What is a Radar Sensor?

Catalog

Ⅰ Introduction

A radar sensor is a conversion device that can convert microwave echo signals into electrical signals. As we all know, traditional radar technology is widely used, such as airborne, shipborne, base radar, etc... In daily life, we can use radar sensors to achieve weather forecasts, traffic control, and resource surveys, etc...

In recent years, with the rapid development of semiconductor technology, the size and power consumption of many radars have been greatly reduced. With the use of millimeter-wave, ultra-wideband technology, and multiple transmission, and multiple receptions, combined with innovative signal processing technology and chips with increasing computing capabilities, the perception function of radar is getting stronger and stronger.

Ⅱ What is radar sensing technology?

The so-called radar sensing is a wireless sensing technology that extracts and discovers the target's position, shape, motion characteristics and motion trajectory by analyzing the received target echo characteristics, and can further infer the characteristics of the target and the environment. Its effect is similar to human eyes and ears.

Compared with other sensors, radar sensor has many unique advantages. For example, compared with visual sensors, radar is not affected by light and darkness. It has the ability to penetrate obstructions, and can better protect personal privacy. Compared with ultrasound technology, radar can sense longer distances and will not cause harm to people and animals.

Radar sensing can support many application scenarios. For example, millimeter-wave radar sensors have been widely used in the field of assisted driving in automobiles to detect pedestrians and vehicles in front and realize collision avoidance warnings. In addition, radar also has many potential applications in homes, smart buildings, autonomous driving, and wearable devices. With the continuous development of new low-power, small-scale radar sensors, radar technology has been applied in many smart devices and electronic products.

Motion recognition

The advantage of radar technology is the detection of motion. Through the Doppler effect of the target echo, it can observe and interpret the motion state of the target, such as the direction and speed of the motion. When using multi-channel sensors, it can also be observed movement of target from different perspectives. By collecting the movement state of the target from different perspectives, and combining instantaneous information and historical information for analysis, the resolution of complex movements can be achieved.

The technology of using radar to recognize movement can be applied in different scenarios. For example, in sports, this technology can be used to detect the motion state and trajectory of people and balls. In the home environment, it can also do human fall detection to prevent the elderly from falling. At present, our technology can process radar data to realize the interpretation of the human body's motion state and trajectory.

Fusion between multiple sensors

In the fusion of radar sensors, more reliable judgments are achieved by combining the advantages and characteristics of different sensors. At present, many researchers have begun to combine radar and video sensing, so that they can achieve obstacle avoidance more reliably. In the future, we will also see more and more applications between radar sensing and artificial intelligence.

Ⅲ Millimeter wave radar sensor

millimeter-wave radar sensor

The millimeter wave radar sensor uses millimeter waves. Usually, millimeter wave refers to the frequency domain of 30 to 300 GHz (wavelength is 1 to 10 mm). Among them, 24GHz radar sensors and 77Ghz radar sensors are mainly used for automobile collision avoidance. The wavelength of millimeter wave is between centimeter wave and lightwave, so millimeter wave has the advantages of microwave guidance and photoelectric guidance. Compared with centimeter wave radar, millimeter wave radar has the characteristics of small size, easy integration, and high spatial resolution. Compared with optical sensors such as cameras, infrared, and lasers, millimeter-wave radar has a strong ability to penetrate fog, smoke, and dust, and has a strong anti-interference ability.

Due to the development and progress of radar technology, millimeter-wave radar sensors have begun to be used in multiple industries such as automotive electronics, security, drones, and intelligent transportation.

Working principle

(1) CW Doppler radar sensor

Doppler radar is a specialized radar that uses the principle of the Doppler effect to measure the speed of targets at different distances. It transmits a microwave signal to a given target, and then analyzes the frequency change of the reflected signal, the difference between the transmitted frequency and the reflected frequency, and can accurately measure the speed of the target relative to the radar.

(2) FMCW radar sensor

The transmitted wave is a frequency-modulated continuous wave whose frequency changes with time according to the law of triangle waves. The frequency of the echo received by the radar is the same as the frequency of the emission. They are both triangular waves, but there is a time difference. The target distance can be calculated using this tiny time difference.

