LAUSR

Radar faces various interferences from the reconnaissance and other devices when conducting target imaging and recognition. The properties of traditional modulation methods, such as linear frequency modulation (LFM) and phase code modulation (PCM), have been investigated in detail. Therefore, it can be intercepted and recognized easily so that the target image is difficult to be obtained. To improve the complexity of radar signals, the pulse signal design and imaging method is proposed in this article based on coded modulation. Taking LFM signal as an example, it is modulated by the code sequences first. As the spectrum of LFM signal is aliasing after coded modulation, the false peaks appear in target high-resolution range profile (HRRP). To eliminate the false peaks in HRRP, the plus-minus coded modulation is designed according to the duty ratio of the first coded modulation signal. Then, the HRRP can be recovered for target imaging. The whole procedure of the coded modulation and imaging is provided and analyzed. In addition, based on different coded modulation signals, the entropy of signal time–frequency image is discussed to illustrate the antijamming performance. Simulations and experiments are conducted to verify the effectiveness of the proposed signal design and imaging method.