Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/06—Systems determining position data of a target
  • G01S13/42—Simultaneous measurement of distance and other co-ordinates
  • G01S13/424—Stacked beam radar
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
  • G01S7/35—Details of non-pulse systems
  • G01S7/352—Receivers
  • G01S7/354—Extracting wanted echo-signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/0209—Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/06—Systems determining position data of a target
  • G01S13/08—Systems for measuring distance only
  • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/06—Systems determining position data of a target
  • G01S13/08—Systems for measuring distance only
  • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
  • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
  • G01S13/343—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using sawtooth modulation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/06—Systems determining position data of a target
  • G01S13/42—Simultaneous measurement of distance and other co-ordinates
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/50—Systems of measurement based on relative movement of target
  • G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
  • G01S13/536—Discriminating between fixed and moving objects or between objects moving at different speeds using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/50—Systems of measurement based on relative movement of target
  • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
  • G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
  • G01S13/584—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
  • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S2013/0236—Special technical features
  • G01S2013/0245—Radar with phased array antenna
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
  • G01S7/35—Details of non-pulse systems
  • G01S7/352—Receivers
  • G01S7/356—Receivers involving particularities of FFT processing

Definitions

• the invention relates to a method for locating a radar target in which FMCW radar measurements are performed with transmit antennas having different field of view which differ in an aperture angle and / or range, wherein received signals are baseband signals
• the invention relates to a method of this kind in which, for at least two of the viewing areas, the respective measurement is an angular resolution measurement performed with different selections of multiple antennas used for transmission and / or reception, searching for radar targets Peaks in two-dimensional spectra of the baseband signals of the measurements of the respective visual fields are performed, and wherein an angular position of a radar target located in a respective visual range is determined from amplitudes and / or phases at the position of a peak corresponding to the radar target in two-dimensional spectra of the baseband signals suitable for the different selections of the antennas used for transmission and / or reception are obtained.
• the invention relates to a radar sensor, in particular for motor vehicles, which is designed to carry out this method.
• FMCM radar sensors are used to record the
• the location results can be used for various assistance functions, for example for an automatic distance control, a
• FMCW Frequency Modulated Continuous Wave
• a transmit signal with ramped modulated frequency is used. The signal is transmitted continuously during the course of the ramp.
• Receive signal is generated by mixing with the transmit signal, a baseband signal, which is sampled and evaluated.
• the frequency of the baseband signal corresponds to the frequency difference between the signal transmitted at a given time and the signal received at the same time. Due to the frequency modulation of the transmission signal, this frequency difference is dependent on the transit time of the signal from the radar sensor to the object and back and thus the distance of the object. Due to the Doppler effect, however, the frequency difference also contains a proportion that is caused by the relative speed of the object. The measurement of the frequency difference on a single ramp therefore still does not allow determination of the distance and the
• Relative speed but provides only a linear relationship between these quantities. This relationship can be represented as a straight line in a distance-speed diagram (d-v diagram).
• FMCW radar sensors are known in which a sequence of identical, relatively short ramps, so-called “rapid chirps” is used, which have a high frequency deviation in relation to their duration and are therefore so steep that in the baseband signal the
• the distance-dependent portion of the frequency shift dominates while the Doppler shift is sampled by the sequence of the ramps.
• a sufficiently high repetition rate of the short ramps is required.
• the time offset between successive short ramps must be less than half the period of the Doppler frequency.
• the radar sensor has a plurality of antennas, which are arranged at a distance from each other on a line, for example a horizontal, so that different azimuth angles of the located objects to differences in the Run lengths that have to cover the radar signals from the object to the respective antenna. These long-term differences lead to corresponding differences in the phase of the signals which are received by the antennas and evaluated in the associated evaluation channels. By matching the (complex) amplitudes received in the various channels with corresponding amplitudes in an antenna diagram, it is then possible to determine the angle of incidence of the radar signal and thus the azimuth angle of the located object.
