Fast Sidelobe Suppression for Moving Targets in Random Frequency and Pulse Repetition Interval Agile Radars
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摘要: 载频与脉冲间隔随机捷变(RFPA)雷达可通过合成宽带获得高距离分辨率。但是,在长时间相参积累过程中,运动目标容易出现距离徙动(RCM)现象,且RFPA信号固有的随机高旁瓣特性会严重降低雷达对目标的检测和估计性能。针对上述两个问题,该文提出了一种基于非均匀Keystone变换的加窗迭代自适应滤波方法(NUKT-WIAA)。首先,采用非均匀Keystone变换(NUKT)对运动目标进行RCM校正,以实现目标能量的有效积累。然后,对每个距离-多普勒单元为中心的矩形处理窗内的NUKT结果进行迭代自适应滤波(IAA)处理,实现对RFPA信号旁瓣的快速抑制。在迭代过程中,采用强散射点筛选策略提高协方差矩阵的计算效率,从而进一步降低所提算法的计算复杂度。仿真结果表明,在多目标和连续杂波场景下,NUKT-WIAA算法能够以较低的计算量和存储量同时实现对运动目标的徙动校正和旁瓣抑制。
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关键词:
- 载频与脉冲间隔随机捷变信号 /
- 距离徙动 /
- 旁瓣抑制 /
- 迭代自适应滤波 /
- 计算效率
Abstract: Random Frequency and Pulse Repetition interval Agile (RFPA) radars can achieve high range resolution using a synthesized wide bandwidth. However, Range Cell Migration (RCM) occurs for moving targets during long coherent integration, and the inherent randomly fluctuating high sidelobes pose a significant challenge for RFPA radars. To address these issues and enhance target detection and estimation performance, a Windowed Iterative Adaptive Approach based on the Non-Uniform Keystone Transform (NUKT-WIAA) is proposed. First, a NUKT is employed to correct the RCM caused by moving targets, effectively concentrating most of the target energy. An IAA is then applied to the NUKT results within a rectangular processing window centered on each range-Doppler cell to achieve fast sidelobe suppression of RFPA signals. A strong scatterer selection strategy is implemented during iterations to enhance the computational efficiency of the covariance matrix, thereby reducing the overall computational complexity of the proposed algorithm. Simulation results reveal that NUKT-WIAA can simultaneously achieve migration correction and sidelobe suppression for moving targets across various scenarios, multiple point targets, range-spread targets, and environments with continuous strong clutter while maintaining low computational complexity and memory usage. -
表 1 RFPA信号波形参数
Table 1. Parameters of RFPA signal
参数 指数 载波频率($ {f}_{\text{c}} $) 8 GHz 脉冲宽度($ {T}_{\text{p}} $) 1 μs 平均脉冲间隔($ {T}_{\text{r}} $) 20 μs 脉冲间隔捷变范围($ {T}_{\text{w}} $) 6 μs 频率捷变范围(B) 400 MHz 采样频率($ {f}_{\text{s}} $) 800 MHz 脉冲间隔概率密度分布 均匀分布 频率概率密度分布 均匀分布 脉冲个数(M) 512 LFM基带信号带宽($ {B}_{0} $) 40 MHz 最小跳频间隔 0.78 MHz 1 NUKT-WIAA算法流程图
1. Flowchart of the NUKT-WIAA algorithm
离线计算: 步骤1:根据式(19)计算并存储$ {a}_{l,k}\left(p,q\right) $,其中,
$ p=0,1,\cdots ,L-1 $,$ q=0,1,\cdots ,K-1 $,$ l=0,1,\cdots ,L-1 $,
$ k=0,1,\cdots ,K-1 $。在线计算: 步骤2.1:根据式(17)计算$ {\boldsymbol{Y}}_{\text{NUKT}} $。 初始化:令$ \hat{x}_{p,q}^{0}={y}_{NUKT}\left(p,q\right) $,其中,$ p=0,1,\cdots ,L-1 $,
$ q=0,1,\cdots ,K-1 $。迭代: 1: For $ i=1,2,\cdots ,I $ 2: If $ i=1,2 $, then 3: 步骤2.2:根据式(34)计算$ {u}^{i} $; 4: Else 5: 步骤2.3:根据式(33)计算$ {\gamma }^{i} $; 6: End If 7: For $ p=0,1,\cdots ,L-1 $ 8: 步骤2.4:根据式(35)确定集合$ {\mathbb{N}}^{i} $; 9: For $ q=0,1,\cdots ,K-1 $ 10: If $ 10\mathrm{\lg }\left({\left| \hat{x}_{p,q}^{i-1}\right| }^{2}\right) \lt {\zeta }_{1} $ then 11: 步骤2.5:$ \hat{x}_{p,q}^{i}=\hat{x}_{p,q}^{i-1} $; 12: Else 13: 步骤2.6:根据式(37)确定$ {\tilde{\boldsymbol{D}}}_{p,q}^{i} $,$ {{\boldsymbol{\varLambda }}}^{i-1} $和$ {\boldsymbol{x}}^{i-1} $; 14: 步骤2.7:根据式(36)计算$ {\tilde{\boldsymbol{R}}}_{p,q}^{i} $; 15: 步骤2.8:根据式(38)计算$ \hat{x}_{p,q}^{i} $; 16: End If 17: End For 18: End For 19: If $ \frac{1}{LK}\sum \limits_{p=0}^{L-1}\sum \limits_{q=0}^{K-1}\left| \hat{x}_{p,q}^{i}-\hat{x}_{p,q}^{i-1}\right| \lt {\zeta }_{2} $ then 20: 输出估计值$ \hat{x}_{p,q}^{i} $; 21: Else 22: 返回第1行; 23: End If 24: End For 输出:$ \hat{x}_{p,q}^{\text{iter}} $,其中,$ \text{iter} $表示算法达到收敛时的迭代次数。 表 2 距离扩展目标参数
