Vehicle guidance using a downward side-looking radar to detect null targets on a driving surface

Abstract

An apparatus determines a lateral position of a land vehicle on a pathway on which one or more targets are distributed on a surface of the pathway in a direction of travel. The targets have different radar-reflectivity than the surface. The apparatus comprises a radar sensor and a processor. The radar sensor is mounted to the vehicle and configured to transmit a radar signal having a beam pattern center aimed downward from the vehicle toward the surface of the pathway and sideways from the vehicle generally perpendicular to the direction of travel. The radar sensor is configured to detect radar from the pathway and to detect a substantial absence of reflections from the targets. The processor is operatively connected to the radar sensor and configured to determine a lateral position of the vehicle from a boundary between the surface of the pathway and at least one of the targets.

Description

VEHICLE GUIDANCE USING A DOWNWARD SIDE-LOOKING RADAR TO DETECT NULL TARGETS ON A DRIVING SURFACE RELATED APPLICATIONS

[0001] This application claims priority to United States provisional patent application no.63 / 761,223, filed February 21, 2025, entitled "Vehicle Guidance Using a Downward Side-Looking Radar With Road Surface Null Targets on or Near the Driving Surface," the entire disclosure of which is hereby incorporated by reference herein.

[0002] This application is also related to the following commonly owned patents and patent applications, the entire disclosures of which are incorporated by reference herein: (1) U.S. Patent No. 11,400,956; (2) U.S. Patent No. 12,077,179; (3) Int’l Patent Appl. No. PCT / US 2023 / 028710 [published as Int’l Patent Appl. Publ. No. WO 2024 / 030302 Al on February 8, 2024); [4) Int’l Patent Appl. No. PCT / US2024 / 027899 (published as Int’l Patent Appl. Publ. No. WO 2024 / 233415 Al on November 14, 2024); (5) Int’l Patent Appl. No. PCT / US2024 / 050650, filed October 10, 2024 [published as Int’l Patent Appl. Publ. No. WO 2025 / 080760 Al on April 17, 2025); and (6) U.S. Provisional Patent Appl. No. 63 / 683,882 filed August 16, 2024.TECHNICAL FIELD

[0003] The field of this disclosure relates generally to vehicle guidance and control. More specifically, this disclosure relates to the use of radar for the lateral guidance or control of a land vehicle.BACKGROUND INFORMATION

[0004] Road lines and pavement markers are commonly deployed on or near a driving surface to demark road or lane boundaries. Curbs, concrete barriers, and other roadside objects also sometimes demark the edge of a road or lane.

[0005] Current technology for lateral vehicle guidance or assistance, e.g., lidar and vision systems, has high resolution and provides good lateral guidance and control under favorable environmental conditions, but does not perform well in snow, fog, smoke, heavy rain, and50066 / 0601 Page 1 of 41other inclement weather. Vision systems do not work well in different lighting conditions. While lidar may work well in different lightning conditions, it is substantially more expensive.

[0006] Radar is known to work well in other contexts (inclement weather, darkness, and low-light). Typically, automotive radar systems detect obstacles in the front, side, or rear of the vehicle for applications such as blind-spot detection, adaptive cruise control, automatic emergency braking, and cross-traffic alerts.SUMMARY OF DISCLOSED EMBODIMENTS

[0007] According to one embodiment, an apparatus determines a lateral position of a land vehicle on a pathway on which one or more discrete or continuous targets are distributed on a surface of the pathway in a direction of travel of the vehicle. The targets comprise material that has different radar reflectivity than the surface of the pathway where no target materials are present. The apparatus comprises a radar sensor and a processor. The radar sensor is mounted to the vehicle and configured to transmit a radar signal having a beam pattern center downward from the vehicle toward the surface of the pathway and sideways from the vehicle generally perpendicular to the direction of travel of the vehicle. The radar sensor is further configured to detect one or more reflections of the radar signal from the pathway and to detect a substantial absence of reflections of the radar signal from the at least one of said one or more discrete or continuous targets. The processor is operatively connected to the radar sensor and configured to determine a lateral position of the vehicle from said one or more targets.

