Introduction to Radar
Ever since radio waves were discovered and their ability to reflect on objects were understood, engineers are finding newer applications based on their detection & ranging properties. The technique, called Radar (Radio Detection and Ranging), works on the principle of a source transmitting the radio wave, being reflected by a surface, and received and processed by a receiver system. One such application, where RADAR is seeing an unprecedented uptake, is the automotive application and more specifically ADAS solutions that deliver enhanced safety and comfort.
So, what does a Radar system consist of?
Most simplistically, a radar system typically consists of the following sub-systems:
- Transmitter- Powered by amplifier signals are generated here using a waveform generator.
- Waveguides- As name suggest they facilitated transmission of radar signals.
- Antenna- Transfers the transmitter energy to signals in space.
- Receiver- Used for detection and capture of signals.
- Processing unit– Uses captured signals and their properties to derive detection, ranging and other useful information.
Automotive radar typically works on 77GHz and falls into three categories –
- Short range radar (SRR) – 0.5 to 20 meters
- Medium range radar (MRR) – 1 to 60 meters
- Long range radar (LRR) – 10 to 250 meters
Applications of Radar in automotive
With autonomous driving gaining traction and regulatory bodies across countries mandating inclusion of certain security features, adoption of advanced driver assistance systems is on the rise. A number of different sensing technologies are being used currently including radar, LiDAR (Light detection and ranging), infrared (IR), ultrasonic and camera based. Each of these technologies has advantages and disadvantages and most of the ADAS systems today rely on multiple technologies to provide reliable solutions to market.
One of the key applications of Radar in ADAS is blind spot monitoring, object detection, and collision warning and mitigation. Both blind spot monitoring and object detection work on the radar technology, whereas collision mitigation systems use the data from the radar-based system and take preventive measure like counter steering and braking to avoid any accidents.
- Object detection systems currently in use utilize vehicles’ parking assist cameras to detect object when the vehicle is relatively at a lower speed. However, at highway speeds these systems do not work as per intent. As a result, radar-based systems are used for object detection at highway speeds. To understand more about radar-based object detection, click here.
- Blind spot monitoring systems currently in use are based on other technologies. Drawbacks of these systems are that they are best suited for metallic objects alone, do not typically work well for curved objects, and their operation is affected by temperature and humidity. These systems also have limited operating range.
Let us understand the advantages and drawback of Radar based ADAS systems such as blind spot detection systems and object detection systems in terms of velocity, working condition and operating range, among other factors.
Advantages of having radar-based driver assist systems over other sensors
It is known that radar works on the principle of transmitting and receiving radio waves after reflection. While other sensors such as camera, LiDAR, ultrasonic systems are in prevalence, Radar based systems have some inherent advantages such as:
- Radar is touted to be an all-weather solution. Real world working conditions such as temperature, humidity etc. do not affect the functioning of radar-based systems. One of the key advantages of radar is that it works seamlessly under varying lighting conditions – night or day.
- Long range radar systems can see really far – LRR can comfortably handle between 30 to 250 meters range.
- Materials that are generally considered as insulators such as rubber do not affect radar-based systems.
- It is relatively easier to accurately measure velocity, distance and exact position of the object using radio waves.
- Radar can easily differentiate between stationery and moving objects which is one of the major shortcomings of proximity sensor-based systems.
- Radar can detect multiple objects simultaneously which cannot be done in proximity based sensors.
- When used in conjunction with existing camera- based systems, 3D image can be created by use of radar by means of angle detection of the object and sensor fusion with existing camera-based data.
Shortcomings of radar-based ADAS system
Even though radar-based systems have an upper hand over proximity-based systems there are quite a few shortcomings of these systems.
- Detecting small objects with Radar is relatively difficult for shorter wavelengths
- Static object detection whose relative velocity is exactly that of the moving object, obtaining necessary reading is quite difficult and requires proprietary algorithms to address this issue.
- Existing radar-based ADAS systems do not work well in closed environments such as tunnels and usually go into standby mode
- Radar based systems have their limitations when it comes to recognizing and classifying objects
- Interference from other radar system, which causes accuracy problem
- Time taken in actual detection and warning sign to the driver is on the higher side, this require serious intervention in reducing processing time so that the waring and other precautionary measure are taken as quickly as possible.
Radar is not only economical compared to other technology but also provides wider range of application. It is a proven technology and with advances in customized software algorithms, it fast becoming one of the most viable option for car manufacturer and OEMs who foresee ADAS and autonomous driving as the future of mobility.
- Interested to know more about implementation details of Radar based ADAS systems, download our whitepaper titled Basic Radar system for Automotive ADAS
- Here is a real-life case study of how we optimized radar based object detection system for an automotive tier-1
- Radar 101: Why are automotive radar systems shifting to 77GHz?
- Modulation techniques for automotive radar application and why FMCW is winning the race
- FMCW CHIRP configurations for SRR, MRR and LRR