Automotive radars, along with other sensors such as lidar, (which stands for "light detection and ranging"), ultrasound, and cameras, form the backbone of self-driving cars and advanced driver assistant systems (ADASs). These technological advancements are enabled by extremely complex systems with a long signal processing path from radars/sensors to the controller. Automotive radar systems are responsible for the detection of objects and obstacles, their position, and speed relative to the vehicle. The development of signal processing techniques along with progress in the millimeter-wave (mm-wave) semiconductor technology plays a key role in automotive radar systems. Various signal processing techniques have been developed to provide better resolution and estimation performance in all measurement dimensions: range, azimuth-elevation angles, and velocity of the targets surrounding the vehicles. This article summarizes various aspects of automotive radar signal processing techniques, including waveform design, possible radar architectures, estimation algorithms, implementation complexity-resolution trade off, and adaptive processing for complex environments, as well as unique problems associated with automotive radars such as pedestrian detection. We believe that this review article will combine the several contributions scattered in the literature to serve as a primary starting point to new researchers and to give a bird's-eye view to the existing research community.

Automotive Radars: A review of signal processing techniques

Millimeter-wave (mmWave) radar is widely used in vehicles for applications such as adaptive cruise control and collision avoidance. In this paper, we propose an IEEE 802.11ad-based radar for long-range radar (LRR) applications at the 60 GHz unlicensed band. We exploit the preamble of a single-carrier physical layer frame, which consists of Golay complementary sequences with good correlation properties that make it suitable for radar. This system enables a joint waveform for automotive radar and a potential mmWave vehicular communication system based on the mmWave consumer wireless local area network standard, allowing hardware reuse. To formulate an integrated framework of vehicle-to-vehicle communication and LRR, we make typical assumptions for LRR applications, incorporating the full duplex radar operation. This new feature is motivated by the recent development of systems with sufficient isolation and self-interference cancellation. We develop single- and multi-frame radar receiver algorithms for target detection as well as range and velocity estimation for both single- and multi-target scenarios. Our proposed radar processing algorithms leverage channel estimation and time–frequency synchronization techniques used in a conventional IEEE 802.11ad receiver with minimal modifications. Analysis and simulations show that in a single-target scenario, a gigabits-per-second data rate is achieved simultaneously with cm-level range accuracy and cm/s-level velocity accuracy. The target vehicle is detected with a high probability (above 99.99 $\%$ ) at a low false alarm rate of 10 $^{-6}$ for an equivalent isotropically radiated power of 40 dBm up to a vehicle separation distance of about 200 m. The proposed IEEE 802.11ad-based radar meets the minimum accuracy/resolution requirement of range and velocity estimates for LRR applications.

IEEE 802.11ad-Based Radar: An Approach to Joint Vehicular Communication-Radar System

For a typical FMCW automotive radar system, a new design of baseband signal processing architecture and algorithms is proposed to overcome the ghost targets and overlapping problems in the multi-target detection scenario. To satisfy the short measurement time constraint without increasing the RF front-end loading, a three-segment waveform with different slopes is utilized. By introducing a new pairing mechanism and a spatial filter design algorithm, the proposed detection architecture not only provides high accuracy and reliability, but also requires low pairing time and computational loading. This proposed baseband signal processing architecture and algorithms balance the performance and complexity, and are suitable to be implemented in a real automotive radar system. Field measurement results demonstrate that the proposed automotive radar signal processing system can perform well in a realistic application scenario.

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Design of an FMCW radar baseband signal processing system for automotive application

This paper reviews the state of the art in spin-torque and spin-Hall-effect-driven nano-oscillators. After a brief introduction to the underlying physics, the authors discuss different implementations of these oscillators, their functional properties in terms of frequency range, output power, phase noise, and modulation rates, and their inherent propensity for mutual synchronization. Finally, the potential for these oscillators in a wide range of applications, from microwave signal sources and detectors to neuromorphic computation elements, is discussed together with the specific electronic circuitry that has so far been designed to harness this potential.

