Aerospace and Electronic Systems Magazine September 2017 - 48

Feature Article:

DOI. No. 10.1109/MAES.2017.160142

Focus-Before-Detection Radar Signal Processing:
Part I-Challenges and Methods
Jia Xu, Beijing Institute of Technology, Beijing, China
Ying-Ning Peng, Tsinghua University, Beijing, China
Xiang-Gen Xia, Shenzhen University, Shenzhen, China, and University of Delaware,
Newark, DE, USA
Teng Long, Er-Ke Mao, Beijing Institute of Technology, Beijing, China;
Alfonso Farina (Retired), SELEX-Sistemi Integrati, Rome, Italy

INTRODUCTION
During the World War II (WWII), radar was invented as an all-day,
all-weather, long-range sensor. Over the past 75 years or so, radar
has acted as the clairvoyance and clairaudience of humans and has
had wide applications [1]-[19] in both defense and civilian fields,
e.g., surveillance, reconnaissance, fire control, border monitoring,
collision avoidance, and traffic control. Along with radar development, radar signal processing (RSP) always plays an important
role. In 1943, North [4] pointed out that the matched filter should
be the foundation of radar to detect targets from echoes generated
by the known transmitting waveform. In 1950, Woodward and Davies [5] introduced the Bayesian statistics theory into the RSP field
and proposed the constant false alarm ratio (CFAR) rule for target
detection. Based on matched filtering and the CFAR rule, the embryonic framework of classic RSP has been formed and used thus
far. In 1953, Woodward [6] further proposed an ambiguity function
as a useful tool to evaluate the range and Doppler discrimination
abilities of a transmitting waveform, which paves the foundation
for radar waveform design. Furthermore, to deal with the tradeoff
between large transmitting energy and high range resolution, the
early unmodulated rectangular waveform has been replaced by
more waveforms with a large time-bandwidth product (TBP), such
as linear frequency modulation (LFM) and phase-coded wave-

Authors' current addresses: J. Xu (deceased), T. Long, E.-K.
Mao, School of Information and Electronics, Beijing Institute
of Technology, Beijing 100081, China. Y.-N. Peng, Department
of Electronic Engineering, Tsinghua University, Beijing 100084,
China. X.-G. Xia, College of Information Engineering, Shenzhen University, Shenzhen 518060, China, and Department of
Electrical and Computer Engineering, University of Delaware,
Newark, DE 19716, USA. A. Farina, SELEX-Sistemi Integrati,
00131 Rome, Italy. Corresponding author is X.-G. Xia, E-mail:
(xxia@ee.udel.edu).
Manuscript received June 24, 2016, revised October 17, 2016,
and ready for publication January 5, 2017.
Review handled by D. O'Hagan.
0885/8985/17/$26.00 © 2017 IEEE
48

forms. These waveforms with large TBP have been widely used to
realize the range compression via matched filter.
So far, modern RSP has experienced fast development in many
related fields, and some of them are exemplified as follows. First,
with the fast development of transmitting and receiving (T/R) modular, phased antenna array (PAA) [8]-[12] has been widely used as
a substitute to the conventional mechanical rotating radar antenna.
Accordingly, the RSP in the spatial domain has undergone quick development based on element-by-element received signals. For example, the adaptive digital beamforming (ABF) can concentrate the
transmitting energy in the mainlobe while simultaneously notching
the active jamming in the sidelobe. In addition, super-resolution direction-of-arrival (DOA) estimation methods have been developed
to accurately measure the DOA of the electromagnetic wave.
Second, to cope with the ground and weather clutter, moving
target indication (MTI) via notch filter design has been widely applied, as well as moving target detection (MTD) via Doppler filter
bank processing [1]-[3]. In addition, to suppress the strong ground
clutter with expanded Doppler bandwidth caused by down-looking
of a moving platform, pulse-Doppler (PD) processing via pulse
repetition frequency (PRF) staggering and space-time adaptive
processing (STAP) [11], [12] have been widely studied.
Third, to cope with the clutter background with long-tail statistical distribution and spatially distributed targets caused by high
spatial resolution, new distributions and CFAR methods [1]-[3]
have been proposed, apart from the well-known cell-average, order
statistics, and nonparametric CFAR methods.
Fourth, with the increase of radar bandwidth and time on target
(TOT), modern synthetic aperture radar/inverse synthetic aperture
radar (SAR/ISAR) [14]-[16] can obtain high-resolution images
for targets or a scene via effective compensations of uncooperative motions caused by either the platform or the targets. Furthermore, high-resolution radars have promoted the development of
automatic target recognition (ATR) and microwave remote sensing
[16], [17].
With the development of the preceding RSP fields, the space-
time cascaded RSP framework [1]-[26] has been set up and widely
applied (Figure 1). The first part of RSP is in the space domain,

