National Lab of Radar Signal Processing, Xidian University, Xi'an 710071, China.
Sensors (Basel). 2020 Feb 20;20(4):1169. doi: 10.3390/s20041169.
It is a challenge to realize wide swath imaging due to the conflict between Doppler ambiguity and range ambiguity for hypersonic vehicle (HSV) radar. In addition, there are many conditions requiring the forward-looking imaging. In a forward-looking synthetic aperture radar (SAR) system, left-right ambiguity arises, since two symmetrical targets have the same Doppler frequency magnitude. After selecting an appropriate pulse repetition frequency (PRF) to avoid Doppler ambiguity, we only need to solve the range ambiguity and left-right ambiguity. To handle these issues, this paper proposes an approach to resolve the range ambiguity and left-right ambiguity using the frequency diverse array (FDA). With the range-angle-dependent property of the transmit steering vector, FDA can distinguish the range ambiguous echoes in the spatial frequency domain. By performing transmit beamforming after range compensation, the echo from the desired range region can be extracted from ambiguous echoes. Then, the back projection (BP) algorithm is used to achieve imaging. Next, the echoes of all channels are processed by two receive beamformers, which are designed for the right and left sides, respectively. With the aforementioned procedures, an unambiguous image can be obtained. Simulation results have verified the effectiveness of the proposed approach.
由于高超音速飞行器（HSV）雷达的多普勒模糊和距离模糊之间的冲突，实现宽测绘带成像具有挑战性。此外，还有许多需要前视成像的情况。在前视合成孔径雷达（SAR）系统中，由于两个对称目标具有相同的多普勒频率大小，因此会出现左右模糊。在选择适当的脉冲重复频率（PRF）以避免多普勒模糊之后，我们只需要解决距离模糊和左右模糊。为了解决这些问题，本文提出了一种使用频率分集阵列（FDA）解决距离模糊和左右模糊的方法。利用发射导向矢量的距离-角度相关性，FDA 可以在空间频域中区分距离模糊回波。通过在距离补偿后进行发射波束形成，可以从模糊回波中提取期望距离区域的回波。然后，使用反向投影（BP）算法进行成像。接下来，通过两个接收波束形成器分别对所有通道的回波进行处理，这两个接收波束形成器分别用于右侧和左侧。通过上述步骤，可以获得无模糊图像。仿真结果验证了所提出方法的有效性。
