What is a Radar Sensor : Working & Its Applications

At present, semiconductor technology has been developing rapidly, so the power consumption and size of radar have been reduced greatly and its function is getting stronger by using multiple transmission & receptions, ultra-wideband technology, millimeter-wave, signal processing technology, ICs with increasing computing capabilities, etc. Traditional radar is widely used like shipborne, base radar, airborne, etc whereas a radar sensor is used in our daily life to obtain weather forecasts, resource surveys, traffic control, etc. This sensor is a conversion device, used to change the microwave echo signals to electrical. So, this article discusses an overview of a radar sensor and its working.

What is Radar Sensor?

The sensor which is used to measure the distance, velocity and movements of objects above wide distances is known as a radar sensor and also measures the relative speed of the noticed object. This sensor uses wireless detecting technology like FMCW (Frequency Modulated Continuous Wave) to detect the motion by figuring out the object’s shape, position, motion trajectory & motion characteristics.

Radar Sensor
Radar Sensor

As compared to other types of sensors, these sensors are not affected by darkness & light. These sensors can detect longer distances & it is secure for people & animals. Here the carrier frequency is modulated constantly in a small range of bandwidth. Once the signal from an object is reflected back, then it is feasible to determine the distance & also the object speed by comparing frequency.

This sensor uses an extremely high carrier frequency to produce a very thin beam cone and also notices even small objects without interference from adjacent objects above large distances.

Radar Sensor Working Principle

The working principle of a radar sensor is to compute the speed of an object along with its direction by detecting the change in frequency wave which is known as Doppler Effect.

A radar sensor includes an antenna that emits a high-frequency (62 GHz) transmitted signal. This transmitted signal also includes a modulated signal with a lower frequency (10 MHz). This sensor gets the signal once it is returned back from an object. So this sensor evaluates the phase shift between the two frequencies. Here, the difference in transmitting time & receiving time will determine the distance between the sensor & an object.


Radar Sensor Block Diagram

The block diagram of the 24 GHz wideband & short-range automotive radar sensor is shown below. This block diagram includes a VCO, PRF (pulse repetition frequency), LNA (low noise amplifier), DSP (digital signal processing) & two antennas.

Automotive Radar Sensor Block Diagram
Automotive Radar Sensor Block Diagram


The term VCO stands for voltage-controlled oscillator which is used to generate an o/p signal whose frequency changes with the amplitude of voltage for an input signal above a reasonable frequencies range.

Power Splitter

A power splitter or power divider is used to divide a single RF line into above one line & split the power.

Power Amplifier

A power amplifier is used to change a signal from a low-power to a higher power.

SP (Signal Processing)

Signal processing focuses on modifying, synthesizing & analyzing signals like images, sound, & scientific measurements.

PRF (Pulse Repetition Frequency)

The pulse repetition frequency is the number of pulses of a repeating signal within a specific unit time, usually measured in pulses for each second.


The mixer is used to generate both the frequencies sum & difference which are applied to it. So the frequencies difference will be of IF (Intermediate Frequency) type.

LNA (Low Noise Amplifier)

It is used to amplify the weak RF signal and this signal is received by using an Antenna. This amplifier’s output can be connected to Mixer.


This system includes transmit & receive channels where the transmit channels are mainly used to drive different antennas & also provide beam steering capabilities. Multiple receive channels provide the angular data regarding the target because there is a phase difference between received signals by dissimilar receive antennas.

The concept used by the 24 GHz SRR (Short Range Radar) sensors is pulsed radar. This sensor includes the transmitting & receiving path, the control & DSP (digital signal processing) circuits.

The target at range ‘R’ can be detected by measuring the elapsed time in between a transmitter signal & a correlated received signal. The simulation process was done using Matlab. The main aim of this radar sensor is to decrease potential danger & traffic accidents faced by the vehicle driver. In this system, different sensors are located in different places of the car so that the exact measurement of object distance & speed of objects in front, behind, or beside.

