Research On Single Frequency Continuous Wave Radar Imaging

Synthetic aperture radar(SAR) imaging which has been widely used in military and civil fields is the key point of research in radar systems. Existing SAR systems require signals with wide bandwidth to achieve high range resolution for imaging. The radio spectrum resources increasingly tense in recent years, and the wideband transmitted signals make the bandwidth congestion more prominent, which pose potentially serious challenges to the future radar designs. Radar imaging with single frequency continuous wave which is a way to reduce the spectrum occupancy, and can reduce the bandwidth requirement of radar RF front-end has great research significance. This paper mainly researches on imaging algorithm theory, algorithm simulation and analysis, autofocus, measurement verification system, distributed fusion imaging. The main work is as follows:Doppler back projection(BP) imaging algorithm has been studied since single frequency continuous wave cannot exploit high range resolution for imaging without bandwidth. The concrete formula deduction, algorithm process and parameters setting analysis are presented. The simulation results verify the spatial resolution can achieve 1/4 wavelength based on the observation of 360 degrees, and targets can be well reconstructed. And, the position errors are simulated and analyzed.Different from BP with wideband signals, the phase error of doppler BP with single frequency continuous wave, which is difficult to be estimated and cannot be solved by using the conventional autofocus method, is deduced for the first time. By establishing the trajectory error model, a doppler BP autofocus method based on maximum image square sharpness for trajectory optimization is presented and the simulation results indicate the feasibility of the proposed method.A turntable imaging based measurement verification system is designed. Imaging experiments using measured data based on ideal trajectory has been done. The measurement results indicate the efficiency of the doppler BP algorithm and implement imaging of point target in small scene.Design the architecture of distributed fusion imaging system in terms of survivability, antijamming, anti-stealth of the modern radar system. A doppler BP fusion imaging method of coherent processing in single platform/incoherent processing between platforms is proposed. The simulation results under the ideal condition indicate that the uniformity of image resolution is improved and the effect of point target reconstruction is promoted.