Automotive Radar System

Abstract

An automotive radar system for detecting target objects in a traffic scene comprises at least one transmit antenna, at least one receive antenna, and a radar circuit connected to the at least one transmit and receive antenna. The transmit antenna is configured to transmit the transmit radar signal having variable polarization. A logic unit of the radar system is configured to receive information on a full polarization state of an incoming radar signal emitted by at least one other radar device located within the traffic scene and the logic unit is configured to determine a transmit polarization state that has maximum isolation from the polarization state of the at least one incoming radar signal. The radar circuit is configured to adjust a polarization of the transmit radar signal transmitted via the at least one transmit antenna to match the determined transmit polarization state.

Claims

1. A radar system comprising: at least one transmit antenna that illuminates target objects in a traffic scene with a transmit radar signal having variable polarization; at least one receive antenna that receives target reflections of the transmit radar signal; a logic unit that determines, based on information received of a full polarization state of at least one incoming radar signal emitted by at least one other radar device located within the traffic scene, a transmit polarization state that has maximum isolation from the polarization state of the at least one incoming radar signal; and a radar circuit connected to the at least one transmit antenna and the at least one receive antenna, and that adjusts a transmitted polarization of the transmit radar signal to match the transmit polarization state determined by the logic unit.

2. The radar system according to claim 1, wherein the logic unit determines the transmit polarization state such that a distance between a location of the transmit polarization on a Poincaré sphere and a reference location defined by the polarization state of the at least one incoming radar signal is maximized.

3. The radar system according to claim 2, wherein the location of the transmit polarization state and the reference location lie opposite to each other on the Poincaré sphere with respect to a center of the Poincaré sphere.

4. The radar system according to claim 1, wherein the logic unit receives information on full polarization states of a multitude of incoming radar signals that are emitted by multiple other radar devices within the traffic scene, and wherein the logic unit determines the transmit polarization state having maximum isolation from an entirety of the polarization states of the multitude of incoming radar signals.

5. The radar system according to claim 4, wherein the maximum isolation from the entirety of the polarization states corresponds to a maximum isolation from an average of the polarization states of the multitude of incoming radar signals.

6. The radar system according to claim 5, wherein the average is a weighted average, and wherein individual weights of the polarization states depend on one or several signal parameters of the multitude of incoming radar signals.

7. The radar system according to claim 6, wherein the one or several signal parameters comprise at least one parameter from a group of parameters including: a respective frequency of any of the multitude of incoming radar signal; a frequency difference between any of the multitude of incoming radar signals and the transmit radar signal; a respective amplitude of any of the multitude of incoming radar signals; a respective bandwidth of any of the multitude of incoming radar signals; a respective distance to the multiple other radar devices emitting any of the multitude of incoming radar signals; an angular position of the multiple other radar devices emitting any of the multitude of incoming radar signals radar signals; a velocity of the multiple other radar devices emitting any of the multitude of incoming radar signals radar signals; and a modulation scheme including at least one of a frequency modulation, an amplitude modulation, or a phase modulation.

8. The radar system according to claim 7, wherein the one or several signal parameters comprise multiple parameters from the group of parameters.

9. The radar system according to claim 8, wherein the one or several signal parameters comprise more than two of the parameters from the group of parameters.

10. The radar system according to claim 1, wherein the transmit radar signal comprises a coherent superposition of a first transmit radar signal having a first transmit polarization and a second transmit radar signal having a second transmit polarization that is different from the first transmit polarization, and wherein the radar circuit adjusts the polarization of the transmit radar signal by simultaneously and coherently generating the first transmit radar signal and the second transmit radar signal by simultaneously and coherently transmitting via the transmit antenna the first transmit radar signal and the second transmit radar signal.

11. The radar system according to claim 1, wherein the radar circuit varies the transmit polarization of the transmitted radar signal between non-orthogonal transmit polarization states.

12. The radar system according to claim 11, wherein the non-orthogonal transmit polarization states comprise elliptic polarization and linear polarization.

