Radar-based vehicle guidance using radar reflectors embedded in road markings on driving surface

Abstract

The present disclosure generally relates to: (1) road marking in which a radar reflective dihedral corner reflector or other suitably oriented directional reflector capable of reflecting radar signals is embedded; (2) arranging radar reflection road surface marks on the driving surface; (3) manufacturing the road surface mark and mounting the road surface mark on a driving surface; (4) a radar transceiver on or within the vehicle for sensing radar reflective road markings and measuring the distance between the vehicle and the markings; (5) a vehicle equipped with such a radar transceiver; and (6) a method of controlling or assisting in the lateral steering or positioning of a vehicle on a driving surface (e.g., a road or a lane of a road) based on the detection of radar-reflected road markings on the driving surface (e.g., along or near a road or lane boundary).

Description

[0001] Related Applications

[0002] Priority is claimed to each of the following U.S. provisional patent applications: (1) No. 63 / 474,257, filed on August 1, 2022, entitled “Vehicle Guidance System”; (2) No. 63 / 474,383, filed on August 10, 2022, entitled “Vehicle Guidance System”; (3) No. 63 / 576,322, filed on January 30, 2023, entitled “Short-Range Radar for use in Vehicle Lateral Guidance and Control”; (4) No. 63 / 576,323, filed on January 30, 2023, entitled “Vehicle Guidance System”; (5) No. 63 / 576,323, filed on March 25, 2023, entitled “Radar-Based Vehicle Guidance System Using Dihedral Corner Reflector Embedded in Pavement and (9) Application No. 63 / 469,920, filed on May 31, 2023, entitled “Radar-Based Vehicle Guidance Using CornerReflectors Embedded in Pavement Markers on a Driving Surface.” The entire disclosure of each of the above patent applications is hereby incorporated by reference. Technical Field

[0003] The field of the present disclosure generally relates to the control of automobiles or similar vehicles. More specifically, the present disclosure relates to the use of radar (radio detection and ranging) reflectors on or near a road or other driving surface to control or assist in the control of a vehicle, particularly the lateral positioning of a vehicle. Background Art

[0004] Figure 1A and Figure 1B Typical pavement markings 445 currently in use on today's roads are shown. Figure 1A The pavement markers 445 shown in FIG. 3 are rectangular, but pavement markers come in many different shapes and sizes. The pavement markers 445 may be placed on top of the pavement, in which case they are referred to as raised pavement markers (RPMs), or may be installed at or slightly below pavement level (e.g., plowable snow markers), or in cuts, pits, or grooves below the road surface 300. Figure 1B As shown, pavement markings 445 are usually installed along the painted lines 305, 307 and 309 on the road 300. The painted line 307 is usually a yellow center line, and the painted white lines 305 and 309 mark the sides of the road. The main function of the pavement markings 445 is to reflect light waves so that the headlights of the vehicle or the sun are reflected back to the driver of the vehicle so that the driver can intuitively see the location of the road lines, especially in bad weather. Figure 1A As shown, the pavement marking has a visible reflector 275 on one or more sides. In addition, the raised pavement reflector can also be used as a rumble guard when a vehicle crosses a road line or pavement marking 445, because the marking 445 is generally 25 mm above the road surface and causes the vehicle tire (s) to hit the raised pavement marking. Over the years, the raised pavement marking 445 has been modified many times with various visible reflective properties, such as cat's eyes, LED (light emitting diode) lights, lidar reflection patterns, etc. The pavement marking 445 reflects visible light well, but the reflectivity of radio frequencies (RF) emitted by radar transceivers is not high, although some pavement markings are made of metal. Pavement markings are commonly used on highways, but can also be used in parking lots, freight yards, freight terminals, and other paved and unpaved areas. Summary of the invention

[0005] The present disclosure generally relates to (1) a pavement marking having embedded therein a radar-reflective dihedral corner reflector or other appropriately oriented directional reflector that reflects radar signals; (2) a method of making such a pavement marking; (3) the arrangement of radar-reflective pavement markings on a driving surface (e.g., a road or a lane of a road), including arrangement along or near a boundary of a road or lane (e.g., a lane line); (4) a method of installing such a pavement marking on a driving surface; (5) a radar transceiver on or in a vehicle for sensing the radar-reflective pavement marking and measuring the distance from the vehicle to the marking; (6) a vehicle equipped with such a radar transceiver; and (7) a method of operating such a radar transceiver and the use of the distance measurement, such as, for example, to control or assist in lateral steering or positioning of a vehicle on a driving surface.

[0006] According to one embodiment, a pavement marking is for a road on which vehicles travel in a direction of travel. The road includes lane lines marked on a top surface of the road substantially parallel to the direction of travel. The pavement marking includes: an optically reflective surface positioned and oriented to face oncoming vehicles when the pavement marking is affixed to the road; and further includes: a dihedral corner reflector including a longitudinal axis and two passive radar reflective surfaces intersecting the longitudinal axis. When the pavement marking is affixed to the road, the dihedral corner reflector is positioned and oriented such that the longitudinal axis is substantially orthogonal to the optically reflective surface, substantially parallel to the direction of travel, and substantially parallel to the lane lines.

[0007] Optionally, the dihedral corner reflector is strictly dihedral, and / or the two passive radar reflecting surfaces are at least substantially orthogonal.

[0008] Optionally, the pavement marking further includes a substantially radar transparent material between the two passive radar reflecting surfaces of the dihedral corner reflector. For example, the substantially radar transparent material may include a material selected from the group consisting of polytetrafluoroethylene, polypropiolactone, polyvinyl chloride, and acrylonitrile-butadiene-styrene. The substantially radar transparent material may be adhered to the dihedral corner reflector using a substantially radar transparent adhesive.

[0009] For example, the dihedral corner reflector may include two metal plates or two surfaces coated with a radar reflective coating. The radar reflective coating may be a paint (eg, a metallic paint) or may be electroplated.

[0010] Optionally, the pavement marking further includes one or more additional dihedral corner reflectors. The total number of dihedral corner reflectors can be, for example, two or at least four. If there are two, the two dihedral corner reflectors can form an inverted T-shape with a common vertical element. If there are two, the two dihedral corner reflectors can be offset from each other in the lateral direction, located on opposite sides of the pavement marking, and oriented to reflect radar signals horizontally in opposite directions.

[0011] In a pavement marking having at least four dihedral corner reflectors, one pavement marking may be positioned along and proximate each side of the pavement marking.

[0012] Optionally, the pavement marking is plowable and / or one of the radar reflecting surfaces of the dihedral corner reflector is a top surface of the road.

[0013] For example, a pavement marking may be approximately 100 mm wide, approximately 100 mm long and approximately 25 mm high.

[0014] According to one embodiment, a pavement marking is used on a road on which vehicles travel in a direction of travel. The pavement marking includes an optically reflective surface and a passive radar reflector characterized by a reflection direction, the optically reflective surface being positioned and oriented so that when the pavement marking is affixed to the road, facing toward oncoming vehicles, a radar signal incident on the reflector is reflected from the passive radar reflector back to a source of the radar signal at a maximum amplitude. The pavement marking is configured for affixment to the road with the reflection direction partially upward from the road and substantially orthogonal to the direction of travel.

[0015] Optionally, the road includes lane markings marked on a top surface of the road substantially parallel to the direction of travel, and the road surface markings are configured to be mounted such that the direction of reflection is substantially orthogonal to the lane markings.

[0016] Optionally, the radar signal source is a vehicle having a directional radar transmitter having a main beam lobe central axis directed laterally and downwardly from the vehicle, and the reflector is positioned and oriented to produce a detectable return signal by reflecting an incident radar signal from the vehicle's radar transmitter directed laterally and downwardly from the vehicle when the vehicle passes beside a pavement marking.

[0017] Optionally, the pavement marking further comprises a substantially radar transparent material located between the reflector and the source. The substantially radar transparent material may be selected from the group comprising, for example, polytetrafluoroethylene, polypropiolactone, polyvinyl chloride, and acrylonitrile-butadiene-styrene. The substantially radar transparent material may be adhered to the reflector with a substantially radar transparent adhesive.

[0018] Pavement markings include, for example, metal or one or more surfaces coated with a radar reflective coating, which may be a paint (eg, metallic paint) or may be electroplated.

[0019] Optionally, the pavement marking further includes one or more additional radar reflectors. The total number of reflectors may be, for example, two or at least four. If there are two, the two reflectors may be horizontally offset from each other, located on opposite sides of the pavement marking, and oriented to reflect radar signals horizontally in opposite directions. If there are at least four, one reflector may be positioned along each side of the pavement marking and close to each side.

[0020] Optionally, the pavement marking is snow plowable; is approximately 100 mm wide, approximately 100 mm long, and approximately 25 mm high; further comprises a radar reflecting backplane; and / or, the reflector is a dihedral corner reflector.

[0021] According to one embodiment, a method can produce a pavement marking for use on a road on which a vehicle travels in a direction of travel. The method provides a visible reflective portion on a first outer side of the pavement marking, the visible reflective portion configured to be visible to a driver of the vehicle when the driver of the vehicle is driving the vehicle generally toward the pavement marking. The method also embeds a dihedral corner reflector in the pavement marking, the dihedral corner reflector including a longitudinal axis and two passive radio frequency reflective surfaces intersecting at the longitudinal axis, the longitudinal axis being substantially orthogonal to the first outer side of the pavement marking.

[0022] Optionally, the embedding step includes placing a substantially radar transparent material between two RF reflecting surfaces of the dihedral corner reflector. Optionally, the method further includes attaching the substantially radar transparent material to the two RF reflecting surfaces of the dihedral corner reflector. The attaching step may include adhering the substantially radar transparent material to the two RF reflecting surfaces of the dihedral corner reflector with a radar transparent adhesive. The substantially radar transparent material may have a quarter circle shape.

[0023] Optionally, the method further includes forming the dihedral corner reflector by an extrusion process, cutting the output of the extrusion process into segments, and selecting one of the segments to embed in the pavement marking. Optionally, the method further includes forming the dihedral corner reflector by welding two metal pieces together. Optionally, the method further includes forming the dihedral corner reflector by bending planar metal pieces. Optionally, the method further includes forming the dihedral corner reflector by a process including applying a radio frequency reflective coating on one or more of the two passive radio frequency reflective surfaces. Optionally, the method further includes forming the dihedral corner reflector by a process including electroplating a radio frequency reflective coating on one or more of the two passive radio frequency reflective surfaces.

[0024] According to one embodiment, a method manufactures a radar reflective pavement marking for use on a road on which a vehicle travels in a direction of travel. The method provides a visible reflective portion on a first outer side of the pavement marking, the visible reflective portion configured to be visible to a driver of the vehicle when the driver of the vehicle is driving the vehicle generally toward the pavement marking. The method also embeds a passive directional radar reflector within the pavement marking, the passive directional radar reflector being positioned and oriented to provide a maximum return signal by reflecting incident radar signals directed partially downward toward the pavement marking and also directed horizontally from a direction substantially orthogonal to both the direction of travel and the first outer side of the pavement marking.

[0025] Optionally, the embedding step includes placing a substantially radar transparent material over the reflector. In addition, the method may further include attaching the substantially radar transparent material to the reflector. The attaching step may include adhering the substantially radar transparent material to the reflector, for example, with a radar transparent adhesive.

[0026] Optionally, the passive directional radar reflector is a dihedral corner reflector.

[0027] Optionally, the method further comprises forming the radar reflector by an extrusion process, cutting the output of the extrusion process into segments; and selecting one of the segments to embed in the pavement marking. Optionally, the method further comprises forming the radar reflector by welding metal pieces together. Optionally, the method further comprises forming the radar reflector by bending metal pieces. Optionally, the method further comprises forming the radar reflector by a process comprising applying a radio frequency reflective coating on one or more surfaces of the radar reflector. Optionally, the method further comprises forming the radar reflector by a process comprising electroplating a radio frequency reflective coating on one or more surfaces of the radar reflector.

[0028] One embodiment is a road on which vehicles travel in a lane in a direction of travel. The road includes a set of pavement markings that are discretely spaced along at least one side of the lane and attached to a top surface of the road. Each pavement marking in the set of pavement markings includes a radar reflecting dihedral corner reflector that includes a longitudinal axis and two passive radar reflecting surfaces that intersect at the longitudinal axis. The pavement marking is secured to the road with the longitudinal axis substantially parallel to the direction of travel.

[0029] Optionally, the road further includes lane markings marked on a top surface of the road substantially parallel to the direction of travel to demarcate the boundaries of the lane, and the road surface markings are fixed to the road such that the longitudinal axis of the radar reflecting dihedral corner reflector is substantially parallel to the lane markings. For example, the road surface marking may be fixed to the road along one of the lane markings.

[0030] For example, the distance between adjacent pavement markings in the set may be between about 0.3 m (meters) and about 8 m.

[0031] Optionally, the roadway further comprises a second set of pavement markings that are discretely spaced along a second side of the lane and attached to a top surface of the roadway. Each pavement marking in the second set comprises a radar reflecting dihedral corner reflector having a longitudinal axis, the radar reflecting dihedral corner reflector comprising two radio frequency reflecting surfaces that are orthogonal to each other and intersect at the longitudinal axis. The pavement marking is secured to the roadway with the longitudinal axis substantially parallel to the direction of travel.

[0032] For example, the road may be a multi-lane road or a two-way road.

[0033] Optionally, the pavement marking set encodes information about the road. For example, the road may include substantially straight sections and curved sections, and the information encoded in the pavement marking set includes data identifying the section as straight or curved.

[0034] Optionally, the roadway further comprises depressions forming rumble strips in the surface of the roadway, wherein at least some of the pavement markings in the set of pavement markings are installed in the depressions.

[0035] One embodiment is a driving surface on which a vehicle travels along a path in a direction of travel. The driving surface includes a set of pavement markings discretely spaced apart along one side of the path and attached to the driving surface. Each pavement marking includes a passive radar reflector characterized by a reflection direction, and a radar signal incident on the reflector is reflected from the passive radar reflector back to a radar signal source at a maximum amplitude. The pavement marking is fixed to the driving surface so that the reflection direction is upward from the driving surface portion and is substantially orthogonal to the direction of travel.

[0036] The driving surface may be, for example, a road, such as a multi-lane road or a two-way road, or a parking lot, a transport terminal, a freight terminal, a loading dock, or a warehouse.

[0037] For example, the driving surface may be a lane, the lane further comprising lane lines marked on the driving surface substantially parallel to the driving direction to demarcate the boundaries of the lane, and the road surface markings are fixed to the road so that the reflection direction is substantially orthogonal to the lane lines. In one arrangement, the road surface markings are fixed to the road along one of the lane lines.

[0038] For example, the distance between adjacent pavement markings in the pavement marking set may be between about 0.3 m and about 8 m.

[0039] Optionally, the driving surface further includes a second set of pavement markings that are discretely spaced along a second side of the path and attached to a top surface of the driving surface. Each pavement marking in the second set includes a passive radar reflector characterized by a reflection direction, and a radar signal incident on the reflector is reflected from the passive radar reflector back to the radar signal source at a maximum amplitude. The pavement markings are fixed to the driving surface so that the reflection direction is upward from the driving surface portion and is substantially orthogonal to the direction of travel.

[0040] Optionally, the set of pavement markings encodes information about the driving surface.

[0041] Optionally, the radar reflector is a dihedral corner reflector.

[0042] According to one embodiment, a radar transceiver is configured to be mounted in or on a land vehicle and used with radar reflective pavement markings distributed along a road on which the land vehicle can travel. The radar transceiver includes a radar transmitter and a radar receiver. The radar transmitter is configured to transmit a radar signal having a transmit beam pattern with a maximum transmit center direction. The radar receiver is configured to receive radar echo reflection signals and has a receive beam pattern with a maximum receive center direction. The radar transceiver is also configured to be mounted in or on a land vehicle, so that when the radar transceiver is mounted on or in a land vehicle, the maximum transmit center direction is downward and to the side of the land vehicle, and when the radar transceiver is mounted on or in a land vehicle, the maximum receive center direction is upward and to the side of the land vehicle.

[0043] Optionally, the radar transceiver operates in a frequency range within the range of about 300 MHz to about 1 THz, or, for example, in a frequency range of about 77 GHz to about 81 GHz.

[0044] For example, the radar transceiver can be a frequency modulated continuous wave radar transceiver, an ultra-wideband pulse radar transceiver, or a type selected from the group consisting of dual frequency phase difference, multi-frequency radar, orthogonal frequency division multiplexing, frequency shift keying, digital code modulation, phase modulated continuous wave, multiple input multiple output, polarization, dual polarization, single pulse and interferometric synthetic aperture radar.

[0045] The radar transceiver of claim 81, wherein the radar transceiver is monostatic or bistatic.

[0046] Optionally, the radar transceiver comprises an antenna array.

[0047] Optionally, the radar transmitter is configured to transmit a polarized radar signal, and the radar receiver may be configured to detect the radar echo reflection signal according to its polarization.

[0048] For example, the radar transceiver may be configured for placement within the front bumper of a vehicle or within a light assembly.

[0049] Optionally, the radar transceiver further includes a signal processor coupled to the radar receiver, the signal processor configured to receive a signal based on the radar echo reflection signal and configured to determine a path length from the radar transceiver to the radar reflecting road surface marking. The signal processor may be further configured to process only a portion of the radar echo reflection signal received in a window corresponding to an expected range of the reflecting target, or to frequency convert the radar echo reflection signal.

[0050] Optionally, the radar reflective pavement marking comprises a dihedral corner reflector.

[0051] According to one embodiment, a method installs radar reflective pavement markings on a road on which a vehicle travels in a direction of travel. The radar reflective pavement markings include a radio frequency reflective dihedral corner reflector having two radar reflective surfaces intersecting along a longitudinal axis. The method includes attaching a plurality of the radar reflective pavement markings to the road in a direction such that the longitudinal axis of each radar reflective pavement marking is substantially aligned with the direction of travel and such that the longitudinal axes of the plurality of the radar reflective pavement markings define a desired path of the vehicle on the road in the direction of travel.

[0052] According to one embodiment, a method is to install radar reflective pavement markings on a driving surface on which a vehicle is driven. The vehicle has a directional radar transmitter having a main beam lobe center axis directed to the side and downward from the vehicle. The method includes attaching a plurality of said radar reflective pavement markings to the driving surface, with each directional radar reflector positioned and oriented to give a maximum or high return signal by reflecting an incident radar signal from the vehicle's radar transmitter directed to the side and downward from the vehicle. Optionally, the directional radar reflector is a dihedral corner reflector.

[0053] According to one embodiment, a vehicle may be used on a road having a plurality of pavement markings installed along the road. Each pavement marking includes a radar reflector. The vehicle includes a radar transceiver and a processor. The radar transceiver is mounted to the vehicle and is characterized by having a beam pattern centered downward and aimed from the side of the vehicle such that reflections from the radar reflectors embedded in the pavement markings are detected as the vehicle moves forward over the pavement markings on the side of the vehicle. The processor is operatively coupled to the radar transceiver and is configured to determine a path length from the radar transceiver to the radar reflectors embedded in the pavement markings based on the reflections.

[0054] Optionally, the radar transceiver is further characterized by a second beam pattern having a second center downward and in a second lateral direction from the vehicle such that reflections are detected from a second radar reflector embedded in the second pavement marking when the vehicle moves past a second pavement marking, wherein the second lateral direction is generally horizontally opposite to the lateral direction, and wherein the second pavement marking is located on an opposite side of the vehicle from the first pavement marking.

[0055] Optionally, the vehicle further includes: a second radar transceiver mounted to the vehicle, wherein the second radar transceiver is characterized by a second beam pattern having a second center aimed downward and in a second lateral direction from the vehicle, such that when the vehicle moves forward over the second pavement marking, reflections from the radar reflector embedded in the second pavement marking are detected by the pavement marking on the side of the vehicle.

[0056] The vehicle may further include an exterior light assembly, and the radar transceiver may be located within the exterior light assembly, or the vehicle may further include a front bumper, and the radar transceiver may be located within the front bumper.

[0057] Optionally, the processor is configured to perform one or more of a lane departure warning function, a lane keeping function, and a lane centering assist function based on a path length from the radar transceiver to a radar reflector embedded in a road surface marking.

[0058] Optionally, the vehicle further comprises a lateral positioning system independent of the radar transceiver, wherein the radar transceiver and the processor form a redundant lateral positioning system.

[0059] The vehicle may be at least partially autonomously driven, and lateral positioning of the vehicle may be performed based at least in part on a path length from a radar transceiver to a radar reflector embedded in a road surface marking.

[0060] Optionally, the radar transceiver is also configured to perform blind spot detection.

[0061] Optionally, the radar reflector is a dihedral corner reflector.

[0062] According to one embodiment, a method determines a lateral position of a land vehicle on a road along the road. The road has radar reflective pavement markings distributed along the road along a direction of vehicle travel. When the vehicle passes over the pavement markings, the method transmits a radar transmit signal from the land vehicle downwardly and laterally to the pavement markings mounted on or near the road. When the vehicle passes over the pavement markings, the method also receives a radar reflective signal on the land vehicle from a radar reflector embedded in the pavement marking. The method also determines a distance between the land vehicle and the pavement marking based on the radar transmit signal and the radar reflective signal.

