HELLA has been producing radar sensors in the 24 GHz narrow-band range for more than a decade. HELLA put its first generation of 24 GHz radar sensors into serial production back in 2005. The sensor systems are ideal for applications that have since become standard functions, such as blind spot detection, lane change assistants and rear-facing parking assistance.
The sensor records speed, angle and distance information for objects within a distance of up to 70 m behind the vehicle and then evaluates the information. The LFMSK (Linear Frequency Modulation Shift Keying) process has been used since the first generation of devices.
This process can be used to sense and determine the distance and relative speed of several objects with just one signal (chirp), the frequency of which changes over time.
In the third generation of radars, an enhanced FM variant is used. Here the modulation bandwidth is limited to max. 200 MHz. The system operates at an average transmission power of 13 dBm (EIRP) in a frequency range of between 24.05 and 24.25 GHz. The resultant spatial resolution of 0.75 m is suited to the rear-end functions undertaken. The monopulse method is used here to determine the angle. On the basis of specific signal-processing approaches, the system uses various receive paths to compare the phases of the radar reflections.
Another safety function, the exit assistant, is integrated in the fourth generation radar sensors. This detects dangerous situations, such as passing cars, before exiting the vehicle and warns all passengers.