IEEE A&E SYSTEMS MAGAZINE

SEPTEMBER 2017



Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine September 2017

No label
Aerospace and Electronic Systems Magazine September 2017 - No label
Aerospace and Electronic Systems Magazine September 2017 - Cover2
Aerospace and Electronic Systems Magazine September 2017 - 1
Aerospace and Electronic Systems Magazine September 2017 - 2
Aerospace and Electronic Systems Magazine September 2017 - 3
Aerospace and Electronic Systems Magazine September 2017 - 4
Aerospace and Electronic Systems Magazine September 2017 - 5
Aerospace and Electronic Systems Magazine September 2017 - 6
Aerospace and Electronic Systems Magazine September 2017 - 7
Aerospace and Electronic Systems Magazine September 2017 - 8
Aerospace and Electronic Systems Magazine September 2017 - 9
Aerospace and Electronic Systems Magazine September 2017 - 10
Aerospace and Electronic Systems Magazine September 2017 - 11
Aerospace and Electronic Systems Magazine September 2017 - 12
Aerospace and Electronic Systems Magazine September 2017 - 13
Aerospace and Electronic Systems Magazine September 2017 - 14
Aerospace and Electronic Systems Magazine September 2017 - 15
Aerospace and Electronic Systems Magazine September 2017 - 16
Aerospace and Electronic Systems Magazine September 2017 - 17
Aerospace and Electronic Systems Magazine September 2017 - 18
Aerospace and Electronic Systems Magazine September 2017 - 19
Aerospace and Electronic Systems Magazine September 2017 - 20
Aerospace and Electronic Systems Magazine September 2017 - 21
Aerospace and Electronic Systems Magazine September 2017 - 22
Aerospace and Electronic Systems Magazine September 2017 - 23
Aerospace and Electronic Systems Magazine September 2017 - 24
Aerospace and Electronic Systems Magazine September 2017 - 25
Aerospace and Electronic Systems Magazine September 2017 - 26
Aerospace and Electronic Systems Magazine September 2017 - 27
Aerospace and Electronic Systems Magazine September 2017 - 28
Aerospace and Electronic Systems Magazine September 2017 - 29
Aerospace and Electronic Systems Magazine September 2017 - 30
Aerospace and Electronic Systems Magazine September 2017 - 31
Aerospace and Electronic Systems Magazine September 2017 - 32
Aerospace and Electronic Systems Magazine September 2017 - 33
Aerospace and Electronic Systems Magazine September 2017 - 34
Aerospace and Electronic Systems Magazine September 2017 - 35
Aerospace and Electronic Systems Magazine September 2017 - 36
Aerospace and Electronic Systems Magazine September 2017 - 37
Aerospace and Electronic Systems Magazine September 2017 - 38
Aerospace and Electronic Systems Magazine September 2017 - 39
Aerospace and Electronic Systems Magazine September 2017 - 40
Aerospace and Electronic Systems Magazine September 2017 - 41
Aerospace and Electronic Systems Magazine September 2017 - 42
Aerospace and Electronic Systems Magazine September 2017 - 43
Aerospace and Electronic Systems Magazine September 2017 - 44
Aerospace and Electronic Systems Magazine September 2017 - 45
Aerospace and Electronic Systems Magazine September 2017 - 46
Aerospace and Electronic Systems Magazine September 2017 - 47
Aerospace and Electronic Systems Magazine September 2017 - 48
Aerospace and Electronic Systems Magazine September 2017 - 49
Aerospace and Electronic Systems Magazine September 2017 - 50
Aerospace and Electronic Systems Magazine September 2017 - 51
Aerospace and Electronic Systems Magazine September 2017 - 52
Aerospace and Electronic Systems Magazine September 2017 - 53
Aerospace and Electronic Systems Magazine September 2017 - 54
Aerospace and Electronic Systems Magazine September 2017 - 55
Aerospace and Electronic Systems Magazine September 2017 - 56
Aerospace and Electronic Systems Magazine September 2017 - 57
Aerospace and Electronic Systems Magazine September 2017 - 58
Aerospace and Electronic Systems Magazine September 2017 - 59
Aerospace and Electronic Systems Magazine September 2017 - 60
Aerospace and Electronic Systems Magazine September 2017 - 61
Aerospace and Electronic Systems Magazine September 2017 - 62
Aerospace and Electronic Systems Magazine September 2017 - 63
Aerospace and Electronic Systems Magazine September 2017 - 64
Aerospace and Electronic Systems Magazine September 2017 - Cover3
Aerospace and Electronic Systems Magazine September 2017 - Cover4
http://www.brightcopy.net/allen/aesm/34-2s
http://www.brightcopy.net/allen/aesm/34-2
http://www.brightcopy.net/allen/aesm/34-1
http://www.brightcopy.net/allen/aesm/33-12
http://www.brightcopy.net/allen/aesm/33-11
http://www.brightcopy.net/allen/aesm/33-10
http://www.brightcopy.net/allen/aesm/33-09
http://www.brightcopy.net/allen/aesm/33-8
http://www.brightcopy.net/allen/aesm/33-7
http://www.brightcopy.net/allen/aesm/33-5
http://www.brightcopy.net/allen/aesm/33-4
http://www.brightcopy.net/allen/aesm/33-3
http://www.brightcopy.net/allen/aesm/33-2
http://www.brightcopy.net/allen/aesm/33-1
http://www.brightcopy.net/allen/aesm/32-10
http://www.brightcopy.net/allen/aesm/32-12
http://www.brightcopy.net/allen/aesm/32-9
http://www.brightcopy.net/allen/aesm/32-11
http://www.brightcopy.net/allen/aesm/32-8
http://www.brightcopy.net/allen/aesm/32-7s
http://www.brightcopy.net/allen/aesm/32-7
http://www.brightcopy.net/allen/aesm/32-6
http://www.brightcopy.net/allen/aesm/32-5
http://www.brightcopy.net/allen/aesm/32-4
http://www.brightcopy.net/allen/aesm/32-3
http://www.brightcopy.net/allen/aesm/32-2
http://www.brightcopy.net/allen/aesm/32-1
http://www.brightcopy.net/allen/aesm/31-12
http://www.brightcopy.net/allen/aesm/31-11s
http://www.brightcopy.net/allen/aesm/31-11
http://www.brightcopy.net/allen/aesm/31-10
http://www.brightcopy.net/allen/aesm/31-9
http://www.brightcopy.net/allen/aesm/31-8
http://www.brightcopy.net/allen/aesm/31-7
https://www.nxtbookmedia.com