[0063] Optionally, the transmitting, receiving and determining steps are repeated for each radar-reflecting road surface marking passed by the vehicle. For example, the transmitting step may be repeated periodically within a period selected within the range of about 0.5 milliseconds to about 1 second.

[0064] For example, the radar reflecting pavement markings may be distributed along one side of the vehicle as it travels along the road, or the road is one lane of a multi-lane road and the radar reflecting pavement markings are distributed along a line demarcating one side of the road.

[0065] Optionally, the road is one lane of a multi-lane road, and the radar-reflecting road surface markings are distributed along a line delimiting one side of a lane adjacent to the lane corresponding to the road of the vehicle.

[0066] Optionally, the method further comprises filtering the radar reflection signal according to a range of expected distances between the land vehicle and road surface markings; performing a frequency transform on the radar reflection signal; and / or, using the distance to guide or assist the vehicle in lateral steering to follow the road.

[0067] Optionally, the method further comprises issuing a warning to the driver of the vehicle if the distance exceeds a maximum threshold or is less than a minimum threshold, and / or, issuing a warning to the outside of the vehicle if the distance exceeds a maximum threshold or is less than a minimum threshold. For example, the warning outside the vehicle comprises flashing lights.

[0068] Optionally, the method further comprises performing one or more of a lane centering assist function and a lane keeping function based on the distance between the land vehicle and the road surface marking.

[0069] The vehicle may optionally include a lateral positioning system independent of the method outlined above, and the method further comprises using the distances in conjunction with the independent lateral positioning system to improve lateral position determination, using the distances measured by the method to calibrate the independent lateral positioning system.

[0070] Optionally, the radar reflective pavement markings used in the method include dihedral corner reflectors.

[0071] As will be appreciated by those skilled in the art from this disclosure, certain embodiments of the pavement markings, radar reflectors, and radars disclosed herein may be able to achieve certain advantages that will be apparent from the following detailed description of example embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1A is an isometric view of a traditional pavement marking.

[0073] Figure 1B is an overhead view of a section of road on which conventional pavement markings have been placed.

[0074] Figure 2A is an isometric diagram of a dihedral corner reflector.

[0075] Figure 2B is an isometric view of a pavement marking augmented with two dihedral corner reflectors according to one embodiment.

[0076] Figure 2C yes Figure 2B Top view of pavement markings.

[0077] Figure 2D yes Figure 2B Side view of a road surface marking.

[0078] Figure 3A is an isometric diagram of a bi-dihedral corner reflector.

[0079] Figure 3B is an isometric view of a pavement marking augmented with a bi-dihedral corner reflector according to one embodiment.

[0080] Figure 3C yes Figure 3B Top view of pavement markings.

[0081] Figure 3D yes Figure 3B Side view of a road surface marking.

[0082] Figure 4A is a diagram showing reflections from / to a radar transceiver according to one embodiment. Figure 2B Side view of a road surface marking.

[0083] Figure 4B is a side cross-sectional view of a dihedral corner reflector with dimensions.

[0084] Figure 4C With dimension marking Figure 2A Isometric view of a dihedral corner reflector.

[0085] Figure 4D is a side cross-sectional view of a bi-dihedral corner reflector with dimensions.

[0086] Figure 4E With dimension marking Figure 3A Isometric view of a dihedral corner reflector.

[0087] Figure 5A is a representative plot of radar cross section versus angle of incidence in one dimension for a dihedral corner reflector according to one embodiment.

[0088] Figure 5B It is a description of Figure 5A Schematic diagram of the incident angles of radiation directed by the corresponding dihedral corner reflector.

[0089] Figure 5C is a schematic diagram illustrating the incident position of radiation directed at a dihedral corner reflector in the longitudinal direction of the reflector.

[0090] Figure 5D is the radar cross section of the dihedral corner reflector relative to Figure 5C Corresponding representative diagram of the incident position along the longitudinal direction of the reflector.

[0091] Figure 5E is a schematic diagram illustrating the angle of incidence of radiation directed at a dihedral corner reflector in another dimension according to one embodiment.

[0092] Fig. 5F is the radar cross section of the dihedral corner reflector relative to Figure 5E Representative graph of the corresponding incident angles.

[0093] Fig. 6A is an exploded isometric view of a pavement marking having two dihedral corner reflectors according to one embodiment.

[0094] Figure 6B is an exploded isometric view of a pavement marking having two dihedral corner reflectors according to another embodiment.

[0095] Figure 6C is an isometric view of a pavement marking having two dihedral corner reflectors according to another embodiment.

[0096] Fig. 7A yes Figure 3B Exploded isometric illustration of road surface markings.

[0097] Figure 7B is an exploded isometric view of another pavement marking having two dihedral corner reflectors according to another embodiment.

[0098] Figure 7C is an exploded isometric view of yet another pavement marking having two dihedral corner reflectors according to yet another embodiment.

[0099] Fig.7D is an exploded isometric view of a pavement marking having four dihedral corner reflectors according to one embodiment.

[0100] Fig. 8A is a front view of a vehicle equipped with a radar transceiver interacting with radar-reflective pavement markings on a driving surface according to one embodiment.

[0101] Figure 8B is a block diagram of a radar-based lateral control system for a vehicle according to one embodiment.

[0102] Figure 8C is a block diagram of a radar-based LDW system for a vehicle according to one embodiment.

[0103] Fig.8D is a block diagram of a radar-based LKA / LKS system for a vehicle, according to one embodiment.

[0104] Fig. 8E is a block diagram of a radar-based autonomous lateral control system for a vehicle, according to one embodiment.

[0105] Fig. 9A is a side view of a vehicle equipped with a radar transceiver interacting with radar-reflective pavement markings on a driving surface according to one embodiment.

[0106] Fig. 9B yes Fig. 9A A top view of the vehicle.

[0107] Fig. 9C is a top view of a vehicle equipped with a radar transceiver on a road with radar reflective pavement markings according to one embodiment.

[0108] Fig. 10A is a front view of a vehicle equipped with two radar transceivers interacting with two radar reflective pavement markings on a driving surface according to one embodiment.

[0109] Fig. 10B is a front view of a vehicle equipped with a two-way radar transceiver interacting with two radar-reflective pavement markings on a driving surface according to one embodiment.

[0110] Fig.11A is a top view of two vehicles equipped with radar transceivers interacting with radar-reflective pavement markings on a multi-lane road according to one embodiment.

[0111] Fig. 11B is a top view of a vehicle equipped with a radar transceiver interacting with radar-reflective pavement markings on a curved road according to one embodiment.

[0112] Fig. 11C is a top view of a vehicle equipped with a radar transceiver interacting with radar-reflective pavement markings on a curved road according to another embodiment.

[0113] Fig.11D is a schematic diagram showing a set of radar-reflective pavement markings in a coded arrangement according to one embodiment.

[0114] Fig.11E is a schematic diagram showing a set of radar-reflective pavement markings in a coded arrangement according to another embodiment.

[0115] Fig.11F is a schematic diagram showing a set of radar reflective pavement markings in a coded arrangement according to yet another embodiment.

[0116] Fig.11G is a schematic diagram showing a set of radar reflective pavement markings in a coded arrangement according to yet another embodiment.

[0117] Fig. 12A is an isometric view of a pavement marking with a dihedral corner reflector according to one embodiment.

[0118] Fig. 12B is an isometric view of a pavement marking with a dihedral corner reflector according to another embodiment.

[0119] Fig. 12C is an isometric view of a pavement marking with a dihedral corner reflector according to yet another embodiment.

[0120] Fig.13A is a cross-sectional view of a pavement marking in a cavity beneath a driving surface according to one embodiment.

[0121] Fig. 13B According to one embodiment, a Fig.13A A top view of a section of road with pavement markings in Figure 1.

[0122] Fig. 13C According to another embodiment, a Fig.13A A top view of a section of road with pavement markings in Figure 1.

[0123] Fig.14A is a cross-sectional view of a pavement marking in a cavity beneath a driving surface according to another embodiment.

[0124] Fig. 14B According to one embodiment, a Fig.14A A top view of a section of road with pavement markings.

[0125] Fig. 14C According to another embodiment, a Fig.14A A top view of a section of road with pavement markings.

[0126] Fig.14D is an isometric view of a plowable snow pavement marking augmented with dihedral corner reflectors according to one embodiment.

[0127] Fig.14E is a top view of a plowable snow pavement marking augmented with a dihedral corner reflector according to another embodiment.

[0128] Fig.14F yes Fig.14E Side cross-sectional view of a plowable snow pavement marking.

[0129] Figure 14G is a side cross-sectional view of a plowable snow pavement marking augmented with a dihedral corner reflector according to another embodiment.

[0130] Fig.14H is a side cross-sectional view of a plowable snow pavement marking augmented with a dihedral corner reflector according to yet another embodiment.

[0131] Fig.15A is an isometric view of a dihedral corner reflector along a curb according to one embodiment.

[0132] Fig. 15B is a schematic diagram showing a dihedral corner reflector in or behind a curb according to one embodiment.

[0133] Fig. 15C is a schematic diagram showing a dihedral corner reflector along a curb according to another embodiment.

[0134] Fig.16A is an isometric view of a pavement marking or portion thereof having three dihedral corner reflectors according to one embodiment.

[0135] Fig. 16B is an isometric view of a pavement marking or portion thereof having front dihedral corner reflectors at different vertical angles according to one embodiment.

[0136] Fig. 16C is an isometric view of a pavement marking or portion thereof having side-facing dihedral corner reflectors according to one embodiment.

[0137] Fig.17 is a block diagram of a UWB pulse radar transceiver according to one embodiment.

[0138] Fig.18 is a block diagram of a pulse radar transceiver with multiple antennas according to one embodiment.

[0139] Fig.19 is a block diagram of an FMCW radar transceiver according to one embodiment.

[0140] Fig. 20 is a block diagram of an FMCW radar transceiver according to another embodiment.

[0141] Fig.21 is a block diagram of a dual-frequency radar transceiver according to one embodiment.

[0142] Fig. 22 is a block diagram of a DCM radar transceiver according to one embodiment.

[0143] Fig.23 is a block diagram of an FMCW radar transceiver with multiple antennas according to one embodiment.

[0144] Fig.24 is a block diagram of a system incorporating multiple detection, guidance and / or control systems, including a radar-based lateral positioning system, according to one embodiment.

[0145] Fig.25 is a top view of a vehicle equipped with a radar transceiver on a road with radar reflective pavement markings according to one embodiment.

[0146] Fig.26 According to an embodiment Fig.25 Table of locations of pavement markings.

[0147] Fig. 27 is a block diagram of a system for controlling vehicle speed based on radar-measured positions of road surface markings, according to one embodiment.

[0148] Fig.28 is a block diagram of a longitudinal vehicle position control system according to one embodiment.

[0149] Fig.29 is an overhead view of a truck and trailer equipped with a radar transceiver on a road with radar reflective pavement markings according to one embodiment.

[0150] Fig. 30A is an isometric diagram of a dihedral / trihedral corner reflector according to one embodiment.

[0151] Fig. 30B is an isometric diagram of a dual dihedral / trihedral corner reflector according to one embodiment.

[0152] Fig.31A Is from Fig. 30A Schematic side view of the reflection of the dihedral portion of a dihedral / trihedral corner reflector.

[0153] Fig.31B Is from Fig. 30A Top view of the reflective dihedral portion of a dihedral / trihedral corner reflector.

[0154] Fig.31C is to use a side radar transceiver from Fig. 30A Top view of the three partially reflective surfaces of a dihedral / trihedral corner reflector.

[0155] Fig.31D is using a forward facing radar transceiver from Fig. 30A Top view of the three partially reflective surfaces of a dihedral / trihedral corner reflector.

[0156] Fig.32A is an exploded isometric view of a pavement marking having two dihedral / trihedral corner reflectors according to one embodiment.

[0157] Fig.32B is an exploded isometric view of a pavement marking having two dihedral / trihedral corner reflectors according to another embodiment.

[0158] Fig.33A is an exploded isometric view of a pavement marking having T-shaped dual dihedral / trihedral corner reflectors according to one embodiment.

[0159] Fig.33B is an exploded isometric view of a pavement marking with T-shaped dual dihedral / trihedral corner reflectors according to another embodiment.

[0160] Fig.33C is an exploded isometric view of a pavement marking with T-shaped dual dihedral / trihedral corner reflectors according to yet another embodiment.

[0161] Fig.34is an exploded isometric view of a pavement marking having four dihedral / trihedral corner reflectors according to one embodiment.

[0162] Fig.35A is a top view of a vehicle equipped with side and forward looking radar transceivers on a road with radar reflective pavement markings according to one embodiment.

[0163] Fig.35B is a top view of a vehicle equipped with side and forward looking radar transceivers on a road with radar reflective pavement markings according to one embodiment.

[0164] Fig.35C is a top view of a vehicle equipped with side and forward looking radar transceivers on a curved road with radar reflective pavement markings according to one embodiment.

[0165] Fig.35D is a top view of a vehicle equipped with side and forward looking radar transceivers at a road intersection with radar reflective pavement markings according to one embodiment.

[0166] Fig.36 is a top view of a vehicle equipped with a side-looking radar transceiver having multiple antennas on a road with radar-reflective pavement markings according to one embodiment.

[0167] Fig.37 is a schematic diagram of a radar transceiver with multiple transmit / receive antennas according to one embodiment.

[0168] Fig.38 is a diagram of a radar transceiver array according to one embodiment. DETAILED DESCRIPTION

[0169] Preliminary Note

[0170] Example embodiments will be described below with reference to the accompanying drawings. Unless otherwise explicitly stated, the sizes, positions, etc. of parts, features, elements, etc. in the drawings and any distances therebetween are not necessarily drawn to scale and may be disproportionate and / or exaggerated for clarity.

[0171] The terms used herein are only used to describe specific example embodiments and are not restrictive. The singular forms "one", "an" and "the" used herein also include plural forms unless the context clearly indicates otherwise. It should be recognized that the terms "including" (and its various tenses), "comprising" (and its various tenses), "having", "having" and "with" used herein indicate the existence of the features, integers, steps, operations, elements and / or parts, but do not exclude the existence or increase of one or more other features, integers, steps, operations, elements, parts and / or their groups. Unless otherwise specified, when describing the range of numerical values, the upper and lower limits of the range and any sub-ranges therebetween are included. Unless otherwise specified, the terms "first", "second" and the like are only used to distinguish one element from another element, and do not mean any relative order, position or ranking. For example, an element may be referred to as a "first element", and another element may be referred to as a "second element", or vice versa. The section titles used herein are only used for organizational purposes and should not be understood as limitations on the subject matter.

[0172] Unless otherwise indicated, the terms "approximately," "about," "substantially," "generally," "approximately," and the like mean that amounts, sizes, formulations, parameters and other quantities and characteristics are not and need not be exact, but are approximate and / or larger or smaller, as necessary, reflecting tolerances, conversion factors, rounding, measurement errors, etc. and other factors known to those skilled in the art.

[0173] Spatially relative terms, such as "right," "left," "front," "back," "below," "below," "down," "above," and "upper," may be used herein to facilitate descriptions of the relationship of one element or feature to another element or feature, as shown in the accompanying drawings. It should be appreciated that spatially relative terms further include different orientations in addition to the orientations described in the drawings. For example, if the object in the drawing is turned over, then an element described as being "below" or "below" other elements or features would be oriented "above" the other elements or features. Thus, the term "below" may, for example, include both "above" and "below" orientations. An object may be oriented in other ways (e.g., rotated 90° or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0174] As used herein, the terms "RF" and "radio" refer to or imply electromagnetic radiation within a frequency range that can be detected and processed electronically. For example, the RF spectrum includes very low frequencies (VLF, e.g., about 3 kHz) and may extend to just below infrared (e.g., about 300 THz). The RF spectrum includes VLF, low frequency (LF), medium frequency (MF), high frequency (HF), very high frequency (VHF), ultra high frequency (UHF), super high frequency (SHF), and extremely high frequency (EHF) bands. The RF spectrum further includes microwave and millimeter wave bands.

[0175] The concepts and innovations described herein with respect to RF or radio radiation and / or radar may also be practiced with other types of radiation or waves including, for example, infrared, visible light, ultraviolet, laser, lidar, and sonar, with appropriate modifications to the transceivers and reflectors.

[0176] Unless expressly stated otherwise, all connections and couplings may be direct (no intermediaries) or indirect (with one or more intermediaries). Unless expressly stated otherwise, all operational connections and couplings may be electronic (connections) through hardware or logical (connections) through software. Likewise, unless expressly stated otherwise, all physical connections and couplings may be rigid or non-rigid, permanent or removable.

[0177] Throughout, like numbers refer to like elements. Thus, like or similar numbers may be described with reference to other figures even if they are neither mentioned nor described in the corresponding figure. Also, even elements not indicated by reference numbers may be described with reference to other figures. In addition, some non-essential elements may be included in the drawings only for the purpose of exhaustiveness. If changes are required to the drawings to improve clarity, these non-essential elements may be removed entirely or retained in outline form.

[0178] The embodiments described herein are merely examples and are intended to be illustrative rather than limiting. Those skilled in the art will recognize, based on the teachings herein, that there are alternatives, variations, and equivalents to the example embodiments and their components described herein. For example, other embodiments are readily achievable, the embodiments described herein may be varied, and there may be equivalents to the elements, components, or steps that constitute the described embodiments.

[0179] For the purposes of clarity and conciseness, certain aspects of components or steps of certain embodiments are not described in excessive detail where these details are obvious to those skilled in the art based on the teachings herein and / or where these details would obscure an understanding of more relevant aspects of the embodiments.

[0180] The foregoing is an explanation of the embodiments of the present invention and should not be construed as limiting the present invention. Although some specific exemplary embodiments have been described, it is readily understood by those skilled in the art that many modifications may be made to the disclosed exemplary embodiments and other embodiments without substantially departing from the novel teachings and advantages of the present invention. Therefore, all of these modifications should be included within the scope of the present invention as defined in the claims. For example, the technician will understand that the subject matter of any sentence or paragraph may be combined with the subject matter of some or all of the other sentences or paragraphs, unless such combination is mutually exclusive.

[0181] It will be readily apparent to those skilled in the art that many changes may be made to the details of the above-described embodiments without departing from the basic principles of the invention described herein.

[0182] Pavement markings with embedded radar reflector(s)

[0183] Figures 2A-2D A pavement marking 284 is shown, such as Figure 2A As shown, a radar reflector known as a dihedral corner reflector 287 is embedded in the pavement marking. Figure 2B 2 is an isometric view of a pavement marking 284 having dihedral corner reflectors 286 and 287 on opposite sides of the pavement marking 284. The dihedral corner reflector 287 can be constructed in a variety of ways. For example, the dihedral corner reflector 287 can be molded or extruded and cut into segments. For example, the dihedral corner reflector 287 can be formed by welding or other means of connecting two strips or plates together, or by bending a plate.

[0184] Figure 2B The dihedral reflectors 286 and 287 are shown incorporated into a pavement marker 284 that also has an optical reflector 275 for human vision, camera, and lidar. In this embodiment, the dihedral reflectors 286 and 287 are attached to the sides of the pavement marker 284, wherein the dihedral reflectors 286 and 287 are substantially parallel to the direction of travel of the vehicle. The method of attaching the dihedral reflectors 286 and 287 to the central body portion of the pavement marker 284 can be, for example, glue, adhesive, snap fit, friction fit, fasteners (e.g., screws, rivets, nails, staples), etc.

[0185] Dihedral corner reflector 287 (and 286) comprises two planar reflectors that intersect along an axis that forms a dihedral angle. The dihedral angle may be 90° or approximately 90° (i.e., right angle, orthogonal, perpendicular, or normal). An incident wave enters the aperture so formed with an incident direction perpendicular to the edge (i.e., the incident direction bisects the 90° angle between the two planes) and returns parallel to its incident direction. Optionally, pavement marking 284 may have a base plate (not shown).

[0186] A dihedral corner reflector is a passive device used to reflect radio waves directly back to the source of the transmission. Dihedral corner reflectors 286 and 287 can be right-angled metals such as aluminum, galvanized steel, copper, brass, magnesium, steel, etc. or any other RF reflective material. Dihedral corner reflectors 286 and 287 can also include metal or other RF reflective coatings on non-metallic surfaces, metal or other RF reflective foils, or electroplating conductive or other RF reflective materials on non-metallic or non-RF reflective surfaces (such as plastics). The dihedral corner reflector can also be formed with one side being a road surface (such as asphalt, concrete) and the other side being a metal surface, because the road surface is sufficiently reflective of RF radiation. For example, when a radar signal is transmitted from the side downward toward the dihedral corner reflector 287 (right side, such as Figure 2A When the radar signal is directed downward at an angle less than 45° (e.g., 25°) (where perfectly horizontal pointing to the horizon is considered 0° and vertically into the ground is 90°), and the radar source is mounted at a low distance from the ground (e.g., 0.3 meters), the ground acts as a smooth reflecting surface for RF waves, and the road surface acts as one side of the dihedral reflector. The road surface has a higher reflectivity when it is wet.