• MI MO multiple input / multiple output
• the signals transmitted with different selections of the transmitting antennas must be orthogonal or time separable to each other. This can be done, for example, by code division,
• Frequency Division Multiplexing Frequency Division Multiplexing or Time Division Multiplexing.
• the code division method requires a lot of effort and allows only a limited orthogonality of the signals.
• Frequency division multiplexing has the disadvantage that the phase and the Doppler shift are dependent on the respective wavelength.
• the time division principle there is the problem that relative movements of the located objects in conjunction with the
• the object of the invention is to provide a method of the type mentioned, which allows a better utilization of an available cycle time for scanning the different fields of view.
• (A) in each case a measurement is carried out in a measuring cycle for the different viewing areas, in which a ramp-shaped frequency-modulated transmission signal is transmitted whose modulation pattern comprises a plurality of time-interleaved sequences of ramps which follow each other within the respective sequence with a time interval with a time lag,
• Viewing areas are temporally interwoven, whereby in a regular pattern between the viewing areas is changed
• sequences are temporally nested inside each other. That is, ramps of the respective other sequences are arranged in gaps between the ramps of a sequence.
• interlaced is used synonymously with the terms “interlocked” or “interwoven”.
• a linear relationship between the distance and the relative velocity of the radar target is determined from a position of the peak in the first dimension of the at least one two-dimensional spectrum, and from a position of the peak in the second dimension of the at least one two-dimensional spectrum determines at least the relative velocity values of the radar target that are periodic with the predetermined velocity period.
• the value of the relative velocity is periodic with a velocity interval where c is the speed of light, f 0 is the average transmission frequency, and Tr2r is the time interval between ramps within a sequence. From a position of the radar target associated peak in a two-dimensional spectrum of the sampled baseband signals is thus one with a
• Ambiguity value of the relative speed of the radar target determined.
• the ambiguity can then be resolved by examining how well the phase relationships between the signals of the sequences, which are expected for the respective values of the relative velocity, correspond to the measured phase relationship.
• the expected phase relationship depends on the relative velocity and the time offset between the respective sequences.
• the ramps are preferably arranged at uneven intervals, so that the modulation pattern despite the regular
• Time interval Tr2r has as little symmetry. Due to the
• Tr2r uniform time interval
• the estimated value is in a measuring range for the
• Ramp centers within a sequence are: Tr2r> c / (4f 0 v max ) where c is the speed of light and f 0 is the mean transmission frequency. This corresponds to a sub-sampling of a maximum to be detected
• Tr2r is at least a multiple of said size on the right hand side of the relationship.
• the estimated value is in a measuring range for the
• Tli is at least a multiple of the said size on the right hand side of the relationship.
• the measurements with different viewing regions preferably each have a modulation pattern which has at least two different, regularly recurring time offsets between ramps of different sequences.
• the measurement may comprise a modulation pattern comprising at least three of the sequences for which the same antenna is used for transmission, these sequences with respect to a first of the sequences have different, a respective further of the sequences associated time offsets. This is useful if only one transmit antenna is available for one view area.
• the measurement may be carried out with a plurality of antennas used for transmission, whereby at least two different transmission switching states, which differ in the selection of the antennas used for transmission, are used, wherein these transmission switching states each comprise at least two of the
• sequences which are interleaved with respect to one another in time and with respect to a first one of the sequences have a time offset associated with a respective further one of the sequences
• This measurement may be, for example, a MIMO-FMCW measurement in which the
• Angular position of a located radar target based on amplitudes and / or
• the first described measurement may be performed having a modulation pattern comprising at least three of the sequences for which the same antenna is used for transmission, and for at least one other of the viewing areas the last described measurement may include a plurality of Send used antennas are executed.
• antennas are arranged in different positions in a direction in which the radar sensor is angle-resolving.
• Signal from the angular position of the located radar target can be given for a standard object at a given distance and with a given distance
• the angular position of a radar target can be determined, for example, by matching the antennas obtained from the different antennas, or (in the case of MIMO measurement) for different selections of antennas used for transmission and reception, amplitudes obtained for the same radar target, and / or phases with the corresponding antenna patterns , Since the measurements of the different viewing areas are temporally interwoven, they are scanned approximately simultaneously. Spectral values, i. Amplitudes and / or phases from the spectrums of different viewing ranges may be used for a common angular estimation of a radar target when locating a radar target in an overlap region of viewing ranges. It can be a comparison of separately created for the viewing areas lists of located radar targets or objects to which the radar targets are assigned, take place.