13. The radar system according to claim 1, wherein the radar circuit evaluates the at least one incoming radar signal after reception by the at least one receive antenna, wherein the radar circuit measures the full polarization state of the at least one incoming radar signal, and wherein the logic unit receives the information on the full polarization state from the radar circuit.

14. The radar system according to claim 13, wherein the receive antenna separates the at least one incoming radar signal into a first signal portion having a first receive polarization and into second signal portion having a second receive polarization that is different from the first receive polarization, and wherein the full polarization state of the at least one incoming radar signal is measured by the radar circuit coherently evaluating the first signal portion and the second signal portion.

15. The radar system according to claim 14, wherein the radar circuit evaluates a multitude of individual incoming radar signals after reception by the at least one receive antenna, wherein the radar circuit measures the full polarization states of the multitude of individual incoming radar signals, wherein the radar circuit differentiates between the multitude of individual incoming radar based on one or several signal parameters of the multitude of individual incoming radar signals, and wherein the logic unit receives information from the radar circuit on the full polarization states of the multitude of individual incoming radar signals.

16. The radar system according to claim 1, wherein the logic unit receives, from the at least one other radar device, and via a communication link, the information on the full polarization state of the at least one incoming radar signal.

17. The radar system according to claim 1, wherein the radar circuit receives the information on the full polarization state of the at least one incoming radar signal, and wherein the radar circuit determines the transmit polarization state and adjusts the polarization of the transmit radar signal repeatedly during operation of the radar system and thereby adjusts the polarization of the transmit radar signal to variations of the at least one incoming radar signal.

18. The radar system according to claim 1, wherein the radar system comprises an automotive radar system of a first vehicle in the traffic scene and the at least one other radar device comprises a second automotive radar system of a different vehicle in the traffic scene.

19. A system for a vehicle, the system comprising: at least one transmit antenna that illuminates target objects in a traffic scene with a transmit radar signal having variable polarization; at least one receive antenna that receives target reflections of the transmit radar signal; a logic unit that receives information on a full polarization state of an incoming radar signal emitted by at least one other radar device located within the traffic scene, and determines a transmit polarization state that has maximum isolation from the polarization state of the at least one incoming radar signal; and a radar circuit connected to the at least one transmit antenna and the at least one receive antenna, and that adjusts a transmitted polarization of the transmit radar signal to match the transmit polarization state determined by the logic unit.

20. A method comprising: operating an automotive radar system having a radar circuit connected to at least one transmit antenna for illuminating target objects in a traffic scene with a transmit radar signal having variable polarization, and further connected to at least one receive antenna for receiving target reflections of the transmit radar signal, wherein operating the automotive radar system comprises: receiving, with the radar circuit, information on a full polarization state of an incoming radar signal emitted by at least one other radar device located within the traffic scene; determining a transmit polarization state that has maximum isolation from the polarization state of the at least one incoming radar signal; and adjusting the variable polarization of the transmit radar signal illuminating the target objects via the at least one transmit antenna to match the transmit polarization state that has the maximum isolation in the traffic scene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Exemplary embodiments and functions of the present disclosure are described herein in conjunction with the following drawings, showing schematically:

[0050] FIG. 1 illustrates a diagram of an automotive radar system according to the present disclosure;

[0051] FIG. 2 illustrates a diagram of a pair of transmit and receive antennas of the radar system together with a multitude of other radar devices;

[0052] FIG. 3 illustrates a diagram of a Poincaré sphere with polarization states of radar signals emitted by the other radar devices;

[0053] FIG. 4 illustrates a diagram of a vehicle equipped with a radar system according to the present disclosure.

DETAILED DESCRIPTION

[0054] FIG. 1 depicts an automotive radar system 1 having an antenna device 100 and a radar circuit 200. The antenna device 100 comprises an arrangement of transmit antennas 110 and an arrangement of receive antennas 120. The individual transmit antennas 110 and the individual receive antennas 120 are each configured as serially-fed patch antennas. Each transmit antenna 110 comprises an array of serially connected radiating patch elements 111 and each receive antenna 120 comprises an array of serially connected radiating patch elements 121.