[0008] According to another embodiment, a method guides or assists in guiding a vehicle along a pathway having a surface and one or more targets on the surface. The targets have radar reflectivity characteristics different from the surface. The method comprises directing radar waves from the vehicle downward and to a side of the vehicle, receiving reflections of the radar waves from the pathway, receiving either no detectable reflections of the radar waves from said the targets or reduced reflections of the radar waves from the targets, and50066 / 0601 Page 2 of 41processing the reflections of the radar waves to determine distances between the vehicle and at least one of said one or more targets.

[0009] According to another embodiment, an apparatus guides a land vehicle along a pathway on which target material with different reflective signals than the pathway is distributed along the pathway in a direction of vehicle travel. The apparatus comprises means for radiating downward and sideways from the vehicle, a radar transmit signal having a beam center aimed partially downward and sideways from the land vehicle toward one or more targets and a surface of the pathway. The apparatus also comprises means for detecting reduced reflections or an absence of detectable reflections from the target material. The apparatus also comprises means for receiving reflections of the radar transmit signal as one or more received signals reflected from a surface of the pathway where no target material is present. The apparatus also comprises means for processing the received reflections to determine a position of the land vehicle relative to at least one edge of target material and the pathway.

[0010] Optionally, the radar sensor may comprise, for example, a FMCW (frequency modulated continuous wave) radar sensor, a UWB radar sensor, a terahertz radar sensor, 4D imaging radar, a UWB (ultra-wide band) impulse radar sensor, a monopulse radar sensor, or a multi-frequency radar sensor. The radar sensor may be part of a 4D imaging radar system. The radar sensor may, for example, operate in a terahertz frequency band. Optionally, the radar sensor comprises a plurality of antennas, and either the transmitting / directing step, the receiving step, or both is performed with multiple antennas.

[0011] In some embodiments, the target is continuous and selected from a group consisting of a painted line, a metallic painted line, a thermoplastic painted line, a metallic tape, a metallic strip, a metallic mesh, an radar-absorbent painted line, an radar-absorbent painted strip, and a pavement marker with lower radar-reflectivity than the surface of the pathway, and a frequency-selective surface.

[0012] In some embodiments, the targets or target materials are discrete and selected from a group consisting of raised pavement markers, markers in slots, markers in grooves,50066 / 0601 Page 3 of 41bot dots, rumble strips, snow plowable markers, radar-absorbent raised pavement markers, short segments of painted lines, short segments of a metallic painted lines, short segments of thermoplastic painted lines, short segments of metallic tape, short segments of metallic strips, short segments of metallic meshes, short segments of an radar-absorbent painted lines, short segments of radar-absorbent painted strips, pavement markers with lower radar-reflectivity than the surface of the pathway, and frequency-selective surfaces.

[0013] In some embodiments, the pathway is one of a road, street, highway, lawn, field, open terrain, room in a building, manufacturing floor, parking lot, warehouse, or depot.

[0014] An incident angle of the radar signal from the radar sensor upon the targets may be less than 90 degrees.

[0015] Optionally, a lateral position of a target is computed from a discontinuity between the target and the surface of the pathway based on different radar reflections received at the radar sensor, wherein the discontinuity represents an edge of the target. Optionally, the method comprises detecting such an edge or discontinuity, and the apparatus may comprise a signal edged detector, such as a differentiator.

[0016] Optionally, the targets are arranged along a line representing the boundary of the pathway or of a lane within the pathway.

[0017] Optionally, the radar beam, waves, or signal has a narrow beamwidth. Optionally, the method may further comprise sweeping the beam laterally across the target.

[0018] Optionally, the method further comprises controlling, based on the distances, the steering of the vehicle so as to follow alongside the targets.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 shows a front view of a radar transceiver mounted on a vehicle scanning surface targets on the road, according to one embodiment.

