Direction of arrival estimation for automotive spread radar systems

1. A method of direction of arrival estimation with an automotive spread radar system, the automotive spread radar system comprising a plurality of at least two transceiver antenna units, which are configured to work in a multiple-input and multiple-output configuration, wherein the transceiver antenna units are arranged at a priori known positions, and the automotive spread radar system is configured to determine, for each specific transceiver antenna unit of the plurality of transceiver antenna units, a range of a target reflecting radar waves that have been transmitted by at least the specific transceiver antenna unit by reading out a plurality of range gates that are assigned to the specific transceiver antenna unit, the method comprising steps of:

for each specific one of the plurality of transceiver antenna units, determining a range of a target occurring in one of separated angular directions lying within an angular range that is arranged about a common direction at least from radar waves that have been transmitted by the specific transceiver antenna unit and have been reflected by the target, by reading out range gates out of the plurality of range gates of the specific transceiver antenna unit,

determining a pattern of occupied range gates from the read-out range gates of the plurality of transceiver antenna units, wherein the pattern of occupied range gates are created by mutually shifted range gate allocations of the plurality of transceiver antenna units, and

estimating a direction of arrival based on relating the determined pattern of occupied range gates to a plurality of expected patterns of occupied range gates for targets occurring in the separated angular directions, the plurality of expected patterns of occupied range gates being predetermined from the a priori known positions of the plurality of transceiver antenna units, and wherein the direction of arrival is estimated without using phase information from reflected radar waves.

2. The method as claimed in claim 1 , wherein the step of determining, for each specific one of the plurality of transceiver antenna units, a range of a target includes determining a range of a target from radar waves that have been transmitted by the specific transceiver antenna unit and at least another one of the plurality of transceiver antenna units and have been reflected by the target, by reading out range gates out of the plurality of range gates of the specific transceiver antenna unit and of the at least one another transceiver antenna units.

3. The method as claimed in claim 1 , wherein prior to the step of determining a range of the target occurring in one of separated angular directions, a step of merging consecutive range gates of each plurality of range gates into packages of a predetermined number of range gates is executed for all transceiver antenna units.

4. The method as claimed in claim 1 , wherein the step of estimating a direction of arrival includes solving the linear equation system

R δm =A·t

wherein t denotes a vector that represents occurring targets detected in the separated angular directions, R δm represents a vector comprising results from reading out the plurality of range gates and A is a matrix that is calculated from the a priori known positions and the separated angular directions, wherein A represents a linear mapping, by which vector t is transformed into vector R δm .

5. A non-transitory computer-readable medium for controlling automatic execution of steps of the method as claimed in claim 1 , wherein the method steps are stored on the computer-readable medium as a program code, wherein the computer-readable medium comprises a part of the automotive spread radar system or a separate control unit and the program code is executable by a processor unit of the automotive spread radar system or a separate control unit.

6. An automotive spread radar system for direction of arrival estimation, comprising:

a plurality of at least two transceiver antenna units, which are configured to work in a multiple-input and multiple-output configuration, wherein the transceiver antenna units are arranged at a priori known positions,

for each specific transceiver antenna unit of the plurality of transceiver antenna units, a plurality of range gates that are configured to indicate a range of a target reflecting radar waves that have been transmitted by at least the specific transceiver antenna unit,

an evaluation and control unit that is configured to:

read out the plurality of range gates for all transceiver antenna units,

determine a pattern of occupied range gates from the read-out range gates of the plurality of transceiver antenna units, wherein the pattern of occupied range gates are created by mutually shifted range gate allocations of the plurality of transceiver antenna units, and

estimate a direction of arrival based on relating the determined pattern of occupied range gates to a plurality of expected patterns of occupied range gates for targets occurring in the separated angular directions, the plurality of expected patterns of occupied range gates being predetermined from the a priori known positions of the plurality of transceiver antenna units, and wherein the direction of arrival is estimated without using phase information from reflected radar waves.

7. The automotive spread radar system as claimed in claim 6 , wherein the plurality of transceiver antenna units is arranged at the a priori known positions to form a one-dimensional linear array.

8. The automotive spread radar system as claimed in claim 6 , wherein the a priori known positions of the plurality of transceiver antenna units are arranged at a front region of a vehicle.

9. The automotive spread radar system as claimed in claim 6 , wherein the evaluation and control unit comprises a processor unit and a digital data memory unit to which the processor unit has data access.

10. The automotive spread radar system as claimed in claim 6 , further comprising modulation means to operate the plurality of at least two transceiver antenna units in a phase-modulated continuous wave mode.