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
  • 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
  • G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
• • 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
  • G01S13/325—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of coded signals, e.g. P.S.K. 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
  • G01S13/06—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
  • G01S13/08—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
  • G01S13/345—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 triangular 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
  • G01S13/08—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
  • G01S13/36—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal
  • G01S13/38—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal wherein more than one modulation frequency is used
• • 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
  • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
  • G01S13/878—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
• • 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
  • 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
  • G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
  • G01S7/0232—Avoidance by frequency multiplex
• • 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
  • G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
  • G01S7/0233—Avoidance by phase multiplex
• • 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
  • G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
  • G01S7/0234—Avoidance by code multiplex
• • 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
  • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
  • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
  • G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
  • G01S13/282—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using a frequency modulated carrier wave
• • 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
  • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
  • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
  • G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
  • G01S13/284—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses
  • G01S13/286—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses frequency shift keyed
• • 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
  • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
  • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
  • G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
  • G01S13/284—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses
  • G01S13/288—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses phase modulated
• • 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
  • G01S2013/9327—Sensor installation details
  • G01S2013/93271—Sensor installation details in the front of the 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
  • 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 the determination of distances and / or relative speeds of objects with an FMCW radar.
• the invention relates to an FMCW radar sensor, an FMCW radar system having a first and at least a second radar sensor, and a radar system for a vehicle fleet, comprising a plurality of FMCW radar sensors.
• Radar sensors are used in motor vehicles, for example for measuring the distances, relative speeds and azimuth angles of vehicles located in the apron of one's own vehicle or other objects.
• the transmission frequency of a continuous radar signal is ramped. From a received signal, a baseband signal is generated by mixing with the transmission signal, which is then evaluated.
• FMCW Frequency Modulated Continuous Wave
• FMCW radar sensors which operate according to the method of chirp sequence modulation, in which the transmission signal comprises at least one sequence of similar frequency modulation ramps (chirps).
• the modulation parameters such as the ramp duration and the frequency deviation as well as the time interval between adjacent ramps of a sequence are the same within a sequence.
• the radar objects are first separated according to their distances, for example, in that a first Fourier transformation of the baseband signal takes place in each case for the individual frequency ramps of the transmission signal. Subsequently, the spectra of the first Fourier transforms of the frequency ramps of a sequence are used as input signal for a second Fourier transformation.
• DE 10100417 A1 discloses a pulse radar in which a transmission signal is modulated according to a pseudo-noise code by amplitude modulation, phase modulation or frequency modulation.
• a receiving branch is a modulation with a delayed code.
• orthogonal codes are used, which are generated for example by counters and EXOR gates from the pseudo-noise code.
• WO 2010/1 15418 A2 discloses a radar system with two transmit antennas arranged in one plane and with a defined lateral spacing and a common receive antenna in which both transmit antennas are operated simultaneously according to a sequence of similar frequency ramps, wherein a switchable inverter controls the phase of the signal the first transmit antenna varies randomly from ramp to ramp by 0 ° or 180 °.
• a second DFT is calculated via the ramp sequence once with a phase correction and once without phase correction to obtain spectra separated for obtaining azimuth information for receive signals originating from the respective transmit antennas .
• the signal originating from the respective other transmitting antenna results in a noise about 30 dB lower.
• the object of the invention is to provide an FMCW radar system and an FMCW radar sensor with chirp sequence modulation, in which unwanted signals from other radar sensors can be effectively suppressed.
• Another approach is to detect interference in the time signal of the radar sensor based on interpolation of the time signal.
• the model assumption is assumed that only a small portion of the time signal is disturbed.
• interference detection and interpolation are no longer possible.
• the object is achieved by a radar system according to claim 1.
• a Fourier analysis is carried out in the form of a two-dimensional, two-stage discrete Fourier transformation.
• a first Fourier transformation maps a coherent oscillation, which corresponds to a distance-dependent signal component, within the radar echo of a frequency ramp through a peak in the one-dimensional spectrum.
• a second Fourier transformation is carried out via the one-dimensional, but in this case phase-demodulated, spectra of the first Fourier transformation and forms a coherent, Doppler portion corresponding vibration over the Radarechos the sequence of frequency ramps by the position of the peak in the spectrum of the second Fourier transform.
• the result of the two-dimensional Fourier transformation is a two-dimensional, discrete or rasterized, ie in distance / velocity Cells divided, spectrum.
