IEEE - Aerospace and Electronic Systems - January 2020 - 20

Feature Article:

DOI. No. 10.1109/MAES.2019.2955575

Entomological Radar Overview: System and Signal
Processing
Teng long, Cheng Hu, Rui Wang, Tianran Zhang, Shaoyang Kong, Weidong Li,
Jiong Cai, Weiming Tian, Tao Zeng, Beijing Institute of Technology, Beijing,
China

INTRODUCTION
INSECT migration is a significant ecological phenomenon
in nature and massive number of insects migrates seasonally, which can lead to huge exchange of biomass and
nutrients across the Earth surface with the impacts on ecosystems, such as population community structure and
dynamics via predators, prey, and competitors [1], [2].
Insect migration also plays an important role in spreading
pollen and pathogenic microorganisms [3]. In addition, as
many migrating insects are agricultural pests, their migration could cause heavy loss of crops [4]. Therefore, it is
crucial to monitor insect migration, both for scientific
research and as an early warning system for pests.
However, migratory insects are small and fly hundreds
of meters above the ground at night, which makes it difficult
to directly observe them. Traditional monitoring techniques
for insect migration such as optical systems, aerial net sampling, and searchlight trapping have many problems and
shortcomings [5]-[7]. Optical systems are severely impaired
at night while the coverage range of aerial net sampling
does not meet the demands of long-range observation. In
addition, aerial net sampling is a labor-intensive and timeconsuming process that is unsuitable for the real-time monitoring of windborne migratory insects [6]. Similarly, searchlight trapping is an indirect sampling method that is easily
influenced by moonlight or other illuminators [7].

Authors' current addresses: Teng Long, Cheng Hu, Rui
Wang, Tianran Zhang, Shaoyang Kong, Weidong Li,
Jiong Cai, Weiming Tian, and Tao Zeng are with the
School of Information and Electronics, Beijing Institute
of Technology, Beijing 100811, China. E-mail:
(cchchb@163.com).
Corresponding author: Cheng Hu.
Manuscript received November 30, 2018, revised
August 26, 2019; accepted October 15, 2019, and ready
for publication November 21, 2019.
Review handled by P. W. Kinman.
0885-8985/19/$26.00 ß 2019 IEEE
20

Radar remains one of the most effective tools for
observing insect flight [8]; it works in all-weather and alltime conditions. The basic principle of the radar is to
transmit radio-frequency electromagnetic (EM) waves
into a region of interest and receive echoes backscattered
by targets. Radar was found to be suitable for monitoring
insect migration in the early 1960s [9]. Ever since the first
insect radar system was built, some special-purpose insect
radars have subsequently been developed, including airborne insect radar, scanning insect radar, tracking insect
radar, and vertical-looking radar (VLR) [11]-[13]. Important milestones have been recorded using these entomological radars to monitor insect migration observation,
such as high-density layering and common orientation of
high-flying migrants [14], [15], which have significantly
extended the knowledge of insect migration for human
beings. A new interdisciplinary field has evolved from this
field, which is now called radar entomology.
Until now, scanning insect radar and VLR are widely
used for insect migration. Scanning insect radar was
invented in the 1960s and remodeled by a commercial
marine radar (wavelength 3.2 cm). The radar used a variable elevation and parabolic dish-type antenna in which
the entire unit was placed in a small vehicle [9]. This simple, low-cost system was found extremely effective for
detecting medium to large insect targets (0.5-4 cm2) with
a detection range of 1-2 km from September-October
1968 in Niger [9], [17], [18]. This expedition is the foundation for radar entomology. The insect radar (wavelength
3.2 cm) used by the Commonwealth Scientific and Industrial Research Organization in Australia comprises a typical scanning insect radar with scanning pencil-beam units
[16] that was purpose-built in 1976 (replacing a unit based
on a military radar trailer) and used regularly over the following 10 years. In addition to the various X-band insect
radars, a scanning radar that operates at the much shorter
wavelength of 8.8 mm (i.e., Ka-band) was built in the
early 1980s to detect small insects [19]. This Ka-band
insect radar made it possible to observe planthoppers
(Delphacidae), which are Rayleigh-region targets with

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