[0187] The reflectivity of the road surface can be increased by applying a radio frequency reflective adhesive (such as conductive epoxy) or a radio frequency reflective paint (such as copper, carbon, nickel and silver conductive paint) to the road surface portion below and / or around the road surface marking. For example, MG Chemicals 841AR is an acrylic nickel conductive paint, and MG Chemicals 841ER is a nickel conductive epoxy. Radio frequency reflective adhesives can also be used to adhere road surface markings of another surface containing dihedral corner reflectors to the road surface. Dihedral corner reflectors can also be formed by brushing or applying a radio frequency reflective coating to the vertical or approximately vertical related sides of existing road surface markings and the near side of the road surface. Dihedral corner reflectors can also be formed by applying a radio frequency reflective coating to milled grooves, pits or cuts in the road surface.

[0188] The pavement marking 284 has optical reflectors 275 similar to current pavement markings to provide optical reflections on the front side facing oncoming vehicles. These optical reflectors in the pavement markings can be used by vision cameras or lidar sensors to add redundancy to lateral guidance.

[0189] Figure 2C and 2DA top view and a side view of pavement marker 284 are shown. Typical dimensions of currently installed raised pavement markers on roads are generally 100 mm x 100 mm x 25 mm. Using these dimensions, dihedral corner reflectors 286 and 287 are approximately 25 mm x 25 mm x 100 mm. These dimensions are suitable for typical current raised pavement markers; longer or taller raised pavement markers can be constructed and installed on roads with higher radar cross sections (RCS).

[0190] Pavement marker 284 (and other pavement markers described herein) may be affixed to any surface on which any vehicle travels, including, for example, one-way, two-way, or multi-lane roads, highways, thoroughfares, driveways, boulevards, parkways, paths, byways, streets, paths, trails, and the like, as well as bridges, tunnels, parking lots, parking structures, shipping yards, freight terminals, shipping warehouses, loading and unloading areas, warehouse lots or yards, and the like, whether paved (e.g., asphalt, concrete, brick, stone) or unpaved. Pavement marker 284 (and other pavement markers described herein) is preferably affixed to the surface such that the longitudinal axes of the dihedral reflectors within pavement marker 284 are generally parallel to the direction of vehicle travel and along one or both sides of the vehicle's path of travel.

[0191] Figures 3A-3D Another embodiment is shown in which the dihedral corner reflector is constructed using a T-shaped piece (more precisely, an inverted T-shaped piece) to form two or dual dihedral reflectors facing in opposite directions. Figure 3A Such a T-shaped dihedral corner reflector 396 is shown where the RF waves are reflected from both sides of the T-shaped material. Figure 3B is an isometric view of a T-shaped reflector 396 mounted in the middle of a pavement marking, with RF transparent (and therefore radar transparent) material 395 on both sides of the T-shaped reflector 396. As described above, the optical reflector 275 is mounted on the front side of the pavement marking 394 facing oncoming vehicles for human, visual or lidar viewing. The T-shaped dihedral reflector 396 can be any metal or other material capable of reflecting RF radiation. In addition, the T-shaped reflector 396 can be constructed using a metal or other RF reflective paint or strip, or by electroplating a material onto the RF transparent material 395. RF transparent materials are materials that RF radiation penetrates with little or no dielectric loss factor, such as, Polypropiolactone (PPL), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE) or acrylonitrile butadiene styrene (ABS). Plastic materials are lightweight, resistant to rain erosion, and have excellent dielectric properties. Figure 3C and 3D A top view and a side view of a T-shaped radar reflective pavement marking 394 are shown.

[0192] The RF transparent material 395 can be a single piece or two pieces. The pieces can be molded, extruded and cut, or manufactured in any other suitable manner. If the RF material 395 is a single piece, there can be a channel down the middle to accommodate the top fin of the T-shaped reflector 396. For example, the channel can be formed during the molding or extrusion process, or it can be formed by a cutting or scoring operation. The RF transparent material 395 piece(s) can also have a step or shelf cutout or cavity to match the horizontal portion of the T-shaped reflector 396. The T-shaped reflector 396 can be attached to the RF transparent material 395 piece(s) by, for example, RF transparent glue or adhesive, friction fit, snap fit, fasteners, etc. An example of RF transparent glue is 3494, which is a one-component, medium viscosity, UV-curable acrylic material used for bonding or sealing. Suitable solvent-based adhesives include toluene and 1,4-dioxane. Pavement marking 384 may optionally have a base plate (not shown).

[0193] Figures 4A-4E The reflectivity quality of a raised pavement marking with a dihedral corner reflector is shown. Figure 4A In FIG. 1 , radar transceiver 116 transmits signal 1119 to dihedral reflector 287 of raised pavement marking 284. Dihedral reflector 287 reflects signal 1118 back from both sides and directly back to radar transceiver 116. Figure 4B The dihedral reflector 287 shown in FIG. 1 includes two planar reflectors whose dimension "a" forms a 90° dihedral angle. If the direction of the incident light beam is perpendicular or approximately perpendicular to the intersection line of the planes, this dihedral reflector can more strongly return the light beam to the source. The measured radar distance "d" is the distance from the center point of the dihedral reflector 287 to the radar transceiver 116.

[0194] The radar transceiver 116 has both transmit and receive functions. The radar transceiver 116 may be two separate subsystems (transmitter and receiver), or may be one combined or integrated unit. The term "radar sensor" is sometimes used to refer to the radar transceiver and sometimes to refer to just the radar receiver, depending on the context.

[0195] Figure 4B-4C The dimensions of the dihedral corner reflector 287 are shown. The short side has dimension a, and the long side ends substantially parallel to the lane markings have dimension b. The RCS of a corner reflector having typical raised pavement marking dimensions (100 mm x 100 mm x 25 mm) at a radar frequency of 77 GHz (which is currently used in automotive applications) can be calculated using the formula for a dihedral corner reflector: RCS = 8πa 2 b 2 / λ 2, where π≈3.1416 and λ is the wavelength of the radar signal. The RCS of this combination is 8*3.1416(0.025) 2 (0.1) 2 / (0.003893) 2 =10.36m 2 The RSC of the vehicle is between 10 and 100m 2 The RCS can be made larger by enlarging dimension a and / or b, and / or by reducing the wavelength (ie, increasing the frequency). Figure 4D-4E The dimensions of the T-shaped dihedral corner reflector 396 are shown. The short side is dimension a, and the long side parallel to the lane marking lines similar to the single dihedral corner reflector 287 is dimension b.

[0196] Figures 5A to 5F Reflection patterns of dihedral corner reflectors 286 , 287 , and 396 on various axes from radar transceiver 116 are shown. Figure 5B Rotation of radar transceiver 116 from the center of the corner reflector is shown. Figure 5A and 5B The relative RCS of the radar transceiver 116 when it is rotated + / -45° in one dimension from the center of the dihedral reflector is shown. RSC represents the return signal strength reflected from the target (the dihedral reflector in this example). Figure 5B As shown, as long as the position of the radar transceiver 116 is within the right angle (90° quadrant) of the dihedral corner reflector, the signal return is good. If the radar transceiver 116 exceeds the rotation of 45° and sees the back of the corner reflector 287, but is not at right angles to the back, the signal is not reflected back well, such as Figure 5A This is the advantage of a dihedral corner reflector over a flat plate or sphere. If the radar transceiver is facing the plate or at a 90° angle to the plate, the plate will reflect the signal back, but if the radar transceiver is rotated in either direction, very little signal will be returned. Figure 5B-5C As shown, the dihedral corner reflectors can be made of different sizes to increase or decrease the RCS when the radar transceiver 116 is directly facing the dihedral corner reflector, thereby increasing or decreasing the magnitude of the return signal strength.

[0197] The angle of the dihedral corner reflector can be less than 90°, or greater than 90°. When the angle of the dihedral reflector is around 90°, as mentioned above, it is an orthogonal dihedral reflector. Figure 5AAs shown, an orthogonal dihedral corner reflector reflects back a maximum signal when the radar signal is aimed at the center of the reflector. An orthogonal dihedral corner reflector is a preferred embodiment of a dihedral corner reflector, but other embodiments of dihedral corner reflectors with different angles may also be used. The received signal strength depends on the angle of the two reflecting surfaces, the orientation of the radar sensor relative to the reflecting road surface markings, the type of radar sensor, the sensitivity of the radar receiver, and the number of transmitting and receiving antennas and their spatial positions and orientations. For the applications described herein, depending on other system parameters, a suitable dihedral corner reflector can be made with an angle range of about ±35° of 90° (i.e., about 55° to about 125°), more preferably ±20° of 90°, even more preferably ±10° of 90°, and even more preferably ±5° of 90°, which is approximately or substantially orthogonal.

[0198] A monostatic radar transceiver has a single antenna for transmitting and receiving, or different transmitting and receiving antennas that are co-located or located very close to each other relative to a radar target (e.g., a dihedral reflector). A monostatic radar transceiver or a radar transceiver with similar features to a monostatic radar transceiver and having a narrow beam may be more sensitive to the angle of the dihedral reflector. For example, a Texas Instruments AWR1843AOP radar transceiver chip using a single transmitting and receiving antenna and an antenna lens with a beam width of 6° loses about 6-10 dB (decibel) of signal strength at a dihedral angle of about 95° compared to a dihedral angle of 90°. Similarly, the signal strength at a dihedral angle of about 85° is about 6-10 dB less than at a dihedral angle of 90°. If the dihedral angle is less than 85° or greater than 95°, the signal strength is much smaller (15-20 dB less) than at a 90° angle.

[0199] For a radar sensor with a bistatic characteristic (i.e., one with different transmit and receive antennas that are not in parallel), such as the Texas Instruments AWR1843AOP, which has three transmit antennas and four receive antennas and a wide beamwidth (e.g., 60-120°), the signal strength at a dihedral angle of 85° or 95° is about 4-6 dB lower than the signal strength at 90°. If the dihedral angle is greater than 95° but less than 110°, the reflected signal is about 10 dB smaller. If the dihedral angle is greater than 110° but less than 125°, the reflected signal is much lower than 10 dB. Similarly, if the dihedral angle is less than 85° but greater than 70°, the reflected signal is 10 dB less. If the acute angle is less than 70°, the drop in the reflected signal is much greater than 10 dB. If the radar sensor has a multi-antenna array (one or more) for transmission and reception, the radar signal reflectivity of the dihedral corner reflector can be higher, depending on the physical arrangement of the antennas.

[0200] In one embodiment, the sensitivity of the reflected signal can be used to implement a lateral position control system. For example, if the radar transceiver 116 is positioned and oriented on the vehicle to provide a maximum return signal from the corner reflector 287 when the vehicle is in the optimal lateral position and the radar system has the necessary sensitivity and the reflectors in the road surface markings have sufficient uniformity, then a simple control system can be designed to minimize the deviation of the return signal from the maximum value by adjusting the position of the vehicle laterally. Alternatively, if the radar beam is steerable, it can be scanned laterally when the maximum reflection is detected.

[0201] According to another embodiment using the sensitivity of the reflected signals, if the radar transceiver 116 is positioned on the vehicle to provide two received signals from two corner reflectors 287 separated by a known lateral distance, the ratio of the amplitudes of the two received signals can determine the vehicle's position relative to the corner reflectors 287. According to another embodiment using the sensitivity of the reflected signals, if two radar transceivers 116 are directed to opposite sides of the vehicle, one on each side, to provide two received signals from two corner reflectors 287 on opposite sides of the vehicle, then the difference in signal strength can be used to infer the vehicle's position. When the vehicle is in the optimal lateral position and the radar receiver has the necessary sensitivity, a simple control system can be designed to minimize the difference in the returned signals by adjusting the position of the vehicle laterally. According to these embodiments and in general, the optimal lateral position can be such that the vehicle is located in the center of the lane, or at some desired predetermined or random offset from the center of the lane.

[0202] Figure 5C Radar transceiver 116 is shown pointed directly at dihedral corner reflector 287. Radar transceiver beam width 1116 is wide enough to cover the length "b" of the dihedral corner reflector in the direction of travel "y". Given the corner reflector length "b" and radar beam width 1116, transmit signal 1119 is reflected back as return signal 1118. The RCS pattern is shown at Figure 5D As long as the radar transceiver passes over the dihedral corner reflector, the signal strength from the reflector is good. Once the radar transceiver passes over the corner reflector, the returning signal drops significantly.

[0203] like Figure 5E As shown, if the radar transceiver 116 is rotated in the direction facing the dihedral reflector 287, then for a narrow beamwidth antenna, the final RCS pattern after rotation is as follows: Fig. 5F When the radar transceiver 116 is Figure 5EAs shown in the rotation, multiple antennas and / or antennas with wider beam widths (one or more) can have larger RCS patterns. Therefore, when the radar transceiver 116 passes the dihedral corner reflector 287 in a direction parallel to the length of the corner reflector, the radar transceiver measures the distance from the center of the corner reflector to the radar transceiver antenna. If the radar transceiver 116 remains substantially parallel to the dihedral corner reflector 287, the distance remains unchanged. If the radar transceiver 116 moves closer to the dihedral corner reflector 287 in a parallel direction, the radar transceiver 116 will measure a closer distance to the corner reflector 287. Before the radar transceiver beam width 1116 enters the line of sight of the dihedral corner reflector 287, there is no distance measurement. When the dihedral corner reflector 287 is seen, if the radar transceiver 116 remains substantially parallel during the brief time it views the dihedral corner reflector 287, the radar transceiver 116 only measures a distance.

[0204] In this application, a dihedral corner reflector may have several advantages over a trihedral corner reflector (which has a corner formed by three orthogonal sides). First, a dihedral corner reflector has two orthogonal or nearly orthogonal sides and can be easily made of right-angled metal, etc., while a trihedral corner reflector has three orthogonal sides and requires a lot of construction effort to attach them together at 90°. Second, a dihedral corner reflector can be manufactured continuously by extrusion, etc. As described in previous literature (see below), a radar guidance system has been designed and successfully tested on an autonomous vehicle using a continuous horizontally oriented dihedral corner reflector on a roadside guardrail. A trihedral corner reflector is a separate reflector that does not have this continuous feature and requires additional design and construction techniques to make a viable guidance system. Third, when the radar transceiver 116 is not substantially parallel to the trihedral corner reflector, the radar transceiver 116 will collect the distance to the trihedral corner reflector and provide different distance measurements as the radar transceiver approaches and moves away from the trihedral reflector. When the radar transceiver 116 is parallel to the trihedral reflector, the distance is shortest. Therefore, the scheme using the trihedral reflector may require more processing to measure the lateral distance than the scheme using the dihedral reflector. Fourth, compared with the dihedral reflector mounted on the ground, the trihedral reflector is more prone to ground reflection (i.e., reflection from the ground near the reflector) and reduces the return signal. Fifth, as Figure 4A As shown, a dihedral corner reflector reflects the signal back to the signal source through two bounces from two dihedral surfaces, while a trihedral corner reflector reflects the signal back through three bounces. Therefore, using polarization (polarization) radar, a dihedral corner reflector is easier to distinguish from the ground surface than a trihedral corner reflector based on the polarization degree of the returning signal.

[0205] The dihedral corner reflector shown and described herein effectively reflects all frequencies equally back to the radar transceiver without being tuned to any particular frequency. That is, the dihedral corner reflector is largely frequency invariant across the entire bandwidth of operation. This property enables the dihedral corner reflector to effectively reflect ultra-wideband frequencies (e.g., FMCW 77-81GHz automotive radar sensors using current bandwidths of 4GHz) equally back to the radar sensor. Due to the properties of the dihedral corner reflector, no frequency is significantly attenuated.

[0206] Figures 6A-6C Several configurations of raised pavement markings with two dihedral corner reflectors are shown. Fig. 6A An embodiment 284 is shown with a body 290 comprising an optical reflector 275, two dihedral metal reflectors 286 and 287, and two quarter-circular RF transparent materials 291 and 293. As shown in these isometric views, the corner reflectors 286 and 287 are attached to the left and right sides of the body 290, with the optical reflector 275 attached to the front. The quarter-circular RF transparent materials 291 and 293 are placed inside the corner reflectors 286 and 287, respectively, to provide protection against road damage. The attachment means for the corner reflectors 286 and 287, the body 290, and the RF transparent materials 291 and 293 can be glue, screws, rivets, slots, or similar attachment mechanisms.

[0207] Figure 6B Another raised pavement marking 384 with two dihedral corner reflectors is shown. In this embodiment, the quarter-circular RF transparent members 294 and 295 have a metal paint or metal foil sprayed or glued on each of the two flat sides to form the dihedral corner reflectors. The bottom plate 277 (which may not be required) provides a good flat protective surface. Another embodiment (not shown) is to have the bottom plate 277 be metal and the body 290 be metal. With the bottom plate 277, the reflective coating on the bottom side of the quarter-circular RF transparent members 294 and 295 is not required.

[0208] Figure 6C Another raised pavement marker 484 is shown with two dihedral corner reflectors. In this embodiment, the body 290 is made of molded plastic or a similar material that is radio frequency transparent, with a slot 292 molded into the body 290. Two metal corner reflectors 296 and 297 can be pushed into the slot. The optical reflector 275 can be glued to the front of the raised pavement marker 484.

[0209] Figures 7A-7D Several configurations of raised pavement markings with (inverted) T-shaped dihedral corner reflectors or bi-dihedral corner reflectors 396 are shown. Figures 7A-7DElements other than the optical reflector 275 shown in FIG. 2 may be extruded and cut, for example, or may be made by other techniques. Fig. 7A An embodiment 584 is shown in which a T-shaped dihedral corner reflector 396 made of metal or other RF reflective material is located in the center of two quarter-circles or similarly shaped RF transparent materials 397 and 398, and an optical reflector 275 is attached to the front to form a road surface marking. The two quarter-circles of RF transparent materials 397 and 398 are attached to the left and right sides of the T-shaped dihedral corner reflector 396, and the optical reflector 275 faces the front when viewed from the isometric view. The quarter-circle RF transparent material provides protection from road damage. The attachment means for connecting the T-shaped corner reflector 396 to the RF transparent materials 397 and 398 can be glue, screws, rivets, slots or similar attachment mechanisms.

[0210] Figure 7B Another structure of a raised pavement marker 684 with a T-shaped dihedral corner reflector is shown. In this embodiment, one of the quarter-circular RF transparent members 1396 is sprayed or glued with a metallic or other RF reflective paint or foil on one side to form a T-shaped dihedral corner reflector. For example, the quarter-circular RF transparent member 1396 can be electroplated with a metal surface on one side. The bottom plate 1300 can be metal or other RF reflective material, forming the bottom of the T-shaped corner reflector and providing a good flat protective surface.

[0211] Figure 7C Another raised pavement marker 784 structure is shown with a T-shaped dihedral corner reflector. In this embodiment, two RF transparent molded plastic or similar pieces 1396 and 1397 are plated or sprayed with metal or other RF reflective material on the sides. Molded plastic piece 1396 is sprayed or plated on the bottom side 1302, while molded plastic 1397 is sprayed or plated on the two flat sides 1399 and 1304. When the two are glued or mechanically connected together, they form a T-shaped dihedral corner reflector. An optical reflector 275 is added to the front to form a raised pavement marker 784.

[0212] Fig.7DAnother structure of a raised pavement marker 884 is shown with a T-shaped dihedral corner reflector 396 made of metal or similar RF reflective material or conductive coated right angle material, etc., with two additional L-shaped dihedral corner reflectors 286 and 287 on the ends of the pavement marker. The center reflector has two square RF transparent materials 1292 and 1293 on each side of the T-shaped reflector 396. Two quarter-circle or similar shaped RF transparent materials 293 are attached to the ends, and an optical reflector 275 is attached to the front, forming the pavement marker 884. The two quarter-circle RF transparent materials 293 are attached to the left and right sides of the L-shaped dihedral corner reflectors 286 and 287, respectively, with the optical reflector 275 facing forward from the isometric view. The quarter-circle RF transparent material 293 keeps the dihedral corner reflectors 286 and 287 clean and provides protection and structural support for the dihedral corner reflectors 286 and 287, while also reducing the possibility of the dihedral corner reflectors 286 and 287 damaging a tire that runs over the pavement marking. The two square RF transparent materials 1292 and 1293 provide similar support and protection. This multiple reflector arrangement provides a greater RCS than a single dihedral corner reflector. Targets of similar size and shape, such as dihedral corner reflectors, separated by one, two, or four wavelengths have a much greater RCS than a single target. Therefore, one or more dihedral corner reflectors spaced at wavelengths can be used in pavement markings to enhance the RCS of the pavement markings to radar transceivers.

[0213] There are many ways to construct raised pavement markings with dihedral corner reflectors; the above embodiments show some preferred combinations.