Spin-Torque and Spin-Hall Nano-Oscillators

As we edge closer to the broad implementation of intelligent transportation systems, the need to extend the perceptual bounds of sensor-equipped vehicles beyond the individual vehicle is more pressing than ever. Research and standardization efforts toward vehicle to everything (V2X), technology is intended to enable the communication of individual vehicles with both one another and supporting road infrastructure. The topic has drawn interest from a large number of stakeholders, from governmental authorities to automotive manufacturers and mobile network operators. With interest sourced from many disparate parties and a wealth of research on a large number of topics, trying to grasp the bigger picture of V2X development can be a daunting task. In this tutorial survey, to the best of our knowledge, we collate research across a number of topics in V2X, from historical developments to standardization activities and a high-level view of research in a number of important fields. In so doing, we hope to provide a useful reference for the state of V2X research and development for newcomers and veterans alike.

V2X Access Technologies: Regulation, Research, and Remaining Challenges

The market for driver assistance systems based on millimeter-wave radar sensor technology is gaining momentum. In the near future, the full range of newly introduced car models will be equipped with radar based systems which leads to high volume production with low cost potential. This paper provides background and an overview of the state of the art of millimeter-wave technology for automotive radar applications, including two actual silicon based fully integrated radar chips. Several advanced packaging concepts and antenna systems are presented and discussed in detail. Finally measurement results of the fully integrated radar front ends are shown.

Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHz Frequency Band

The ambition of achieving road traffic without serious injuries, since 1997 referred to as “Vision Zero,” has influenced the development of new car generations during the last decades. Since the early beginnings, radar sensors have taken responsibility for receiving this goal and played a major role for achieving the subsequent vision of accident-free driving. An increasing list of applications already covers comfort and safety functions for various traffic conditions. Besides already established applications like adaptive cruise control (ACC) as illustrated in Figure 1, other examples are the lane change assistant (LCA), watching for traffic when starting an overtaking maneuver (see Figure 2) and cross traffic alert (CTA), warning of approaching vehicles at a junction. However, those examples are just a few of the constantly increasing list of functions [1][2].

Reflection, Refraction, and Self-Jamming

A method for ascertaining and compensating for a misalignment angle of a radar sensor of a vehicle, includes generating a first set of data which contains information about a measured alignment of the radar sensor with respect to an instantaneous movement of the vehicle; generating a second set of data which contains information about a measured alignment of the reference axes defined at the vehicle with respect to the instantaneous movement of the vehicle; ascertaining a misalignment angle by comparing the generated first set of data to the generated second set of data; compensating for the ascertained misalignment angle by changing an emission direction of the main lobe of the antenna characteristic as a function of the ascertained misalignment angle.

Method and device for ascertaining and compensating for a misalignment angle of a radar sensor of a vehicle

Radarsensor fur Kraftfahrzeuge, mit einem monolithischen integrierten Mikrowellenschaltkreis (10), der einen Oszillator (16) zum Erzeugen eines Sendesignals und einen Mischer (20) zum Erzeugen eines Zwischenfrequenzsignals (IF) aus einem Empfangssignal umfasst, wobei der monolithische integrierte Mikrowellenschaltkreis weiter wenigstens einen Sensor (28; 32; 38; 42; 58; 62; 64; 66) und eine Uberwachungsschaltung (30; 62) umfasst, die dazu eingerichtet ist, eine vom Sensor gemessene Messgrose mit einem Sollzustand der Messgrose zu vergleichen, und wobei die Uberwachungsschaltung (30) dazu eingerichtet sein kann, basierend auf dem Vergleichsergebnis einen Schaltungsteil (50) des monolithischen integrierten Mikrowellenschaltkreises (10) zu steuern.

Radarsensor mit Überwachungsschaltung

Radar sensors are key components of modern driver assistance systems. The application of such systems in urban environments for safety applications is the primary goal of the project “Radar on Chip for Cars” (RoCC). Major outcomes of this project will be presented and discussed in this contribution. These outcomes include the specification of radar sensors for future driver assistance systems, radar concepts, and integration technologies for silicon-germanium (SiGe) MMICs, as well as the development and evaluation of a system demonstrator. A radar architecture utilizing planar antennas and highly integrated components will be proposed and discussed with respect to system specifications. The developed system demonstrator will be evaluated in terms of key parameters such as field of view, distance, and angular separability. Finally, as an outlook a new mid range radar (MRR) will be introduced incorporating several concepts and technologies developed in this project.

Raik Schnabel

Papers

Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHz Frequency Band

Reflection, Refraction, and Self-Jamming

Method and device for ascertaining and compensating for a misalignment angle of a radar sensor of a vehicle

Radarsensor mit Überwachungsschaltung

Development of a mid range automotive radar sensor for future driver assistance systems