时延-频率匹配滤波器在距离扩展目标检测中的应用

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"这篇研究论文探讨了一种新颖的时间延迟-频率匹配滤波器（t-f-MF）在混频器输出中的应用，用于在白高斯噪声背景下设计一种新的距离扩展目标检测方法。该方法首先证明了目标的混频器输出是由多个正弦信号组成的，然后构建了混频器输出的匹配信号。接下来，利用匹配信号得到混频器输出的t-f-MF。目标信号的t-f-MF能量集中在零频率附近，而白高斯噪声的能量则分散在整个频率域中。" 这篇研究论文主要关注的是雷达信号处理领域的一个重要问题——如何在存在噪声的情况下有效地检测距离扩展的目标。距离扩展目标（Range-spread target）是指由于多路径传播、雷达回波扩散等原因导致其回波信号在时间和频率上具有较宽分布的目标。 1. 时间延迟-频率匹配滤波器（t-f-MF）: 这是一种特殊类型的滤波器，设计目的是优化对特定时间延迟和频率特征的信号检测。在本研究中，t-f-MF被应用于混频器输出，混频器是雷达接收机中的关键部件，它将接收到的射频信号转换到中频以便进一步处理。 2. 目标信号分析：论文指出，目标的混频器输出可以看作是多个不同频率的正弦信号的组合。这可能是因为目标反射的雷达波经过了不同的传播路径，产生了不同时间延迟的信号。 3. 匹配信号构造：为了从噪声中提取目标信号，研究人员首先构造了与预期目标特征相匹配的信号，即匹配信号。这个过程涉及到对原始混频器输出信号的预处理，以增强目标信号的特性并抑制噪声。 4. t-f-MF的应用：通过匹配信号，论文提出了计算混频器输出的t-f-MF的方法。t-f-MF的主要优点在于它能够将目标信号的能量集中在零频率附近，形成一个能量尖峰，而噪声的能量则在更广泛的频率范围内分布，从而提高了信噪比，增强了目标检测能力。 5. 白高斯噪声处理：在雷达系统中，白高斯噪声是最常见的干扰源之一，其功率在所有频率上均匀分布。论文提出的方法通过t-f-MF有效地区分了目标信号和噪声，提高了目标检测的精度和可靠性。 6. 结论与应用：这项研究提供了一种新颖的检测策略，对于改进雷达系统在复杂环境下的目标检测性能有重要意义，特别是在面对距离扩展目标时。这种方法可能适用于各种雷达应用场景，如空中交通监控、海洋探测、军事侦察等。通过深入理解和应用t-f-MF，雷达系统设计者可以开发出更高效的信号处理算法，以应对噪声背景下的目标检测挑战，提高雷达系统的整体性能。

Range-spread target detection using time

delay-frequency matched filter

ISSN 1751-8784

Received on 14th June 2015

Revised on 14th October 2015

Accepted on 23rd November 2015

doi: 10.1049/iet-rsn.2015.0315

www.ietdl.org

Lei Zuo

1,2

✉

, Ming Li

1,2

, Zheng Liu

1,2

, Runqing Cao

National Lab of Radar Signal Processing, Xidian University, Xi’an Shaanxi 710071, People’s Republic of China

Collaborative Innovation Center of Information Sensing and Understanding at Xidian University, People’s Republic of China

✉ E-mail: lzuo@mail.xidian.edu.cn

Abstract: A novel time delay-frequency matched filter (t-f-MF) of a mixer output is presented in this study and it is used to

design a new range-spread target detector in the background of white Gaussian noise. First, the mixer output of a target is

proved to be composed of several sinusoidal signals, and then the matched signal of the mixer output is constructed.

Next, the authors use the matched signal to obtain the t-f-MF of a mixer output. The en ergy of the t-f-MF for the target

signal concentrates around zero frequency, whereas that for the white Gaussian noise spreads over the entire

frequency domain. According to this, the authors design a range-spread target detector that is capable of detecting a

target with high velocity. The proposed detector is evaluated by measured radar data. Experimental results show that

the proposed detector outperforms the con ventional detectors. The results also sh ow that the detecto r is rob ust

against the target gesture.

