Zeng Tao, Chang Shaoqiang, Fan Huayu, Liu Quanhua
Radar Research Laboratory, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China.
Department of Electronic Engineering, Tsinghua University, Beijing 100084, China.
Sensors (Basel). 2018 Mar 26;18(4):985. doi: 10.3390/s18040985.
The linear stepped frequency and linear frequency shift keying (FSK) signal has been widely used in radar systems. However, such linear modulation signals suffer from the range-Doppler coupling that degrades radar multi-target resolution. Moreover, the fixed frequency-hopping or frequency-coded sequence can be easily predicted by the interception receiver in the electronic countermeasures (ECM) environments, which limits radar anti-jamming performance. In addition, the single FSK modulation reduces the radar low probability of intercept (LPI) performance, for it cannot achieve a large time-bandwidth product. To solve such problems, we propose a novel chaos-based stepped frequency (CSF) synthesized wideband signal in this paper. The signal introduces chaotic frequency hopping between the coherent stepped frequency pulses, and adopts a chaotic frequency shift keying (CFSK) and phase shift keying (PSK) composited coded modulation in a subpulse, called CSF-CFSK/PSK. Correspondingly, the processing method for the signal has been proposed. According to our theoretical analyses and the simulations, the proposed signal and processing method achieve better multi-target resolution and LPI performance. Furthermore, flexible modulation is able to increase the robustness against identification of the interception receiver and improve the anti-jamming performance of the radar.
线性步进频率和线性频移键控（FSK）信号已在雷达系统中得到广泛应用。然而，此类线性调制信号存在距离 - 多普勒耦合问题，这会降低雷达多目标分辨率。此外，在电子对抗（ECM）环境中，固定的跳频或频率编码序列很容易被截获接收机预测到，这限制了雷达的抗干扰性能。另外，单一的FSK调制降低了雷达的低截获概率（LPI）性能，因为它无法实现大的时间 - 带宽积。为了解决这些问题，本文提出了一种新型的基于混沌的步进频率（CSF）合成宽带信号。该信号在相干步进频率脉冲之间引入混沌跳频，并在子脉冲中采用混沌频移键控（CFSK）和相移键控（PSK）复合编码调制，称为CSF - CFSK/PSK。相应地，还提出了该信号的处理方法。根据我们的理论分析和仿真结果，所提出的信号和处理方法具有更好的多目标分辨率和LPI性能。此外，灵活的调制能够增强对截获接收机识别的鲁棒性，并提高雷达的抗干扰性能。
