Millimeter-wave radar sensor solutions for parking

Parking assistance sensors are integrated into vehicles to help drivers park more accurately by detecting surrounding obstacles. These sensors provide real-time feedback, often through visual or audible alerts, to help the driver find a parking space. The goal is to minimize the chance of a collision, even in challenging conditions with multiple moving objects around the vehicle.
 
Parking assistance systems typically use various technologies, each with its own advantages and disadvantages. Currently, one of the most popular technologies is ultrasonic sensors, which can detect objects at close range but have some performance drawbacks. Radar sensors, an emerging parking technology, offer more advanced features that help overcome the performance drawbacks of ultrasonic sensors and lead to new features and applications.
 
The ultrasonic parking sensor emits high-frequency sound waves that are undetectable to the human ear. When sound waves hit an object, such as a wall or another vehicle, they bounce back to the sensor. By measuring the time it takes for the sound waves to return, the sensor can determine the object's distance based on the known speed of sound. If the object is within a critical distance, the system alerts the driver with an audible alarm. Typically, four or six ultrasonic sensors are integrated into the bumper to provide a 180-degree field of view.
 
Radar sensors emit electromagnetic waves and analyze the reflected signals to determine the distance, horizontal and vertical angles, and speed of objects within the vehicle. Millimeter-wave radar technology uses electromagnetic waves in the millimeter wavelength range, with the standard frequency being 79 GHz for exterior automotive applications. Once the sensor emits waves, they propagate through the air and reflect off objects in their path, such as other vehicles, walls, or pedestrians.

The sensor receives the reflected waves and calculates the distance of each detected object from the vehicle based on the time it takes for the reflected waves to return. Today's radar sensors use MIMO (Multiple Input Multiple Output) technology with multiple transmitters and receivers, providing a larger field of view and the ability to detect all objects in a single scan, including distance, angle to the sensor, and their relative speed.
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When comparing ranges, millimeter wave radar outperforms ultrasonic sensors at both minimum and maximum detectable distances. Millimeter-wave radar sensors can detect objects up to 5 centimeters from the vehicle, while ultrasonic sensors have a detection distance of 10-20 centimeters. Ultrasonic sensors have a maximum range of about 8 meters, with some systems reaching 20 meters. In comparison, radar sensors can detect objects up to 60 meters away from a person and up to 100 meters away from a vehicle with a field of view (FoV) of 180°.
 
Field of View (FoV) is the width of a sensor's field of view and is typically measured in degrees. Radar parking sensors typically have a 120°horizontal FoV, but the new generation of millimeter-wave radar sensors have a horizontal FoV of up to 180°, covering the entire area behind the vehicle.