MULTI-TARGET PARAMETER ESTIMATION BASED ON
VELOCITY COMPENSATION IN FMCW RADAR
Qi-yong Liu
1
, Yu-Xue Sun
1
, Qun Zhang
1
, Xian-jiao Liang
2
1
Inst. of Information and Navigation, Air Force Engineering University, Xi’an, Shaanxi, 710077,
China
295100 PLA Troop, Guangzhou, Guangdong, 510405, China
lqyong0515@163.com
Keywords:
Multi-target, STLFMCW radar, Parameter
estimation, Envelope migration, Range-velocity
de-coupling
Abstract
The de-coupling of range and velocity can be easily
solved in symmetry triangular linear frequency
modulation continuous wave (STLFMCW) radar.
However, the peaks pairing may bring out ghost targets or
miss some targets in multi-target situation. To solve this
problem, a parameter estimation algorithm is proposed
based on velocity compensation. Firstly, a velocity matrix
containing targets velocities is obtained by peaks pairing
of one-dimensional range profile. Secondly, envelope
migration of one-dimensional range profile can be
compensated with the velocity. And the vague parameters
can be obtained by repairing the compensated peaks with
the first sweep peaks. Finally, accurate parameters are
obtained by rejecting the ghost targets. The effectiveness
of the proposed method is demonstrated by simulations.
1 Introduction
With the advantages of low transmitting power, no range
blind zone, lightweight and low cost, frequency
modulation continuous wave (FMCW) radar has been
widely used for detection and imaging of the target [1-2].
But the range and velocity coupling is a common problem
in moving target’s parameters estimation, which affects
the estimation accuracy [3]. This problem can be readily
solved in symmetry triangular linear frequency
modulation continuous wave (STLFMCW) radar [4].
However, in STLFMCW radar, it may bring out ghost
targets and miss some targets when the peaks of up-chirp
and down-chirp signal are pairing [5, 6]. Especially, when
the target’s one-dimensional range profile happened to
overlapping.
To solve this problem, an estimation algorithm based on
velocity compensation is proposed. Firstly, a velocity
matrix containing targets velocities is obtained by peaks
coupling of one-dimensional range profile. Secondly,
envelope migration of one-dimensional range profile can
be compensated with the velocity. Compensated peaks can
be repair with the first sweep peaks to get vague
parameters. Finally, accurate parameters are obtained by
rejecting the ghost targets.
2 Analysis of range migration
The signal models of transmitted signal and the received
signal are shown in Figure 1. Where,
is the
modulation bandwidth,
is the modulation period, and,
,
is the chirp rate,
is the carrier
frequency,
is the sweep period,
is the
delay time from the target.
Figure 1.
Signal models of STLFMCW
In dechirp-on-receive systems, the received and
transmitted signals are combined in order to reduce the
required A/D system sample rate. The beat frequencies for
the up-chirp and down-chirp are presented as, respectively,
and
.
2
i
i di ri m
v
f f f t
c
(1)
2
i
i di ri m
v
f f f t
c
(2)
Where,
is the Doppler frequency of the target.
is the range frequency of target. The third term is the
migration term.
means the i-th target. For long time
accumulation condition, the third term will cause the beat
frequencies shifting.
There is a conclusion from equation (1) and (2). When the
imaging time is adequate long, the envelopes of up-chirp
signal and down-chirp signal will bring out migration. But
the size and direction of the migration are similar in
up-chirp signal and down-chirp signal for the same target.
Thus, it can’t affect computing of the velocity. The