• the phase demodulation is preferably done by multiplying the one-dimensional spectra of the frequency ramps by the respective conjugate-complex element of the code sequence used in the receiver.
• the second Fourier transformation already contains the summation of the respective terms and therefore provides the value of the autocorrelation or cross-correlation as a factor of the amplitude in the corresponding distance / velocity cell of the two-dimensional spectrum.
• the phase demodulation according to the invention results in a power peak of a radar echo after the second Fourier transformation only if, after the phase demodulation, a coherent oscillation of the phase position of the radar echoes is present over the sequence of the frequency ramps.
• This condition is met by radar returns whose transmit signal has been phase-modulated with the code sequence that correlates with the code sequence used for the phase demodulation.
• the baseband signal of a radar echo contains a portion of the at least one second radar sensor, then the corresponding peaks obtained after the first Fourier transformation have no coherence over the sequence of the frequency ramps after the phase demodulation.
• the cross-correlation of the code sequences here provides the factor zero.
• the object is further achieved by a radar system according to claim 6.
• the separate processing of the radar echoes of the partial transmission signals until the determination of a two-dimensional spectrum corresponds for example to the evaluation steps described above.
• the phase demodulation and summation of the two-dimensional spectra for the sub-signals results in a summed spectrum only a power peak of a radar echo when the separate spectra add up to a spectrum in which a coherent oscillation of the summed phase angles of Radarechos on the consequences of the frequency ramps is available.
• the sum of the autocorrelation functions at zero time shift is obtained as a factor of the amplitude in the corresponding range / velocity cell.
• the sum of the cross-correlation functions is obtained as a factor of the amplitude. This equals zero according to the code set orthogonality relationship, regardless of the value of a time shift between the code sequences.
• Fig. 1 is a block diagram of an FMCW radar sensor; a schematic representation of a sequence of frequency modulation ramps of a transmission signal;
• FIG. 3 is a block diagram for explaining the evaluation of a baseband signal; a schematic representation of a motor vehicle with an FMCW radar system in a situation with self-interference; a diagram showing distance information from sub-signals of a baseband signal, for explaining the evaluation of Fig. 3; a diagram showing velocity and distance information from a waveform over the sub-signals, for explanation of the evaluation of Fig. 3; an exemplary representation of a transmission signal with two sub-transmission signals in the form of a respective sequence of frequency modulation ramps, for explaining a phase demodulation when using code sets with multiple codes; a block diagram for explaining the evaluation of a baseband signal in a transmission signal with two ramp sets such as in FIG.
• FIG. 7 a schematic representation of a motor vehicle with an FMCW radar system in a situation with foreign interference; a diagram showing distance information from sub-signals of a baseband signal in a ramp set, for explaining the evaluation of Fig. 8; a diagram showing velocity and distance information from waveforms on sequences of sub-signals in a ramp set, to explain the evaluation of Fig. 8; a distance-speed diagram after the summation of signal processing results for the two ramp sets, to explain the evaluation of Fig. 8; and a distance-speed diagram for explaining the interpretation of multispeed FMCW radar signals.
• the FMCW radar sensor 10 shown in FIG. 1 is installed at the front of a motor vehicle. It comprises an oscillator 12 for generating a transmission signal, a frequency modulation device 14 for controlling the frequency of the oscillator 12 and a control and evaluation unit 16, which is connectable to a vehicle bus system 17. An output of the oscillator 12 is connected to a transmitting antenna element 20 via a controllable phase modulator 18. Further, an output of the oscillator 12 is connected to a mixer 22. This is adapted to mix a receive signal received by a receive antenna element 24 with the frequency modulated signal of the oscillator 12 to produce a baseband signal s.
• the baseband signal is sampled and digitized by an analog-to-digital converter 26.
• the mixing and digitizing is done while preserving the phase relationships between the received signal and the transmission signal.
• the control and evaluation unit 16 controls the frequency modulation device 14 and comprises a signal processing unit 28 for evaluating the samples of the baseband signal s.
• FIG. 2 shows an example of a modulation scheme of the transmission signal output by oscillator 12 and phase-modulated by phase modulator 18.
• the frequency f of the transmission signal is plotted as a function of time t.
• the frequency modulation device 14 is set up to modulate the signal of the oscillator 12 in accordance with a chirp sequence modulation with at least one sequence of frequency ramps 30 which follow one another at regular intervals, in particular a series of linear ramps of the same slope, the same center frequency and same hubs.