[0055] Each transmit antenna 110 is a dual-polarized antenna that is configured to transmit a first transmit radar signal 14 with a first transmit polarization, namely with linear vertical polarization, and to transmit a second transmit radar signal 15 with a second transmit polarization, namely with linear horizontal polarization. The transmit antenna 110 receive the first and second radar signals 14, 15 from the radar circuit 200, whereby each transmit antenna 110 is a dual-port antenna that is configured to receive the first transmit radar signal 14 via a first antenna port and the second transmit radar signal 15 via a second antenna port.

[0056] Likewise, each receive antenna 120 is a dual-polarized antenna that is configured to separate incoming radar signals into a first signal portion 24 that corresponds to a component of the incoming radar signals having a first receive polarization, namely linear vertical polarization, and into a second signal portion 25 that corresponds to a component of the incoming radar signals having a second receive polarization, namely linear horizontal polarization. Furthermore, each receive antenna 120 is configured as a dual-port antenna that outputs the first signal portion 24 via a first antenna port and the second signal portion 25 via a second antenna port.

[0057] The radar circuit 200 comprises a first integrated circuit 251 and a second integrated circuit 252. Each integrated circuit 251, 252 comprises three transmit chains 210 and four receive chains 220. Every transmit antenna 110 is connected to two separate transmit chains 210, whereby one of the transmit chains 210 provides the first transmit radar signal 14 and the other one of the transmit chains 210 provides the second transmit radar signal 15 of the respective transmit antenna 110.

[0058] The individual transmit chains 210 generate the first and second transmit radar signals 14, 15 from a common oscillator signal 242 that is provided by a reference oscillator 240 of the respective integrated circuit 251, 252. The individual transmit chains 210 of the integrated circuits 251, 252 are controlled by respective control units 230 of the individual integrated circuits 251, 252. Thereby, the control units 230 control individual signal parameters of the first and second transmit radar signals 14, 15, such as frequency, amplitude, frequency chirp, burst timing or the like.

[0059] The first and second integrated circuits 251, 252 of the radar circuit 200 are synchronized and configured to coherently generate all first and second transmit radar signals 14, 15 output by the radar circuit 200. Coherent generation of the radar signals 14, 15 establishes well-defined and controllable phase relationships among the individual first and second transmit radar signals 14, 15. A synchronization mechanism of the first and second integrated circuit 251, 252 comprises exchanging a synchronization signal 202 for synchronizing the oscillators 240 of the integrated circuits 251, 252. Furthermore, the synchronization mechanism comprises a synchronization of the control units 230 via a trigger signal 204 to provide a common timing basis.

[0060] For each transmit antenna 110, the radar circuit 200 is configured to simultaneously transmit the respective first transmit radar signal 14 and the respective second transmit radar signal 15, so that each transmit antenna 110 transmits a transmit radar signal that is a coherent superposition of the respective first and second radar signal 14, 15. For adjusting the polarization of the transmit radar signals transmitted by the individual transmit antennas 110, the integrated circuits 251, 252 comprise, for each transmit antenna 110, a first phase shifter 214 and a first variable attenuator 215 that are located in a signal path connecting the transmit chain 210 that generates the respective first transmit radar signal 14 with the respective transmit antenna 110. Furthermore, the integrated circuits 251, 252 comprise, for each transmit antenna 110, a second phase shifter 216 and a second variable attenuator 217 that are located in a signal path connecting the transmit chain 210 that generates the respective second transmit radar signal 15 with the respective transmit antenna 110. By way of example, the phase shifters 214, 216 are configured as 6-bit phase shifters.

[0061] By adjusting the first and second phase shifters 214, 216 and the first and second variable attenuators 215, 216 connected to the same transmit antenna 110, the radar circuit 200 adjusts the relative phase offsets and amplitude differences of the first and second radar signal 14, 15 that are transmitted via the respective transmit antenna 110. In this way, the radar circuit 200 variably adjusts the polarization of the transmit radar signal transmitted by the respective transmit antenna 110. For example, by setting a relative phase offset of 0° and zero amplitude difference, the radar circuit 200 generates a transmit radar signal that has a polarization of 45°. Likewise, by setting a relative phase offset of 90° and zero amplitude difference, the radar circuit 200 generates a transmit radar signal that has a circular polarization as resulting polarization.