1 Introduction

A high resolution radar (HRR) can resolve a target into a number of

individual scatterers [1, 2]. When the range resolution of the radar is

lower than the physical dimensions of the target, the target spreads

over several range cells and is called a range-spread target or a

distributed target. Over the past decades, range-spread target

detection has attracted considerable attention for two advantages:

HRRs provide abundant information of the target, and returned

signals received by HRRs ﬂuctuate less than those received by low

resolution radars. Many detection schemes for range-spread targets

have been extensively investigated in [3–12], including the

generalised likelihood ratio test (GLRT)-based detector [6–9], the

Rao or Wald principle test [10 , 11], and the detector with the

autoregressive Gaussian model [11, 12].

In addition, there is another kind of algorithm to detect

range-spread targets [13–18], which is based on high resolution

range proﬁles (HRRPs) or mixer outputs (the inverse discrete

Fourier transform [DFT] of HRRPs). A detector, called the

scatterer density dependent GLRT (SDD-GLRT), is presented in

[13] to detect range-spread targets in white Gaussian noise. Using

a single HRRP, the SDD-GLRT is realised by a well-designed

non-linear map and an integrator. Then, instead of using a single

HRRP, detection algorithms using multiple HRRPs are developed

to improve the detection performance [14–16]. Two methods to

detect range-spread targets with manoeuvring ﬂight in white

Gaussian noise are discussed in [14, 15]. One exploits the

waveform entropy of the arithmetic average of multiple successive

HRRPs [14]. The other uses a two-dimensional non-linear

shrinkage map relevant to the local statistics of the range-pulse

image [15]. Both detectors can non-coherently integrate multiple

HRRPs of a target. However, they are seriously affected by the

target motion, including the translational velocity and the

rotational velocity. An alternative way to detect range-spread

targets is to exploit two mixer outputs [16, 17]. The detector in

[16] assumes that two adjacent HRRPs are highly correlated. Thus,

this detector is only suitable for the target with a low velocity.

Despite the fact that the detector in [17] reduces the effect of the

translational velocity, it is invalid for the target with a high

rotational velocity or a main part rotating rapidly. In [18], the

frequency rate of a noisy mixer output is used to detect a

target with a high velocity. However, it has a high calculation

complexity.

In this paper, we deal with the problem of detecting a range-spread

target in white Gaussian noise, where the target travels with high

velocity. The high velocity results in serious range migration,

which heavily degrades the performance of the method using

multiple mixer outputs. To detect a range-spread target, we

construct the matched signal of the noisy mixer output. Based on

the matched signal, the time delay-frequency matched ﬁlter

(

t-f-MF) of the noisy mixer output is derived. The energy of the

t-f-MF for the target signal concentrates around zero frequency,

whereas that for the white Gaussian noise spreads over the entire

frequency domain. Therefore, regarding the energy around zero

frequency of the t-f-MF at zero time delay as test statistic, we

obtain our detector. The proposed detector only relies on one

mixer output and is not affected by the range migration. Thus, the

proposed detector can detect a target with a high velocity.

The performance assessment of this detector is carried out by the

recorded radar data. Experimental results show that the proposed

detector outperforms conventional methods and is robust against

the target gesture.

The remainder of this paper is organised as follows. In Section 2,

the signal model of the range-spread target is introduced and the

mixer output is proved to be a sum of sinusoidal signals. In

Section 3, we propose the detector using the constructed matched

signal. The detector is evaluated by the recorded database of two

aircrafts and experimental results are presented in Section 4.

Finally, the paper is concluded in Section 5.

2 Signal model of range-spread target

In HRR systems, the high-bandwidth linear frequency modulation

signal is used to get the high range resolution. Therefore, the

range cell is much smaller than the target size along the radar line

of sight (LOS) and the scatterers distribute over several range cells

[2]. Consequently, the returned signal is the superposition of the

returned signals of individual scatterers, which is commonly

processed by stretch processing. This technique consists of the

following steps: First, the returned signals are mixed with a

reference signal, which is the replica of the transmitted waveform

IET Radar, Sonar & Navigation

Research Article

IET Radar Sonar Navig., 2016, Vol. 10, Iss. 4, pp. 742–748

742

The Institution of Engineering and Technology 2016

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