Signal Processing - March 2017 - 23

targets, while another might look at radar estiobjectives of a radar system are to detect
Advances in circuit
mation problems concerning their location and
the presence of one or more targets of
technology reinforced by
velocity in space relative to the radar [10], [11].
interest and estimate their range, angle, and
new signal processing
This article's goal is to review principal
motions relative to the radar [1].
algorithms, machine
developments in signal processing techTo the everyday person, tangible applicalearning, artificial
niques applied to estimating significant target
tions of radar include speed guns used by law
enforcement officers to detect speeding drivintelligence, and computer- parameters such as range, velocity, and direction. The article also discusses the characers. Action heroes in movies sometimes drive
vision techniques have
terization of radar waveforms and advanced
a fancy car with attractive features that can
made self-driving cars
estimation techniques that enhance the opertrack an enemy's speed and location, move
a reality.
ation of automotive radars. In particular, we
swiftly and automatically amid obstacles,
review each topic with adequate mathematiand debut its night vision feature during the
cal framework so as to make this a good start-up document for the
movie's climax. The ambition of having all of these add-ons to
newcomer in the field.
a car has become feasible with the flourishing mm-wave circuit
technology and advanced signal processing techniques. Advances
in circuit technology reinforced by new signal processing algoAutomotive radar classification
rithms, machine learning, artificial intelligence, and computerBoth autonomous and human-driven cars are increasingly using
vision techniques have made self-driving cars a reality.
radars to improve drivers' comfort and safety. For instance, park
Such cars also rely on different sensors such as a laser, a camassist and adaptive cruise control provide comfort, while warnera, ultrasound, global positioning system, and radar. Among
ing the driver of imminent collisions and overriding control of
these sensors, radar offers the possibility of seeing long distances
the vehicle to avoid accidents improve the safety. Figure 1 depicts
ahead of the car in poor visibility conditions, which can help avoid
various such radar subsystems that form ADASs. Each subsyscollisions [2]. For example, Google's self-driving car [3] has radars
tem has unique functionality and specific requirements in terms
mounted on both front and rear bumpers of the vehicle to detect
of radar range and angular measurement capability (Table 1).
objects in its surroundings.
The next section explains the fundamentals of location and speed
Automotive radars were first deployed several decades ago.
estimation using the radar measurements.
The evolution of automotive radar from its inception to the
present has been thoroughly discussed in [4]. With highly inteBasic automotive radar estimation problems
grated and inexpensive mm-wave circuits implemented in silicon,
A radar can simultaneously transmit and receive EM waves in
compact automotive radar safety systems have become a popular
frequency bands ranging from 3 MHz to 300 GHz. It is
feature [5], [6]. Since then, review articles written on automotive
designed to extract information [i.e., location, range, velocity
radar mostly covered the circuit implementation, market analysis,
and radar cross section (RCS)] about targets using the EM
and architectural-level signal processing [7]-[9]. However, there
waves reflected from those targets. Automotive radar systems
are many aspects of automotive radar signal processing techniques
typically operate at bands in 24 GHz and 77 GHz portions of
scattered throughout the literature. For example, a part of the litthe EM spectrum known as mm-wave frequencies so that higher
erature may concentrate on detecting the presence or absence of
velocity and range resolution can be achieved. Fundamental

Blind Spot
Detection

Long Range
Radar

Park Assist

Medium Range
Radar

Precrash

Blind Spot
Detection

Precrash

Park Assist

Short Range
Radar

Rear Collision
Warning

Cross Traffic Alert

e
ruis

rol

C
tive

ap
Ad

Figure 1. An ADAS consists of different range radars.
IEEE SIgnal ProcESSIng MagazInE

March 2017

Table of Contents for the Digital Edition of Signal Processing - March 2017