• successive ramps have a same ramp slope and an equal difference
• Ramp slope and the same ramp center frequency and particularly preferably have a same frequency deviation. If, except for the optional nonzero frequency difference between ramp and ramp, the
• the available measurement time can be used particularly well.
• influences of an object acceleration on the phase relationship between the baseband signals of the individual sequences can be kept as small as possible.
• such favorable values can be selected for the time offset between the sequences and the time interval of the ramps within a sequence, which are as "incommensurate" as possible, ie are not multiples of each other.
• the modulation pattern includes pauses between the ramps.
• the modulation pattern preferably has at least one pause, which regularly recurs between every two successive ramps of a sequence, with one
• Time interval from pause to pause which is equal to the time interval between the ramps of a sequence.
• Modulation pattern arranged alternately ramps of the respective sequences, i. the sequences largely overlap in time.
• the respective time offset between sequences is less than twice the time interval between the ramps within a respective sequence, more preferably less than this time interval.
• the latter is equivalent to the fact that in a measurement of a field of view between two successive ramps of the first sequence always a respective ramp of the respective further sequences of ramps is sent.
• the two-dimensional spectrums separately calculated for each of the sequences for a respective field of view become a two-dimensional spectrum of the baseband signals, in particular one
• Determining values for the relative speed is used. Merging, for example, is non-phase coherent, preferably a non-phase coherent summation of the squares of the absolute values of the spectral values into a power spectrum. Thereby, the detection of a peak can be improved.
• ⁇ 12 2 ⁇ - / 0 ⁇ 12 ⁇ (2) is used, which has an expected phase difference ⁇ 12 between a phase of the spectral value of the respective spectrum of another sequence and a
• T12 and ⁇ 12 for the second sequence can generally Tli, m, p or ⁇ 1 ⁇ ⁇ ⁇ for the ith
• a control vector a (v) dependent on the relative velocity v becomes a measurement according to the equation
• the control vector a (v) in this notation is a column vector whose components each describe the expected phase difference of the ith sequence from the partial measurement of the first sequence, the expected phase difference being respectively determined as the phase of a complex exponential function.
• the number of components of the vector is I.
• the common prefactor is a
• Viewing areas p is replaced by a number l p .
• control vector a (v) makes it possible to establish a relationship (unique under suitable conditions) between the relative velocity v of the radar target and the received complex spectral values at the position of the peak and from the phase relationships of the received signals to the relative velocity v of the radar target shut down.
• the velocity can not be calculated exactly, but only estimated, for example by means of a maximum likelihood estimation. This is carried out separately for the different viewing areas.
• a measurement vector is defined, for example, for a reception channel n, possibly a transmission switching state m, and a field of view p
• step (d) in the event of a disturbance in the phase relationship between said spectral values corresponding to a situation in which two different relative velocity radar targets occupy the same position in the at least one two-dimensional spectrum, the presence of the disturbance is recognized by expected degree of agreement of the phase relationship with the expected phase relationships is not achieved.
• FIG. 1 shows a diagram of an FMCW radar sensor with two transmitting antennas and four receiving antennas for MI MO radar measurements and another transmitting antenna;
• Fig. 2 shows a modulation pattern with seven sequences of similar ramps which are transmitted repeatedly
• Fig. 3 is a speed / distance diagram with a
• FIG. 4 shows a more detailed block diagram of an evaluation device of an F M C W radar sensor.
• Fig. 1 is a diagram of a simple example of a (MIMO) FMCW radar sensor 10 is shown, which in this example, two transmitting antennas 12 and four receiving antennas 14 for MIMO measurements in a first
• Viewing range and another antenna 15 has a different field of view. In practice, larger numbers of antennas are possible.
