Aerospace and Electronic Systems Magazine September 2017 - 32

RCS Measurements and ISAR Images of Small UAVs

CONCLUSIONS
RCS measurement of a toy drone and a professional quadcopter
has been carried out. A significant finding of this work is that
Swerling distribution is in very good agreement with the RCS statistical distribution of the quadcopters we tested. This is not an
obvious fact. Swerling Case I distribution was obtained in a very
heuristic hypothesis (a random set of equal scatters on a planar
surface) and-at least in the open literature-it has never been
tested with quadcopters or other small UAVs. Another finding that
is worth mentioning is that mean RCS in vertical and horizontal
polarization are nearly equal.

ACKNOWLEDGMENT
The authors are grateful to Prof. Alberto del Bimbo, director of
MICC (Media Integration and Communication Center), who kindly made the AirVision quadcopter available all the necessary time
to compile the RCS measurements.

Figure 9.

3D-ISAR image of AirVision quadcopter.

REFERENCES

Figure 9 shows the contour plot of the 3D image of the bigger
UAV. The height of the platform was varied of 26 cm at step of 1.0
cm. The shape of the motors (a couple of motors in line to be more
precise) are clearly recognizable, as well as the legs and the head
of quadcopter.
Finally, by using the whole measurement set (9,270 single acquisitions), we calculated the RCS statistical distribution, as shown
in Figure 10, that resulted in very good agreement with the wellknown Swerling Case I distribution [12]:
p (σ ) =

1

σ

e

−

σ
σ

[1]
[2]

[3]

[4]

(4)

where σ is the mean value of RCS. Indeed the χ2 goodness-of-fit
test rejected the null hypothesis at the 1% significance level.

[5]

[6]
[7]

[8]

[9]
[10]
[11]

[12]

Figure 10.

RCS distribution of AirVision quadcopter using the whole measurement
set for 3D ISAR. The full line is the Swerling distribution.

32

IEEE A&E SYSTEMS MAGAZINE

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SEPTEMBER 2017

http://edition.cnn.com/2015/10/07/politics/faa-anti-dronetechnology/ http://edition.cnn.com/2015/10/07/politics/faa-anti-dronetechnology/ http://www.nytimes.com/2016/01/10/opinion/sunday/drone-regulations-should-focus-on-safety-and-privacy.html?_r=0 http://www.nytimes.com/2016/01/10/opinion/sunday/drone-regulations-should-focus-on-safety-and-privacy.html?_r=0 http://www.nytimes.com/2016/01/10/opinion/sunday/drone-regulations-should-focus-on-safety-and-privacy.html?_r=0

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