提出了一种基于扫频激光器的超宽带线性调频(LFM)信号产生和传输的方法。该方法使用扫频激光器产生频率随时间周期性变化的光信号,注入马赫-曾德尔调制器后产生载波抑制双边带光信号,利用嵌有光纤光栅(FBG)的Sagnac环完成双边带光信号的分离。Sagnac环的透射光信号经延时后与反射光信号拍频,从而产生了超宽带LFM信号。仿真分别产生了载频30 GHz、带宽16 GHz、时宽带宽积8000的超宽带连续波LFM信号和超宽带脉冲波LFM信号。所提方案解决了天线拉远场景中超宽带LFM信号经光纤传输时的功率周期性衰落问题。在多目标探测分析中,方案产生的信号表现出高精度临近目标分辨能力。所提方案具有载频、时宽、啁啾率和啁啾符号独立调谐的优点,可实现高载频、超宽带LFM信号的产生和功率周期性衰减抑制传输。

In this study, a novel approach is proposed to generate and transmit the ultra-wideband linear frequency modulation (LFM) signal using frequency-sweeping lasers. In this approach, the frequency-sweeping continuous-wave light from frequency-sweeping lasers is introduced into the Mach-Zehnder modulator to generate a carrier-suppression double sideband (CS-DSB) signal. The Sagnac loop containing a fiber Bragg grating is used to separate the CS-DSB signal. Beat occurs in the reflected light of the Sagnac loop and the transmitted light after some delay; hence, the ultra-wideband LFM signal is generated. The simulation results denote the generation of the ultra-wideband continuous and pulse LFM signals with carrier frequency of 30 GHz, bandwidth of 16 GHz, and time-bandwidth product of 8000. The proposed approach solves the problem of power periodic fading observed when the ultra-wideband LFM signal is transmitted through an optical fiber in case of antenna stretching. Furthermore, using the proposed approach, the carrier frequency, time duration, chirp rate, and chirp sign can be independently tuned, providing an effective strategy for generating and transmitting the ultra-wideband LFM signal.