• the transmission Antennas 12, 15 are fed by a control and evaluation unit 16 and emit radar signals which are reflected at an object 18 and received by each of the receiving antennas 14.
• the field of view of the transmitting antenna 15 has a greater range and a narrower opening angle than the field of view of the transmitting antennas 12.
• the transmitting and receiving antennas can each consist of a patch antenna array.
• the received signals are mixed down to baseband signals and evaluated in the control and evaluation unit 16.
• the radar sensor 10 is, for example, installed in front of a motor vehicle and serves to measure distances d, angles and relative velocities v of objects 18, for example of vehicles in front.
• Transmission signal is modulated within a radar measurement with sequences of rising or falling ramps.
• Antenna system has been shown, in which the transmitting antennas 12, 15 are different from the receiving antennas 14.
• a monostatic antenna concept can be used in which the same antennas are used for transmitting and receiving.
• the antennas 12, 14 are arranged in different positions in a direction in which the radar sensor 10 is angle-resolving.
• the receiving antennas 14 are evenly spaced on a straight line (ULA; Uniform Linear Array).
• UAA Uniform Linear Array
• the transmitting and receiving antennas do not necessarily have to be arranged on the same line.
• the straight lines on which the antennas are arranged run horizontally.
• the antennas would be arranged on vertical lines. It is also conceivable two-dimensional
• the radar sensor 10 is operated in the time division multiplex method, wherein measurements with different viewing ranges are temporally interwoven with each other.
• At any one time at most one of the transmitting antennas 12, 15 is active and transmits the transmission signal.
• the activity phases of the individual antennas 12, 15 alternate cyclically. In Fig. 1, the case is shown in which only the lower of the two transmitting antennas 12 is active.
• FIG. 2 shows the transmission frequency f of the transmission signal 20 plotted against the time t.
• two sequences 22, 26 and 32, 36 of ramps 24, 28 and 34, 38 are transmitted with identical ramp parameters with each transmitting antenna 12, which are interleaved in time.
• the ramps 24, 28 with the same ramp index j have a time offset T12, l, l.
• Sequences 32, 36 have the ramps 34, 38 with the same ramp index j a time offset T12,2, l. Within the sequence 22, the ramps 24, 28 with the same ramp index j have a time offset T12, l, l. In a measurement for the field of view of the transmitting antenna 15 are with the
• Transmit antenna 15 three sequences 40, 42, 44 of ramps 41, 43 and 45, respectively, which are interleaved in time.
• the ramps 43 each have a time offset T12, l, 2 to the ramps 41 with the same ramp index j
• the ramps 45 each have a time offset T13, l, 2 to the ramps 41 with the same ramp index.
• the time offset of a further sequence i to a first sequence is here and hereinafter referred to as Tli, m, p.
• Tli, m, p the time offset of a further sequence i to a first sequence.
• the successive ramps are shifted from one another by a time interval Tr2r.
• the time interval Tr2r is the same for all sequences of all fields of view.
• a break P is between two
• the ramp center frequency corresponds to the mean transmission frequency f 0 here .
• FIG. 4 schematically shows a more detailed block diagram of the operations performed by the control and evaluation unit 16 for determining the relative velocity v, the distance d and the object angle ⁇ .
• the received, sampled baseband signals b i>m> p are each one
• the first dimension corresponds to a transformation of the baseband signals obtained for the individual ramps.
• the second dimension corresponds to one
• Tli, m, p sub-measurements corresponding to each sequence become a phase difference between the complex amplitudes
• Phase difference between two partial measurements with the same transmitting antenna but no direct inference to the relative velocity v. Because of the periodicity of the phases results from the Phase difference (or the two phase differences at p 2) an ambiguity for the associated value of the relative velocity v.
• Power spectra are summed together by summation or averaging to form an integrated two-dimensional power spectrum 56, 57.
• Power spectrum 56, 57 which is indicated here as Bin k, I, corresponds to the position of the peak in the individual spectra ⁇ , ( ⁇ , ⁇ , ⁇ ). From the first
• Relative velocity v and the distance d of the radar target obtained.
