IEEE - Aerospace and Electronic Systems - January 2020 - 22

Entomological Radar Overview: System and Signal Processing
Table 1.

System Parameters of Scanning Insect Radars Used in
America and China
Parameters

Values
APMRUÃ

KC2 (China)

Wavelength

3.2 cm

Pulsewidth

0.05/0.25/1.0
ms

0.08/0.3/0.6/
1.2 ms

Horizontal
scan rate

20-60 r/min

8 r/min

Peak power

25 kW

10 kW

Antenna
diameter

1.22 m

1.5 m

Polarization
Elevation

horizontal
polarization

0-90

À2-60

Ã. Areawide Pest Management Research Unit in America

Figure 1.
Elevation angles and radar detection range design of the scanning
insect radar proposed by Drake [14].

such as collective orientation. This motivated more entomologists to develop insect radars in America, Australia,
and China. Table 1 shows the system parameters of two
scanning insect radars used in America and China.
Scanning insect radars can be used to measure the vertical density profile of insect migration. Unlike military
radars that have full elevation coverage, scanning insect
radars are designed to perform the azimuthal scanning at
several discrete elevation angles and only the continuity
of height coverage is achieved. To reduce the overlap in
height coverage, the elevation angles are optimally
designed based on the radar detection range. For example,
the design by Drake in [14] shown in Figure 1 contain a
total of 11 elevation angles, including 0.7 , 1.8 , 3 , 5 ,
8 , 12 , 18 , 28 , 45 , 58 , and 70 , with a height coverage
of about 5-1300 m. The detection range is around 900-
1400 m for elevation angles less than 45 and around
1100-1400 m for other elevation angles.
To calculate the vertical density profile of aerial
insects, it is essential to estimate the insect quantity and
the corresponding volume in each height layer. For the
insect quantity, it should be noted that it is not possible to
detect all the insect targets in a radar beam. The detection
depends on the signal-to-noise ratio (SNR). If an insect's
echo signal power is submerged by noise, as is the case
for some small insect species, the insect cannot be
detected successfully. An SNR of over 16 dB is required
to ensure a detection probability of 90% and a false alarm
rate of 10À6, based on the basic principle of constant false
alarm rate, also referred to as detectable SNR [31].
22

3
1.8
0.7

Using the radar equation for monostatic radars, the
SNR can be expressed as
SNR ¼ C0

s RCS Á G2 ðuÞ
R4

(1)

where C0 is a constant related to the system parameters
such as transmitted peak power, system loss, etc., s RCS
represents the RCS of the target, R represents the slant
range from the radar to target, and GðuÞ is the antenna
gain, where u represents the target's position in the
antenna beam in terms of the angle deviation from the
central axis of the main lobe. For a parabolic antenna, the
antenna gain can be approximated as a Gaussian function
as follows [32]:
GðuÞ ¼ G0 exp À2:776 Á

u2
u3dB 2

!
(2)

where G0 is the maximal antenna gain and u3dB is the halfpower beamwidth.
This shows that the detectable SNR is a function of the
RCS of the insects, the slant range, and the antenna gain.
Meanwhile, these parameters also affect the volume calculation for each height layer, as shown in Figure 2. In other
words, for a certain height layer, the deviation angle u
from the central axis of the main lobe varies with the
target's RCS. This implies that insects with different
RCSs yield different detectable volumes. Therefore, the
aerial density of insects should be calculated according to

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