[0020] Figure 2 is a top view of a multiple-lane highway with vehicles using radar transceivers, according to one embodiment.50066 / 0601 Page 4 of 41

[0021] Figure 3A is a side view of a radar transceiver sweeping in elevation of road surface targets, according to one embodiment.

[0022] Figure 3B is a diagram of a radar transceiver received amplitude vs. swept elevation angles, according to one embodiment.

[0023] Figure 3C is a diagram of the amplitude vs. distance measured from the radar to a painted line, according to one embodiment.

[0024] Figure 4A is a top view of a radar transceiver with a wide azimuth beam viewing a painted line, according to one embodiment.

[0025] Figure 4B is a side view of a radar transceiver with a narrow elevation beam vertically sweeping a painted line along the road surface, according to one embodiment.

[0026] Figure 5 is a block diagram of a radar transceiver with multiple transmit and receive channels that provide a narrow beam, vertically sweeping a painted line along the road surface, according to one embodiment.

[0027] Figure 6A shows a top view of radar transceivers with wide-azimuth beams viewing a painted line, according to one embodiment.

[0028] Figure 6B is a side view of radar transceivers with narrow elevation beams viewing a painted line, according to one embodiment.

[0029] Figure 7 is a block diagram of a radar transceiver with multiple transmit / receive antennas, according to one embodiment.

[0030] Figure 8 is a block diagram of a radar transceiver with multiple transmit / receive antennas, according to another embodiment.

[0031] Figure 9A is a side view of the radar signals reflecting at an angle from a material that is smooth and metallic-like.50066 / 0601 Page 5 of 41

[0032] Figure 9B is a side view of the radar signals reflecting at an angle from another material that is not smooth, according to one embodiment.

[0033] Figure 9C is a side view of the radar signals reflecting at an angle from another rough material, according to one embodiment.

[0034] Figure 10A is a side view of the radar signals reflecting directly at the material, which is smooth and metallic-like, according to one embodiment.

[0035] Figure 10B is a side view of the radar signals reflecting directly at the material, which is not smooth, accordingto one embodiment.

[0036] Figure 10C is a side view of the radar signals reflecting directly at a rough material, according to one embodiment.

[0037] Figure 11 is a diagram of the roughness of the surface vs. the incident angle of the radar transceiver, accordingto one embodiment.

[0038] Figure 12A is a side view of the radar signals reflecting at an angle from the road surface and from a material that is smooth and metallic-like, according to one embodiment.

[0039] Figure 12B is a side view of the radar signals reflecting at an angle from the road surface and from a material that is smooth and has a low dielectric constant, according to one embodiment.

[0040] Figure 12C is a side view of the radar signals reflecting at an angle from the road surface and from a material that is smooth and somewhat metallic-like, according to one embodiment.

[0041] Figure 12D is a side view of the radar signals reflecting at an angle from the road surface and from a material that is radar-absorbent, according to one embodiment.

[0042] Figure 13A is an isometric diagram of a conventional pavement marker, according to one embodiment, accordingto one embodiment.50066 / 0601 Page 6 of 41

[0043] Figure 13B is a top view of a segment of a road on which conventional pavement markers have been placed, according to one embodiment, according to one embodiment.

[0044] Figure 14A is a cross-sectional view of a cavity in or below a driving surface, according to one embodiment.

[0045] Figure 14B is a top view of a section of a road in which cavities of Figure 14A have been arranged, according to one embodiment.

[0046] Figure 14C is a top view of a section of a road in which long cavities of Figure 14A have been arranged, according to another embodiment.

[0047] Figure 15A is a cross-sectional view of a pavement marker in a cavity below a driving surface, illustrating a reflection from / to a radar transceiver, according to one embodiment.

[0048] Figure 15B is a top view of a section of a road in which pavement markers of Figure 15A have been arranged, according to one embodiment.