[0214] Vehicle guidance based on radar-measured distance to road markings

[0215] Figures 8A-8D Several embodiments of lateral guidance schemes are described. Fig. 8A A front view of a vehicle 180 is shown with the radar transceiver 116 mounted thereon, and pavement markings 284 with dihedral reflectors 286 and 287 mounted on the road. The vehicle 180 may be any land vehicle including, for example, a car, truck, bus, van, motorcycle, etc. Figure 8B is a block diagram of a lateral guidance system 810 designed to follow lane markings without a human driver. Fig. 8AAs shown, the front mounted radar transceiver 116 is mounted on one side of the vehicle, and the road surface marking 284 is mounted on the road lane marking or within a set distance from the lane marking on the road 300. The road surface marking 284 can be a raised road surface marking or mounted at or below the road surface level. The radar transceiver 116 transmits a signal 1119 in the direction of the road surface marking 284 and receives a signal 1118 reflected from the road surface marking 284 via the dihedral reflector 286. Fig. 8A As shown, the orientation of the road marking 284 causes the dihedral reflectors 286 and 287 to be approximately parallel to the lane markings and the direction of vehicle travel. This orientation provides a maximum return signal when the radar transceiver 116 passes over the road marking 284.

[0216] like Figure 8B As shown, the radar transceiver 116 uses known radar technology to measure the distance between the road surface marking 284 and the radar transceiver 116, and provides it to the lateral guidance controller 800. The radar transceiver 116 or an associated processor (which may be a general purpose processor, a signal processor, a digital signal processor (DSP) or a similar device, and which may perform its processing through software, hardware, firmware or some combination of the foregoing devices) measures the distance d between the dihedral reflector 286 embedded in the road surface marking 284 and the radar transceiver 116. R The actual lateral distance from the vehicle 180 to the road marking 284 is different from the radar measured distance d R The control distance d required to keep the vehicle in the center of the lane or at any predetermined distance from the road markings is C and radar measurement distance d R is an input to the lateral steering controller 800. The lateral steering controller 800 sends a signal to a steering motor or controlled device in the steering mechanism 802. The steering mechanism 802 controls the steering wheel 804. The steering wheel 804 and steering mechanism 802 are used for a road vehicle, but the vehicle can also be an off-road tracked vehicle and the controller can use a hydraulic actuator. By controlling the steering wheel 804, the desired lateral distance between the vehicle 180 and the reflector road surface marking 284 can be maintained. It should be noted that in some cases there may be only a single steering wheel, such as a bicycle, tricycle, three-wheeled forklift, etc.

[0217] Radar transceiver 116 may generate a continuous radar transmission signal and / or continuously monitor for reflections, or the radar transceiver may periodically and repeatedly transmit discrete radar signals (e.g., pulses) and monitor for reflections, depending on the type of radar technology employed. Radar transmission signals are typically directed partially downward and laterally from vehicle 180, and pavement markings 284 are designed to reflect a portion of the incident radar signal upward and laterally back to the source of the radar signal (i.e., transceiver 116) on vehicle 180.

[0218] Radar transceiver 116 and / or lateral guidance controller 800 may filter reflections based on range and / or amplitude to distinguish dihedral reflectors 286 and 287 from other objects. Pavement marking 284 is located within a known range of the vehicle. Because the radar cross section of dihedral reflector 286 is large for automotive frequencies, and because pavement marking 284 is located within close range of radar transceiver 116, the amplitude of the return signal is typically significantly higher than the road surface and other road objects (e.g., dead animals, cardboard, rocks, beverage cans, etc.). In addition to filtering for amplitude and range, other radar processing techniques may be used to distinguish pavement markings from the road surface and other objects. For example, polarization may distinguish dihedral reflectors from the road surface and other objects on or near the road. In addition, fixed or approximately fixed pavement marking spacing may also be used to filter out erroneous signals based on time. For example, reflections arriving between two pavement markings may be excluded as possible false targets. A Kalman filter or other known filtering technique can filter out reflected signals based on the fixed spacing / timing of the pavement markings and / or other known or predictable properties of the pavement markings. Thus, the pavement markings 284 can be distinguished from other objects, and many pavement markings 284 on the driving surface can be consistently the same or similar, with similar dihedral reflectors 286, 287 and similar RCS.

[0219] Figure 8C 8 is a block diagram of a lateral guidance system 840 that can warn the driver visually, audibly, and / or vibratingly if the vehicle deviates from its lane. This embodiment represents a lane departure warning (LDW) system. The radar transceiver 116 transmits a signal 1119 in the direction of a road surface marking 284 in which a reflector may be embedded, and receives a signal 1118 reflected from the road surface marking 284. The distance between the road surface marking 284 and the radar transceiver 116 is measured by the radar transceiver 116 using known radar technology and provided to the Figure 8C Lateral steering controller 820 is shown. Radar transceiver 116 measures the distance d from the dihedral reflector embedded in pavement marking 284. R .like Fig. 8A As shown, the actual lateral distance from the vehicle 180 to the road marking 284 is different from the radar measured distance d Rand the geometry of the mounting of the radar transceiver 116 attached to the vehicle 180. If the vehicle is traveling too close to or too far from the road surface marking 284, (e.g., less than a minimum threshold or more than a maximum threshold), indicating a lane departure, the guidance controller 820 may send a sound to a speaker 824 (or multiple speakers) to alert the driver of the lane departure, send a signal to a display screen 826 to visually alert the driver of the lane departure, and / or control the vibration 828 of the seat, steering wheel or other vehicle components. If the turn signal 822 is on, indicating that the driver intends to initiate a lane change or turn in the direction of the detected lane departure, the guidance controller 820 may disable the lane departure alert. Whether the lane departure alert is enabled or disabled by the previous turn signal may be a configurable setting set by the driver, the factory or a maintenance technician. When a lane departure is detected, the guidance controller 820 may also be configured to actuate a turn signal indicator 822 (e.g., a flashing light) on the side of the vehicle corresponding to the detected lane departure. This may warn other drivers, vehicles, pedestrians, cyclists, etc. that a lane departure is occurring or may occur. In this way, safety for others can be improved compared to a situation where no lane change indication is provided.

[0220] Fig.8D 8 is a block diagram of a lateral guidance system 850 that can warn the driver if the vehicle deviates from its lane through visual, auditory and / or tactile warnings, and, if the driver does not take corrective action, the system 850 can automatically take action to keep the vehicle in its lane. This embodiment represents a lane keeping assist (LKA / LKS) system. The radar transceiver 116 transmits a signal 1119 in the direction of the road surface marking 284 and receives a signal 1118 reflected from the road surface marking 284. Fig.8D As shown, the distance between the pavement marking 284 and the radar transceiver 116 is measured by the radar transceiver 116 using well-known radar technology and provided to the lateral guidance controller 830. The radar transceiver 116 measures the distance d from the dihedral reflector embedded in the pavement marking 284. R The actual lateral distance from the vehicle 180 to the road marking 284 is different from the radar measured distance d Rand the geometry of the mounting of the radar transceiver 116 attached to the vehicle 180. If the vehicle 180 is traveling too close or too far from the road surface marking 284, indicating a lane departure, the guidance controller 830 may send a sound to the speaker 824 (or multiple speakers) to alert the driver to the lane departure, and / or send a signal to the display screen 826 to visually alert the driver to the lane departure, and / or cause a vibration or other tactile stimulus to the driver. If no driver response is detected, the controller 830 controls the steering mechanism 802 to control the wheels 804 to keep the vehicle in the lane. If the turn signal 822 is turned on to signal a lane change or turn in the direction of the detected lane departure, the guidance controller 830 may not issue an alarm or take action.

[0221] and Fig.8D Another embodiment similar to the LKA / LKS system shown in can implement lane centering assist (LCA). The LCA system controls the steering of the vehicle 180 to keep the vehicle in the lane without driver effort, but the system can be overridden by the driver.

[0222] Fig. 8E 1 is a block diagram of a lateral steering control system 8500 that controls the steering of a vehicle to keep the vehicle in its lane. This embodiment represents an autonomous lateral control system. Radar transceiver 1160 transmits signals in the direction of road markings and receives signals reflected from road markings. The distance between the road markings and radar transceiver 1160 is measured by radar transceiver 1160 using well-known radar technology and provided to Fig. 8E Lateral guidance controller 8004 is shown. Radar 1160 measures the distance d from the dihedral reflector embedded in the road marking. R The actual lateral distance from the vehicle to the road marking is related to the measurement distance of the radar and the mounting geometry of the radar transceiver 1160 attached to the vehicle. The ideal control distance d from the road marking C Subtract the radar measured distance d R , to determine the error d ERROR, which is input into the lateral steering controller 8004. The vehicle speed 8008, the road geometry preview information 8006 and the wheel angle 8028 are sent to the lateral steering controller 8004. There may be other sensors, such as IMU (Inertial Measurement Unit), GPS (Global Positioning System), visual camera, LiDAR, etc. (not shown), which can be used to enhance the lateral control system 8500. The output of the steering controller 8004 controls the steering mechanism 8020, which controls the angle of the wheel and controls the lateral position of the vehicle on the lane relative to the road surface markings together with the vehicle dynamics device 8040. The lateral steering controller system 8500 can have a variety of different control algorithm embodiments to control the steering of the vehicle along the road surface markings. Some embodiments are fuzzy control algorithm, PID (Proportional Integral Derivative) control algorithm, adaptive PID control algorithm, Stanley control algorithm, MPC (Model Predictive Control) control algorithm, neural network control algorithm, improved sliding mode control algorithm, multi-rate control algorithm and LQR (Linear Quadratic Regulator) control algorithm.

[0223] Desired control distance d from road markings C It can be a predetermined distance based on the assumed lane width, vehicle width and radar transceiver location on the vehicle. Alternatively, the desired control distance d from the road markings C The vehicle's approximate location may be used to account for different lane widths and / or different road surface marking locations on different roads. For example, a database may store a set of desired control distances for different roads or geographic locations, and the database may be queried based on the vehicle's geographic location (e.g., a location determined by GPS) sufficient to determine which road or set of roads the vehicle is traveling on. Furthermore, since lane widths and / or road surface marking locations may be different in different directions on the same road, the desired control distance d from the road surface markings may be different. C It may depend on the direction the vehicle is traveling, which may be determined by a compass sensor and / or GPS measurements.

[0224] In another embodiment, the required control distance d may be determined dynamically by measuring the distances of different, laterally displaced markers as the vehicle travels along the road. C. For example, lane width can be measured indirectly by: (a) measuring the distance (one or more) to the road surface markings that mark the adjacent lane boundary on a given side of the vehicle; (b) measuring the distance (one or more) to the road surface markings that mark the next lane boundary on the same side of the vehicle; (c) subtracting these measured distances to calculate the adjacent lane width, assuming that the vehicle's current lane width is the same. If the vehicle is equipped with right-looking and left-looking radar transceivers, two desired control distances (right and left) can be used, and the control strategy can be to balance these two distances (e.g., using zero difference between the right and left distances as a nominal set point) so that the vehicle is centered in its lane. In addition, for different vehicles, the required control distance d C It may be possible to deviate from the true center of the lane so that the tire tread does not wear the road surface in the same area.

[0225] Figures 9A-9C Various embodiments of pavement markings 284 with dihedral corner reflectors placed on road 300 are shown. Fig. 9A A side view of an embodiment is shown in which pavement markings 284 are placed or distributed at equal or varying intervals along the side of a road 300. A radar transceiver 116 mounted on a vehicle 180 transmits a radar signal 1111 to the pavement marking 284 and receives a return signal 1110 to determine the distance between the pavement marking 284 and the radar transceiver 116. As previously described, an optical reflector is located in front of the pavement marking 284, facing the oncoming vehicle 180, and a dihedral reflector is mounted within the pavement marking 284, facing the radar transceiver 116.

[0226] Fig. 9B A top view of one embodiment with a vehicle 180 is shown, where pavement markings 284 and 1284 are mounted on both sides of the road at different separation distances. Vehicle 180 has two radar transceivers 116 and 117 mounted to the front side / front of vehicle 180. Radar transceiver 116 sees pavement markings 284 on the right side of the vehicle, and radar transceiver 117 sees pavement markings 1284 on the left side of the road. If the separation distance between the pavement markings is zero, meaning a continuous dihedral reflector, then Figure 8BThe lateral guidance controller in the embodiment may be similar to the controller used in the guardrail-based radar guidance system developed by the PACCAR Technical Center, which guidance system was described by Richard A. Bishel in "Dual-Mode Truck: Automated and Manual Operation" published in SAE Technical Paper Series #931837 (1994), which is incorporated herein by reference in its entirety; or similar to the controller used in the wire guidance system developed by Ohio State University, which guidance system was described by R. Fenton, R. Mayhan, R. Bishel, R. Kneifel, R. Magee, S. Murthy, L. Rakocy, R. Smith and L. Thayer in "Fundamental Studies in Automatic Truck Operation" published in Report No. FHWA / RD-80 / 198 (Aug. 1981). If the pavement markings are spaced about 1-4 meters apart, the controller may be similar to the lateral controller used with embedded magnets developed by the Partners for Advanced Transportation Technology (PATH) in California, as described in "The Design of a Look-Down Feedback Adaptive Controller for the Lateral Control of Front-Wheel-Steering Autonomous Highway Vehicles" by Seibum B. Choi, IEEE Transactions On Vehicular Tech., Vol. 49, No. 6, November 2000, the entire contents of which are incorporated herein by reference. The lateral controller by Ohio State University and PACCAR Technology Center provides good lateral vehicle control at highway speeds without any augmented sensors and using only a radar transceiver.

[0227] Embodiments based on dihedral reflectors in pavement markings may have several advantages over the approaches described in the above-mentioned documents. For example, pavement markings mounted on the ground allow the radar transceiver to be mounted low on the vehicle and pointed downward, so that the reflectors in the pavement markings can be seen when crossing multiple lanes, even when there are other vehicles in other lanes. Such pavement markings can be used to provide guidance for vehicles in any lane of a multi-lane road, not just the lane adjacent to the guardrail. Second, pavement markings in which dihedral reflectors are embedded are very inexpensive to install, and pavement markings are already widely used throughout the country and even around the world, and existing infrastructure can be used to manufacture and install pavement markings. In fact, the radar-reflective pavement markings described herein can be installed in the same way that conventional pavement markings are currently installed. For example, the radar-reflective pavement markings described herein can be easily and inexpensively installed between lane markers, as is currently done on multi-lane highways, and / or, along the outer or inner lane lines of a marked lane. In addition, in some cases, multiple discrete radar-reflective pavement markings can be seen by the vehicle and can provide the distance to each pavement marking for lateral control, including selecting which lane to drive in. Furthermore, the radar reflective pavement markings described herein may be used with many different types of radar transceivers.

[0228] Fig. 9C Another embodiment is shown, where multiple radar transceivers 117 can be installed at multiple locations on the left side of the vehicle 180, and similarly one or more radar transceivers 116 can be installed on the right side of the vehicle 180. The radar transceivers 116 and 117 can be installed in the side marker lights, headlights, fog lights, daytime running lights, or turn signal lights of the vehicle to minimize the impact on the exterior design. The radar transceivers 116 and 117 can be installed on or in the bumper (such as the front bumper) of the vehicle 180. The radar transceivers 116 and 117 can be installed behind the exterior of the vehicle 180 body made of radio frequency transparent materials (usually plastic and / or fiberglass). In another embodiment, one or more radar transceivers 117 can see the road surface markings 1284, and one or more radar transceivers 116 can see the road surface markings 284. In addition, the radar transceiver 119 can be installed in the middle front of the vehicle 180, and considering the road surface markings 284 and 1284, it can be viewed in two directions along the left and right sides of the vehicle 180. These additional radar transceivers can provide redundancy and more timely distance measurements.Many other combinations of installing one or more radar transceivers on vehicle 180 are also possible to provide more powerful lateral guidance control.

[0229] Figures 10A-10B An embodiment of a radar transceiver(s) mounted on a vehicle 182 is shown. Fig. 10A1 is another embodiment of multiple radar transceivers 116 and 117 mounted along both sides and the front of the vehicle 182. Mounting multiple radar transceivers 116 and 117 on each side and the front provides redundancy. The radar transceiver beam width 1106 emitted from the radar transceiver 116 can see the road marking 284, and the radar transceiver beam width 1107 emitted from the radar transceiver 117 can see the road marking 284. The antennas on the radar transceivers 116 and 117 can be polarized to prevent multiple vehicles with similar radar transceivers from interfering with each other. For example, the antennas can be horizontally, vertically, right-hand circularly, or left-hand circularly polarized.

[0230] Fig. 10B Another embodiment of a radar transceiver 119 is shown mounted at the front center of the vehicle 182 and senses the distance to the road surface markings 284 and 1284 on both sides of the vehicle 182 using radar beams having beam widths 1108 and 1109, respectively. One embodiment of the radar transceiver 119 may have one antenna 1190 right-hand circular polarization (RHCP) and another antenna 1192 left-hand circular polarization (LHCP). Another embodiment may employ a horizontally polarized antenna 1190 and a vertically polarized antenna 1192 to prevent interference from passing vehicles with similar transceivers. Alternatively, the radar transceiver 119 according to another embodiment includes two separate transceivers, one facing right and one facing left. Mounting the radar transceiver(s) at or near the center of the vehicle 182 may provide additional distance between the radar sensor 119 and the road surface markings 284 and / or 1284. Radar sensors 116, 117, and 119 may be mounted at any lateral distance along the front bumper of the vehicle. The tires of vehicle 182 may pass over pavement markings 284 without losing the radar signal. If this occurs, and the turn indicator in the direction of drift is not first actuated, then detection of passing over a pavement marking (i.e., drifting into another lane) may trigger a warning and / or corrective action (e.g., correct steering, reduce vehicle speed, etc.) to the driver. For example, the warning may be audible, visual, and / or tactile.

[0231] Fig.11A An embodiment is shown where the left and right radar transceivers 116 and 117 on vehicles 180 and 182, respectively, can use different antenna polarizations and view both pavement markings 284 and 1284 through two beamwidths 1106 and 1107, respectively. The different polarizations of the antennas can minimize radio frequency interference when vehicle 180 passes vehicle 182. Fig. 10B shown but in Fig.11AThe radar transceiver 119, not shown in the figure, can view both road markings 284 and 1284 through two beam widths 1108 and 1109, respectively. The longer distance allows the tires of the vehicle to pass over the road marking 284 and still obtain a valid distance signal from the road marking. In this embodiment, the arrangement of the radar can provide greater lateral deviation without losing the effective radar signal. The radar transceivers 116 and 117 can also be installed at any position along the front of the vehicle to provide greater lateral deviation without losing the effective radar signal.

[0232] Figures 11A-11C A top view showing different configurations of distance separation of pavement markings with dihedral corner reflectors. Fig.11A 3000 and has two vehicles 180 and 182 in the highway lanes between painted lines 304 and dihedral corner reflector pavement markings 284 and 1284. The separation distance 190 between the pavement markings 284 can be constant or variable. The separation distance 190 can be small (e.g., 0.3 meters or continuous) or large (e.g., 22.4 meters). Depending on the type of road, current markings are typically spaced 6.1 meters, 12.2 meters, or 22.4 meters apart on straight roads and gradual curves. Current pavement markings are typically spaced 0.3-6.1 meters apart on sharp curves. On straight roads, such as Fig.11A As shown, the pavement markings 284 may be separated by a constant distance, but offset by half the spacing for every other lane. Providing radar transceivers 116 and 117 on both sides of the vehicle 180 allows the radar transceivers to track the dihedral reflector pavement markings 284 and 1284 on both sides and make the separation distance 190 of the pavement markings 284 on each side greater. If the lateral controller 800 (in Figure 8B In the example of FIG. 1 , the lateral controller 800 (in the example of FIG. 1 ) requires road markings spaced at least 4 meters apart on the lane to achieve good lateral control. Then, road markings 284 or 1284 spaced 8 meters apart on both sides of the lane can also achieve similar controller performance. Figure 8BIn one embodiment, the lateral steering controller 110 on the vehicle 180 views the pavement markings 284 on the right side of the vehicle 180 via radar beam 1106. The radar transceiver 117 on the same vehicle 180 views the pavement markings 1284 on the leftmost lane via radar beam 1107. Therefore, the onboard lateral steering controller in the vehicle 180 may decide to stay in the same highway lane and follow the dihedral reflector pavement marking 284 on the right side of the vehicle, or to perform a lane change maneuver and follow the dihedral reflector pavement marking 1284 on the leftmost side of the vehicle 180. The same strategy can be used with vehicle 182 having similar radar transceivers 116 and 117. Another sensor not shown, such as radar, vision, ultrasonic or lidar, or the same radar transceivers 116 and 117 with vehicle detection capabilities (in addition to providing lateral range), can determine if there is another vehicle in the left or right lane and allow such a lane change maneuver. If the antennas on the radar transceivers 116 on vehicles 180 and 182 are left-hand circularly polarized, and the antennas on the radar transceivers 117 on all vehicles 180 and 182 are right-hand circularly polarized, then when vehicle 180 passes vehicle 182, the radar signal emitted by the radar transceiver 116 on vehicle 180 will not interfere with the radar signal emitted by the radar transceiver 117 on vehicle 182 due to the different polarizations.