• c is the speed of light
• F is the ramp stroke
• T is the ramp duration of a single ramp
• f 0 is the mean transmission frequency. If the frequency difference of successive ramps of a sequence is zero, the
• Peak position in the second dimension I only information about the
• Fig. 3 shows schematically a diagram in which the relative velocity v is plotted against the distance d.
• the linear relationship between v and d is shown as a straight line.
• the information about the relative speed of the radar target obtained from the sampling of the Doppler frequency has an ambiguity according to the predetermined interval according to equation (1).
• the periodic values determined from the frequency bin I are the
• Relative velocity v shown by dashed lines. The intersections with the v-d line are marked. They correspond to possible
• Control vector a (v) of an ideal measurement as a function of v calculated according to equation (3), which is here for 1 2 sequences:
• the measurement vector a k , i (n, m, p) is defined accordingly, wherein instead of the expected, speed-dependent complex values, the complex amplitudes (spectral values) at the position k, l of the peak of the two-dimensional spectra of the partial measurements are used as components of the vector as given in equation (4); a normalization takes place in the definition of the likelihood function.
• ⁇ ⁇ ⁇ , ⁇ , ⁇ denotes the hermetically adjoint vector
• Components are complex conjugate to the components of the vector a k , i (n, m, p).
• the likelihood function thus corresponds to a normalized sum of the squares of the (complex) scalar products between the measurement vector and the control vector of the transmission channels for a respective field of view p, the summation being carried out over the different transmission channels wherein a transmission channel denotes a combination of reception channel n and transmission switching state m.
• the relative velocity spectrum S (v, p) generally corresponds to a superimposition of periodic functions of the relative velocity v.
• the maxima of the likelihood function correspond to the most probable values of the parameter v. That alone is taken for granted
• Relative velocity spectrum S (v, p) ambiguous.
• a maximum corresponds in each case to an optimum match, on average, of the ideal phase shifts resulting for the relevant value of v with the measured ones
• the ambiguity resulting from the position of the peak can thus be resolved by the additional information from the phase relationship.
• an estimated value for the distance d belonging to the selected estimated value for the relative velocity v is determined.
• the second function block 58 outputs the determined estimates for the
• the estimated relative velocity v can be used to compensate for the phase shifts caused by the relative velocity v of the spectral values of the individual sequences relative to a reference sequence.
• the time signals corresponding to the different sequences of ramps are thus initially processed separately.
• the detection of a radar target 18 then takes place in the power spectrum 56 obtained by noncoherent integration. Based on the detection and the complex amplitudes at the position of the peak then the ambiguity of the velocity v is resolved.
• the noncoherent matching of the spectra to the power spectrum 56 is performed jointly for all receive channels and all transmit antennas. This improves the peak detection.
• the evaluation device 16 may be configured to detect such a disturbance of the measurement on the basis of a threshold exceeding the deviation of the maximum match, i. the maximum value of the values of the relative velocity spectrum S (v, p) in question, of the expected maximum value 1. The evaluation device 16 can then output a fault signal.
• a temporarily occurring multiple occupancy of a peak in the spectrum 56, 57 can also be recognized from the fact that the evaluation device 16 recognizes a misdetection over a plurality of measuring cycles during a tracking of detected objects carried out on the basis of the estimated values of v and d of a radar target 18.
• different modulation parameters of the ramps are used for a plurality of successively executed radar measurements, for example different center frequencies, ramp slopes, time intervals Tr2r and / or time offsets Tli, m, p.
• different modulation parameters of the ramps are used for a plurality of successively executed radar measurements, for example different center frequencies, ramp slopes, time intervals Tr2r and / or time offsets Tli, m, p.
• Coherent receiving channels ie, taking into account the phase, with added respective weighting factors.
• S (v, p) the summations over n are omitted accordingly.
• the baseband signals b may also be output directly to the angle estimator 60, or spectrums calculated separately from the baseband signals b may be output to the angle estimator.

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• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Radar Systems Or Details Thereof (AREA)

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