Functionality and technology of radar sensors

Baumer radar sensors operate on the FMCW method (Frequency Modulated Continuous Wave). Here the radar sensor emits a frequency (f) which is continuously changed over time (t). In this way a frequency sweep is created. The difference between minimal and maximal frequency is called bandwidth (B_sweep). 

The frequency sweep repeats periodically with the sweep time Ts. One modulation type is the sawtooth option as shown in the illustration. As an alternative, triangle wave modulation can be used. The time duration between of this periodically modulation is called sweep time (T_s). During the sweep time, the frequency is continuously increased, e.g. from 122 to 123 GHz.

When the emitted radarwave hits an object within the radar cone, a portion of the signal is reflected. This can be detected as a echo signal in the radar sensor.

Due to frequency sweep the echo signal has a lower frequency then the emitted signal. The difference between the current frequency and the received frequency (frequency beat f_b) is detected by the radar sensor as measured signal.

The distance R between radar sensor and object is determined out of the detected frequency sweep (fb), sweep time (Ts) and band width (Bsweep).

Shortcuts:

t_d = Runtime shift
T_s = Sweep time
R = Range
c = Speed of light
f_b = Frequency beat 
B_sweep = Bandwidth