I am unable to measure distances over X meters. What's wrong?

The radar reflection from the object you're trying to measure is likely too weak. The amount of reflected energy depends on several factors, including the object's size, reflectivity, and angle.

To improve the maximum range, you can increase the signal quality setting. Using a higher signal quality setting transmits more pulses per measurement, resulting in more energy returning to the radar sensor.

Another way to enhance object detection at greater distances is by adding a lens or horn antenna. These components help focus the radar beam, directing more energy toward the target object.


Does the threshold method affect the accuracy of the measurements?

No, the threshold is only used to filter out weak reflections from the result.


What threshold method do you recommend?

We typically recommend the default CFAR threshold method. In situations where you do not want to filter out any reflections, the fixed-strength threshold method with a low fixed-strength threshold value can be considered.


How can I measure the distance to objects very close to the radar sensor?

Measuring close to the sensor can result in interference from the strong direct leakage signal, which appears as high amplitude values around distance 0.


It is possible to measure distances as close as about 3 cm from the sensor by enabling "close range leakage cancellation" in the distance detector. However, this setting requires detector calibration without any target object in front of the sensor. It also makes the detector calibration sensitive to temperature changes. For this reason, we only recommend using close range leakage cancellation when measuring in an environment with a stable temperature and when the use case allows detector calibration while the sensor is installed in its intended geometry without any target object in front of it.


Starting from software version 1.8.1, we have made improvements to the distance detector that enable measurements down to about 6 or 7 cm from the sensor when using the CFAR threshold method with "Close-range leakage cancellation" disabled. We recommend using this configuration whenever possible to avoid constraints on detector calibration conditions.


Why do I see ghost reflections at double the distance?

When measuring close to the sensor, the radar signal may bounce multiple times between the target and the PCB before reaching the sensor. The same effect often occurs in an enclosed tank, where the signal may reflect multiple times between the target and the ceiling before reaching the radar sensor.


Sometimes, these secondary reflections can have a higher strength than the direct reflection.

In such cases, setting the peak sorting method to "closest" can help filter out unwanted reflections more effectively.



Where can I get more information about the distance detector?

The Distance Detector User Guide is available in our SDK packages and on our developer site: https://developer.acconeer.com/home/a121-docs-software/.

The distance detector algorithm is described here: https://docs.acconeer.com/en/latest/detectors/a121/distance_detector.html.

Python source code is available here: https://github.com/acconeer/acconeer-python-exploration/tree/master/src/acconeer/exptool/a121/algo/distance.