Analysis and suppression of radial velocity estimation error for moving targets in wideband LFMCW radar
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摘要:
宽带线性调频连续波(LFMCW)雷达可采用去斜处理实现距离高分辨，从而获取运动目标精细的距离变化信息。针对其运动目标多普勒速度谱存在干扰分量的问题，通过模型推导，分析了该现象产生原因及对目标速度估计的影响，提出了一种基于局部频谱细化的测速误差抑制方法；引入快时间Chirp-z变换对差频信号进行频谱细化，实现在计算量不增加的条件下降低测量误差，提升目标速度估计准确性。通过仿真对比实验验证了所提方法的性能。结果表明：所提方法可有效抑制离散域脉冲压缩引起的残差相位，对宽带LFMCW雷达的测速误差具有较好的抑制作用，对噪声具有更强的鲁棒性，且在计算量上远小于传统的快速傅里叶变换(FFT)方法。
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关键词:
- 宽带雷达 /
- 去斜处理 /
- 运动目标 /
- 快时间Chirp-z变换 /
- 径向速度估计
Abstract:Stretch processing is typically used by broadband linear frequency modulation continuous wave (LFMCW) radars to achieve high range resolution in the precise measurement of moving targets. However, the sampling echoes of the motion target could cause interference components on the Doppler velocity spectrum. To address such an issue, this paper proposes a novel method to reduce its influence on the estimation of target radial velocity in wideband LFMCW radar. The phenomenon is first studied in theory by using the mathematical model of wideband LFMCW radar echoes. On this basis, a suppression method of radial velocity estimation error for moving targets is proposed. The Chirp-z transform in the fast-time domain is introduced in the refined processing over the beat frequency signal spectrum. It could help improve the estimation accuracy of target radial velocity with much less computational cost. Finally, comparative simulations are carried out to evaluate the performance of the proposed method. The results show that the proposed method can effectively suppress the residual phase caused by pulse compression in the discrete fast-time domain and the estimation error of target radial velocity in the wideband LFMCW radar. Additionally, it performs better in terms of computing cost than the traditional fast Fourier transform (FFT) based approach and is robust to noise.
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图 1 快时间离散与连续时基带回波信号相位对比
Figure 1. Comparison of phases of baseband echoes in discrete and continuous fast time
图 3 基于FFT的运动目标回波多普勒速度谱
Figure 3. Doppler velocity spectrum of radar echoes from a moving target using FFT
图 4 基于本文方法的运动目标速度估计
Figure 4. Radial velocity estimation of moving target using the proposed method
图 5 传统FFT方法与本文方法的速度估计均方根误差对比
Figure 5. Comparison of RMSE of radial velocity estimates using traditional FFT and the proposed method
表 1 雷达系统仿真参数
Table 1. Simulation parameters of radar system
参数 数值 载波频率fc /GHz 10 脉宽τp/μs 5 带宽B/GHz 1 脉冲重复间隔Tp/s 1/200 采样率fs/MHz 100 
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表 2 传统FFT方法与本文方法在相同速度分辨率条件下的计算量对比
Table 2. Comparison of the computational cost between traditional FFT and the proposed method with the same velocity resolution
方法 计算量 传统FFT方法 8418696 本文方法 309 066
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