Applications

(1) Military: Mainly used in missile guidance, target surveillance and interception, artillery fire control, and tracking, radar measurement, terrain tracking, missile fuze, ship navigation, etc.;

(2) Automotive electronics: Mainly used for forward collision avoidance, sideward collision avoidance, backward collision avoidance, automatic cruise, automatic start and stop of cars, blind spot monitoring, pedestrian detection, and automatic driving of cars;

(3) Security system: Mainly used for high-end security systems, such as airport intrusion detection, prison perimeter security, indoor intrusion alarm, millimeter-wave radar/visual fusion detection, military area protection, island security, oil depot security system, power grid security system, stereo garage Life detection

(4) Intelligent traffic radar:

Traffic bayonet radar: stop rod detection, advance detection, stop rod plus advance detection, vehicle queue length measurement;

Arterial road management: traffic flow detection, classification, and statistical analysis; accident monitoring (detecting slowed or stopped vehicles); retrograde detection;

Law enforcement sensors: vehicle speed detection at intersections or roads, red-light law enforcement at intersections or roads, mobile law enforcement (speed measurement or rear-end collision law enforcement, installed on police cars);

Movable signal lights, highway exit prompts, radar speed signs, toll stations, intelligent parking lot management;

(5) UAV radar:

Radar altimeter: automatic landing, absolute altitude measurement, terrain reminder (terrain reminder and warning), altitude change measurement (vertical velocity component), terrain mapping, used for standard UAVs, small UAVs, fixed-wing and rotary-wing aircraft, vertical Take-off and landing aircraft, and other drones;

Airdrop height sensor: absolute altimeter of the airdrop guidance unit, precise airdrop;

Early warning: detection and tracking of objects in the space where the drone is located, recent object detection (position and relative speed), collision warning;

(6) Medical treatment: heartbeat and breathing detection, special patient monitoring, sleep disorder detection, life detection, baby monitoring;

(7) Intelligent lighting: parking lot automatic lighting system, street lamp automatic lighting system, corridor automatic lighting system;

(8) Industrial control: automatic door sensor, escalator sensor, AGV anti-collision sensor, elevator automatic induction, heavy machinery anti-collision, robot anti-collision;

(9) Sports: measuring speed, such as golf tachometer, sports speed measurement, and object running track analysis;

(10) Sanitary ware: used to sense whether a person is close, such as smart toilet, faucet sensor, soap dispenser, hairdryer;

(11) Teaching and training: Provide a portable real radar system that can be used for indoor and outdoor teaching and experimentation for ordinary colleges and universities, aviation schools, maritime academies, and military academies.

Ⅳ The key component of autonomous driving: radar sensor

In the technological development of autonomous vehicles, the perception and understanding of the surrounding environment by autonomous vehicles is the basic prerequisite for autonomous driving. Therefore, the basis for autonomous driving is the coordination of various sensors. Let the car "see six directions and hear all directions". Only by accurately and timely sensing the roads, other vehicles, pedestrians, and other information around the vehicle can the driving behavior of autonomous vehicles have a reliable basis for decision-making.

autonomous vehicle and radar sensor

The "ears" of autonomous driving are the radar sensors on the car. Radar was originally developed for military and avionics applications. Millimeter wave radar is more commonly used in automobiles. The working frequency of millimeter wave radar is between 30~300GHz, and the wavelength is between centimeter wave and lightwave. Therefore, millimeter wave radar has the advantages of microwave guidance and photoelectric guidance. It also has strong penetrating power. But the performance of the millimeter wave radar will be greatly reduced in heavy rain, and the millimeter-wave is an important radar frequency band, and the interference is large on many occasions.

The first radar sensor used in automobiles was developed in a research project about 40 years ago, but it was not until 1998 that radar sensors were applied to commercial vehicle projects. Initially, radar sensors were used for adaptive cruise control. Later, a collision warning has also been added to the radar sensor.

Radar sensors have a wide range of applications and are diverse. In automotive applications, frequency modulated continuous wave (FMCW) radars are mainly used. FMCW radars use indirect distance or air travel time measurement and use the frequency difference between the transmitted signal and the received signal as an indirect ranging means.

Radar sensors are the basic technical accessories of autonomous vehicles, and their importance is self-evident. It is used to sense surrounding objects, pedestrians or vehicles, determine relative positions, and then use other sensors to make the car take corresponding measures, such as the initial adaptive cruise, front vehicle collision warning, which are all completed by radar sensors. Autopilot radars use more advanced lidars with faster response speeds.

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