[0049] Figure 15C is a top view of a section of a road in which pavement markers of Figure 15A have been arranged, according to another embodiment.

[0050] Figure 16 is an isometric view of a snow-plowable pavement marker, according to one embodiment.

[0051] Figure 17A is a block diagram of a radar transceiver, according to one embodiment.

[0052] Figure 17B is a block diagram of a radar transceiver combined with other sensors, according to one embodiment.

[0053] Figure 18 is a block diagram of a radar-based LDW / LKA / LKS system for a vehicle, according to one embodiment.50066 / 0601 Page 7 of 41

[0054] Figure 19 shows a front view of multiple radar transceivers scanning road-surface targets mounted at the front center and sides of the vehicle, along with GNSS, IMU, and vision sensors, according to one embodiment.

[0055] Figure 20 is a block diagram of radar transceivers combined with other sensors using various fusion techniques, according to one embodiment.

[0056] Figure 21 is a top view of a vehicle equipped with radar transceivers and inertial measurement units on a road having pavement markers and painted lines, according to one embodiment.

[0057] Figure 22 is a block diagram of a system that combines multiple detection, guidance, and / or control systems, including a radar-based lateral positioning system, according to one embodiment.

[0058] Figure 23 is a block diagram of a radar-based LDW / LKA / LKS system for a vehicle, according to another embodiment.

[0059] Figure 24 is a block diagram of a radar-based autonomous lateral control system for a vehicle, according to another embodiment.DETAILED DESCRIPTIONPreliminary Notes

[0060] Example embodiments are described below with reference to the accompanying drawings. Unless otherwise expressly stated, the sizes, positions, etc., of components, features, elements, etc., as well as any distances therebetween, are not necessarily to scale, and may be disproportionate and / or exaggerated for clarity.

[0061] The embodiments described herein are merely examples, set forth by way of illustration only and not limitation. Those skilled in the art will recognize, in light of the teachings herein, that there are alternatives, variations, and equivalents to the example embodiments described herein and their component parts. For example, other embodiments are readily possible, variations can be made to the embodiments described50066 / 0601 Page 8 of 41herein, and equivalents may exist for the components, parts, or steps that make up the described embodiments.

[0062] For the sake of clarity and conciseness, certain aspects of components or steps of certain embodiments are presented without undue detail where such detail would be apparent to those skilled in the art in light of the teachings herein and / or where such detail would obfuscate an understanding of more pertinent aspects of the embodiments.

[0063] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a,” "an” and "the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be recognized that the terms "comprise,” "comprises,” "comprising,” "include," "includes,” "including,” "has,” "have,” and "having,” when used in this document, are open-ended and specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range, as well as any sub-ranges therebetween. Unless indicated otherwise, terms such as "first,” "second,” etc., are only used to distinguish one element from another and not to imply any relative order, placement, or ranking. For example, one element could be termed a "first element,” and similarly, another element could be termed a "second element,” or vice versa. The same is true of labels like (a), (b), (c); (A), (B), (C); or (1), (2), (3), etc. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0064] Unless indicated otherwise, the terms "about,” "thereabout,” "substantially,” "approximately,” etc. mean that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. Depending on context, the term "substantially” may alternatively mean to a large degree or extent.50066 / 0601 Page 9 of 41

[0065] Spatially relative terms, such as "right," left,” "below,” "beneath,” "lower,” "above,” and "upper," and the like, may be used herein for ease of description to describe one element’s or feature’s relationship to another element or feature, as illustrated in the drawings. It should be recognized that the spatially relative terms are intended to encompass different orientations in addition to the orientation depicted in the drawings. For example, if an object in the figures is turned over, elements described as "below” or "beneath” other elements or features would then be oriented "above” the other elements or features. Thus, the term "below" can, for example, encompass both an orientation of above and below. An object may be otherwise oriented e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

[0066] Unless clearly indicated otherwise, all functional or operative connections may be direct or indirect. Similarly, unless clearly indicated otherwise, all physical connections may be rigid or non-rigid, permanent or temporary, direct or indirect {e.g., via intermediary components).