[0233] In another embodiment, Fig. 11B It is shown that the separation distance 194 between the pavement markings 284 can be smaller at a curve on the road 301 to allow the radar transceivers 116 and 117 to measure more radar distances and thus correct the steering of the vehicle 180 more frequently to stay in the middle of the lane. On a straight section or coming out of a curve, a larger separation distance 192 can be used.

[0234] In another embodiment, Fig. 11C A special arrangement of pavement markings 285 is shown at the beginning and end of a curved section of road 301. This arrangement of pavement markings 285 will be referred to as a "coded section" and allows the radar transceiver to pick up additional information to inform the controller (at the beginning of the curved section). Figure 8B For example, the controller ( Figure 8B) can take action upon receiving this information of the coded road segment to minimize lateral errors entering and exiting the curved road segment. The coded road segment 285 can be used to communicate current or upcoming road geometry (e.g., curved or straight road segments, narrow lanes), intersections, hazards, road conditions, school zones, hospital zones, construction zones, railroad crossings, road changes, no-parking zones, speed limits, speed limit changes, or other information. At highway turns 301, the distance 192 between the road surface markings 284 can be smaller so that the radar transceivers 116 and 117 can measure more radar distances and thus correct the steering of the vehicle 180 more frequently to keep it in the center of the lane. When on a straight road segment or coming out of a curve, a larger separation distance can be used.

[0235] Figures 11D-11G Different exemplary embodiments of encoding sections 285 are shown. Fig.11D One embodiment of a coded road segment 285 is shown with several road surface markings 284 spaced a shorter distance 2851 and 2852 than the larger typical distances 190, 192, or 194. For example, a radar transceiver may interpret this closer spacing and separation as information about an upcoming curve or straight section (if within a curve). Fig.11E A further exemplary embodiment of a coded road section 285 is shown, in which not only are the distances 2851 and 2852 between the markings 284 shorter, but also the lateral distances 2853 between the road markings 284 are different.

[0236] Fig.11F Another embodiment of a coded road segment 285 is shown in which pavement markings are characterized by different lengths and spacings. Pavement marking 284 has a common length, but pavement marking 288 has a longer length 2857. The distance 2855 between pavement markings 284 and 288 is different from the distance 2856 between pavement markings 288 and 284, respectively.

[0237] Fig.11G Another embodiment of a coded road segment 285 is shown, where the pavement markings 284 and 289 are different sizes and the spacings 2851 and 2852 are different. The pavement marking 289 can be smaller or larger than the pavement marking 284 (e.g., Fig.11G ). In addition, pavement markings 284 and 289 may have different radar reflection characteristics to provide encoded information. That is, one or more of the spacing, length, reflectivity, or other detectable factors of the markers / reflectors may be varied to encode information that the controller may decode from the characteristics of the reflected signal.

[0238] Pavement marking changes

[0239] Figures 12A-12C Other embodiments of L-shaped dihedral corner reflector pavement markings are shown. Fig. 12A Pavement marking 282 is shown having optical reflector 275 on the front side and dihedral corner reflectors 286 and 287 on the sides with one side of the dihedral corner reflector lying generally flat on the ground and the other side of the dihedral corner reflector generally perpendicular or transverse to the ground. Fig. 12B Another embodiment of a dihedral corner reflector pavement marking 283 is shown where the front side of the marking has similar optical reflectors, but the dihedral corner reflectors 286 and 287 are mounted at an angle to the ground or road surface. The dihedral corner reflectors may be mounted at an angle to the direction of travel. Fig. 12C Another embodiment of a dihedral corner reflector pavement marking 288 is shown in which the dihedral corner reflectors 286 and 287 are facing upward at an angle. There are many other possible variations for mounting the dihedral corner reflectors 286 and 287 on the pavement marking.

[0240] Figures 13A-13C An embodiment is shown in which a T-shaped dihedral pavement marking is installed in a rumble strip or parallel cut slots, grooves or dimples beneath the driving surface. Fig.13A A front side view of a rumble strip 310 is shown, which is a cut in the road surface 300 that makes a sound when a tire runs over the rumble strip 310 to alert the driver. A T-shaped dihedral corner reflector pavement marking 394 is installed in the rumble strip 310 along with a T-shaped dihedral corner reflector 396. Fig. 13B A top view of a T-shaped dihedral corner reflector pavement marking 394 is shown installed in one of the rumble strips 310 along a roadway having a painted line 910 . Fig. 13C Another embodiment is shown in which a T-shaped dihedral corner reflector pavement marker 394 is installed in a highway recess 312 of an existing pavement marking installation so that a snowplow or other equipment will not tear it off the road surface.

[0241] Figures 14A-14D Embodiments are shown for installing dihedral pavement markings below the surface in rumble strips, parallel cut slots, or snowplowable pavement markings. Fig.14A A front side view of a rumble strip 310 is shown, which is a cut in the road surface 300 that makes a sound when a tire runs over the rumble strip 310 to alert the driver. A dihedral reflector pavement marking 1288 is installed in the rumble strip 310, wherein the dihedral reflectors 1286 and 1287 on each side of the pavement marking 1288 are installed in the inside of the rumble strip side, parallel to the vehicle travel direction. Fig. 14B A top view of a dihedral corner reflector pavement marking 1288 is shown installed in one of the rumble strips 310 along a roadway having painted lines 910 . Fig. 14CAnother embodiment is shown where a dihedral corner reflector pavement marker 1288 is installed in a highway groove 312 where an existing pavement marker is installed so that a snowplow or other equipment will not tear it off the road surface. Another embodiment is to use milled rumble strips as dihedral corner reflectors by spraying a conductive paint on the milled rumble strips. Fig.14A A milled rumble strip 310 is shown, but instead of installing pavement markings 1288, the milled rumble strip 310 is coated with a conductive paint to form two dihedral reflectors 1286 and 1287. Fig. 14C As shown, a longer length of milled road groove 312 may be coated with a conductive paint along the entire length of the rumble strip 312. This will provide a greater RCS for the radar transceiver to view.

[0242] Figures 14D-14H Other embodiments of including dihedral reflectors in plowable snow pavement markings are shown. Specifically, Fig.14D An isometric view of dihedral reflectors 1285 and 1289 mounted in a plowable pavement marker 1290 is shown. A snowplow rides on top of the sides 1206 and 1208, which are typically metal. An optical reflector 1275 (typically made of plastic) is mounted in the middle of the frame of the plowable pavement marker 1290 so that the marker 1290 can be seen by the driver or a visual sensor. The dihedral reflector 1285 reflects RF waves (e.g., microwaves) from one side of the pavement marker 1290 back to a radar sensor, and the dihedral reflector 1285 reflects RF waves back to a radar sensor on the other side of the plowable pavement marker 1290. The plowable pavement marker 1290 can be mounted in the center or inside lane line and viewed by radar sensors mounted on vehicles in two different lanes. Alternatively, the plowable pavement marker 1290 can be mounted in the outside lane line, in which case the dihedral reflector on the inside can be omitted or not used. Dihedral corner reflectors 1285 and 1289 can be made of right angle metal material, or a conductive coating on a right angle surface made of plastic, fiberglass or composite material or part of a cast iron snow plowable structure. Snow plowable pavement marking 1290, when installed in the road, is visible not only to drivers, vision sensors and lidar, but also to radar sensors.

[0243] Fig.14E A top view of a plowable marking 1298 is shown according to another embodiment, wherein two-sided reflectors 1285 and 1289 extend the entire length of the plowable pavement marking 1298. An optical reflector 1275 is mounted in the center of the plowable pavement marking 1298. The sides 1208 and 1206 are typically made of cast iron or a different type of metal. Fig.14F Shown with Fig.14E Side view of the same plowable snow road marking 1298. Right angle dihedral reflectors 1285 and 1289 are visible in this view.

[0244] Figure 14G Another embodiment is shown installed in a concrete or asphalt pavement 300. Sides 1206 and 1208 are Figures 14D-14F Optical reflector 1275 may be larger to fill the entire length of the inside of plowable sign 1295. Dihedral reflectors 1285 and 1289 along with optical reflector 1275 are part of the insert (the sign within the plowable structure or frame). Figure 14G Cutouts 1207 and 1280 in pavement 300 are shown for mounting plowable pavement markers 1295 in pavement 300. As can be seen, plowable pavement markers 1295 are mounted at or slightly above ground level. Plowable pavement markers 1295 may be glued (e.g., using epoxy glue) or otherwise secured in cutouts 1207 and 1280. Dihedral reflectors 1285 and 1289 are part of an insert (a pavement marker within a plowable structure or frame) mounted inside plowable pavement markers 1295 to reflect RF waves back to a radar sensor. Optical reflector 1275 may reflect light waves to the driver or vision camera, and may also reflect laser waves back to a lidar sensor.

[0245] Fig.14H Another embodiment of a plowable pavement marker 1308 installed in pavement 300 is shown. In this embodiment, an additional T-shaped corner reflector 1209 is installed in the center of the insert pavement marker, and therefore also in the center of the plowable pavement marker 1308. The additional reflector 1209 makes the radar cross section of the plowable pavement marker 1308 larger to the radar sensor. If the spacing between the reflectors is greater than the resolution of the radar sensor, the T-shaped reflector 1209 will appear as an additional target. This feature can provide additional information, for example, for determining the type of pavement marking or lane location. Fig.14H Only one T-shaped corner reflector is shown, but multiple reflectors may be added depending on the desired radar cross section or additional information required.

[0246] Figures 15A-15C Other embodiments of installing dihedral corner reflectors along the roadside using different types of pavement markings or schemes are shown. Fig.15A Sidewalk 1422, curb 1420, and corner reflector markers 1488 painted or mounted continuously or at intervals along road surface 300 are shown. Fig. 15B A corner reflector marker 1584 is shown mounted behind a concrete curb 1424. Radar waves can penetrate the concrete and reflect off the metal corner reflectors buried behind the concrete. Fig. 15C Another embodiment is shown in which corner reflectors 1684 are mounted on the surface of the concrete curb 1424 at varying intervals along the curb 1424 or continuously.

[0247] Figures 16A-16C Another embodiment is shown where corner reflectors are on one, two, three or four sides of the pavement marking. Fig.16A A pavement marking 580 is shown with three side dihedral corner reflectors 586, 587, and 589. The front dihedral corner reflector 589 faces the direction of travel, and a forward-looking radar mounted in the front can reflect the signal from the front reflector 589 to provide lateral and longitudinal information of the vehicle relative to the reflector 589. The dihedral corner reflector 589 can be mounted at an angle to the direction of travel to provide both longitudinal and lateral information from the same dihedral corner reflector. Alternatively, the pavement marking can have a parallelogram shape instead of a rectangular shape, so that the side dihedral corner reflectors remain facing the side while the forward reflector(s) are tilted slightly toward the center of the lane. Using the measured distance of the front-mounted radar (which can be at the same angle as the dihedral corner reflector to obtain maximum radar reflectivity) and the angle of the mounted dihedral corner reflector, the lateral distance from the side of the vehicle to the corner reflector can be calculated by the law of sines (lateral distance = sine (angle) / measured distance). The longitudinal distance from the front of the vehicle to the corner reflector can be calculated by the cosine law (longitudinal distance = cosine (angle) / measured distance). Fig. 16B Another embodiment of a pavement marking 582 is shown in which a front mounted corner reflector 590 is angled upward from the ground to provide a more reflective target for a forward looking radar. Fig. 16C Another embodiment 583 is shown including only one dihedral corner reflector 586 for use with roadside pavement markings.

[0248] Radar transceiver architecture and processing

[0249] Fig.17An embodiment of an ultra-wideband (UWB) pulse radar transceiver unit is shown. In this embodiment, the UWB pulse radar unit generates short pulses through a pulse generator 430, amplifies the signal through an amplifier 440, and transmits the short pulses through an antenna 436. The signal 1140 then propagates to the surface and reflectors (not shown). When the signal encounters the surface and reflectors, some of the signal is reflected from the surface, but significantly more of the signal is reflected from the reflectors and propagates back to the antenna 435. The returned surface signal can be filtered out by several known methods. One method is to select only signals that exceed a certain amplitude threshold. Another method is to receive the signal without a reflector and then use the basic signal to filter out the surface signal. There are many other schemes to filter out all or part of the surface signal. The signal 1142 from the surface and reflector is amplified by an amplifier 449 and sent to a sampler / data acquisition unit 442. The sampler / data acquisition unit 442 samples the signal 1142 received from the initial transmission signal 1140 generated by the computer 428 at different times. Computer 428 initiates the pulses via pulse generator 430, but computer 428 is also used to generate timing signals via timing delay 441 to sample the input delays. The input signal 1142 is sampled on time at different delays and the amplitude of the input signal 1142 is recorded at these different times. At a certain time, the return signal will have a certain amplitude, which represents the signal returning from the reflector. Computer 428 processes the information from sampler / data acquisition unit 442 to at least approximately determine the distance from the radar unit to the reflector by the time delay between the transmitted pulse and the received pulse. The time delay between the transmitted signal 1140 and the received signal 1142 is related to the distance between the radar unit and the reflector. Pulse radar uses pulses of short duration and wide bandwidth to provide high-resolution distance measurements. Advantages of this embodiment may include high accuracy and low power consumption. If the pulses are or are encoded as pseudo-random noise sequences, and the computer performs correlation processing on the transmitted pulses and the received signal, a noisy radar can be implemented. Noisy radar is useful in reducing interference.

[0250] Fig.18A pulse radar system 2480 is shown, which has multiple transmitter and receiving antennas 1151-1155 aligned with a corner reflector 459. In this embodiment, the pulse radar system 2480 includes an antenna array 1150, a pulse radar subsystem 454, and a computer 480. The antenna array 1150 includes multiple antennas 1151-1155, typically two to hundreds of antennas. The antenna can be any type known in the art, such as a printed antenna, a waveguide antenna, a dipole antenna, or a Vivaldi broadband antenna. The antenna array 1150 can be linear, or two-dimensional, flat, or conformal to the region of interest. The pulse radar system 2480 generates an RF signal and transmits the RF signal through the antenna array 1150 including antennas 1151-1155. The output signal is reflected from the corner reflector 459 and reflected back to the antenna array 1150. The pulse radar unit 454 receives the signal returned from the antenna array 1150. The signal can be, for example, a pulse signal, a step frequency signal, or the like. The generating circuit within the pulse radar system 2480 may include an oscillator, a synthesizer, a mixer, or it may be based on a pulse directional circuit, such as a logic gate or a step recovery diode. The conversion of the signal may include down-conversion, sampling, and / or other similar techniques. The pulse radar system 2480 may use multiple antennas for transmission and reception at a time, or select one transmitting antenna and one receiving antenna at a time. The pulse radar system 2480 preferably has a data acquisition function to collect and digitize the signals from the antenna array 1150. The data acquisition function typically includes an analog-to-digital converter, a data buffer, and a filtering function. The computer 480 may convert the signal 481 into a response describing the characteristics of the reflector 459, and execute an algorithm that converts the response set into image data (two-dimensional or three-dimensional) of the reflector. The reflector 459 image can be determined with respect to the arrangement of the antenna array 1150; therefore, the orientation of the reflector 459 can be determined with respect to the antenna array 1150.

[0251] Fig.19A frequency modulated continuous wave (FMCW) radar transceiver is shown, such as, for example, 60 GHz and 77 GHz FMCW radar transceivers from Texas Instruments. In this embodiment, a processor 425 generates a DC (direct current) signal through a DAC (digital-to-analog converter) 421 to control a VCO (voltage controlled oscillator) 410. The VCO 410 generates a signal 1130 called an FMCW chirp and transmits the signal 1130 through an antenna 414. There is usually a power amplifier before the antenna 414 to increase the signal strength. The return signal 1132 is received through the antenna 416 and combined with the transmitted signal by the modulator 418 through the path 412. There is usually a low noise amplifier to increase the level of the received signal. The modulator 418 is an orthogonal modulator and provides both real and imaginary parts. The output of the modulator 418 is a beat frequency, which is amplified and filtered by the filter 419 and then sent to the A / D (analog-to-digital) converter 420. Processor 425 receives the signal from A / D converter 420 and processes the signal using a frequency transform, such as a fast Fourier transform (FFT), to obtain distance and amplitude information. Performing an FFT on the first frequency ramp, which is typically 10-250 microseconds in length and is called a fast chirp in FMCW modulation, can provide adequate lateral distance measurement. This fast chirp allows distance measurements to be made in short time intervals (e.g., less than one millisecond). Using Chirp-Z transforms and scaled FFTs can achieve higher ranging accuracy without significantly affecting memory or speed. Chirp-Z transforms are a generalization of discrete Fourier transforms (DFTs). Scaled FFT techniques only process the frequencies of interest, rather than the entire frequency spectrum. In this case, this is feasible because the lateral distance of the vehicle from the road markings is roughly known within a certain range of distances, and it corresponds to a frequency range or band. These techniques can improve the accuracy of measuring distances and thereby achieve or improve lateral control of the vehicle. Other techniques similar to those described above can also be used to improve accuracy. FMCW radar transceivers can obtain not only distance, but also speed, signal amplitude and phase. Through multiple receiving antennas, the angle of arrival (AoA) can also be determined, thereby determining the direction of the object.

[0252] Some types of automotive radar transceivers use a sequence of frames to transmit RF signals. For example, with FMCW, there is a chirp (frequency ramp); with digital coded modulation DCM, there is a sequence of chips (digital code stream); and with UWB pulse radar, one or more pulses (frequency broadband) are transmitted to an object and reflected signals are received from different objects. These radar types can distinguish multiple targets and are characterized by the number of frames per second (fps), which is related to the processing speed of deriving the range, speed and position of the target. The faster the frame rate, the faster the target can be identified. Typically, automotive radars have a frame rate of 8-50fps, but higher frame rates can be achieved by using shorter chirps, chips or pulse sequences, respectively. For example, the frame rate can be as low as 1fps or as high as 2000fps. For example, the IWR1443 from Texas Instruments has a frame rate of 909fps (frame time of 1.1ms) in one configuration for one type of radar application. CW radar transmits a continuous frequency and has no frames. For example, a dual-frequency CW or multi-frequency CW radar transmits and receives signals continuously; there are no frames. However, multi-frequency CW radar implies a much different process to acquire more than one target.

[0253] For example, for a downward-looking sideways radar transceiver on a vehicle moving along a road at 25 m / s, the radar transceiver will see a 0.1 m long dihedral corner reflector road marking in about 4 milliseconds (observation time = length of dihedral corner reflector / vehicle speed). In order for the radar transceiver to not miss the dihedral corner reflector road marking, the frame rate should be greater than 250fps (1 / 0.004s). The length of the dihedral corner reflector can be very short, such as 0.05 meters, or very long, such as 1 meter. Typically, the spacing between road markings on a road can be as short as 0.5 meters to as long as 25 meters.

[0254] To minimize the frame rate, the frames can be timed synchronously based on the speed and the dihedral reflector road marking spacing. The start time of the frame is the end of the interval time period from when the radar transceiver views the last dihedral reflector road marking to the next dihedral reflector road marking. The interval time period is equal to the road marking spacing distance divided by the average vehicle speed during the time period. For example, if the spacing distance between road markings is 1 meter and the vehicle is traveling on the road at a speed of 25 meters per second, the interval time period Tsp is 40 milliseconds (Tsp = road marking spacing distance / vehicle road speed). If the radar transceiver starts the frame synchronously with the interval time period, the frame rate of the radar transceiver is approximately 25fps (1 / 0.04 seconds). For example, the IWR1843BOOST from Texas Instruments can start the frame using a software start command or a hardware SYNC_IN pin signal. The frame rate of the radar transceiver can vary based on the vehicle speed and the dihedral reflector road marking spacing. Synchronizing the frame to the starting position of the dihedral corner reflector allows more radar observation time for the dihedral corner reflector, does not miss the dihedral corner reflector pavement markings, and reduces or eliminates the need for high-speed radar processing. The frame period can be in the range of about 0.5 milliseconds to about 1 second. A Kalman filter can be used to assist in tracking pavement markings and reducing missed pavement markings.

[0255] Fig. 20 A radar transceiver with additional synchronization capabilities is shown, such as the 60 GHz and 77 GHz FMCW radar transceivers from Texas Instruments. In this embodiment, processor 425 generates a DC signal via DAC 421 to control VCO 410. The DAC signal is synchronized with the A / D signal via line 423 to provide high accuracy distance measurement. VCO 410 generates signal 1130 and transmits signal 1130 via antenna 414. Signal 1132 is received via antenna 416 and combined with the transmit signal via path 412 by modulator 418. The output of modulator 418 is amplified and filtered by filter 419 before being sent to A / D converter 420. Processor 425 receives the signal from A / D converter 420 and processes the signal for distance, velocity, amplitude, and phase information. As previously described, both the transmit and receive signals at the antenna typically have amplifiers (not shown) to enhance signal strength.

