A Range and Velocity Ambiguity Resolution Method Based on Ambiguity Matrix Completion and Elimination with Low SNR

In space-borne surveillance radar, the medium pulse repetition frequency (MPRF) is preferred to avoid the transmit pulse eclipsing in range domain meanwhile to obtain a large unambiguous Doppler detectable zones, especially for ultra-high speed targets. However, there exist great challenges in acquiring the unambiguous information of targets due to the serious range and velocity ambiguity. In this paper, a new method is proposed to resolve two-dimensional (2D) ambiguity and suppress the ghosts simultaneously. Firstly, a 2D ambiguity matrix consists of all the possible range and velocity information from multiple PRFs is constructed. The element of this matrix is calculated by counting the target number located in the same position. Secondly, the element value related to detected target will be replaced by the updating strategy. Then the accurate range and velocity information can be obtained by calculating the mean range-Doppler value measured from different PRFs. The numerical results show that the proposed algorithm has a lower computation complexity with less ghosts in low-SNR case compared to the 1D clustering method.

I. Introduction

Space-borne surveillance radar for space targets (especially for ballistic missile) detection and tracking has got much attention in recent years. With the development of ballistic missile technique, this kind of targets is of more and more threaten. The flight path in midcourse is less than 900 seconds so that the early warning is essential for strategic decision-making. The relative velocity of radar and ballistic missile can exceed dozens of Mach at most where the “range, velocity and beam crossing” will happen, and the ballistic missile usually make up with stealth materials. Constrained for short CPI (coherent processing intervals) and small radar cross section, the SNR (signal to noise ratio) in a single CPI is much lower than the required 13dB. In addition, the range swath of space-borne radar is larger than hundreds of kilometers. In order to obtain a better range and velocity ambiguity resolution, the radar system prefers the HPRF (High Pulse Repetition Frequency) and several PRF combinations to detect weak single/multiple targets, suppress the ghosts, resolve the 2D ambiguity and finally get the real information.