Radar modulation method with a high distance resolution and little signal processing outlay
View Patent ↗A method of controlling a radar system is presented, for detecting the surroundings using transmission means for emitting transmission signals which contain a sequence of at least approximately identical individual signals, the sequence of individual transmission signals being repeated cyclically, said method being characterized in that over the sequence of the individual signals the frequency position thereof—optionally apart from a varying and at least approximately mean value-free component—is changed at least approximately linearly and, in the process, the slope of the linear frequency position change over the individual transmission signals is at least sometimes varied from sequence to sequence, in particular in order to increase the radial distance and/or relative speed measurement accuracy and/or in order to be more robust in respect of interference with other radar systems.
1 . A method of controlling a radar system, the method comprising:
emitting transmission signals which contain a sequence of identical individual signals,
wherein over the sequence of the individual signals, a center frequency position of the individual signals, and a time interval thereof, are changed approximately linearly, the amount of the relative change in the time interval being at least approximately twice as large as the amount of the relative change in the frequency position and the algebraic signs of these changes being opposite.
2 . The method according to claim 1 , wherein a random or pseudo-random component is superimposed on the frequency position, the time interval and/or the phase position of the individual signals.
3 . The method according to claim 1 , wherein the frequency of the individual signals is linearly modulated and the slope of the frequency modulation is at least identical for all the individual signals.
4 . The method according to claim 3 , in which during K frequency ramps, numbered k=0, . . . , K−1, in each case I digital received values, numbered i=0, . . . , 1−1, are acquired in each case for multiple receiving channels and a two-dimensional discrete Fourier transform is carried out over the I·K received values in each case, the dimension resulting from the received value index dimension i following transformation being distance gates j=0, . . . , J−1 and the dimension resulting from the frequency ramp dimension being Doppler gates I=0, . . . , L−1.
5 . The method according to claim 4 , in which the linear changes in the frequency position and in the time interval of the individual frequency ramps lead to the received signals from transmission signals reflected by objects after the two-dimensional discrete Fourier transform also leading to sharp power peaks when the objects are moving towards or away from the radar system.
6 . The method according to claim 5 , wherein the linear change in the frequency position of the frequency ramps is taken into account in that, for the determination of the radial relative speed of an object, the position of its power peaks after the two-dimensional discrete Fourier transform is corrected in the Doppler gate dimension I by a component linearly dependent on the distance gate dimension j, with the linearity factor resulting from the quotient of the change in the frequency position over the frequency ramps and the change in the frequency within the reception period during the individual frequency ramps and the position of the power peak being determined results in non-integer values here for the distance gate dimension j and/or the Doppler gate dimension I.
7 . The method according to claim 5 , wherein the linear change in the frequency position of the individual frequency ramps is taken into account in that after a one-dimensional discrete Fourier transform over the I received values per frequency ramp k=0, . . . , K−1, the phases of the values resulting in the distance gate dimension j are in each case corrected by a phase component proportional with respect to the product 2π·j k/K, with the proportionality factor resulting from the quotient of the change in the frequency position over the frequency ramps and the change in the frequency within the reception period during the individual frequency ramps and the correction is realized by multiplication with a complex vector of length 1 and corresponding phase.
8 . The method according to claim 1 , wherein the sequence of K individual transmission signals is repeated cyclically and, the slope of the linear frequency position change over the individual transmission signals is varied from sequence to sequence in one of the sequences.
9 . The method according to claim 8 , wherein the individual transmission signals represent frequency ramps and two cycles having an inverse slope are utilized for an accurate radial distance and/or relative speed measurement of an object, and
wherein the sum and the difference of its positions of the power peak resulting in the two cycles after the two-dimensional discrete Fourier transform are only substantially used in the Doppler gate dimension, but not in the distance gate dimension.
10 . The method according to claim 1 , wherein the sequence of K individual frequency ramps is repeated cyclically and, the slope of the frequency ramps itself is varied from sequence to sequence in one of the sequences.
11 . The method according to claim 1 , wherein the sequence of K individual transmission signals is repeated cyclically and their mean time interval is at least varied from sequence to sequence in one of the sequences.
12 . The method according to claim 1 , wherein multiple receiving channels are realized by multiple transmitting and/or receiving antennas and, in addition to the two-dimensional discrete Fourier transform over I·K received values in each case, there is a digital beam shaping over receiving channels or in order to generate receiving channels.