[0067] Like numbers refer to like elements throughout. Thus, the same or similar numbers may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, even elements that are not denoted by reference numbers may be described with reference to other drawings. Additionally, the drawings may include non-essential elements that are included only for the sake of thoroughness. These non-essential elements may be removed entirely or left only in outline form if drawing changes are desired to create greater clarity.

[0068] Not every feature shown in every drawing is labeled with a reference number, even though the same feature may be labeled with a reference number on other drawings. Reference numbers have been omitted where they are believed to unnecessarily clutter a drawing. However, all rights are reserved to add reference numbers to the drawings to clarify aspects of the embodiments. Moreover, some views omit some features shown in other views. Finally, the drawings sometimes illustrate variations between drawings, even when those drawings are intended to depict the same embodiment.50066 / 0601 Page 10 of 41Downward Side- Looking Radar(s) Viewing Road Surface Target Materials

[0069] Figure 1 shows an embodiment with a downward side-looking radar transceiver 117 attached to the side of a vehicle 180 and viewing objects on the road surface 300. Radar signals, 1119 and 1119’ of the radar transceiver 117 are aimed downward towards the ground and to the side of the vehicle 180. For this embodiment, two radar signals 1119 and 1119’ are shown in Figure 1 for the radar transceiver 117. The radar transceiver 117 receives reflected signals 1118 off of a road surface 300, which is typically concrete, smooth asphalt, or worn asphalt, and is defined as a rough surface with radar-reflectivity from the road surface, but a much lower reflective signal is received from the painted line 1445, which is smooth and may contain metallic materials. Painted lines are on the majority of roads, pathways, and highways to indicate the boundaries of the lanes within which vehicles can travel. The radar transceiver 117 transmits a signal 1119’ that reflects off the painted line, but a small portion may be reflected back toward the transceiver 117. The larger portion of the transmit signal 1119’ is reflected off a smooth surface as a radar reflection signal 1120 to the side, away from the transceiver 117, like a mirror surface. Low return reflectivity from the painted line surface 1445 is noted as a null condition.

[0070] The lateral distance may be determined from the boundary between the road surface 300 and the painted line 1445 by receiving radar signals 1118, but receiving little to no signals from the painted line. If an oblique-incident radar beam is swept over the surface from the road surface 300 before the painted line 1445 i.e., on the near side of the painted line 1445 with respect to the vehicle 180), on the painted line 1145, and on the far side of the painted line 1445, the radar received signals will be higher in amplitude from the road surface 300 versus the painted line 1445. The radar transceiver 117 (or an operably connected processor) can measure the distance at either boundary (near or far) between the painted line 1445 and the road surface 300. The near and far distance can be averaged. Alternatively, a single approximate distance can be measured corresponding to the painted line overall and its null. The painted line 1445 will provide no or minimal reflected radar signals back to the radar transceiver 117; however, the road surface 300 will provide reflected radar signals back to the radar transceiver 117. With reflections from the road50066 / 0601 Page 11 of 41surface, the radar transceiver 117 can measure the distance. The lateral distance from the painted line 1445 to the vehicle can be determined from the radar transceiver 117's mounting geometry and the measured distance.

[0071] Figure 2 is atop view of a multi-lane highway 3000 with two vehicles 180 and 182 in the highway lanes between road lines 1445, 1447, 1448, and 1449. The gap and line segments on opposite sides of a lane (e.g., lines 1447) can be offset so that wherever there is a gap in one line, there is a line segment in the other line so that a continuous lateral distance can be measured by the radar transceivers 116 and 117. Providing radar transceivers 116 and 117 on both sides of the vehicle 180 allows them to track painted lines 1445 and 1447 on both sides of the vehicle.