• the frequency modulation ramps are also referred to as chirps, frequency ramps, or simply ramps.
• the phase modulator 18 is adapted to modulate the phases of the chirps according to a code sequence C m , hereinafter also referred to as code C m .
• the number of ramps of the sequence is L and is equal to the length of the code C m .
• the chirp sequence modulation and the phase modulation can be synchronized via the vehicle bus 17 with a modulation of a further radar sensor 10 ', so that at the respective sequences of the frequency ramps or respective code sequences, the time locations of successive corresponding ramps or elements of the Code sequence have little or no time offset.
• the time offset is less than the duration of a ramp.
• the sequential ramps or elements of the code sequences are mostly overlapped on a timely basis, most preferably almost simultaneously (i.e., completely overlapping in time).
• the average frequency of the transmission signal is on the order of 76 gigahertz, and the frequency deviation F of each ramp is on the order of a few megahertz.
• the ramp duration T is smaller in Fig. 2 than the time interval T ⁇ , in which the ramps 30 follow each other.
• T r2r is on the order of a few microseconds down to a few milliseconds.
• FIG. 3 shows a block diagram of a method implemented in the signal processing unit 28 for evaluating the baseband signal s.
• a first Fourier transformation 32 ensues by subjecting the partial signals of the baseband signal s corresponding to the chirps to a discrete Fourier transformation 32i in the form of a fast Fourier transformation (FFT) in order to determine a respective complex frequency spectrum 33.
• FFT fast Fourier transformation
• the spectrum 33 contains a peak at a respective frequency position f d .
• the sequence of the chirps 30 results in a constant relative velocity v of the located object, a harmonic oscillation of the phase of the peak.
• Their frequency position f v is proportional to the mean relative velocity v.
• the signal within a ramp 30 has the phase offset ⁇ m (l).
• the one-dimensional frequency spectra 33 are subjected to a phase demodulation 34 in which the phase offsets modulated onto the transmission signal are demodulated by opposite phase offsets.
• a respective demodulation 34i is performed by multiplying the complex spectrum 33 by C * m (l), the conjugate complex of C m (l).
• a second Fourier transformation 38 takes place, for example in the form of a respective FFT 38i, which is executed for a respective frequency range of the one-dimensional, phase demodulated spectra 33 'via the current ramp index I corresponding to a distance d.
• the values of the frequency spectra 33 'belonging to a frequency position of the frequency spectra 33' are shown hatched in FIG. 3.
• the frequency spectrum calculated with the second FFT shows the peak associated with the respective object at the Doppler frequency f v , corresponding to a peak position (f d , f v ) in the obtained two-dimensional spectrum.
• the further evaluation and object detection is carried out by a detection unit 40.
• the phase demodulation can take place before the first FFT 32 is calculated.
• the series connection of the first FFT 32 and the second FFT 38 corresponds to a two-dimensional FFT of the phase-demodulated sequence of radar returns.
• FIG. 4 shows an example in which, by using different code sequences of two FMCW radar sensors 10, 10 'in a motor vehicle 42, self-interference in the form of an interference signal received from one radar sensor 10 and from the other radar sensor 10' to a transmitting antenna 20 'comes, is suppressed.
• the radar sensors 10, 10 ' have different installation locations and in particular are mounted separately on the vehicle.
• An interfering signal from a second radar sensor 10 'of the own vehicle is received by an object 46 at a distance of 3.32 m and at a relative speed of 0 m / s, for example a preceding vehicle.
• the transmission signals, and in particular the ramp sequences of the radar sensors 10, 10 ' are synchronized with one another via an on-board vehicle bus system of the motor vehicle 42.
• the first radar sensor 10 uses a code sequence C m for the phase modulation, the second radar sensor 10 'uses an orthogonal code sequence C q .
• the code sequences are also referred to below as codes.
• Hadamard codes are binary codes in which the codes of a code set consist of mutually orthogonal lines of Hadamard matrices.
• the elements of a code also referred to as code values, are limited to the values +1 and -1, corresponding to phase offsets of 0 ° and 180 °, respectively.
• the elements of the code can be defined by one bit each.
• the spectrum after the first FFT is multiplied by the conjugate complex of the associated element of the code train. Since the duration of a ramp is much greater than the propagation time of the signal to a real destination and back, the received signal may be considered to be synchronous with the transmitted signal, corresponding to a time offset of zero. This is referred to below as the synchronization condition.
