Automotive
How radar can be used for vehicle detection and collision avoidance in challenging environments
By Rolf Horn, applications engineer at DigiKey M
otion monitoring and position sensors can enable collision avoidance, ensure safety, and enhance productivity in
logistics, manufacturing, mining, transport, agriculture, and other industries. The sensors can be mounted on vehicles or placed at strategic fixed locations. They must be configurable to fit specific application needs and have multi-functional sensing capabilities, including object detection based on distance, angular position, and velocity. The ability to detect multiple targets at once is needed in busy or complex environments.
Applications like loading docks and forklift speed control benefit from using a technology unaffected by dirt, dust, wind, precipitation, and other environmental conditions. Customizing parameters like the detection window shape and target setpoints can further enhance performance. This article starts with a review of the importance of the operating frequency on several key radar specifications, then moves to a comparison of available radar technologies like frequency modulated continuous wave (FMCW) and pulsed coherent radar (PCR), detection schemes, beam patterns, and sensing zones. Next, a software suite is presented that can speed the development of advanced systems using radar sensors.
It closes with application examples of how all those factors are used in the Banner Engineering Q90R series of radar sensors to provide multi-functional sensing capabilities for reliable detection in demanding environments, including sensing the presence of trucks at a loading dock and controlling forklift speed for enhanced safety. Radio detection and ranging (radar) is an active sensor technology that emits
16 February 2025
Figure 1: The operating frequency of radar sensors has a strong influence on the ability to identify a range of target materials based on their dielectric characteristics. (Image source: Banner Engineering)
high-frequency RF energy. The energy is reflected off objects in its path, and the characteristics of the reflected energy can be used to detect objects, determine their distance, and, in some cases, measure the speed they are moving toward or away from the sensor.
The operating frequency is a fundamental characteristic that determines the performance of a radar sensor. Industrial radar sensors are available that operate at 24 GHz, 60 GHz, and 122 GHz, parts of the industrial, scientific, and medical (ISM) frequency bands, and can be used without a special license.
The operating frequency of a radar sensor has a significant impact on several specifications, including: Range- Low-frequency radar sensors like 24 GHz have the longest range.
Accuracy - High-frequency radar sensors like 122 GHz have higher accuracy and can detect smaller objects.
Dead zone - A radar sensor’s dead zone, Components in Electronics
or blocking distance, is caused by the target being too close. In general, higher- frequency sensors have smaller dead zones.
Weather resistance - Sensing functions are immune to wind, fog, steam, and temperature changes. Radar is generally resistant to interference from rain or snow. 24 GHz radar has the best ability to ignore interference from rain and snow.
Target materials - While it’s most resistant to interference from weather, 24 GHz radar is the most limited in its ability to sense a wide range of materials. 60 GHz or 122 GHz radar sensors can detect high and low dielectric materials (Figure 1).
Beyond frequency
Frequency is a defining characteristic of radar sensors. Still, other important specifications include radar technology like FMCW versus PCR, detection schemes including adjustable field versus retro- reflective sensors, and the field of view,
window shape, and target setpoints. FMCW emits a continuous signal that’s modulated and increases or decreases in frequency over a fixed bandwidth. By measuring the frequency of a reflected signal, the radar knows the time it has taken for the signal to reflect off the target and return. That time of flight (ToF) information determines the target range. Some benefits of FMCW include simultaneous measurement of range and velocity without needing separate antennas or pulses, superior range resolution, the ability to distinguish between closely spaced targets, and higher accuracy in challenging environments.
PCR radar transmits a pulse, turns the transmitter off, waits to receive an echo from the target, then turns the transmitter back on to send a new pulse and continue the cycle. Like FMCW, a form of ToF analysis is used to determine the range and velocity of the target. The use of pulses means that PCR radar uses less power than FMCW.
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