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首页论文研究 - 自适应MTI滤波器的优化
论文研究 - 自适应MTI滤波器的优化

移动目标指示(MTI)是雷达在杂乱环境中找到移动目标的有效手段。 本文介绍了MTI的基本原理,如何避免盲目速度问题以及MTI滤波器的优化。 实现基于特征向量法优化的在不同情况下使用交错码设计的多级自适应运动目标指示(AMTI)滤波器。
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Int. J. Communications, Network and System Sciences, 2017, 10, 206-217
http://www.scirp.org/journal/ijcns
ISSN Online: 1913-3723
ISSN Print: 1913-3715
DOI: 10.4236/ijcns.2017.108B022
August 14, 2017
Optimization of Adaptive MTI Filter
Wenxu Zhang, Shudi Ma, Qiuying Du
College of Information and Communication Engineering, Harbin Engineering University, Harbin, China
Abstract
Moving target indication (MTI) is an effective means for radar to find moving
targets in clutter environment. This paper introduces the basic principles
of
MTI, how to avoid the blind speed problem and the optimization of MTI fi
l-
ter. Implementing the multi-
notch adaptive moving target indication (AMTI)
filter that designed by using the stagger code in varied cases, which is
based on
a feature vector method optimization.
Keywords
Adaptive Moving Target Indication (AMTI), Stagger Code, Feature
Vector
Method, Multi-Notch
1. Introduction
MTI band-stop filter as a “single channel”, followed by detection is relatively
simple. When the target speed is large and the repetition frequency is low, make
sure that there is no distance blur, through the “variable week” variable repeat
cycle or repeat and “time varying” [1]. Can overcome the blind speed problem,
the drawback is no improvement in noise. In general, the mess is not very strong,
the radar can handle a limited number of pulses, suitable for the use of repetitive
and time-varying weighted system. The adaptive has a variety of ways to achieve,
in which the performance is better “first order” and “second order”. The first-
order basic method is to use the interval-based velocity measurement and the
zero-point distribution method to determine the weighting parameters of the
clutter cancellation filter to obtain the filter whose notch is aligned with the cen-
ter of the clutter spectrum [2]. Its advantages are simpler, the disadvantage is
that it cannot be adaptive with the clutter spectrum, so sometimes the perfor-
mance is worse. The second-order basic method is to estimate the clutter cova-
riance matrix, and then use matrix inversion or feature decomposition feature
vector method to determine the filter weight coefficient.
This paper first analyzes the moving target indication (MTI), on this basis, the
How to cite this paper:
Zhang, W.X., Ma
,
S.D. and
Du, Q.Y. (2017)
Optimization of
Adaptive MTI Filter
.
Int. J. Communic
a-
tions
,
Network and System Sciences
,
10
,
206
-217.
https://doi.org/10.4236/ijcns.2017.108B022
Received:
May 31, 2017
Accepted:
August 11, 2017
Published:
August 14, 2017

W. X. Zhang et al.
207
MTI is optimized, and the appropriate filter coefficients are designed by the fea-
ture vector method, which can effectively suppress the clutter. And the use of
stagger code design MTI filter to eliminate the impact of blind speed. For mo-
tion clutter, the spectral center is not at zero frequency, and is time-varying. In
order to suppress such clutter, this paper adopts adaptive motion clutter sup-
pression technique AMTI, and designs multi-notch AMTI filter [3].
2. Research on Adaptive Clutter Suppression Algorithm
The earliest MTI filter is a delay line canceller, is currently one of the most
commonly used MTI filter. According to the different number of cancellation,
but also divided into single delay line canceller, double delay line canceller and
multi-delay line canceller [4].
Single delay line canceller as shown in
Figure 1, the impulse response of the
single delay line canceller is expressed as
( )
ht
, and output
( )
yt
is equal to the
convolution between the impulse response
( )
ht
and the input
( )
xt
[5].
The impulse response of the counter is:
( ) ( )
( )
r
ht t t T
δδ
= −−
(1)
The power gain of the single delay line canceller is:
( )
2
2
4 sin
2
r
T
H
ω
ω
=
(2)
Double delay line canceller as shown in
Figure 2. The response of the double
delay line canceller is
( ) ( ) ( )
( )
22
rr
ht t t T t T
δδ δ
= − −+ −
(3)
DelayT
r
Σ
+
-
x(t)
y(t)
h(t)
Figure 1. Single delay line canceller.
DelayT
r
Σ
+
-
x(t)
y(t)
h(t)
DelayT
r
Σ
+
-
Figure 2. Double delay line canceller.

W. X. Zhang et al.
208
The double delay line canceller impulse response is:
( )
( )
( )
4
2 22
11
16 sin
2
r
T
H HH
ω
ω ωω
= =
(4)
The adaptive moving target indication (AMTI) filter is usually composed of a
FIR filter with a horizontal structure. The output of the MTI filter is:
( ) ( ) ( )
1
0
N
T
i
i
Y n W X n wx n i
−
=
= = −
∑
(5)
where
W
is the weight vector and
( )
Xn
is the input signal vector. The fre-
quency response of this filter is:
( )
( )
1
0
exp 2
N
ii
i
H f w j fT
π
−
=
= −
∑
(6)
In the radar system, in order to avoid the occurrence of blind effects, usually
the use of “variable T” approach, that is, by regularly changing the radar launch
pulse period so that the frequency of blindness is greater than the target possible
Doppler frequency. Adaptive clutter suppression is compatible with parametric
techniques, meaning that the clutter suppression filter must be time-varying. For
the determined
N
value, the frequency characteristic of the MTI filter is de-
termined only by the weight vector, so the calculation of the weight vector is the
core of the MTI process, according to different design methods, the optimal
weight vector is generally different. In engineering practice, the improvement
factor is often used to measure the performance of MTI system. The improve-
ment factor of the MTI filter is defined as
( ) ( )
0
/ //
o ii
I SC SC=
. Obviously, the
greater the
I
, the better the effect of the system on clutter suppression. It has
been proved that the optimal weight vector of the MTI filter should be the ei-
genvector corresponding to the minimum eigenvalue of the covariance matrix of
the input clutter, in order to maximize the average improvement factor of the
MTI. At this point the improvement factor is
max min
1/I
λ
=
[6].
2.1. Optimal Design of Filter
The so-called optimization design requires a set of optimal filter coefficients, to
maximize the improvement factor, a lot of design methods. In the case of the va-
riable T, the better methods are feature vector method, matching algorithm, ze-
ro-point allocation method and linear prediction method [7]. The feature vector
method is the solution that minimizes the clutter output power when the target
gain is constant. The zero-point assignment method is to set the frequency re-
sponse zero at the notch when designing the band-stop filter. The matching al-
gorithm and the linear prediction method are the solutions that minimize the
clutter output power when one of the elements of the weight vector is constant.
So the feature vector method has better performance [8].
The feature vector method is a clutter suppression method based on the
maximum improvement factor.
It is usually assumed that the clutter has a Gaussian power spectrum, the
spectral center is
0
f
, the spectral width is
f
σ
, and the spectral density function
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