[0256] Fig.21Another embodiment shown is a dual frequency radar transceiver that determines the distance of the road reflector 284 relative to the vehicle 180 by the phase difference of the two received signals. A high frequency generator 600 is mixed with a low frequency 602 using a single sideband mixer 604 to form two frequencies f1 and f2. The two frequency signals are combined in an adder 606, amplified by an amplifier 607, and then sent out from a transmitter antenna 608, which is aimed at the road reflector 284 by a signal 1610. Signal 1612 is reflected back to the receiver antenna 610 and amplified by a low noise amplifier (LNA) 611. The received signal 1612 is mixed with f1 and f2 and filtered by filters 616 and 618, respectively. The resulting signal is sent to a phase detector 620, which detects the phase difference of the two signals. The phase difference is related to the travel distance between the dual-frequency radar and the road reflector 284: Phase difference = 4πfd / c, where π≈3.1416, f is the difference frequency, d is the distance, and c is the speed of light. Frequencies can be sent at different time intervals, time division multiplexing, or frequency division multiplexing. The difference frequency sets the maximum range and range resolution. The higher the difference frequency, the better the range resolution, but the lower the maximum range. The center frequency f1 of the radar transceiver at Ohio State University mentioned above is 10.5GHz, and the differential frequency is 300MHz. This provides a clear range of 0.5 meters, and the range accuracy is less than 1 centimeter (cm). The radar at the PACCAR Technology Center uses a dual-frequency time-division multiplexing wave radar with a center frequency of 10.5GHz and a differential frequency of 20MHz. This provides a clear range of 7.5 meters. In order to improve the range accuracy, an orthogonal detection scheme is used to monitor the 10.5GHz cycle, and the range accuracy provided is better than 1.5 cm. Another embodiment may transmit and receive multiple frequencies to determine the distance to the reflector 284. Three or more frequencies may be transmitted to the reflector using hardware similar to the dual frequency radar but with more components and frequencies. Two frequencies, such as 77 GHz and 77.01 GHz, may provide an unambiguous range of 15 meters, and a third frequency, such as 78 GHz, may provide a range accuracy of better than 1 centimeter.

[0257] Fig. 22A digital code modulation (DCM) radar transceiver is shown. A unique digital code, i.e., a chip sequence, is generated by a digital code generator 1421 and mixed with a reference frequency generated by a signal generator VCO 410 using a modulator 1604. The chip is a binary value used to modulate the phase of an RF sinusoidal signal. The signal is amplified using an RF power amplifier 1607 and sent through an antenna 414. The return signal is received by an antenna 416 and amplified by an RF LNA 1611. The return signal is mixed with a reference signal using a modulator 418. The output signal of the modulator 418 is filtered by a filter 419 and sampled by an A / D converter 420. A radar processor 425 receives the signal from the A / D converter 420 and learns the reference code from the digital code generator 1421. By correlating the transmitted code with the received code, the radar processor 425 can determine the distance and velocity to the corner reflector. The angle with the target or corner reflector can be determined by multiple transmitting and receiving antennas.

[0258] Fig.23 Another example of a FMCW radar transceiver is shown, but with multiple transmit antennas 414 and multiple receive antennas 416. In particular, Fig.23 A FMCW MIMO (multiple input, multiple output) radar transceiver is shown. The radar processor 426 drives the synthesizer 411 to provide a chirp or frequency ramp of the transmit signal. The signal is amplified by the RF power amplifier 413 and transmitted through multiple transmit antennas 414. The received signal is obtained by the antenna 416 and amplified by the RF low noise amplifier (LNA) 415. The transmit signal is orthogonally mixed with the receive signal using the modulator 418, so that both the phase and speed of the signal can be determined. The output of the modulator 418 is filtered by the filter 419 and A / D converted by the A / D converter 420 to a signal read by the radar processor 426. Using multiple antennas, the system can determine the angle to the target (AoA) to help distinguish different targets.

[0259] Additionally, if the transmit antenna 414 and the receive antenna are polarized, for example, orthogonal linearly polarized antennas, then the radar system is a polarimetric radar, which has the additional capability of distinguishing between dihedral reflectors and other objects (e.g., the ground) based on the polarization scattering matrix. Figure 4AAs shown, the radar reflection from the dihedral reflector is a double bounce signal (two reflections from two dihedral reflective surfaces), while the reflection from the ground or road surface has only one bounce (one reflection from the ground or road surface). The phase change of the polarization electric field of the single bounce reflection and the double bounce reflection is different, and this difference can be detected to distinguish it from the dihedral reflector from the ground. In particular, the phase of the vertical to vertical polarization direction is different for even bounces, such as from a dihedral reflector (two reflections from two dihedral reflective surfaces) than for odd bounces (such as one reflection from the ground or three reflections from three reflective surfaces of a trihedral reflector). Therefore, the phase change of the polarization electric field can distinguish whether the reflection is from the ground or the dihedral reflector. In addition, the even bounce reflector always returns the same perceived circular polarization as the incident wave. For example, a left-handed circularly polarized wave is reflected from a dihedral reflector as a left-handed circular wave, while a circularly polarized wave is reflected from the ground as a right-handed circular wave. Dual polarization radar transmits and receives pulses in two polarization dimensions, horizontal and vertical. Therefore, the return frequency measures the horizontal and vertical dimensions of the road marking, providing information on the size and shape of the road marking as well as the distance to the road marking. Using these measurements, the dual-polarization radar can filter out other clutter objects and provide a more accurate distance to the road marking.

[0260] A typical FMCW radar sensor, such as the Texas Instruments AWR1843AOP, provides object range by performing an FFT on the processed received signal (i.e., the beat frequency). The radar sensor can provide velocity by performing a second FFT on several consecutive received signals (chirps with a ramped transmission frequency) by detecting the phase change from one chirp to the next. The radar sensor can provide direction by performing a third FFT on several received signals from different receive antennas using AoA. This results in a radar cube that contains range, velocity, and direction. Using dihedral corner reflectors in road markings, the exact lateral distance to the radar sensor can be determined by performing a single FFT on the first frequency step (usually 10-250 microseconds) (called a fast chirp in FMCW modulation). This fast chirp allows distance to be measured in short time intervals (e.g., less than one millisecond). Typically, the lateral velocity measurement is small and close to zero, so a second FFT is not required. Additionally, since the vehicle will be parallel to the road markings, the angle of maximum received signal to the road markings will be toward the corner reflectors. The processing software within or in conjunction with the radar sensor can use both techniques: a single FFT on a fast chip to process precise lateral distance measurements to the desired reflecting road markings, and multiple FFTs for distance, speed, and multiple receive antennas to detect other objects around the vehicle, such as blind spot detection, or to perform lane change maneuvers and lane departure detection.

[0261] Deep learning methods can be used to enhance the detection of dihedral reflectors from other objects on the road, thereby reducing the probability of missing road surface markings amid other radar clutter. For example, using a convolutional neural network (CNN) or a recurrent neural network (RNN) on the radar cube, or just using range measurement and some other properties such as polarization and amplitude, can improve the distance measurement to the desired reflective road surface markings.

[0262] Phase modulated continuous wave (PMCW) radar, orthogonal frequency division multiplexing (OFDM) radar, and other digital radar technologies can also determine the distance to reflective road surface markings. Combinations of one or more of the above technologies can also be used. For example, FMCW technology and PMCW technology can be used in the same radar sensor to determine redundant distances to reflectors. Alternatively, two or more radar transceivers with the same or different characteristics can also be used in combination at different distances.

[0263] The radar sensor may be of any type previously described, such as FMCW, PMCW, OFDM, DCM, multi-frequency radar, multi-frequency phase radar, MIMO radar, UWB FMCW, UWB pulse radar, FSK (frequency shift keying) radar, monopulse radar or any combination of these types. The radar preferably operates at a radio frequency between 0.3 and 1000 GHz (300 MHz and 1 THz).

[0264] The radar beam emitted by the radar transceiver preferably has a single or primary lobe characterized by a beam direction and a beam shape. The beam direction is typically characterized by a vector along the center or center point of the lobe. The placement and pointing of the radar transceiver is preferably such that the beam direction is oriented toward the expected location of the dihedral reflector in the road surface marking when the vehicle is centered in its lane. For example, the beam shape may be Gaussian and characterized by a beam width, which is typically measured from the half-power point on opposite sides of the beam center. The beam may be circularly symmetric about the central direction vector, or may be asymmetric. The beam width is preferably narrow enough so that only one reflector is detected at a time in a given line of reflectors (although reflectors in parallel, more distant lines may also be detected within the beam width), but wide enough to capture the marker within an expected area of ​​variation based on vehicle drift, marker position tolerances, etc. Range-based gating or filtering may be employed to ignore reflected signals from objects outside the range of interest.

[0265] The beam shape and / or direction may be static or variable. Well-known beam shaping techniques may be applied to dynamically or non-dynamically change the beam. For example, when the beam is generated by an antenna array, well-known electronic beam steering and beam shaping techniques (e.g., delay-sum, window functions, etc.) may be employed to electronically change (e.g., steer) the beam. For example, the beam may be switched between a relatively narrow width directed toward a nominal road marking location and a relatively wide width directed more upward for blind spot detection, as described in detail below.

[0266] In some embodiments, a mechanical beam shaping device may be used. For example, an RF lens may be used to change the shape of the beam, including its width. If the radar transceiver is located in the headlight, the outer headlight housing (or a relevant portion thereof) may be formed of a suitable material and made into an RF lens. As another example, an RF reflector (such as a horn) may also change the shape and / or width of the beam.

[0267] Combination with other automotive radar systems

[0268] Another embodiment is to combine a current automotive radar transceiver that can provide object detection in front of, to the side of, and / or to the rear of a vehicle with a radar transceiver for detecting radar-reflective pavement markings. That is, the same radar transceiver on a vehicle can be used for both object detection and pavement marking ranging. For example, a side or corner automotive radar can: (1) treat reflective pavement markings as stationary, highly reflective targets and measure the lateral distance to the reflective pavement markings mounted on the road; and also (2) process other objects along that side, such as moving vehicles within the blind spot of the vehicle driver. The same radar transceiver can be used not only for blind spot detection, but also for detecting objects in the vehicle using, for example, known beam steering techniques (such as Fig.23 The same radar transceiver unit may be used for intersection traffic alert, lane change assistance and traffic jam assistance. For example, this may be a dual-purpose side radar transceiver that can process both large objects on the ground, such as vehicles in the blind spot, and small objects on the ground, such as reflective road markings, for lateral distance measurement. Fig.23A typical FMCW radar transceiver is shown, which can perform object location for both stationary and moving objects. The FMCW radar transceiver may contain or utilize software to distinguish between targets and provide range measurements of objects, the location of objects, the return signal strength of objects, and / or the relative speed difference between objects and the radar transceiver. Similarly, as a vehicle moves along a road, the front radar can see combined reflective markings (described below), markings with multiple dihedral / trihedral reflectors, or multiple dihedral reflectors in addition to other vehicles in front of the vehicle. The automotive radar can treat other vehicles within a certain distance in front of the vehicle as moving targets and combined reflective pavement markings along the road on both sides of the lane as stationary targets. The distance to the combined reflective pavement markings can be used to determine the geometry of the road in front of the vehicle. This dual-purpose forward-looking radar transceiver can detect objects in front of the vehicle for avoidance, or in the case of adaptive cruise control, tracking the vehicle, but can also provide the geometry of the road for use as preview information by the lateral steering controller. Similarly, the dual-purpose rearward-facing radar transceiver can see other vehicles approaching the vehicle and can also see combined reflective pavement markings to obtain additional information about the geometry of the road.

[0269] In one embodiment, the radar transceiver can be packaged in a turn signal, a marker light, or other light assembly on a vehicle. For example, the radar transceiver can be integrated with such a light, or added as a retrofit add-on under the housing of an existing vehicle light.

[0270] When the radar transceiver is used to provide blind spot monitoring, a light on the vehicle can be turned on or flashed (alternately turned on and off) to signal to a person or other vehicle in the blind spot that the object has been detected in the blind spot. That is, the detection of an object in the blind spot can cause a processor associated with the radar sensor to turn on or flash a light on the vehicle. Alternatively, another indication (visual or audible) can be actuated when an object is detected in the blind spot. If the actuated light or indication is located outside the vehicle near the blind spot, the light or indication can prompt other drivers, cyclists, pedestrians, etc. to move relative to the vehicle so as not to be in the vehicle's blind spot. For example, a short circuit in a turn signal lamp can cause the light to flash at twice the standard flash rate, thereby signaling an intention to turn or change lanes. An indication can also be issued on the dashboard or elsewhere in or near the cab / compartment to indicate to the driver that an object is present in the blind spot. If the light is a self-powered turn signal lamp combined with a radar transceiver, the operation of actuating the light can be performed locally in the light (completed by the processor therein) without adding additional burden to the vehicle's computing system. According to another embodiment, when the radar transceiver detects an object in the blind spot, a number of selected pixels of each headlight or turn signal lamp may be actuated to project a visual warning, such as a high-definition quality warning symbol, to alert the driver and other drivers of the blind spot detection.

[0271] Combination with other vehicle guidance systems

[0272] For redundancy and / or increased reliability, the radar guidance technology described herein may be combined with other guidance technologies based on other technologies. For example, the radar transceiver 116 may be integrated with other sensors, such as, for example, a GPS receiver 901, a lidar sensor 902, a vision sensor 903, a forward-looking radar 904, or other position sensors 905, such as Fig.24 As another example, the processing of signals from various sensors (including the radar sensor described herein) can be performed by a general purpose processor or computer (which can have multiple processors). Joint processing of various types of sensors can improve the performance of any one sensor type alone. For example, the output of the onboard processor 437 using a Kalman filter can provide highly reliable position information 914, steering information 912, and speed information 918.

[0273] Fig.25 Another embodiment is shown in which dihedral pavement markings 2841-2847 and 3841-3846 are placed along the road. Pavement markings 2841-2847 are spaced X21-X27 along one side of lane 303, respectively. On the other side of the lane are pavement markings 3842-3846, which may be similarly spaced. As vehicle 1800 travels along lane 303, vehicle 1800 equipped with radar transceivers 1161 and 1171 having sufficient directionality and a sufficiently accurate position determination system (such as DGPS (differential GPS)) can record the location of the pavement markings. Using sufficiently directional radar and sufficiently accurate position sensors on the vehicle to record the location of the radar reflecting pavement markings, the longitude and latitude readings of each marking and the distances between the pavement markings (such as X21-X27) can be included in a database. Fig.26 A table of one embodiment of a pavement marking database is shown. In the table, pavement markings are identified using the road name and the direction of travel as an alphanumeric string, for example US30, the direction is east, and the pavement marking number would be US30E2841. Other methods may also or alternatively be used to identify the location of pavement markings. The pavement marking locations in this example are longitude and latitude coordinates. The distance from the previous marker X21 to the next marker X22 may also or alternatively be recorded. Thus, Fig.26 Can represent the exact location of reflective pavement markings on the road.

[0274] Fig.26 The database may also be augmented with other information, including, for example, the location of known hazards (e.g., potholes). With an accurate database of the location of road markings and known hazards, the speed and positioning of the vehicle may be adjusted to avoid the hazard or to reduce or minimize the impact of the hazard on the vehicle.

[0275] Using an accurate database of pavement marking locations, the speed and longitudinal position of the vehicle can be determined from the position of the vehicle along the road. The speed of the vehicle is determined by knowing the distance between pavement markings (e.g., X22) and the travel time between pavement marking 2841 and pavement marking 2842 as viewed by radar transceiver 1161. This is the actual speed of the vehicle. The speed can also be obtained from forward-looking radar or vehicle wheel speed. Fig. 27 An embodiment of using the position information of road surface markings to control vehicle speed is shown. Vehicle speed controller 9080 can control the engine (gasoline vehicle) or electric motor (electric vehicle) or engine / motor 9020. Engine / motor 9020 drives vehicle power plant 9050, which generates vehicle speed. Desired vehicle speed V DESIRED is input to the vehicle speed controller 9080. The sign database 9006 may be queried to determine the actual speed based on the time the radar transceiver 1167 observes the two signs and the actual distance between the signs in the sign database 9006. The sign database 9006 may have input from other sensors such as coded signs 9090, GPS receiver 901, and vehicle to infrastructure (V2I) communications 9180. The controller 9080 receives the error between the actual speed and the desired speed and derives an appropriate response to control the engine / motor 9020. The vehicle speed controller 9080 may obtain input from other vehicles through vehicle-to-vehicle communications (not shown) to change the speed based on traffic conditions.

[0276] Another embodiment uses the signature database 9006 for longitudinal distance control of the vehicle. Fig.28 A longitudinal distance control system is shown that controls the position of the vehicle along the road. The desired distance X at any point is determined by a central computer for the vehicle road through vehicle-to-infrastructure (V2I) communication 9180 or by an onboard computer through vehicle-to-vehicle (V2V) communication 9170 DESIRED If the desired distance is determined by the highway central computer via V2I communications, then the controlled vehicle will be in an automated highway system in which the positions of all vehicles along the road are known. If determined by the onboard computer via V2V communications 9170, then the vehicle is controlled in a platoon with other vehicles. A combination of these two schemes can be used to provide platooning of vehicles on an automated highway to improve safety and traffic flow. Fig.28A block diagram is shown for a longitudinal control system in which the difference between the desired distance and the actual distance traveled is input into the vehicle longitudinal controller 9004. The controller 9004 compensates for vehicle dynamics and road conditions and controls the engine / motor mechanism 9120 which in turn controls the vehicle dynamics (transmission and wheels) and is affected by road conditions. Actual distance X ACT is calculated using radar transceiver 1167 viewing road markings at different times and marking database 9006 of road marking locations. Actual distance X ACT The position of the vehicle along the road may be determined from the pavement markings, from the forward looking radar 904, or from the wheel speed sensors 1904, by the marker database 9006. The marker database 9006 may have the actual location of the pavement markings and determine the location of the vehicle along the road at any point in time by processing the radar transceiver information from the radar transceiver 1167. The marker database 9006 may have other sensor inputs to help determine the vehicle location, such as coded markers 9090, GPS receiver 901, and V2I communications 9180. For example, the vehicle longitudinal controller 9004 may be similar to a controller using discrete embedded magnets, as described in "Vehicle Longitudinal Using Discrete Markers" by David W. Love and Masayoshi Tomizuka, published by the California PATH Program at the University of California as California PATH Research Report UCB-ITS-PRR-94-28 (December 1994), which is incorporated herein by reference in its entirety.

[0277] Fig.29 Another embodiment shown utilizes the location of road surface markings to determine the position of the trailer on the road. Fig.29 A tractor-trailer combination is shown having a tractor 1801 and two trailers 1802 and 1804 connected to the tractor 1801. In addition to the side radar steering transceiver on the front of the tractor for controlling the lateral displacement of the tractor (as described above), the position of the trailer can also be determined by using multiple side and top looking radar transceivers 9116-9119 (with radar beams 9126-9129) on one side of the trailer to observe road surface markings 284 on one side, and side and top looking radar transceivers 9216-9219 (with radar beams 9226-9229) on the other side of the trailer to observe road surface markings on the other side (not shown).

[0278] According to another embodiment, the radar-based measurement and guidance techniques described herein may be used to test or calibrate other guidance systems based on other technologies (eg, lidar, vision, other radars, etc.).

[0279] Pavement marking with embedded integrated radar reflector(s)

[0280] There are many ways to construct a raised pavement marking with dihedral corner reflectors. The above embodiments show some preferred combinations. Another embodiment is a combination of one or more dihedral reflectors and one or more trihedral reflectors embedded in the pavement marking. Fig. 30A The dimensions of the two-sided / three-sided combination corner reflector 3287 are shown. The combination corner reflector 3287 is a two-sided reflector 287 (L-shaped), similar to Figures 2A-2D 3287. The addition of this element 2287 to the end creates a three-sided corner reflector for one end of the reflector 3287. The side dimension is "a", and the long end dimension, which is substantially parallel to the lane markings, is "b". The element height and width of the added element 2287 have similar dimensions "a". Alternatively, the added element 2287 can have a different shape, such as a triangle, for example. The two-sided / three-sided combination corner reflector 3287 is different from a strict dihedral corner reflector (e.g. Figures 2A-4E The difference between the dihedral corner reflector shown in FIG) is that the latter has no end pieces, such as Fig. 30A Side reflector end element 2287 shown in . As used herein, a dihedral corner reflector in the strict sense has exactly two sides and does not include a third side.

[0281] Fig. 30B Another embodiment shown illustrates the dimensions of a T-shaped dihedral / trihedral combination corner reflector 2396. The side has a dimension "a", and the long end, which is parallel to the lane markings and similar to the single dihedral corner reflector 287, has a dimension "b". A new element 4396 is added to the T-shaped dihedral corner reflector 396 to form a new combined dihedral / trihedral reflector 2396. The dimensions of element 4396 are height "a" and length "2a". End element 4396 is attached to the end of the T-shaped dihedral reflector 396 to form a combined dihedral / trihedral reflector 2396.

