MIMO radar system

Patent metadata

Field	Value
Publication number	US-11733352-B2
Application number	US-202117174992-A
Country	US
Kind code	B2
Filing date	Feb 12, 2021
Priority date	Feb 27, 2020
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

A MIMO radar system. The system includes transmitter and receiver arrays, and a control and evaluation unit, designed to: transmit transmission signals according to a time and frequency multiplex scheme in each of multiple repeatedly implemented measuring cycles, the time space and frequency space being divided into non-overlapping time slots and frequency sub-bands and only one single transmitting antenna being active in each time slot and transmitting in only one single frequency sub-band, carry out preliminary distance estimations and Doppler estimations, each based on signals of an individual transmitting antenna, in a first evaluation stage based on signals received in one measuring cycle, and carry out joint distance, Doppler, and angle estimations using a multi-dimensional estimation algorithm in a second evaluation stage based on phases of the signals transmitted by various transmitting antennas, results of the first evaluation stage being refined by increasing the accuracy and/or by eliminating ambiguities.

First claim

What is claimed is:

1. A MIMO radar system, comprising:
a transmitter array having multiple transmitting antennas situated at a distance from one another in an angle resolution direction;
a receiver array having multiple receiving antennas situated at a distance from one another in the angle resolution direction; and
a control and evaluation unit to perform the following:
transmitting transmission signals via the transmitter array according to a time multiplex and frequency multiplex scheme in each of multiple repeatedly implemented measuring cycles, a time space and frequency space being divided into non-overlapping time slots and into frequency sub-bands and only one single transmitting antenna of the transmitting antennas being active in each time slot and transmitting in only one single frequency sub-band,
performing preliminary distance estimations and Doppler estimations in a first evaluation stage based on signals received in one measuring cycle of the measuring cycles, and
performing a joint distance estimation, Doppler estimation and angle estimation using a multi-dimensional estimation algorithm in a second evaluation stage based on phases of the signals transmitted by the transmitting antennas, results of the first evaluation stage being refined by increasing accuracy and/or eliminating ambiguities,

wherein a frequency modulation unit controls a high frequency (HF) oscillator, which generates sequences of signals as frequency ramps for the multiple transmitting antennas,
wherein an amplifier, which is configured to either block or forward the amplified signals to an associated one of the antennas, is situated in each of multiple transmission channels,
wherein the oscillator and the amplifier are activated by a multiplex unit according to a time and frequency multiplex scheme so that each of the multiple transmitting antennas transmits a frequency-modulated signal in a particular frequency sub-band within a particular time slot,
wherein in a processing stage, data sampled per time slot are subjected to a four-dimensional Fourier transform (4D-FFT), resulting in a four-dimensional spectrum including the dimensions of: “Distance 1 ”, “Doppler 1 ”, “Azimuth 1 ”, and “Elevation 1 ”,
wherein the four-dimensional spectra are non-coherently integrated by addition of absolute values of complex amplitude, which provides an amplitude distribution in a four-dimensional parameter space, wherein each point in the four-dimensional space is assigned a particular amount of the amplitude sum, and each located object stands out in this space as a peak or a local maximum with a particular distance, a particular Doppler shift, a particular azimuth angle and a particular elevation angle.

2. The radar system as recited in claim 1 , wherein the transmission signals include sequences of frequency ramps, whose ramp slope for a distance measurement is configured according to a FMCW principle, and Doppler measurements are based on relative phases of the signals obtained in a sequence of the frequency ramps.

3. The radar system as recited in claim 2 , wherein an equally long row of equidistant time slots is assigned to each transmitting antenna of the transmitting antennas.

4. The radar system as recited in claim 3 , wherein the time slots, which are assigned to the transmitting antennas, are interleaved with one another so that a frequency ramp of a first transmitting antenna of the transmitting antennas is followed by a number of frequency ramps, which are transmitted by other transmitting antennas of the transmitting antennas and/or in other sub-bands, before a next frequency ramp of the sequence is transmitted by the first transmitting antenna in the same sub-band.

5. The radar system as recited in claim 1 , wherein the time slots assigned to the transmitting antennas are organized in blocks so that in a first block, a first transmitting antenna of the transmitting antennas transmits a complete sequence of ramps and then in the next block, another transmitting antenna of the transmitting antennas transmits a complete sequence.

6. The radar system as recited in claim 1 , wherein the control and evaluation unit is further configured to subject phases of signals transmitted and received at various measuring points in time to a distance-dependent and velocity-dependent coordinate transformation, in order to compensate for relative velocities of objects in an elapsed time between the measuring points in time.

7. The radar system as recited in claim 1 , wherein in the first evaluation stage, an angle estimation also already takes place based on phases of the signals which are received by the multiple receiving antennas, but have been transmitted by the same transmitting antenna.

8. The radar system as recited in claim 1 , wherein the transmitter array is configured for unambiguous angle measurements and the receiver array is configured for ambiguous higher-resolution angle measurements.

9. The radar system as recited in claim 1 , wherein the receiver array is configured for unambiguous angle measurements and the transmitter array is configured for ambiguous higher-resolution angle measurements.

10. The radar system as recited in claim 1 , wherein the receiving antennas and/or the transmitting antennas are situated equidistantly in the angle resolution direction.

11. The radar system as recited in claim 10 , wherein the receiving antennas are situated equidistantly in the angle resolution direction and the angle estimation takes place based on the receiver array via a fast Fourier transform.

12. The radar system as recited in claim 1 , wherein the dimension “Azimuth 1 ” indicates a distribution of complex amplitudes across a location angle range in the azimuth, based on the data of the receiving antennas, which are situated in a same row in the azimuth direction, wherein the dimension “Elevation 1 ” indicates the distribution across the elevation angle range, based on the data of receiving antennas, which are situated in the same column in the elevation direction, wherein the dimension “Doppler 1 ” indicates a Doppler spectrum obtained by slow sampling in intervals ts, wherein the dimension “Distance 1 ” indicates a distance spectrum based on rapid sampling on individual frequency ramps, a unique spectrum being obtained for each transmitted ramp.

13. The radar system as recited in claim 12 , wherein results in the Distance 1 dimension are unambiguous but low-resolution, because only a respective narrow sub-band is used in each time slot, and wherein the results in all three remaining dimensions are ambiguous due to the respective undersampling, so that there is greater temporal distance between successive ramps of a sequence or greater spatial distance between the receiving antennas.

14. The radar system as recited in claim 1 , wherein the particular Doppler shift, the particular azimuth angle and the particular elevation angle are each ambiguous so that only one of multiple hypotheses relating to the relative velocity and only one of multiple hypotheses relating to azimuth angle and elevation angle is assignable to the object.

15. The radar system as recited in claim 1 , wherein in the four-dimensional parameter space, the four-dimensional coordinates of the peaks found are searched, each of which represents a detection result, wherein for each of these points, there are n-time-division-multiple (nTDM) complex amplitudes, which form a vector including nTDM components and are then further evaluated to resolve remaining ambiguities and to improve a distance resolution, wherein for this purpose, the complex amplitudes obtained in the various ti

Assignees

• Bosch Gmbh Robert

Inventors

• Hakobyan Gor
• Gonser Markus

Classifications

• G01S7/354

  Extracting wanted echo-signals (Doppler systems G01S13/50) · CPC title

• G01S7/42 Primary

  Diversity systems specially adapted for radar · CPC title

• G01S7/2813

  Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays (specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00) · CPC title

• G01S7/414

  Discriminating targets with respect to background clutter · CPC title

• H04B7/0413

  MIMO systems · CPC title