• the correlation sum of the codes is equal to the code length L. This corresponds to the synchronous multiplication of the two codes.
• the amplitude is greater than the amplitude of the received signal due to the integration of the 1st FFT over K samples per ramp and the integration of the 2nd FFT over the L ramps of a follower by a factor KL.
• the cross-correlation function of the two codes for the first Fourier transformation and the phase demodulation with the code C m results as a prefactor of an amplitude of the second Fourier transformation a time offset equal to zero, r Cm, c q (0).
• an interference signal is a signal originating from the radar sensor 10 'and reflected at the object 44.
• interfering signals originating directly from the radar sensor 10 ' can also be suppressed. These can correspond, for example, to a dummy object.
• An interfering signal of a radar sensor 10 "mounted on the vehicle rear of a preceding vehicle 46 is received from a distance of 1.66 m at a relative speed of 0 m / s.
• a measuring cycle comprises two partial transmission signals 47, 47 'in the form of interleaved sequences of frequency ramps 30, 30'.
• the two sequences are also referred to below as ramp sets 47, 47 '.
• the frequency ramps 30 and 30' have an identical ramp stroke, ramp slope and center frequency of the ramps.
• the ramp sets may differ, for example, from one another by a different ramp stroke, a different center frequency and / or a different ramp gradient. In the example shown, the ramp sets only differ by the different sign of the ramp slope.
• Each ramp set is phase modulated with an associated code sequence of a code set, the code sequence assigning a phase offset to each frequency ramp of the sequence.
• the ramp set 47 (ramps 30) is modulated with a code sequence C m i and the ramp set 47 '(ramps 30') is modulated with a code sequence C m2 .
• Groups of code sets with this property are also referred to as mutually orthogonal.
• the signal of the radar sensor 10 is coded with the code set Cm.
• the signal of the foreign radar sensor 10 "is coded with a code set Cq.
• the separation can be realized, for example, by a time offset, different ramp parameters, and / or by a polarization of the antennas used for the individual ramp sets.
• a time offset and a different slope are used in the form of a different sign of the ramp gradient.
• the processing initially corresponds to the processing explained with reference to FIG. 3.
• the first Fourier transformation 32 is performed.
• a code set is used which correlates with the code set C m i, C m2 used for the phase modulation, here for example is identical.
• the phase demodulation 34 is performed by multiplication with the conjugate-complex C * m, i or C * m, 2 of the respective code, and the second Fourier transform 38 is performed over the ramps of the respective ramp set.
• the obtained two-dimensional spectra of the first ramp set 47 and the second ramp set 47 ' are added and passed on to the detection unit 40 for further evaluation. Since the distance of a target only changes by a very small value during the time offset of the ramp sets 47, 47 ', the summaries of the two-dimensional frequency spectra add the complex amplitudes coherently.
• FIG. 10 shows schematically over the ramp index I of a single ramp set 47 or 47 'the information about the distance d obtained from the first FFT.
• the signal from the external radar sensor is received by the radar sensor 10 5, 12 ms later than the radar echo of the target.
• the respective phase demodulations and the second Fourier transformation 38 are then carried out for the frequency spectra of the respective ramp sets 47, 47 '.
• the result for the two ramp sets is a two-dimensional spectrum over d and v according to FIG. 11.
• the summation of the spectra results in a spectrum according to FIG. 12.
• the amplitudes of the apparent target sum to zero.
• an amplitude results due to the summation of the autocorrelation functions
• the interfering signal is effectively suppressed, and the real target can be detected from the two-dimensional spectrum.
• a code set may be randomly selected from a group of mutually orthogonal codes.
• interference of signals from radar sensors of two vehicles using the same code group reduces the likelihood that the vehicles will simultaneously use the same code.
• different values of at least one parameter of the frequency ramps of the ramp sets 47, 47 ' may be used in successive measuring cycles. If, for example, different ramp slopes are used, the probability is increased that an interfering signal has a different ramp slope than the signal of its own radar sensor. The energy of the interfering signal is then distributed in the baseband signal over frequencies and causes a noise background of the useful signal. For example, different durations or numbers of the ramps of the ramp sets and / or different center frequencies may also be used.
• phase modulation and demodulation are each done with the same code
• a code f m or a code set f m1 , f m2 instead for the phase demodulation which is correlated with the code C m but is not identical, the code set f m1 , f m2 with the at least one other Code set C q satisfies the code set orthogonality condition. This is indicated by dashed lines in FIGS. 1, 3 and 8.
