Rapid-chirps-FMCW radar
Method for determining distances and relative velocities of simultaneously located objects using an FMCW radar, in which the frequency of a transmission signal is modulated in the form of periodically recurring ramps, the transmission signal is mixed with a received signal to form an intermediate frequency signal and, for determining the distance and/or the relative velocity of the objects, the change in the phase of the intermediate frequency signal is evaluated from one ramp to the next characterized in that the modulation pattern includes at least two ramps, which differ only by a fixed frequency offset and follow one another in a certain time interval, and an unambiguous approximate value is calculated for the object distance on the basis of the phase difference φ 1 −φ 2 of the intermediate frequency signals for these two ramps.
1. A method for determining distances and relative velocities of multiple simultaneously located objects using an FMCW radar, the method comprising:
modulating, via a modulator, a frequency of a transmission signal in the form of a modulating pattern that includes periodically recurring ramps;
mixing, via a mixer, the transmission signal with a received signal to form intermediate frequency signals;
evaluating, via an evaluation unit, to determine at least one of a distance and a relative velocity of the objects, a phase difference corresponding to a change in a phase of the intermediate frequency signals from one ramp to a next one, wherein the modulation pattern includes at least two ramps that differ only by a fixed frequency offset and follow one another in a time interval, and calculating an unambiguous approximate value for the distance based on the phase difference of the intermediate frequency signals for the at least two ramps;
wherein the modulation pattern includes two sets of ramps that are identical to one another and are interlinked so that one ramp without a frequency offset alternates with one ramp having a frequency offset, wherein the ramps are offset by a fixed frequency offset and are successive in time,
wherein the intermediate frequency signals of a two-dimensional Fourier transform obtained in successive identical ramps are subjected to a two-dimensional Fourier transform to determine corresponding frequencies, including a first frequency and a second frequency, and corresponding phases, including a first phase and a second phase,
wherein an approximate object distance is determined from the phase difference, and
wherein the approximate object distance is compared with distance values associated with the first frequency and the second frequency, and the distance value closest to the approximate object distance is determined to be a true distance of the object.
2. The method as recited in claim 1 , wherein a plurality of object distances to be considered is calculated by evaluating the intermediate frequency signals of multiple successive identical ramps, and wherein one of the calculated distances which comes closest to the approximate value is selected as a final object distance.
3. An FMCW radar sensor, comprising:
a control and evaluation unit for determining distances and relative velocities of multiple simultaneously located objects using an FMCW radar, by performing the following:
modulating a frequency of a transmission signal in the form of a modulating pattern that includes periodically recurring ramps,
mixing the transmission signal with a received signal to form intermediate frequency signals,
evaluating, to determine at least one of a distance and a relative velocity of the objects, evaluating a phase difference corresponding to a change in a phase of the intermediate frequency signals from one ramp to a next one, wherein the modulation pattern includes at least two ramps that differ only by a fixed frequency offset and follow one another in a time interval, and
calculating an unambiguous approximate value for the distance based on the phase difference of the intermediate frequency signals for the at least two ramps;
wherein the modulation pattern includes two sets of ramps that are identical to one another and are interlinked so that one ramp without a frequency offset alternates with one ramp having a frequency offset, wherein the ramps are offset by a fixed frequency offset and are successive in time,
wherein the intermediate frequency signals of a two-dimensional Fourier transform obtained in successive identical ramps are subjected to a two-dimensional Fourier transform to determine corresponding frequencies, including a first frequency and a second frequency, and corresponding phases, including a first phase and a second phase,
wherein an approximate object distance is determined from the phase difference, and
wherein the approximate object distance is compared with distance values associated with the first frequency and the second frequency, and the distance value closest to the approximate object distance is determined to be a true distance of the object.
4. The FMCW radar sensor as recited in claim 3 , wherein a plurality of object distances to be considered is calculated by evaluating the intermediate frequency signals of multiple successive identical ramps, and wherein one of the calculated distances which comes closest to the approximate value is selected as a final object distance.