[0072] The radar transceiver 116 on the vehicle 180 may also see the line 1445 in the far-right lane with the radar beam 1108. An onboard lateral guidance controller in the vehicle 180 can decide to remain in the same highway lane and follow the painted line 1447 on the left side of the vehicle 180, or execute a lane-change maneuver and follow the painted lines 1448 on the far-left side of the vehicle 180. The vehicle 182, which uses similar radar transceivers 116 and 117, can follow the same strategy. Another sensor, not shown (e.g., radar, vision, ultrasonic, or lidar), or the same radar transceivers 116 and 117 with vehicledetection capabilities (in addition to providing lateral distance), can determine whether another vehicle is in the left or right lane and enable a lane-changing maneuver. If the antennas on the radar transceiver 117 mounted on left sides of the vehicles 180 and 182 are left-hand circular polarized and antennas on the radar transceiver 116 mounted on the right side of the vehicles 180 and 182 are right-hand circular polarized, then radar signals from radar transceiver 117 on the vehicle 180 will not interfere, because of the different polarizations, with radar signals from the radar transceiver 116 on the vehicle 182 as the vehicle 182 passes by the vehicle 180 (or vice versa).

[0073] Figures 3A-3C show an embodiment in which the radar transceiver 117 transmits signals to the road surface 300 and to the painted line 1445, and receives reflected signals from the road surface 300 but little to no signals from the painted line, creating a null condition. In Figure 3A, the radar transceiver 117 transmits narrow beams 1101 and 110250066 / 0601 Page 12 of 41towards the painted line 1445. The radar transceiver 117 can use multiple TX / RX [transmit / receive antennas to produce multiple beams, or a single beam can be used and swept vertically across the road surface 300 before the painted line 1445 to after the painted line 1445 (i.e., laterally from the near side to the far side of the painted line with respect to the vehicle] or vice versa (in the opposite direction]. Figure 3B shows the approximate amplitude of the received signals for swept angles from 30 to 55 degrees. There will be a region approximately d3 wide along the painted line 1445 where little to no return radar signals are received, a null situation. The distances dl and d2 are distance measurements from the boundary between the road surface 300 and the front of the painted line 1445, and the boundary between the back of the painted line 1445 and the road surface 300, respectively. If the geometry of the radar transceiver 117 mounted on the vehicle is taken into account, distances dl and d2 represent the lateral distances to the radar transceiver 117, where d2=dl+d3. Figure 3C shows the amplitude of the received radar signals vs. the lateral distances from the radar transceiver 117. In the null condition of the painted line, the distance may not be measured because there is very little received signal, but it can be estimated from the distances measured from the radar signals' boundaries of the painted line 1145 and the road surface 300. A useful distance measurement for controlling a vehicle may be dl alone, d2 alone, or some combination of dl and d2 (e.g., their average], or some approximation to any of the foregoing.Radar Beam

[0074] Figures 4A-4B show an embodiment in which the radar transceiver 117 has a wide azimuth beam but a narrow elevation beam. Figure 4A shows a top view of the radar transceiver 117 transmitting a wide-azimuth beam 1107 towards the painted line 1145, which yields a strong return from the road surface 300. The beam 1107 can be narrow or wide in the azimuth direction. Figure 4B shows the side view of the radar transceiver 117, with the beam 1107 showing a narrow beam in the elevation direction. The radar transceiver can use a single TX / RX antenna swept vertically by electronic (beam steering] or mechanical [servo-controlled] means, or multiple TX / RX antennas spaced vertically and oriented similarly to the painted line 1445.50066 / 0601 Page 13 of 41

[0075] Figure 5 is a block diagram of a system for electronically steering beams 9581-9585 using multiple TX / RX antennas 9516 (denoted "T / R" in Figure 5), with phase control of the transmitted signals from the TX / RX antennas 9516. The beams 9581-9585 cover the painted line 1445 and at least a part of the nearby road surface 300 in the lateral direction. The radar transceiver 4506 can control the phasing of the transmitted signals to electronically steer the beams and can also receive reflected radar signals and process them to calculate distances from the radar 4506 on the vehicle to the road surface 300 around the painted line 1445.

