FMCW vehicle radar system

1. A vehicle radar system comprising, a control unit and a signal generator that is arranged to generate a least one Frequency Modulated Continuous Wave (FMCW), chirp signal, where the chirp signal comprises a corresponding plurality of frequency ramps, and where each frequency ramp within the plurality of frequency ramps runs from a first frequency to a second frequency, wherein when a frequency ramp has reached the second frequency, the control unit is arranged to control the signal generator to start outputting an output signal with an output frequency for initializing a further frequency ramp by a frequency control signal corresponding to a desired frequency, where the desired frequency is formed of an initial desired frequency part and at least one further desired frequency part, where the initial desired frequency part runs from the second frequency to an intermediate frequency having a magnitude between the first frequency and the second frequency, and where the further desired frequency part runs from the intermediate frequency to the first frequency for the further frequency ramp, where the duration of the initial desired frequency part falls below the duration of the further desired frequency part.

2. The vehicle radar system according to claim 1 , further comprising the radar system is arranged to provide input to a safety control unit that in turn is arranged to control a safety system, where the radar system, the safety control unit and the safety system are comprised in a vehicle.

3. The vehicle radar system according to claim 1 , further comprising in that the radar system is configured to:

process of the frequency ramps in a cycle using a first, Fast Fourier Transform (FFT), to acquire target information at different ranges in a plurality of complex vectors that corresponds to the number of the frequency ramps in a cycle; and

analyze one vector element at a time for all complex vectors using a second FFT and then create a two-dimensional matrix in the Doppler domain comprising data regarding range and relative speed.

4. The vehicle radar system according to claim 1 , wherein the signal generator comprises a VCO.

5. The vehicle radar system according to claim 4 , wherein the VCO is comprised in a phase-locked loop, where the VCO is arranged to output a signal with a present output frequency.

6. The vehicle radar system according to claim 5 , wherein the signal generator comprises,

a reference oscillator that is arranged to output a first signal of a certain frequency, which signal is fed into a frequency converting unit, which frequency converting unit is arranged to multiply or divide the first signal, resulting in a second signal having a reference frequency that is fed into a phase frequency detector, where the present output frequency is fed back to the phase frequency detector via a frequency divider.

7. The vehicle radar system according to claim 6 , further comprising in that the frequency control signal is arranged to set divide-by ratios in the frequency divider or the frequency converting unit.

8. A method for operating a vehicle radar system comprising the steps of,

generating a least one Frequency Modulated Continuous Wave (FMCW) chirp signal, where each chirp signal uses a corresponding plurality of frequency ramps, where each frequency ramp within the plurality of frequency ramps runs from a first frequency to a second frequency;

controlling an output frequency for initializing a further frequency ramp when a preceding frequency ramp has reached the second frequency, using a frequency control signal corresponding to a desired frequency, where the desired frequency comprises an initial desired frequency part and at least one further desired frequency part, where the initial desired frequency part runs from the second frequency to an intermediate frequency having a magnitude between the first frequency and the second frequency, and where the further desired frequency part runs from the intermediate frequency to the first frequency for the further frequency ramp, where the duration of the initial desired frequency part falls below the duration of the further desired frequency part.

9. The method according to claim 8 , wherein the method further comprises the step of providing input to a safety control unit that in tum is used to control a safety system in a vehicle.

10. The method according to claim 8 , further comprising in that a VCO is used for outputting a signal with a present output frequency, working in a phase-locked loop.

11. The vehicle radar system according to claim 1 , further comprising, the slope of the initial desired frequency part is greater than the slope of the further desired frequency part.

12. The vehicle radar system according to claim 1 , further comprising, a magnitude of change in frequency over the initial desired frequency part is greater than a magnitude of the change in frequency over the further desired frequency part.

13. The vehicle radar system according to claim 1 , wherein the output frequency falls below the intermediate frequency during the initial desired frequency part without falling below the second frequency.

14. The method for operating a vehicle radar system according to claim 8 , further comprising, the slope of the initial desired frequency part is greater than the slope of the further desired frequency part.

15. The method for operating a vehicle radar system according to claim 8 , further comprising, a magnitude of change in frequency over the initial desired frequency part is greater than a magnitude of the change in frequency over the further desired frequency part.

16. The method of operating a vehicle radar system according to claim 8 , wherein the output frequency falls below the intermediate frequency during the initial desired frequency part without falling below the second frequency.