• a "mismatched filter" -
• phase demodulation of the baseband signal may also be performed before the first FFT, e.g. the phase demodulation is done with the code sequences of a code set in separate channels.
• phase demodulation may be accomplished with the code used in the transmit signal by mixing the mixer with a received signal with the phase modulated transmit signal to produce the baseband signal.
• Multi-valued codes can also be used.
• Binary codes allow a structurally simple structure, since for a phase offset of 180 ° only the amplitude of the signal is to be inverted.
• a sensor design can also be modulated with at least one sequence of frequency ramps that is phase-and-amplitude-modulated according to a code sequence.
• orthogonal codes may also be used, for example Fourier codes.
• the described modulation method with frequency ramps of the same center frequency f 0 according to FIG. 2 or FIG. 7 can be modified by setting, for example within a ramp set or a ramp sequence, the center frequency f 0 of the respective Ramps according to a linear, higher frequency ramp with lift F S
• 0W then corresponds to an FMCW equation for the higher-level ramp.
• the described codes have the advantage that they exist for any code length and the favorable correlation property is present for each code length. This provides great flexibility in the design of radar signals and radar systems. For example, transmission signals with few ramps can be used. This can result in a shorter transmission time and reduced requirements for memory and the data transmission rate of the evaluation unit.
• the described modulation methods use short, fast frequency ramps, so that the frequency spectra of the sub-signals corresponding to the ramps are dominated by the distance-dependent frequency component.
• a functional relationship between v and d can be determined from a first Fourier analysis of a partial signal assigned to a ramp, for example according to the FMCW equation. In order to determine v and d, it is then possible, for example, to use information obtained from the second FFT and / or to match values over a plurality of sequences of ramps of different ramp parameters.
• a respective first Fourier transformation of the respective radar returns of the frequency ramps of the transmission signal can take place; from at least one obtained one-dimensional spectrum first information in the form of a functional relationship between the distance d and the relative velocity v of a geor- object, which assigns different distances d to the different relative speeds v, wherein, for example, the functional relationship may correspond to an FMCW equation for a respective frequency ramp; performing at least one second Fourier transform in a second dimension over the time course of the sequence of the phase-demodulated, one-dimensional spectra of the radar echoes of the successive frequency ramps; from at least one obtained spectrum of the second Fourier transform, or, in the case of the partial transmit signals, from the summation of the obtained spectra of the second Fourier transform, further information about the relative velocity and optionally distance of the located object are obtained, the further information, for example, information in form a functional relationship according to an FMCW equation for the superordinate, slow ramp of the center frequencies of the frequency ramps can be; and the distance d
• the first information may be compared with the second information in consideration of an ambiguity of the second information determined by a range of uniqueness for the relative speed v and optionally the distance d.
• a method is also referred to as multispeed FMCW (MS-FMCW).
• MS-FMCW multispeed FMCW
• the use of the orthogonal codes or code sets which fulfill the orthogonality condition has the particular advantage that even with MS-FMCW modulation patterns with relatively few, comparatively long ramps, a very good suppression of self-interference and / or foreign interference can be achieved. It is thus possible with a reduced sampling rate of the A / D converter nevertheless achieve a good separation ability of the relative velocity v.
• the spectrum of the second Fourier transform represents a spectrum of a two-dimensional Fourier analysis, or a sum of two such spectra of the partial transmit signals.
• the distance and the relative speed are thus determined in particular on the basis of a value of the frequency spectrum of a two-dimensional determined by dimensional Fourier analysis, or based on a summation of such two-dimensional frequency spectra.
• the first information can already be determined from a one-dimensional spectrum of a first Fourier transformation. It is also possible on the basis of a peak in the two-dimensional frequency spectrum to determine the first information from the position of the peak in the first dimension of the frequency spectrum and to determine the further information from the position of the peak in the second dimension of the frequency spectrum.
• Fig. 13 shows an example of a v-d diagram of first and second information of a ramp sequence of an MS-FMCW measurement with a slow, higher frequency ramp of the center frequencies of the short ramps.
• a frequency ramp results, instead of a value for d, the straight line slightly inclined with respect to the vertical, corresponding to a linear relationship between the relative speed v and the distance d (first information).
• the phase demodulation results from the peak of the spectrum of the second FFT (or from the peak of the sum of the spectra of the second FFT) another, here flat, dashed line, which is subject to ambiguity.

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