What is a Doppler Radar Sensor and How does It Work?


When you hear the word Doppler Radar, you might be familiar with the word “radar” but not “doppler”. So, in this blog, we will help you to understand Doppler Radar, how it works, and what kind of applications are there for this technology.

What is Radar?

Radar is a system that we have used for a very long time. In a basic radar system, a narrow beam of energy, called radio waves is transmitted from an antenna with a short wavelength in short pulses. Between every pulse, a receiver is listening for waves that are traveling back to the antenna, as the waves strike objects in the atmosphere. By taking the time it took for the wave to return to the antenna, the distance towards the object from the antenna can easily be calculated. Radar systems use this technique to detect airplanes in the sky and display green points indicating where the airplanes are.

What is the Doppler Effect?

Let’s talk about the doppler effect before talking about doppler radar. Doppler effect occurs when a source is moving relative to an observer. When a moving source is approaching an observer the frequency of the waves experienced by the observer is higher than the frequency of the source, whereas when the source is moving away from an observer, the frequency of waves experienced by the observer is lower than the frequency of the source. The change in frequency between the original source wave and the wave experienced by the observer is called the “doppler shift”.

ref: www.toppr.com

What is a Doppler Radar?

Doppler radar works by sending a beam of electromagnetic radiation waves from the transmitter (TX Antenna), with a precise frequency, at a moving object.

Once the electromagnetic radiation wave comes in contact with an object, it travels back towards the receiver (RX Antenna). However, when the wave got reflected from the moving object, the wave now has a different frequency compared to the original frequency emitted.

Then the change in this frequency can be used to calculate the velocity of the moving object. This change in frequency is just like the “doppler shift” that we mentioned earlier.

Doppler Radar modules offered by Seeed

We offer a couple of Doppler Radar modules for you to realize radar projects quickly and easily at home!

Grove – Doppler Radar (BGT24LTR11) – 24GHz Transceiver

The Grove – Doppler Radar is based on the BGT24LTR11 Silicon Germanium MMIC which is a 24GHz radar transceiver. It is driven by an XMC1302 MCU based on Arm® Cortex®-M0. This comes in a compact package and runs on very low power, providing high-precision measurements of objects’ movement and speed. 

Millimeter-Wave Doppler Radar (SYH24A1) – 24GHz Transceiver

Millimeter-Wave Doppler Radar (SYH24A1) is a radar detection module based on the millimeter-wave doppler radar system for human motion and detection. It is based on the SYH24A1 IC which is a 24GHz radar transceiver. This comes in a compact package and runs on very low power, providing high-precision measurements.


We hope you got a clear understanding about doppler radars by reading this blog and hope to see you build awesome projects using out doppler radar modules.

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June 2020