Radar Tutorial

This chapter gives you a concise overview of radar technology, covering its key principles and practical applications. You'll gain an understanding of how radar sensors operate and the various factors that influence their performance

Distance Measurement with Radar

Radar operates by emitting electromagnetic waves, which travel through the air at nearly the speed of light. When these waves encounter an object, they are reflected back towards the radar sensor. By analyzing the time delay and the frequency shift of the reflected waves, the radar sensor can accurately determine the distance and velocity of the object. This technology ensures precise and reliable measurements, making radar sensors essential for various applications.

Radar penetrates non-conductive Materials

Radar sensors can penetrate non-conductive materials such as plastic, rubber, cardboard, glass, and similar substances because radar waves are only partially reflected by these dielectric materials. Conversely, when radar waves encounter metals or closed water surfaces, they are fully reflected. This ability to penetrate certain substances or objects makes radar distance sensors highly versatile and suitable for a wide range of applications.

Radar sensors can detect the distance to objects behind glass, plastic or other non-conducting materials. At the interface of the dielectric material, there is a weak reflection, which allows for the determination of the distance to the object. However, most of the radar waves radiate unhindered through this material, so that the distance to an object that is positioned behind the dielectric material can be determined. To protect the radar sensor from irradiation or explosions, glass, heat-resistant plastics or a mica plate can be used. Only a limited amount of the radar signal is reflected, so that the radar sensor detects the distance to the object behind it with high accuracy.

Radar allows you to measure through non-conductive materials: While water drops and high humidity, dust and smoke do not have a big impact on the radar signal, closed water surfaces are more or less impossible to penetrate.

Opening Angle: Defining the Focus of the Radar Sensor

The measuring spot size of the radar distance sensor, influenced by the opening angle (or aperture angle), significantly affects target detection and interference reflections. Imagine the radar signal as a flashlight beam: a poorly focused flashlight illuminates a wide area but does not reach large distances, while a highly focused flashlight shines further and more precisely on specific objects.

Similarly, for radar sensors, a larger aperture angle results in a larger measuring spot, increasing the field of view but reducing measurement range and accuracy due to signal dispersion and interference. Conversely, a smaller opening angle provides a smaller, more focused measuring spot, enhancing signal strength and accuracy.

The figure below illustrates how the opening angle affects measuring spot size and signal strength. A smaller opening angle offers a stronger signal and higher accuracy.

Use the OndoSense radar spot size calculator to determine your sensor's measuring spot size based on distance. Select your radar sensor from the list or input the opening angle and lens diameter for a calculation of the radar spot size in relation to a certain distance to the target object.

Position the sensor closer: Measure closer to the target to reduce the measuring spot size and minimize interference. Small opening angle = Increased Focus: A small opening angle reduces interference reflections and improves measurement accuracy. Opening angle and detection orientation: A smaller opening angle limits the maxmimum tilt the target object can have against the orientation of the sensor while still ensuring a stable signal output.

Radar Resolution and averaging across the Measuring Spot

Radar Resolution: Radar resolution is critical for determining how well a radar distance sensor can distinguish between two closely spaced objects. It defines the minimum distance at which two objects can be separately detected. If the radar signals (peaks) from these objects can be distinguished, their distances can be accurately measured, as shown in the figure below.

Averaging across the measuring spot: When objects are positioned close together or surfaces have complex structures, and the distances between reflection points are smaller than the sensor’s resolution, the sensor automatically averages the distance values. This ensures stable, consistent measurements, even on uneven or irregular surfaces. Stronger reflections are given more weight in the averaging process, leading to accurate and reliable readings. By smoothing out the impact of surface irregularities, averaging enhances the sensor’s overall performance. For more advanced applications, OndoSense can create customized radar algorithms to further improve measurement precision.

If the radar signals (peaks) from these objects can be distinguished, their distances can be accurately measured. If the peaks from these objects or an uneven surface cannot be distinguished, the distance is averaged across the measuring spot as shown in the figure below.

Object Detection: Radar resolution enhances the sensor's ability to accurately detect and distinguish objects that are close to each other, ensuring reliable distance measurements for each individual object. Measurement Averaging: When multiple reflection points are within the sensor’s resolution range, the sensor effectively averages the distances, providing a consistent measurement even in complex surface scenarios.