信道信号噪声比整体高于1200，说明设计系统的串扰抑制性能较强且比较稳定。

Abstract:

The superimposed pilot of the aviation communication and navigation radar system, by sharing time-frequency resources, can avoid the additional occupation of the spectrum by the independent pilot channel, making the frequency of the pilot crosstalk signal exhibit random walk characteristics. As a result, it is easy to ignore the frequency domain characteristics of the crosstalk signal in the superimposed pilot channel, leading to a relatively high average crosstalk value in the frequency band. For this purpose, a crosstalk suppression system for the superimposed pilot channel of aviation communication and navigation radar is designed. This hardware design adopts a heterogeneous architecture of FPGA+DSP. The AD module design, combined with an accurate terminal matching scheme, ensures the accuracy of AD conversion while enabling the system to maintain high-speed data transmission performance in complex electromagnetic environments. In the software section, based on the EMD decomposition algorithm and KL divergence, the crosstalk signal is separated from the superimposed signal of the collected aviation communication and navigation radar and pilot channel, which serves as the basic signal for crosstalk suppression. The controller based on crosstalk observation is used as the crosstalk suppression controller to obtain the frequency domain characteristics of the crosstalk signal separated from the superimposed pilot channel. By using the feedforward controller with frequency domain selectivity, precise suppression is achieved according to the dynamic frequency domain distribution characteristics of the crosstalk signal. The experimental test results show that the actual performance of crosstalk suppression in the superimposed pilot channel of the aviation communication and navigation radar designed system is quite good, and the superimposed signal becomes smooth after crosstalk suppression. The average residual near-end crosstalk of the designed system in each frequency band is all below 10dB, indicating that the amount of crosstalk that the system fails to completely suppress is relatively low. The signal-to-noise ratio of the superimposed pilot channel of the aviation communication and navigation radar in the designed system is generally higher than 1200, indicating that the crosstalk suppression performance of the designed system is strong and relatively stable.