[0282] Figures 31A-31D Reflections from the radar transceiver 116 at different locations for a single L-shaped combined dihedral / trihedral corner reflector 3287 are shown. Other embodiments have similar results. Fig.31A The radar transceiver 116 is shown aligned with the center of the dihedral corner reflector cross section, transmitting signals 1119 and receiving signals 1118 similar to the dihedral reflector described previously. The distance "d" between the radar transceiver 116 and the reflector 3287 can be measured. As previously described Figure 5AAs shown, the relative RCS of the radar transceiver 116 when rotated + / - 45° from the center of the dihedral corner reflector returns a strong signal strength reflected from the target (in this case, the dihedral corner reflector). As long as the radar transceiver 116 is positioned within a right angle range of the corner reflector, the signal return is very good. If the radar transceiver 116 is rotated more than 45° and sees the back of the combined reflector 3287, but is not at a right angle to the back, the signal will not be reflected back very well. This is the advantage of a corner reflector over a flat plate or sphere. If the radar transceiver is facing the plate or at 90° to the plate, the plate will reflect the signal back, but if the radar transceiver is rotated in either direction, very little signal will be returned.

[0283] Fig.31B A top view of the combined reflector 3287 is shown, and the radar transceiver 116 is shown pointed directly at the dihedral portion of the combined reflector 3287. The beam width of the radar transceiver is wide enough to cover the length "b" of the dihedral corner reflector in the direction of travel "y". At a given length "b" of the corner reflector and the radar beam width, the transmit signal 1119 is reflected back as the return signal 1118. As long as the radar transceiver passes the dihedral corner reflector, the signal strength of the reflector is good. Once the radar transceiver passes the corner reflector, particularly the end element 2287, the returned signal drops significantly. Therefore, as the radar transceiver 116 passes the combined reflector 3287 in a direction parallel to the length of the corner reflector, the radar transceiver measures the distance from the corner reflector to the radar transceiver antenna. If the radar transceiver 116 remains substantially parallel to the combined reflector 3287, the distance remains constant over a period of time. If radar transceiver 116 moves closer to combined reflector 3287 in a parallel direction, radar transceiver 116 will measure a closer distance to combined reflector 3287 .

[0284] Fig.31C A top view of the radar transceiver 116 is shown, wherein the radar is looking toward the angle formed by the three surfaces of the combined three-sided reflector at a distance away from the combined reflector 3287, and is moving toward the combined reflector 3287 in a direction parallel to the long section of the combined reflector 3287. The beam width of the radar transceiver is wide enough to enable the radar transceiver 116 to transmit a signal 2119 and receive a signal 2118 from a certain distance from the combined reflector 3287. When the radar transceiver approaches the combined reflector 3287, the three-sided reflector formed by the end element 2287 and the two-sided reflector portion can provide a strong return signal. As the radar transceiver approaches the combined reflector 3287, the measured distance d b will change and decrease until Fig.31BAs shown, the radar transceiver 116 is facing the combined reflector 3287. The radar transceiver 116 then measures a constant distance d over a period of time. When the radar transceiver 116 passes the combined reflector 3287, the signal return will drop significantly and will not report short range distances.

[0285] Fig.31D A top view of forward looking radar transceiver 1168 is shown at a distance away from combination reflector 3287. Here, the main beam is aimed at the trihedral reflector of combination reflector 3287. Radar transceiver 1160 transmits signal 3119 to combination reflector 3287, and the trihedral component reflects signal 3118 back to radar transceiver 1160. The distance d between radar transceiver 1168 and combination reflector 3287 is measured. p .

[0286] In this application, the combined dihedral / trihedral corner reflector has several advantages over a trihedral corner reflector alone and a strictly dihedral corner reflector. First, the combined dihedral / trihedral corner reflector provides a constant distance over a period of time similar to a dihedral corner reflector when viewing the corner reflector sideways, but also allows the signal to return close to the combined reflector as a trihedral corner reflector. This allows the combined reflector to be viewed for a longer period of time and can reduce the processing required. The second advantage is that the forward-looking radar can see the combined reflector. The radar system can provide a preview of the road geometry ahead of the vehicle. Since the road geometry can be seen while driving along the road, there is less need to store information in the database. The third advantage is that the forward-looking radar can provide the vehicle's position within the lane using the geometry of various road surface marking locations.

[0287] Fig.32A and 32B Several configurations of raised pavement markings with combined dihedral / trihedral corner reflectors are shown. Fig.32A One embodiment is shown with a body 290 comprising an optical reflector 275, two combined dihedral / trihedral corner reflectors or combined corner reflectors 2286 and 2288, and two quarter-circle RF transparent materials 293 with end caps. As shown in these isometric views, the combined corner reflectors 2286 and 2288 are attached to the left and right sides of the body 290, and the optical reflector 275 is attached to the front. The quarter-circle RF transparent materials 293 are placed inside the combined corner reflectors 2286 and 2288, respectively, to provide protection from road damage. The combined corner reflectors 2286 and 2288, the body 290, and the RF transparent materials 293 can be attached by glue, screws, rivets, molded slots, or similar attachment mechanisms.

[0288] Fig.32BAnother embodiment 2384 for constructing a raised pavement marking with a combined dihedral / trihedral corner reflector is shown. In this embodiment, the quarter-circular RF transparent materials 1294 and 1296 are sprayed or glued with a metallic or other RF reflective coating or foil on the two flat angled sides to form a dihedral corner reflector, and the quarter-circular end cap 1301 is sprayed or glued with a metallic or other RF reflective coating or foil to form a trihedral reflector. The bottom sides 1302 and 1303 are also coated with a metallic paint or metal foil on the quarter-circular RF transparent materials 1294 and 1296, respectively.

[0289] Figures 33A-33C Several configurations of raised pavement markings with T-shaped combined dihedral / trihedral corner reflectors are shown. Fig.33A An embodiment 1588 is shown in which a T-shaped combined dihedral / trihedral corner reflector 2396 made of metal or other RF reflective material is centered between two quarter-circles or similarly shaped RF transparent materials 397 and 398, and an optical reflector 275 is attached to the front to form a road surface marking 1588. The two quarter-circles of RF transparent materials 397 and 398 are attached to the left and right sides of the T-shaped combined dihedral / trihedral corner reflector 2396, with the optical reflector 275 facing forward when viewed from the isometric view. The quarter-circles of RF transparent materials provide protection from road damage. The attachment means connecting the T-shaped combined corner reflector 2396 to the RF transparent materials 397 and 398 can be glue, screws, rivets, molded slots, or any other suitable attachment mechanism(s).

[0290] Fig.33B Another embodiment 1688 for constructing a raised pavement marking with a T-shaped combined corner reflector is shown. In this embodiment, one of the quarter-circular RF transparent pieces 3396 has a metal or other RF reflective coating or foil sprayed or glued on one side of the combined corner reflector and on the end cap 1301. The other RF transparent piece 3397 has an end cap 1301 with a similar coating. The quarter-circular RF transparent material 3396 can be plated with a metal surface on both sides (inside and end cap). The bottom plate 1300 is metal or another RF reflective material that forms the bottom of the T-shaped corner reflector and provides a good flat protective surface.

[0291] Fig.33CAnother embodiment 1788 for constructing a raised pavement marking with a T-shaped combined corner reflector is shown. In this embodiment, two molded plastic or similar RF transparent materials 3396 and 3397 that are RF transparent are plated or sprayed with metal on the sides. The molded plastic RF transparent material 3396 is sprayed or plated on the bottom side 1303, while the molded plastic RF transparent material 3397 is sprayed or plated on the right angle face 1399 and both sides of the bottom face 1303. When the two are bonded or mechanically connected together, they form a T-shaped dihedral corner reflector. An optical reflector 275 is added to the front to form a raised pavement marking 1784.

[0292] Fig.34 Another embodiment 2888 is shown, where a T-shaped dihedral / trihedral corner reflector 2396 is made of metal or other RF reflective material or conductive coated right angle material, etc., with two additional combined corner reflectors 2286 and 2288 on the end of the pavement marking. The center reflector has two square RF transparent materials 1293 on each side of the T-shaped reflector 2396. And two quarter-circle or similarly shaped RF transparent materials 393, and an optical reflector 275 attached to the front, which form the pavement marking 2888. The two quarter-circle RF transparent materials 393 are attached to the left and right sides of the combined corner reflectors 2286 and 2288, respectively, and the optical reflector 275 faces forward from the isometric view. The quarter-circle RF transparent material provides protection from road damage. The dual reflector arrangement provides a larger radar cross section than a single dihedral corner reflector. For example, according to "Introduction to Radar Systems" by Merrill I. Skolnik (3rd edition, 2002, published by McGraw-Hill), pages 45-46, targets of similar size and shape, such as dihedral corner reflectors, separated by one, two, or four wavelengths will have their radar cross section increased significantly, from a minimum of zero to a maximum of four times the cross section of a single scatterer. Therefore, one or more dihedral / trihedral corner reflectors separated by wavelengths can be used in pavement markings to enhance the radar cross section of the pavement markings to radar transceivers.

[0293] There are many ways to construct a raised pavement marking with a combination dihedral / trihedral corner reflector. The above embodiments show only some preferred forms. Another embodiment is formed by four vertical RF reflective plates located on an RF reflective base plate, two of which are arranged parallel to each other and oriented north-south, and the other two are arranged parallel to each other and oriented east-west. From a top view, this embodiment resembles a tic-tac-toe board (but typically with a larger center square), and it includes four strict trihedral corner reflectors (one near each corner), as well as multiple combined dihedral / trihedral corner reflectors along the inner portion of each side and along each side of the center square. Various types of directional radar systems on vehicles, including side-looking, forward-looking, and even rear-looking radar transceivers, can see such an embodiment from all directions.

[0294] There are many ways to construct raised pavement markings with dihedral corner reflectors; the above embodiments illustrate only some preferred forms. One advantage of the above embodiments with combined dihedral / trihedral corner reflectors 2284, 2384, 1588, 1688, 1788, and 2888 is the ability to use forward-looking radar transceivers 1166, 1170, and 1198 to view upcoming combined reflector pavement markings, such as Fig.35A As shown. Fig.35A As shown, the vehicle 180 has side-looking radar transceivers 116, 117, and 119 mounted on the vehicle 180 for measuring the lateral distance between the combined two-sided / three-sided road surface markings 2284 and the radar transceivers 116, 117, and 119. However, the vehicle 180 also has forward-looking radar transceivers 1166, 1170, and 1198 for measuring the distance to the combined two-sided / three-sided road surface markings or combined reflector road surface markings 2284 in front of the vehicle 180. There are many advantages to knowing the distance between the vehicle 180 and the combined reflector road surface markings 2284. For example, one advantage is that multiple combined reflector road surface markings 2284 on one side will provide road curvature information along that side of the road / lane, thereby providing preview information about the upcoming road geometry. The lateral guidance control system can use this information to provide a better lateral controller for the vehicle 180 and reduce errors when entering and exiting a curve. Likewise, the combined reflector pavement marking 2284 on the other side of the vehicle 180 can provide road curvature information for that side of the road / lane, thereby providing redundancy in determining road geometry. Another advantage is that if the location of the combined reflector pavement marking 2284 mounted on the road is known, and the forward-looking radar transceivers 1166, 1170, and 1198 measure the forward distance to the combined reflector, processing this information will provide additional lateral and longitudinal distances, which will enable the onboard controller to determine the location of the vehicle 180 relative to the combined reflector pavement marking 2284 and the vehicle's location in the road 300.

[0295] Fig.35BA top view of forward looking radar transceiver 1198 observing a plurality of combined reflector pavement markings 2284 and measuring distances d1, d2, d3, d4, and d5 to combined reflector pavement markings 2284 is shown. Forward looking radar transceiver 1198 may be mounted on the left or right side of the bumper. Fig.35B A forward looking radar is shown mounted in the center of the front of the vehicle. One or more forward looking radar transceivers may be mounted on the front of the vehicle to view the combined reflector pavement markings 2284. The forward looking radar transceivers may also be looking slightly downward toward the combined reflector pavement markings 2284, or the beam width may be wide enough to view the combined reflector pavement markings 2284. A typical FMCW radar sensor, such as the Texas Instruments AWR1843AOP, can measure these distances, the speed to the marking, and the angle to the combined reflector pavement markings 2284. Fig.35B As shown, using the cosine law, the following formula can be used: α1 = arccos[(s m 2 +d2 2 -d1 2 ) / 2*s m *d2] determine the angle α1, where s m is the spacing 192 between the markers on the road 300, and d1 and d2 are the distances to the markers measured by the radar. Using the sine law, the right side of the vehicle ( Fig.35B The lateral distance x1 of the combined reflector pavement marking 2284 or lane marking on the side of the vehicle 180 where the radar sensor 116 is mounted. Using geometry and the laws of cosines and sines, the accurate lateral distance from the radar transceiver 1198 to the road line or combined reflector pavement marking 2284 can be determined by using many lane markings on both sides of the vehicle 180. Using similar geometry and the laws of sines, the longitudinal position of the vehicle 180 relative to the combined reflector pavement marking 2284 can also be determined. Using a Kalman filter or other filtering technique on all of these lateral distance measurements can provide a more accurate lateral distance and longitudinal position of the vehicle 180 in the lane 300.

[0296] Fig.35C A top view of a forward-looking radar transceiver 1198 is shown observing several combined reflector pavement markings 2284 around a curved section of road 300 and measuring the distance d to the combined reflector pavement markings 2284 on both sides of the vehicle. 11 d 12 d 13 d 14 d 15 d 16 and d 17 . To the right side of the vehicle ( Fig.35CThe distance d of the combined reflector road surface marking 2284 on the side where the radar sensor 116 is installed 11 -d 13 The distance d from the combined reflector pavement marking 2284 on the left side of the vehicle 14 -d 17 is shorter because the road 300 curves to the right. Likewise, if the road curves to the left, the opposite is true. In this example, the vehicle is traveling in the center of the road 300. If the vehicle were traveling closer to either side, the measurement results could be compensated.

[0297] Fig.35D An embodiment of using a combination pavement reflector within a road intersection is shown. Vehicle 180 with radar transceivers 116, 117 and 1198 (sensors mounted on the right, left and front, respectively) can choose to follow three paths when passing through the road intersection: (A) turn right, (B) go straight, or (C) turn left. If vehicle 180 follows path A, radar transceivers 116 and 1198 will track the combination pavement marking 5284 on the left side of the vehicle. The combination pavement marking 5284 is the same as the combination reflector pavement marking 2284, but specifies a bending area. In addition, the combination pavement marking 5284 is spaced closer to provide a more continuous RF reflection path and minimize any lateral position error from the required vehicle turning radius.

[0298] If vehicle 180 follows path B, radar transceivers 116, 117, and 1198 will be used to go straight through the intersection. Radar sensor 117 will track the combined reflector pavement marking 2284 in the middle of the lane, and then radar sensor 116 will receive pavement marking 580 to the right of the vehicle in the middle of the intersection. Pavement marking 580 is a three-sided two-sided reflector, similar to Fig.16A The road marking 580 shown is the same. And then the radar sensor 117 will receive the road marking 580 on the right side of the vehicle as the vehicle passes through the intersection, and then all radar transceivers 116, 117 and 1198 will sense the combined reflector road marking 2284 again.

[0299] If vehicle 180 follows path C, radar sensor 117 will pick up combined reflector pavement marker 5484 on the far left side of vehicle 180 and track those combined reflector pavement markers 5484 at a greater distance as the vehicle turns left. Once through the intersection, radar transceivers 116, 117, and 1198 will again track combined reflector pavement marker 2284. Combined reflector pavement marker 5484 is identical to combined reflector pavement marker 2284, but is spaced closer together. Likewise, combined reflector pavement markers 5684 and 5884 are installed on two additional curbs. Instead of installing combined reflector pavement markers 5284, 5484, 5684, and 5884, the curb pavement around the curve may be painted similar to Figures 15A-15C The unlabeled markings are designated as combination reflector pavement markings 2284 and are not shown for clarity. Other combinations of markings may also be used at intersections. For example, combination markings may be installed at intersections to increase redundancy for vehicle maneuvers.

[0300] Multiple radar sensors for continuous monitoring

[0301] Fig.36 Another embodiment shown utilizes multiple radar transceivers attached to the left and right sides of the vehicle 180 or multiple transmit / receive antennas using the same radar transceivers 1165 and 1175. As the vehicle 180 moves forward, the multiple radar transceivers 1165 on the right side of the vehicle 180 continuously see the road surface markings 284. Similarly, the multiple radar transceivers 1175 on the left side of the vehicle 180 can continuously see the road surface markings 1284 on the left side or driver's side of the vehicle 180. The spacing between the road surface markings 284 and 1284 is a distance d. m The array of radar transceiver arrays 1165 and 1175 covers a distance d on vehicle 180. total If the array spacing d of radar transceivers 1165 and 1175 is total Equal to or greater than the spacing d of pavement markings 284 and 1284, respectively. m , the lateral distance between the vehicle radar and the road surface markings can be measured continuously or quasi-continuously (discrete measurements are made frequently enough to be sufficiently close to continuous measurement).

[0302] InSAR (Interferometric Synthetic Aperture Radar) is a processing technique that uses radar images of a target collected by multiple radar transceivers or multiple receive / transmit antennas to determine lateral distance. InSAR can be applied to road markings. As a vehicle passes over a road marking, multiple radar images of the same area collected from similar locations at different times can be compared. The movement of the vehicle toward or away from the road marking can be measured in the time between images.

[0303] This embodiment may use a lateral controller that is the same or similar to the controller that has been shown to achieve satisfactory control using continuous marking references along the road. Fig.36 As shown, the spacing of pavement markings 284 and 1284 alternates in distance, so that the right pavement marking 284 can be seen by multiple radar transceivers 1165 half of the time, and the left pavement marking 1284 can be seen by multiple radar transceivers 1175 the other half of the time. By alternating the spacing, the number of radars in the radar array is reduced by half.

[0304] Fig.37 Schematic diagram of a radar sensor with multiple transmit / receive antennas is shown. This embodiment can be used with an array of radar transceivers 1165 and / or 1175. Radar processor 4260 activates frequency synthesizer 4160 to provide a suitable FMCW signal, which can be amplified by power amplifier / phase shifter 4130 and transmitted to the radar transceivers spaced apart by a distance d. ant The receiving antenna may be part of a paired antenna TX / RX (transmit / receive) combination array 4300 and receives return signals, which may be amplified by a low noise amplifier (LNA) 4150. The received signal is mixed with the transmitted signal by a modulator 4180. The signal output of the modulator 4180 is filtered by a filter block 4190 to provide a beat or instantaneous frequency from the modulator 4180. The filtered signal is sampled by an A / D converter 4120 and sent to a radar processor 4260 to calculate the measured distance, velocity, phase and / or amplitude. Fig.37 Only six TX / RX pairs are shown, but more pairs can be created. If only one pair is provided, more radar transceivers are needed to provide arrays 1165 and / or 1175. Radar processor 4260 can control power amplifier / phase shifter 4130 to turn on the various antennas in a time sequence to minimize interference between antenna pairs.

[0305] Fig.38 An embodiment of an array of radar transceivers 1165 and / or 1175 is shown, where six TX / RX antenna combinations 4308 and 4306 are installed in array 4302 to form a multi-antenna array of radar. The spacing 4304 of the six TX / RX combinations is a distance d ant , whose length may be equal to the width P of the pavement marking 284 w For example, if the width of the road marking P w is 0.1 m, then the distance d ant It can be equal to or less than 0.1 m. m is 3.0 m, then the total array length d totalIt can be 3.0 meters or longer. Fig.36 The alternating spacing marks shown, the array length d total will be 1.5 m or longer. If the array length is 3.0 m, 30 (d total / d ant =3.0m / 0.1m)TX / RX combination can provide continuous lateral distance for road markings.

[0306] in conclusion

[0307] The above embodiments, descriptions and terms are presented by way of illustration and example only and are not meant to be limiting. The scope of the present invention shall be determined solely by the following claims, claims filed in continuation patent applications or post-grant proceedings, and claims equivalent to these claims.

Claims

1. A road surface marking for use on a road on which vehicles travel in a direction of travel, wherein the road includes lane lines marked on a top surface of the road substantially parallel to the direction of travel, the road surface marking comprising: an optically reflective surface positioned and oriented to face oncoming traffic when the pavement marking is attached to a roadway; as well as A dihedral corner reflector comprising a longitudinal axis and two passive radar reflecting surfaces intersecting at the longitudinal axis, wherein the dihedral corner reflector is positioned and oriented such that, when the pavement marking is attached to a road, the longitudinal axis is substantially orthogonal to the optically reflecting surfaces and is substantially parallel to a direction of travel and to lane markings.

2. The pavement marking according to claim 1, wherein: The dihedral corner reflector is strictly dihedral.

3. The pavement marking according to claim 1, wherein: The two passive radar reflecting surfaces are at least approximately orthogonal.

4. The pavement marking of claim 1, further comprising: A substantially radar transparent material between the two passive radar reflecting surfaces of the dihedral corner reflector.

5. The pavement marking according to claim 4, wherein: The substantially radar transparent material comprises a material selected from the group consisting of polytetrafluoroethylene, polypropiolactone, polyvinyl chloride and acrylonitrile-butadiene-styrene.