Every sensor in this system transmits the signals to calculate, if there is anybody in the region of the car then informs the driver regarding it. These signals cover upto 30 m distance but, if the distance in between the target & car was less than two meters, then the car generates an alarm sound to give an alert to the driver so that the car driver can take the appropriate action to avoid a collision.

Radar Sensor Types

There are different types of radar sensors which include the following.

Types of Radar Sensor
Types of Radar Sensor

Millimeter-Wave Radar Sensor

The sensor which uses millimeter waves is known as a millimeter-wave radar sensor. Generally, millimeter waves have a 30 to 300 GHz frequency domain. Among them, 77Ghz & 24Ghz radar sensors are used in automobiles for collision avoidance. The millimeter-wave wavelength ranges in between centimeter wave & lightwave. The advantages of millimeter-wave are photoelectric guidance and microwave guidance.

Millimeter-wave radar has many characteristics as compared to centimeter wave radar-like spatial resolution is high, simple integration, and small size. As compared to optical sensors like lasers, infrared, cameras, this sensor has a strong capacity to penetrate smoke, dust, fog & anti-interference capacity. These radar sensors are used in security, automotive electrons, intelligent transportation, and drones.

CW Doppler Radar Sensor

A CW Doppler radar sensor or continuous wave Doppler radar operates at 915 MHz frequency. This radar sensor works with Doppler Effect for measuring the object’s speed at various distances. This sensor transmits a microwave signal to a target & analyzes the change in frequency in the reflected signal, the difference between the reflected & transmitted frequencies, and also measures the target speed precisely which is relative to the radar.

FMCW Radar Sensor

The term “FMCW” stands for frequency modulated continuous wave radar. This sensor frequency will be changed with the time based on the triangle wave’s law. The echo signal frequency which is received by the radar is similar to the emission frequency. They both are triangular waves but there is a tiny difference in time. So this tiny difference is used to calculate the target distance.

Radar Sensor Vs Ultrasonic Sensor

The difference between the radar sensor and the ultrasonic sensor includes the following.

Radar Sensor

Ultrasonic Sensor

The radar sensor is used to change the signals from microwave echo to electrical. An ultrasonic sensor is used to measure the distance to an object with ultrasonic sound waves.
These sensors work with electromagnetic waves. These sensors work by producing sound waves.
Similar to ultrasonic, the waves from this sensor will reflect the target & travel at a known speed very fast. The sound waves travel at the speed of sound to the target where they reflect the target & come back to the sensor.
The electromagnetic waves of this sensor will respond in a different way to particular materials because they are reflected off the exterior. The sound waves of this sensor will not respond to particular materials.
These sensors are affected through different variables These sensors are affected by temperature.
These sensors are used in oil & gas, pulp & paper, clarifiers, granular solids, plastic pellets, pharmaceuticals, etc. These sensors are used for measuring the flow of liquid, solids level, open-channel flow, object profiling & presence detection.

Radar Sensor Interfacing with Arduino

The interfacing of the RCWL0516 doppler radar sensor with Arduino nano R3 is shown below. The required components used in this interfacing are; Arduino Nano R3 -1, RCWL0516 Doppler Radar Sensor-1, LED-1 & 220-ohm resistor.

The RCWL-0516 is basically a motion detection sensor. It can recognize motion via doppler microwave technology with the help of walls or other materials. It will be triggered not only by the presence of people but also by other active objects.

The sensor in this project uses microwave Doppler radar technology to identify active objects. So the doppler radar works by transmitting a microwave signal to an object after that monitors the change within the returned signal’s frequency

The pinout RCWL0516 doppler radar sensor includes the following

  • Pin1 (3V3): The regulated output is 3.3V
  • Pin2 (GND): It is a Ground pin
  • Pin3 (OUT): This is an output pin that Triggers high if motion is detected.
  • Pin4 (VIN): The supply voltage ranges from 4 to 28V
  • CDS: Sensor disable or low input

The difference within the frequency of the received signal can also estimate the velocity of a target with respect to the sensor.

