Article
Detection of Low RCS Supersonic Flying Targets with
a High-Resolution MMW Radar
Nezah Balal, Yael Balal * , Yair Richter and Yosef Pinhasi
Faculty of Engineering, Ariel University, Ariel 40700, Israel; nezahb@ariel.ac.il (N.B.);
yairrichter@gmail.com (Y.R.); yosip@ariel.ac.il (Y.P.)
* Correspondence: yaelba@ariel.ac.il
Received: 14 April 2020; Accepted: 6 June 2020; Published: 9 June 2020
Abstract:
In this study, the detection of a low radar cross-section (RCS) target moving at a very high
speed using a high-resolution millimeter-wave radar is presented. This real-time detection is based
on the transmission of a continuous wave and heterodyning of the received signal reflected from the
moving target. This type of detection enables one to extract the object’s movement characteristics, such
as velocity and position, while in motion and also to extract its physical characteristics. In this paper,
we describe the detection of a fired bullet using a radar operating at an extremely high-frequency
band. This allowed us to employ a low sampling rate which enabled the use of inexpensive and
straightforward equipment, including the use of small antennas that allow velocity detection at high
resolution and with low atmospheric absorption.
Keywords: Doppler radar; millimeter wave radar; catalog targets
1. Introduction
The real-time detection of small, high-speed objects, such as fired bullets, is essential for security
and civilian applications [
1
–
4
]. This type of detection enables one to track and identify the sources
of gunshots as well to determine the instantaneous velocity of objects, calculate the drag constant of
objects, and analyze the ballistic movement of objects.
The devices currently available for this type of detection operate in the optical field, and thus
require the use of an extensive array of sensors located at various points as well as synchronization
between all these sensors [
5
–
8
]. When the detection location is known, it is possible to use high-speed
photography. Using this method limits the number of images that can be taken per second. Therefore,
the maximum speed of the object to be detected and the computational speed resolution of this system
are limited.
Doppler radar-based systems have several advantages over optical systems for real-time detection.
The Doppler frequency, which is directly linked to the relative speed between the moving object and
the radar, can be measured at a relatively low sampling rate, and therefore, no unique or expensive
equipment is required for such measurements. Measuring the instantaneous Doppler frequency
enables one to calculate the instantaneous velocity of an object at a high resolution.
In this article, we propose a real-time detection system based on a millimeter-wave (MMW)
Doppler radar that transmits a continuous wave (CW) waveform. The reflected wave, scattered from a
moving target is shifted in frequency due to the Doppler effect. Millimeter wave (MMW) radars are
becoming more and more commercial and applicable due to recent technological developments [
9
–
11
].
They are employed as detection measures in many applications, such as collision avoidance radars in
automobiles [
12
,
13
]. Detecting a target with a Doppler MMW radar has several advantages compared
to other remote sensing technologies operating in infrared or optical wavelengths, mainly in foggy
conditions and stationary background clutter scenarios [
14
–
16
]. Although millimeter waves are
Sensors 2020, 20, 3284; doi:10.3390/s20113284 www.mdpi.com/journal/sensors
