Range-ambiguous Clutter Separation and Suppression Method for Airborne Bistatic Radar Based on Beam Pattern Reconstruction
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摘要: 空时自适应处理(STAP)是机载雷达地/海杂波抑制和运动目标检测的关键技术。然而,在距离模糊条件下,机载双基地雷达所面临的杂波非平稳性会破坏训练样本的独立同分布假设,导致传统STAP方法性能显著下降。针对该问题,该文首先分析了基于常规波束形成的解模糊方法中存在的主瓣增益损失与旁瓣抑制之间的固有矛盾;继而提出一种基于阻塞矩阵级联自适应波束形成的距离模糊杂波分离方法,虽在一定程度上提升了性能,但因引入噪声畸变而存在局限性。为克服上述方法的不足,该文进一步提出一种基于波束图重构的距离模糊杂波抑制方法。在主瓣杂波估计和子阵处理的基础上,该方法通过构建包含波束保形约束与旁瓣控制项的优化问题,直接设计空域滤波器权值,从而在分离不同模糊距离杂波的同时,有效兼顾主瓣目标增益与低旁瓣性能。随后,对分离后的杂波进行角度-多普勒补偿,并利用子阵级多普勒三通道联合处理空时自适应处理(3DT-STAP)完成最终抑制。仿真结果表明,与典型方法相比,该文所提方法能够更有效地分离不同模糊距离区间的杂波,主瓣凹口宽度显著收窄,且输出信杂噪比损失控制在3 dB以内,显著提升了距离模糊场景下的杂波抑制性能与目标检测能力。Abstract: Space–Time Adaptive Processing (STAP) is a key technique used for ground/sea clutter suppression and moving target detection in airborne radar. However, under range ambiguity conditions, the inherent clutter nonstationarity in airborne bistatic radar violates the independent and identically distributed assumption required for training samples, significantly degrading the performance of conventional STAP methods. To address this issue, this study first analyzed the limitations of the Conventional Beamforming (CBF)-based disambiguation approach, which exhibits a trade-off between mainlobe gain loss and sidelobe suppression. A method based on a cascaded blocking matrix and adaptive beamforming is proposed for separating range-ambiguous clutter. Although this method improves upon the CBF-based approach, it introduces noise distortion, which limits further improvements in clutter separation and suppression accuracy. Hence, a novel method based on beam pattern reconstruction is proposed to overcome this drawback. This method formulates an optimization problem incorporating beam-maintenance and sidelobe-control terms to design spatial filter weights, effectively separating range-ambiguous clutter while preserving the mainlobe target gain and suppressing sidelobe clutter. Subsequently, angle-Doppler compensation is applied to the separated clutter, followed by final suppression using a subarray-based STAP method incorporating a joint three-channel Doppler transform. Simulation results revealed that compared with typical methods, the proposed approach more effectively separated clutter, significantly narrowed the mainlobe notch width, and limited the output signal-to-clutter-plus-noise ratio loss to <3 dB, thereby markedly enhancing clutter suppression performance and target detection capability under range ambiguity conditions.
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表 1 双基地机载雷达系统参数
Table 1. Bistatic airborne radar system parameters
参数 数值 参数 数值 载频$ {f}_{\text{c}} $ 1.25 GHz 脉冲重复频率$ {f}_{\text{r}} $ 3000 Hz接收机瞬时带宽$ {B}_{0} $ 2 MHz 工作波长$ \lambda $ 0.24 m 雷达距离分辨率$ \Delta R $ 150 m 最大不模糊距离$ {R}_{\mathrm{u}} $ 100 km 俯仰向阵元个数M 1 方位向阵元个数N 32 阵元及子阵阵元间距d 0.12 m 相干脉冲数K 32 发射机高度$ {h}_{\mathrm{t}} $ 10 km 接收机高度$ {h}_{\mathrm{r}} $ 6 km 双基基线距离$ {L}_{\text{tr}} $ 150 km 方位角$ {\theta }_{\mathrm{t}} $与$ {\theta }_{\mathrm{r}} $的取值范围 0~$ 2\text{π} $ 发射偏航角$ {\theta }_{\text{tp}} $的取值范围 $ -\text{π} $~$\text{π} $ 接收偏航角$ {\theta }_{\text{rp}} $的取值范围 $ -\text{π} $~$\text{π} $ 发射载机速度$ {v}_{\mathrm{t}} $ 150 m/s 接收载机速度$ {v}_{\mathrm{r}} $ 200 m/s 1 基于波束图重构的机载双基地雷达距离模糊杂波分离与抑制方法
1. Range-ambiguous clutter separation and suppression method for airborne bistatic radar based on beam pattern reconstruction
滑窗重叠子阵预处理:根据约束条件$ {N}_{\text{e}} > {N}_{\text{r}} $和$ \Delta \psi\ge {102}^{\circ}/{N}_{\text{e}} $,获得子阵数据$ {\boldsymbol{X}}_{lp} $; 步骤1:距离模糊杂波分离:通过Capon谱估计得到接收锥角$ {\hat{\psi }}_{lq} $,然后通过式(38)计算空域自适应滤波器权值$ {\boldsymbol{w}}_{lq} $,最后根据式(39)得到
解模糊后数据$ {\boldsymbol{Z}}_{{{N}_{\text{s}}}K×{{N}_{\mathrm{r}}}L} $;步骤2:ADC补偿:通过式(40)构造补偿矩阵$ {\boldsymbol{T}}_{\mathrm{ADC},i} $,通过式(41)计算$ {\tilde{\boldsymbol{Z}}}_{i} $; 步骤3:杂波抑制:构造降维矩阵$ {\bar{\boldsymbol{T }}}_{k}={\tilde{\boldsymbol{F}}}_{k}\otimes {\boldsymbol{I}}_{\tilde{N}} $,然后通过式(42)计算空时自适应滤波器权值$ {\bar{\hat{\boldsymbol{w}} }}_{k} $。给定待检测距离单元的数据$ {\boldsymbol{Z}}_{\text{cut}} $,最
终通过式(44)得到输出$ {\bar{\tilde{\boldsymbol{Z}} }}_{\text{cut}} $。表 2 不同配置下的目标参数
Table 2. Target parameters under different bistatic configurations
参数 数值 交叉 共线 目标信噪比$ \mathrm{SN}{\mathrm{R}}_{\text{t}} $ 10 dB 10 dB 双基距离和 $ {R}_{\text{s}} $ 321.9 km 352.8 km 目标径向速度 $ {v}_{\text{t}} $ –144 m/s 115.2 m/s 目标归一化多普勒频率 $ \bar{f}_{\text{d,T}}^{} $ –0.2 0.16 目标所在多普勒通道数 k 16 34 目标所在距离单元数 i 2146 2352 第i个距离单元的主瓣
杂波中心 ($ {\bar{f}}_{\text{d},0} $, $ f_{\text{s},0}^{} $)(–0.24, –0.43) (0.2, 0.36) 表 3 不同方法在旁瓣区的平均输出SCNR
Table 3. Average output SCNR in the sidelobe region for different methods
方法 旁瓣区平均SCNR (dB) 交叉配置 共线配置 理论值 39.03 39.03 CBF 9.30 8.86 波束图重构 36.33 34.58 阻塞矩阵级联ABF 37.19 36.82 -
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