RCWL0516 Radar Sensor Interfacing with Arduino
RCWL0516 Radar Sensor Interfacing with Arduino

This radar sensor module uses an RCWL0516 IC that assists in repeating triggers & a 360-degree detection region without a blind spot. It can identify motion through walls, other materials & includes a 7 meters susceptibility range.

Connect the Arduino to the RCWL-0516 & LED as shown in the above interfacing diagram.

We know that this radar sensor provides high output once motion is detected. Here, a CDS pin is used to allow motion detection. Once the code is ready then connect the Arduino board to the system & upload the code. After that, you need to open the serial monitor at a 9600 baud rate & make a few motions before the radar sensor. So, observe LED & serial monitor.

int Sensor = 12;
int LED = 3;
void setup() {
pinMode (Sensor, INPUT);
pinMode (LED, OUTPUT);
Serial.println(“Waiting for motion”);
void loop() {
int val = digitalRead(Sensor); //Read Pin as input
if((val > 0) && (flg==0))
digitalWrite(LED, HIGH);
Serial.println(“Motion Detected”);
flg = 1;
if(val == 0)
digitalWrite(LED, LOW);
Serial.println(“NO Motion”);
flg = 0;


The advantages of radar sensors include the following.

  • The radar sensor is independent of different weather conditions
  • Bears excessive cold & heat
  • It works in bad lighting conditions
  • It works in the dark
  • Its maintenance is free
  • It provides a great range of functions
  • This sensor is used for indoor & outdoor purposes
  • This sensor has many features as compared to other sensors


The disadvantages of radar sensors include the following.

  • It cannot differentiate & resolve numerous targets which are extremely close like our eye.
  • It cannot identify the color of the objects.
  • It cannot observe objects which are too deep and in the water.


The applications of radar sensors include the following.

  • Radar sensors are used where vehicle detection is required or avoiding a collision when equipment is moving. Vehicle detection mainly includes trucks, trains, cars, toll booths, shipping canals, railroads, etc. Collision avoidance includes ports, manufacturing, low-visibility factory environments & onboard mobile equipment.
  • Military
  • Security system
  • Automotive electrons
  • Intelligent traffic radar
  • UAV radar
  • Intelligent lighting
  • Industrial control
  • Medical treatment
  • Sports

What does a radar sensor do?

The radar sensor is used to detect, track, locate, and identify various types of objects at significant distances. This sensor works by transmitting electromagnetic energy to targets & detects the echoes that come back from them.

What are the 5 main components of radar?

The five main components of radar mainly include an antenna, transmitter, receiver, diplexer, and phase-locked loop.

Why is it illegal to have a radar detector?

In certain countries, using a radar detector is illegal, because it may result in fines, seizure of the vehicle.

Can radar detect humans?

Radar cannot detect humans who are walking or stationary across the field of radar but the radar can simply detect the motion components.

What causes a dead zone for radar?

The curvature of the earth may avoid the radar detecting an objective in the maximum range, so it results in a dead zone for each radar system where one object can’t be detected. But in the atmosphere of earth, electromagnetic waves are usually refracted downward or bent.

What happens if you get pulled over with a radar detector?

If drivers get pulled over with a radar detector for speeding & are found a radar detector in the vehicle then a speeding ticket will be issued by cops.

The advancements in radar sensor using mmWave technology provides flexibility & high accuracy for several in-cabin monitoring applications while delivering a tiny form factor that can be included simply & modestly within a vehicle. At present, the advanced radar sensors used in different applications are; OPS243-A doppler radar sensor, mmWave radar sensor, ARS540, ARS430, ARS410, ARS441, etc.

Thus, this is all about an overview of a radar sensor and its working with applications. This sensor uses wireless sensing technology to discover and extract the target’s shape, position, motion, etc. As compared to other types of sensors, these sensors have many advantages. For instance, as compared to the visual sensor, the radar sensor is not affected by darkness and light. This sensor can penetrate obstacles. Similarly, with ultrasound technology, this sensor can detect longer distances without harming animals and people. Here is a question for you, what is the radar sensor range?