[0062] The radar circuit 200 is further configured to coherently evaluate the first and second signal portions 24, 25 received from the individual receive antennas 120. Each receive antenna 120 is connected via its antenna ports to two receive chains 220 of the radar circuit 200. One of these receive chains 220 evaluates the first signal portion 24 and the other one of these receive chains 220 evaluates the second signal portion 25. For coherently evaluating the first and second signal portions 24, 25, the individual receive chains 220 mix and down-convert the received signal portions 24, 25 with the oscillator signal 242 provided by the synchronized oscillators 240 of the integrated circuits 251, 252. Furthermore, the receive chains 220 digitize the received signal portions 24, 25 for further signal processing and evaluation, for example after down-conversion. The receive chains 220 also condition the received signal portions 24, 25 via frequency filters and/or variable attenuators and/or phase shifters.

[0063] The radar device 1 is configured to determine absolute phase and amplitude values of the first and second signal portions 24, 25 evaluated by the individual receive chains 220. By coherently combining the first and second signal portions 24, 25 received via the same receive antenna 120, the radar device 1 reconstructs the full polarization state of incoming radar signals.

[0064] With alternative embodiments of the radar device 1, the radar circuit 200 may be configured as a single integrated circuit. Additionally or alternatively, the radar circuit 200 may comprise only one transmit chain 210 for each individual transmit antenna 110. In this case, each transmit chain 210 may generate a common feed signal that is subsequently split into the first and second transmit radar signal 14, 15 of the respective transmit antenna 110, for example by a power divider, such as a T-junction or Wilkinson power divider. These power dividers may be integral part of the integrated circuits 251, 252 of the radar circuit 200.

[0065] The radar device 1 further comprises a logic unit 30 that is connected to the control units 230 of the radar circuit 200 via communication connections. The logic unit 30 forms together with the radar circuit 200 and the antenna device 100 part of a radar device mountable to a vehicle.

[0066] FIG. 2 exemplarily depicts a radiating element 111 of one of the transmit antennas 110 and a radiating element 121 of one of the receive antennas 120 of the radar device 1. All other radiating elements 111 of the transmit antennas 110 are configured as it is disclosed for the transmit antenna 110 shown in FIG. 2 and all other radiating elements 121 of the receive antennas 120 of the radar system 1 are configured as it is disclosed for the receive antenna 120 shown in FIG. 2. The antennas 110, 120 are directed towards a traffic scene 2 that comprises several other radar devices 40.

[0067] The individual receive antennas 120 of the radar device 1 receive incoming radar signals 41, 42, 43, 44 that are emitted by the other radar devices 40 present in the traffic scene 2. For the traffic scene 2 depicted in FIG. 2, the receive antennas 120 receive a first incoming radar signal 41 having a first polarization state 45, a second incoming radar signal 42 having a second polarization state 46, a third incoming radar signal 43 having a third polarization state 47 and a fourth incoming radar signal 44 having a fourth polarization state 48. Thereby, the first polarization state 45 amounts to right-hand circular polarization, the second polarization state 46 to horizontal linear polarization, the third polarization state 47 to left-hand elliptical polarization and the fourth polarization state 48 to vertical linear polarization.

[0068] At the receive antennas 120, the incoming radar signals 41, 42, 43, 44 are decomposed into first signal portions 24 that correspond to polarization components of the radar signals 41, 42, 43, 44 having the first receive polarization 122, namely vertical linear polarization, and into second signal portions 25 that correspond to polarization components of the radar signals 41, 42, 43, 44 having the second receive polarization 124, namely horizontal linear polarization. The receive antennas 120 thereby receive the individual signal portions 24, 25 with a common phase center 102.

[0069] The receive antennas 120 are configured as dual-polarized differential patch antennas that have a set of first connection points located at opposite sides of the common phase center 102, the first connection points providing the first signal portion 24, and a set of second connection points located at opposite sides of the common phase center 102 and rotated by 90° with respect to the first connection points, the second connection points providing the second signal portion 25.

