弹载平台聚束SAR成像脉冲重复频率设计

Design of pulse repetition frequency for missile-borne spotlight SAR imaging

针对弹载平台高速、非水平非匀速直线运动和对目标区域大斜视角观测的特点,对影响脉冲重复频率(pulse repetition frequency,PRF)设计的模糊性限制、发射脉冲的遮掩、天底回波干扰等主要因素进行了详细分析,推导了平台非理想运动和视角状态下最大瞬时多普勒带宽和天底回波可忽略的速度俯仰角范围的简单表达式。提出了一种基于穷举法的聚束合成孔径雷达(synthetic aperture radar,SAR)成像导引头PRF设计方法,该方法在同时满足距离和方位上不模糊的情况下,发射最少个数的PRF实现对雷达波束覆盖区域无距离遮挡观测。通过仿真产生的聚束SAR成像导引头弹道,验证了分析的正确性和设计方法的有效性。

According to the characteristics of the missile-borne synthetic aperture radar（SAR）platform with high speed,curvilinear trajectory and high squint angle,this paper gives a detailed analysis of the main factors should be considered when designing the pulse repetition frequency（PRF） of a spotlight SAR seeker,such as the range and azimuth unambiguous constraints,and the effect of the eclipsing and the nadir returns.It also deduces a simple formula of the maximal instantaneous Doppler bandwidth of echo signal based on nonideal movement radar platform and squint modes.And the bound of the pitch flightpath angle is achieved to assure the nadir returns can be neglected too.Then,an exhaustive method to design the PRF for a spotlight SAR imaging seeker is proposed,which avoids the range and azimuth ambiguities,and achieves minimal PRFs to acquire the returns from the main beam footprint without blind regions.The correctness of the analyses and the validity of the method are demonstrated using a simulated trajectory for a spotlight SAR imaging seeker.