6. The pavement marking according to claim 4, wherein: A substantially radar transparent material is adhered to the dihedral corner reflector with a substantially radar transparent adhesive.

7. The pavement marking of claim 1, wherein: The dihedral corner reflector includes two metal plates.

8. The pavement marking of claim 1, wherein: The dihedral corner reflector includes two surfaces coated with a radar reflective coating.

9. The pavement marking of claim 8, wherein: The radar reflective coating is paint.

10. The pavement marking of claim 9, wherein: The coating is a metallic coating.

11. The pavement marking of claim 8, wherein: The radar reflective coating is electroplated.

12. The pavement marking of claim 1, further comprising: One or more additional dihedral corner reflectors.

13. The pavement marking of claim 12, wherein: The total number of the dihedral corner reflectors is two.

14. The pavement marking of claim 13, wherein: The two dihedral corner reflectors form an inverted T-shape with a common vertical element.

15. The pavement marking of claim 13, wherein: The two dihedral corner reflectors are laterally offset from each other, located on opposite sides of the pavement marking, and oriented to reflect radar signals horizontally in opposite directions.

16. The pavement marking of claim 12, wherein: The total number of the dihedral corner reflectors is at least four.

17. The pavement marking of claim 16, wherein: A dihedral corner reflector is positioned along and adjacent each side of the pavement marking.

18. The pavement marking of claim 1, wherein: The pavement markings are snow-plowable.

19. The pavement marking of claim 1, wherein: One of the radar reflecting surfaces of the dihedral corner reflector is the top surface of the road.

20. The pavement marking of claim 1, wherein: The pavement marking is approximately 100 mm wide, 100 mm long and 25 mm high.

21. A road surface marking for use on a road on which vehicles travel in a travel direction, the road surface marking comprising: an optically reflective surface positioned and oriented to face oncoming traffic when the pavement marking is attached to the roadway; as well as A passive radar reflector characterized by a reflection direction from which a radar signal incident on the reflector is reflected back to a radar signal source at a maximum amplitude, wherein the pavement marking is configured to be attached to a roadway such that the reflection direction is partially upward from the roadway and substantially orthogonal to a direction of travel.

22. The pavement marking of claim 21, wherein: The road includes lane markings marked on a top surface of the road, the lane markings being substantially parallel to a direction of travel, and wherein the pavement markings are configured to be mounted such that the reflection direction is substantially orthogonal to the lane markings.

23. The pavement marking of claim 21, wherein: The radar signal source is a vehicle having a directional radar transmitter having a main beam lobe central axis directed laterally and downwardly from the vehicle, and wherein the reflector is positioned and oriented to produce a detectable return signal by reflecting an incident radar signal from the vehicle's radar transmitter directed laterally and downwardly toward the vehicle when the vehicle passes beside a pavement marking.

24. The pavement marking of claim 21 further comprising: A substantially radar transparent material between the reflector and the source.

25. The pavement marking of claim 24, wherein: The substantially radar transparent material is selected from the group consisting of polytetrafluoroethylene, polypropiolactone, polyvinyl chloride and acrylonitrile-butadiene-styrene.

26. The pavement marking of claim 24, wherein: The substantially radar transparent material is adhered to the reflector with a substantially radar transparent adhesive.

27. The pavement marking of claim 21, wherein: The reflector includes metal.

28. The pavement marking of claim 21, wherein: The reflector includes one or more surfaces coated with a radar reflective coating.

29. The pavement marking of claim 28, wherein: The one or more surfaces are painted surfaces.

30. The pavement marking of claim 29, wherein: The painted surface is coated with a metallic paint.

31. The pavement marking of claim 28, wherein: The one or more surfaces are plated surfaces.

32. The pavement marking of claim 21 further comprising: One or more additional radar reflecting reflectors.

33. The pavement marking of claim 32, wherein: The total number of reflectors is two.

34. The pavement marking of claim 33, wherein: The reflectors are horizontally offset from one another, located on opposite sides of the pavement marking, and oriented to reflect radar signals horizontally in opposite directions.

35. The pavement marking of claim 32, wherein: The total number of the reflectors is at least four.

36. The pavement marking of claim 35, wherein: One reflector is positioned along and adjacent to each side of the pavement marking.

37. The pavement marking of claim 21, wherein: The pavement markings are snow-plowable.

38. The pavement marking of claim 21, wherein: The pavement marking is approximately 100 mm wide, 100 mm long and 25 mm high.

39. The pavement marking of claim 21, wherein: The pavement marking further comprises: Radar reflective floor.

40. The pavement marking of claim 21, wherein: The reflector is a dihedral corner reflector.

41. A method of making a road surface marking for use on a road on which a vehicle travels in a travel direction, the method comprising: providing a visible reflective portion on a first outer side of the pavement marking, the visible reflective portion being configured to be viewed by a driver of the vehicle when the vehicle is traveling substantially toward the pavement marking; as well as A dihedral corner reflector is embedded in the pavement marking, the dihedral corner reflector including a longitudinal axis and two passive radio frequency reflecting surfaces intersecting at the longitudinal axis, wherein the longitudinal axis is substantially orthogonal to a first outer side of the pavement marking.

42. The method of claim 41, wherein the embedding step comprises: A substantially radar transparent material is placed between the two RF reflecting surfaces of the dihedral corner reflector.

43. The method of claim 42, further comprising: A substantially radar transparent material is attached to the two RF reflecting surfaces of the dihedral corner reflector.

44. The method of claim 43, wherein: The basic radar transparent material has the shape of a quarter circle.

45. The method of claim 43, wherein the attaching step comprises: A substantially radar transparent material is adhered to the two radio frequency reflecting surfaces of the dihedral corner reflector with a radar transparent adhesive.

46. ​​The method of claim 41, further comprising: Forming a dihedral corner reflector by an extrusion process; cutting the output of the extrusion process into segments; as well as One of the segments is selected to be embedded in the pavement marking.

47. The method of claim 41, further comprising: A dihedral corner reflector is formed by welding two metal pieces together.

48. The method of claim 41, further comprising: Dihedral corner reflectors are formed by bending flat pieces of metal.

49. The method of claim 41, further comprising: The dihedral corner reflector is formed by a process that includes applying a radio frequency reflective coating to one or more of the two passive radio frequency reflective surfaces.

50. The method of claim 41, further comprising: The dihedral corner reflector is formed by a process that includes electroplating an RF reflective coating on one or more of the two passive RF reflective surfaces.

51. A method of making a radar reflective pavement marking for use on a road on which a vehicle travels in a direction of travel, the method comprising: providing a visible reflective portion on a first outer side of the pavement marking, the visible reflective portion being configured to be visible to a driver of the vehicle when the vehicle is driven substantially toward the pavement marking; as well as A passive directional radar reflector is embedded within the pavement marking and is positioned and oriented to provide a maximum return signal by reflecting incident radar signals directed downwardly toward the pavement marking portion and also directed horizontally from a direction substantially orthogonal to both the direction of travel and a first outer side of the pavement marking.

52. The method of claim 51, wherein: The embedding step comprises: Place basic radar transparent material over the reflector.

53. The method of claim 52, further comprising: A primary radar transparent material is attached to the reflector.

54. The method of claim 53, wherein: The attaching step comprises: The base radar transparent material is adhered to the reflector with a radar transparent adhesive.

55. The method of claim 51, wherein: The passive directional radar reflector is a dihedral corner reflector.

56. The method of claim 51 further comprising: forming a radar reflector by an extrusion process; cutting the output of the extrusion process into segments; as well as Select one of the segments to embed into the pavement marking.

57. The method of claim 51 further comprising: The radar reflector is formed by welding metal pieces together.

58. The method of claim 51 further comprising: The radar reflector is formed by bending a metal piece.

59. The method of claim 51 further comprising: The radar reflector is formed by a process that includes applying a radio frequency reflective coating to one or more surfaces of the radar reflector.

60. The method of claim 51, further comprising: The radar reflector is formed by a process that includes electroplating a radio frequency reflective coating on one or more surfaces of the radar reflector.

61. A road on which a vehicle travels in a lane along a travel direction, the road comprising: A set of pavement markings discretely spaced apart along at least one side of a lane and attached to a top surface of a roadway, wherein each pavement marking in the set of pavement markings comprises a radar reflecting dihedral corner reflector including a longitudinal axis and two passive radar reflecting surfaces intersecting at the longitudinal axis, wherein the pavement marking is attached to the roadway with the longitudinal axis substantially parallel to a direction of travel.

62. The road of claim 61, further comprising: Lane markings are marked on the top surface of the road substantially parallel to the direction of travel to demarcate the boundaries of the lane, wherein the pavement markings are attached to the road with the longitudinal axes of the radar reflecting dihedral corner reflectors substantially parallel to the lane markings.

63. A road according to claim 62, wherein The pavement marking is attached to the road along one of the lane lines.

64. The road of claim 61, wherein: The distance between adjacent pavement markings in the pavement marking set is between about 0.3 meters and about 8 meters.

65. The road of claim 61, further comprising: a second set of pavement markings discretely spaced apart along a second side of the lane and attached to a top surface of the roadway, wherein each pavement marking in the second set of pavement markings comprises a radar reflecting dihedral corner reflector having a longitudinal axis, the radar reflecting dihedral corner reflector comprising two radio frequency reflecting surfaces that are orthogonal to each other and intersect at the longitudinal axis, wherein the pavement markings are attached to the roadway with the longitudinal axis substantially parallel to the direction of travel.

66. The road of claim 61, wherein: The road is a multi-lane road.

67. The road of claim 61, wherein: The road is a two-way road.

68. The road of claim 61, wherein: The set of pavement markings encodes information about the road.

69. A road according to claim 68, wherein The road further comprises: A generally straight section of road; and Curved road, The information encoded in the road surface marking set includes data identifying whether a road segment is straight or curved.

70. The road of claim 61, further comprising: A rumble strip depression is formed in the surface of the roadway, wherein at least some of the pavement markings of the set of pavement markings are installed in the depression.

71. A driving surface on which a vehicle travels along a path in a driving direction, the driving surface comprising: A set of pavement markings discretely spaced along one side of a path and attached to a driving surface, wherein each pavement marking A passive radar reflector is included that is characterized by a reflection direction from which a radar signal incident on the reflector is reflected back to a radar signal source at a maximum amplitude, wherein the pavement marking is attached to a driving surface such that the reflection direction is upward from a portion of the driving surface and is substantially orthogonal to the direction of travel.

72. A driving surface according to claim 71, wherein: The driving surface is a road.

73. A driving surface according to claim 72, wherein: The road is a multi-lane road or a two-way road.

74. A driving surface according to claim 71, wherein: The driving surface is a parking lot, a transport station, a freight terminal, a loading and unloading area or a warehouse.

75. A driving surface according to claim 72, wherein: The path is a roadway, and the driving surface further comprises: Lane markings, which are substantially parallel to the direction of travel, are marked on the driving surface to demarcate the boundaries of the lane, wherein the road surface markings are attached to the road so that the reflection direction is substantially orthogonal to the lane markings.

76. A driving surface according to claim 75, wherein: The pavement marking is attached to the road along one of the lane lines.

77. A driving surface according to claim 71, wherein: The distance between adjacent pavement markings in the pavement marking set is from about 0.3 meters to about 8 meters.

78. The driving surface of claim 71, further comprising: a second set of pavement markings discretely spaced along a second side of the path and attached to a top surface of the driving surface, wherein each pavement marking in the second set of pavement markings A passive radar reflector characterized by a reflection direction from which a radar signal incident on the reflector is reflected with maximum amplitude back to a radar signal source, wherein the pavement marking is attached to a driving surface such that the reflection direction is upward from the driving surface portion and is substantially orthogonal to the direction of travel.

79. A driving surface according to claim 71, wherein: The set of pavement markings encodes information about the driving surface.

80. The driving surface of claim 71, wherein: The radar reflector is a dihedral corner reflector.

81. A radar transceiver configured for installation in or on a land vehicle and for use with radar-reflective pavement markings distributed along a roadway on which the land vehicle is drivable, the radar transceiver comprising: a radar transmitter configured to transmit a radar signal having a transmit beam pattern having a center direction of maximum transmission; as well as A radar receiver configured to receive a radar echo reflection signal, wherein the radar receiver is configured to have a receiving beam pattern having a maximum receiving center direction, Wherein, the radar transceiver is configured to be installed in or on a land vehicle, so that when the radar transceiver is installed on or in a land vehicle, the maximum transmission center direction is downward and sideways to the land vehicle, and so that when the radar transceiver is installed on or in a land vehicle, the maximum reception center direction is upward and sideways to the land vehicle.

82. The radar transceiver according to claim 81, wherein: The radar transceiver operates in a frequency range within a range of about 300 MHz to about 1 THz.

83. The radar transceiver according to claim 82, wherein: The radar transceiver operates in a frequency range of about 77 GHz to about 81 GHz.

84. The radar transceiver of claim 81, wherein: The radar transceiver is a frequency modulated continuous wave radar transceiver.

85. The radar transceiver of claim 81, wherein: The radar transceiver is an ultra-wideband pulse radar transceiver.

86. The radar transceiver of claim 81, wherein: The type of radar transceiver is selected from the group consisting of dual frequency phase difference, multi-frequency radar, multi-frequency phase radar, orthogonal frequency division multiplexing, frequency shift keying, digital code modulation, phase modulated continuous wave, multiple input multiple output, polarization, dual polarization, single pulse, noise radar and interferometric synthetic aperture radar.

87. The radar transceiver of claim 81, wherein: The radar transceiver is monostatic.

88. The radar transceiver of claim 81, wherein: The radar transceiver is bi-static.

89. The radar transceiver according to claim 81, wherein: The radar transceiver includes an antenna array.

90. The radar transceiver of claim 81, wherein: The radar transmitter is configured to transmit a polarized radar signal.

91. The radar transceiver of claim 90, wherein: The radar receiver is configured to detect a radar echo reflection signal according to its polarization.

92. The radar transceiver of claim 81, wherein: The radar transceiver is configured for placement within a front bumper of a vehicle.

93. The radar transceiver according to claim 81, wherein: The radar transceiver is packaged in the vehicle light assembly.

94. The radar transceiver of claim 81, further comprising: A signal processor coupled to the radar receiver is configured to receive a signal based on the radar echo reflection signal and is configured to determine a path length from the radar transceiver to the radar reflecting road surface marking.

95. The radar transceiver of claim 94, wherein: The signal processor is configured to process only a portion of the radar echo reflection signal received within a window corresponding to an expected range of a reflecting target.

96. The radar transceiver of claim 94, wherein: The signal processor is configured to perform frequency conversion on the radar echo reflection signal.

97. The radar transceiver according to claim 81, wherein: The radar reflective pavement marking includes a dihedral corner reflector.

98. A method of installing a radar reflective pavement marking on a road on which a vehicle travels in a direction of travel, wherein the radar reflective pavement marking comprises a radio frequency reflective dihedral corner reflector having two radar reflective surfaces intersecting along a longitudinal axis, the method comprising: A plurality of the radar reflective pavement markers are attached to the roadway in an orientation such that a longitudinal axis of each radar reflective pavement marker is substantially aligned with a direction of travel and such that the longitudinal axes of the plurality of radar reflective pavement markers define an ideal path of a vehicle on the roadway along the direction of travel.

99. A method of installing radar reflective pavement markings on a driving surface on which a vehicle is driven, the vehicle having a directional radar transmitter having a main beam lobe central axis directed to the side and downward from the vehicle, the method comprising: A plurality of such radar reflective pavement markings are attached to a driving surface with each directional radar reflector positioned and oriented to give a maximum or high return signal by reflecting incident radar signals from a vehicle's radar transmitter directed to the side and downward of the vehicle.

100. The method of claim 99, wherein: The directional radar reflector is a dihedral corner reflector.

101. A vehicle for use on a road along which a plurality of pavement markings have been installed, each pavement marking including a radar reflector, the vehicle comprising: a radar transceiver mounted to the vehicle, wherein the radar transceiver is characterized by a beam pattern having a center pointing downward and aimed away from the side of the vehicle so that reflections from radar reflectors embedded in the pavement markings can be detected as the vehicle moves forward over pavement markings on the side of the vehicle; as well as A processor is operatively coupled to the radar transceiver and configured to determine a path length from the radar transceiver to a radar reflector embedded in the pavement marking based on the reflection.

102. The vehicle of claim 101, wherein: The beam pattern having the center aimed downward and laterally from the vehicle is a first beam pattern having a first center aimed downward and in a first lateral direction from the vehicle, wherein the pavement marking is a first pavement marking on a first side of the vehicle, wherein the radar transceiver is further characterized by a second beam pattern having a second center aimed downward and in a second lateral direction from the vehicle such that a reflection from a second radar reflector embedded in the second pavement marking is detected when the vehicle moves past the second pavement marking, wherein the second lateral direction is approximately horizontally opposite to the lateral direction, and wherein the second pavement marking is located on an opposite side of the vehicle from the first pavement marking.

103. The vehicle of claim 101, wherein: the radar transceiver is a first radar transceiver, the beam pattern having the center aimed downwardly and laterally from the vehicle is a first beam pattern having a first center aimed downwardly from the vehicle and in a first lateral direction, wherein the pavement marking is a first pavement marking located on a first side of the vehicle, the vehicle further comprising: a second radar transceiver mounted to the vehicle, wherein the second radar transceiver is characterized by a second beam pattern having a second center aimed downwardly from the vehicle and in a second lateral direction such that reflections from the radar reflector embedded in the second pavement marking are detected by the pavement marking on the side of the vehicle as the vehicle moves forward over the second pavement marking.

104. The vehicle of claim 101, further comprising: An external light fixture assembly, wherein the radar transceiver is located within the external light fixture assembly.

105. The vehicle of claim 101, further comprising: The front bumper, in which the radar transceiver is located.

106. The vehicle of claim 101, wherein: The processor is configured to perform one or more of a lane departure warning function, a lane keeping function, and a lane centering assist function based on a path length from the radar transceiver to a radar reflector embedded in a road surface marking.

107. The vehicle of claim 101, further comprising: A lateral locating system independent of the radar transceiver, wherein the radar transceiver and the processor form a redundant lateral locating system.

108. The vehicle of claim 101, wherein: The vehicle is at least partially autonomously driven, and wherein lateral positioning of the vehicle is performed based at least in part on a path length from a radar transceiver to a radar reflector embedded in a road surface marking.

109. The vehicle of claim 101, wherein: The radar transceiver is also configured to perform blind spot detection.

110. The vehicle of claim 101, wherein: The radar reflector is a dihedral corner reflector.

111. A method for determining the lateral position of a land vehicle along a path having radar-reflecting pavement markings distributed along the path in a direction of travel of the vehicle, the method comprising: transmitting a radar transmission signal from a land vehicle downwardly and laterally toward a pavement marking mounted on or near the roadway as the vehicle passes over the pavement marking; receiving, at the land vehicle, a radar reflection signal from a radar reflector embedded in the pavement marking as the vehicle passes over the pavement marking; as well as The distance between the land vehicle and the road marking is determined based on the radar transmission signal and the radar reflection signal.

112. The method according to claim 111, wherein: The transmitting, receiving and determining steps are repeated for each radar-reflecting road surface marking passed by the vehicle.

113. The method according to claim 111, wherein: The transmitting step is periodically repeated with a period selected within the range from about 0.5 milliseconds to about 1 second.

114. The method of claim 111, wherein: As the vehicle travels along the path, radar reflects the road surface markings along one side of the vehicle.

115. The method of claim 111, wherein: The path is one lane of a multi-lane road, and wherein the radar-reflecting road surface markings are distributed along a line delimiting one side of the path.

116. The method of claim 115, wherein: The path is a lane of a multi-lane road, and wherein the radar-reflective road surface markings are distributed along a line delimiting a side of a lane adjacent to the lane corresponding to the path of the vehicle.

117. The method of claim 111, further comprising: The radar reflection signal is filtered according to a range of expected distances between the land vehicle and the road surface markings.

118. The method of claim 111, further comprising: Perform frequency conversion on the radar reflected signal.

119. The method of claim 111, further comprising: The distance is used to laterally guide or assist in steering the vehicle to follow the path.

120. The method of claim 111, further comprising: If the distance exceeds a maximum threshold or is less than a minimum threshold, a warning is issued to the driver of the vehicle.

121. The method of claim 120, further comprising: If the distance exceeds a maximum threshold or falls below a minimum threshold, a warning is issued outside the vehicle.

122. The method of claim 121 wherein the warning to the exterior of the vehicle comprises flashing flashing lights.

123. The method of claim 111, further comprising: One or more of a lane centering assist function and a lane keeping function are performed based on a distance between the land vehicle and a road surface marking.

124. The method of claim 111, wherein: The vehicle comprises a lateral positioning system independent of the method of claim 1, the method further comprising: The distance is used in conjunction with an independent lateral positioning system to improve lateral position determination.

125. The method of claim 111, wherein: The vehicle comprises a lateral positioning system independent of the method of claim 1, the method further comprising: Use the distance to calibrate an independent lateral positioning system.

126. The method of claim 111, wherein: Radar reflective pavement markings include dihedral corner reflectors.

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