[0070] The individual transmit antennas 110 are also configured as dual-polarized differential patch antennas. Each transmit antenna 110 has a set of first connection points located at opposite sides of a common phase center 102 of the respective transmit antenna 110, the first connection points feeding the first transmit radar signals 14, and a set of second connection points located at opposite sides of the common phase center 102 and rotated by 90° with respect to the first connection points, the second connection points feeding the second transmit radar signals 15.

[0071] The control units 230 of the radar circuit 200 adjust the amplitudes and phases of first and second transmit radar signals 14, 15 fed to the individual transmit antennas 110 and thus a polarization 12 of the transmit radar signals 10 transmitted by the individual transmit antennas 110. The control units 230 thereby adjust the polarization 12 of the transmit radar signals 10 in a way to match a transmit polarization state that is provided by the logic unit 30 and maximizes isolation of the transmit polarization 12 from the polarization states 45, 46, 47, 48 of the incoming radar signals 41, 42, 43, 44.

[0072] To determine the transmit polarization state, the logic unit 30 receives information on the full polarization states 45, 46, 47, 48 of the incoming radar signals 41, 42, 43, 44 from the control units 230 that coherently evaluate the first and second signal portions 24, 25 obtained from the incoming radar signals 41, 42, 43, 44. The logic unit 30 determines a weighted average of the full polarization states 45, 46, 47, 48 and determines the transmit polarization state having maximum polarization isolation from this weighted average. Thereby, this transmit polarization state corresponds to a location on the Poincaré sphere that maximizes a distance to the location of the weighted average of the polarization states 45, 46, 47, 48.

[0073] FIG. 3 depicts the location of the full polarization states 45, 46, 47, 48 on a surface of the Poincaré sphere 300. The Poincaré sphere 300 is defined as the unit sphere in a coordinate system that is spanned by three orthogonal Stokes vectors, namely a first Stokes vector 301, a second Stokes vector 302 and a third Stokes vector 303. Locations that lie on opposite sides of the Poincaré sphere 300 with respect to its center 305 represent orthogonal polarization states. The polar coordinates of a given polarization state on the Poincaré sphere 300 are given by angles ϕ and υ that define the shape and orientation of the polarization ellipse 320 of the respective polarization state, as also depicted in FIG. 3. Thereby, ϕ denotes the orientation angle of the polarization ellipse and υ denotes its ellipticity.

[0074] The reference location 320 for determining the transmit polarization state 330 of the transmit radar signal 10 corresponds to the location of the weighted average of the polarization states 45, 46, 47, 48. The logic unit 30 then determines the transmit polarization state 330 in a way that the location of the transmit polarization state 330 on the Poincaré sphere 300 is on the hemisphere that is opposite to the reference location 320. As depicted in FIG. 3, the location of the transmit polarization state 330 may be opposite to the reference location 320 with respect to the center 305 of the Poincaré sphere 300.

[0075] FIG. 4 depicts a vehicle 500 that is equipped with a radar system 1 according to the present disclosure, whereby the entire radar system 1 is configured as a radar device mounted to the vehicle 500. With other embodiments, the logic unit 30 may be located separate from the radar device and the radar device may comprise the remaining components of the radar system 1. In the embodiment shown in FIG. 4, the radar system 1 is configured as a front radar of the vehicle 500 and a radiation field 501 of the antenna device of the radar system 1 is directed in the forward direction of the vehicle 500. The radar system 1 is part of a vehicle control system 502 of the vehicle 500 and is connected to a control device 504 of the vehicle control system 502. The control device 504 is configured to perform advanced driver's assist functions, such as adaptive cruise control, emergency brake assist, lane change assist or autonomous driving, based on data signals received from the radar system 1. These data signals represent the positions of target objects in front of the radar system 1 mounted to the vehicle 500. The control device 504 is configured to at least partly control the motion of the vehicle 500 based on the data signals received from the radar system 1. For controlling the motion of the vehicle, the control device 504 may be configured to brake and/or accelerate and/or steer the vehicle 500.