Table 2. Parameters of range-spread targets
目标索引 散射点索引 距离(m) 速度(m/s) SNR (dB) RCM单元 目标索引 散射点索引 距离(m) 速度(m/s) SNR (dB) RCM单元 R1 S1 1505.81 43.95 –6 3 R2 S9 1504.50 64.09 0 4 S2 1505.63 43.95 0 3 S10 1504.69 64.09 25 4 S3 1505.44 43.95 30 3 S11 1504.88 64.09 3 4 S4 1505.25 43.95 3 3 S12 1505.06 64.09 –5 4 S5 1505.06 43.95 –10 3 R3 S13 1504.88 69.58 –35 4 S6 1504.88 43.95 15 3 S14 1505.06 69.58 5 4 S7 1504.69 43.95 1 3 S15 1505.25 69.58 1 4 S8 1504.50 43.95 17 3 S16 1505.44 69.58 7 4 表 3 点目标参数
Table 3. Parameters of point targets
目标索引 距离(m) 速度(m/s) SNR (dB) RCM单元 T1 1504.69 56.76 27 4 T2 1504.88 78.74 30 4 T3 1505.44 75.07 –10 5 T4 1505.06 58.59 –17 4 T5 1505.63 36.62 0 2 T6 1504.88 38.45 –7 3 T7 1505.81 49.44 –35 3 T8 1501.50 106.20 20 6 T9 1506.88 1.83 –7 1 T10 1511.06 87.89 15 5 表 4 距离扩展目标功率估计误差(dB)
Table 4. Power estimation errors of range-spread target(dB)
目标索引 散射点索引 MF-IAA MF-IAF NUKT-WIAA 目标索引 散射点索引 MF-IAA MF-IAF NUKT-WIAA R1 S1 1.12 –0.25 –0.05 R2 S9 17.81 0.03 0.01 S2 –6.93 0.13 0.18 S10 –1.57 0.00 0.00 S3 –3.65 0.03 –0.03 S11 5.79 0.06 0.05 S4 14.07 0.36 0.17 S12 1.16 –0.01 –0.03 S5 29.30 0.81 0.51 R3 S13 36.34 0.88 –0.61 S6 7.04 0.08 0.13 S14 2.71 0.05 0.03 S7 18.98 0.66 0.00 S15 1.20 0.01 –0.01 S8 1.47 –0.01 0.01 S16 1.07 0.00 0.05 表 5 点目标目标功率估计误差(dB)
Table 5. Power estimation errors of point targets(dB)
目标索引 MF-IAA MF-IAF NUKT-WIAA T1 –2.74 0.00 0.00 T2 –3.26 0.00 0.00 T3 1.59 –0.02 0.06 T4 1.64 0.04 0.00 T5 –0.05 0.00 0.00 T6 1.41 0.00 –0.01 T7 2.49 –0.11 0.04 T8 –0.08 0.00 0.00 T9 0.07 0.02 0.01 T10 0.08 0.00 0.00 表 6 目标参数
Table 6. Target parameters
目标索引 距离(m) 速度(m/s) SNR (dB) RCM单元 T1 1504.88 –45.78 0 –3 T2 1507.31 –9.16 –10 –1 T3 1505.81 –20.14 10 –2 T4 1503.94 –16.48 2 –1 T5 1503.94 –9.16 6 –1 T6 1507.31 9.16 –5 1 T7 1506.56 9.16 7 1 T8 1505.44 21.97 4 2 T9 1504.50 16.48 –13 1 T10 1509.56 43.95 –35 3 表 7 存储需求对比
Table 7. Storage memory comparison
算法 存储需求 MF-IAA $ M{L}^{2}K $ MF-IAF $ {L}^{2}{K}^{2}+LKMN $ NUKT-WIAA $ {L}^{2}{K}^{2} $ 表 8 计算复杂度对比
Table 8. Computational complexity comparison
算法 预处理部分 迭代部分 MF-IAA $ \mathcal{O}\left[LMN\right] $ $ \mathcal{O}\left\{\left(iter\times LK\right)\left[{\left(M{k}_{\text{l}}\right)}^{3}+\left(LK+1\right){\left(M{k}_{\text{l}}\right)}^{2}+2M{k}_{\text{l}}\right]\right\} $ MF-IAF $ \mathcal{O}\left[LKMN\right] $ $ \mathcal{O}\left\{\left(iter\times LK\right)\left[{\left({k}_{\text{r}}{k}_{\text{d}}\right)}^{3}+\left(LK+1\right){\left({k}_{\text{r}}{k}_{\text{d}}\right)}^{2}+2{k}_{\text{r}}{k}_{\text{d}}\right]\right\} $ NUKT-WIAA $ \mathcal{O}\left[{M}^{2}N+\left(K+1\right)LM\right] $ $ \mathcal{O}\left[\displaystyle\sum \nolimits_{i=1}^{iter}\left(LK-{G}^{i}\right)C\left({k}_{\text{r}},{k}_{\text{d}},{\alpha }^{i}\right)\right] $ 表 9 运行时间对比
Table 9. Time cost comparison
算法 迭代次数 运行时间(s) MF-IAA 14 29037.76 MF-IAF 13 1037.46 NUKT-WIAA 7 12.59 注:计算机主要配置:英特尔CPU I9-10850K,处理器频率为3.60 GHz,内存为16 GB,软件为MATLAB profiler 2019a。 -
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