[0076] Figures 6A-6B show top and side views of an embodiment in which a radar transceiver 1117 comprises multiple radar sensors or multiple TX / RX antennas aligned vertically. Figure 6A shows the top view of the radar transceiver 1117 with multiple beams 1200, 1202, 1204, and 1206 at different heights on the vehicle, but with the same mounting angle. In this example, the beams can determine the distance to the road surface 300 before and after the painted line 1445 from the return signals from the road surface 300. The beam 1204 will not generate any return reflection signal detectable by the transceiver 117, or its return reflection signals will be noticeably smaller since the smooth painted line reflects the majority of the transmitted signal away from the radar transceiver 1117. The beam 1202, for example, generates a measurement of the distance at the near boundary of the painted line 1445, and the beam 1206, for example, generates a measurement of the distance at the far boundary of the painted line 1445. Figure 6B shows the side view of beams 1200, 1202, 1204, and 1206, and the radar transceiver 1117, indicating that the beam angles are the same.

[0077] Figure 7 shows an example of an FMCW radar transceiver, but with multiple transmit antennas 414 and multiple receive antennas 416. In particular, Figure 7 shows an FMCW MIMO (multiple-input, multiple-output) radar transceiver. A radar processor 426 drives a synthesizer 411 to provide a chirp or frequency ramp of a transmitting signal. The signal is amplified by a power amplifier 413 and transmitted via multiple transmit antennas 414. The received signal is captured by antennas 416 and amplified via low-noise amplifiers (LNAs) 415. The transmitted signal is quadrature-mixed with the received signal using50066 / 0601 Page 14 of 41modulator 418, so both the phase and velocity of the signal can be determined. The output of the modulators 418 is filtered by filters 419, and A / D converted via an A / D converter 420 to a signal read by the radar processor 426. With multiple antennas, the system can determine the angle of arrival (AoA) to the target, helping discriminate among different targets.

[0078] Also, if the transmit antennas 414 and receive antennas 416 are polarized, e.g., circularly or orthogonally linearly polarized, then the radar system is a polarimetric radar with the added capability of distinguishing the different road surfaces 300 from the different painted lines 1445 based on a polarized scattering matrix. A scattering matrix for the road surface 300 is different from that of a scattering matrix of the painted line 1445, where the different dielectric materials of the painted line will affect the scattering matrix even in the limited signal return signal. A polarized scattering matrix is a matrix in radar polarimetry that characterizes how a target transforms the polarization state of incident electromagnetic waves into that of the scattered waves. For example, a polarized scattering may relate the incident and scattered electric field vectors in a horizontal / vertical as follows:<The four complex elements, Shh, Shv, Svh, Sw, in this scattering matrix represent the scattering amplitudes for co-polarized (Shh, Sw) and cross-polarized (Shv, Svh) combinations.

[0079] The circular polarization scattering matrix Screlates to incident right / left-handed (RHCP / LHCP) waves to scattered fields, typically expressed as follows:where diagonal elements represent co-polarization and off-diagonal elements represent cross-polarization. This matrix may be useful for interpreting backscattering, where oddbounce (e.g., sphere or flat surface) signals are SRLand even-bounce (e.g., dihedral) signals are SRR.50066 / 0601 Page 15 of 41

[0080] The radar reflection from a painted line reflector 1445 is a no-bounce signal or an odd-bounce signal similar to the road surface 300, with a different scattering matrix than the road surface 300. The phase change in the polarized electric fields differs, and this difference can be detected to distinguish a painted-line reflector 1445 from the ground surface 300. The phase change in the polarized electric fields can therefore distinguish whether a reflection originates from the ground surface or another object. The road surfaces 300, such as concrete, smooth asphalt, and worn asphalt, have different scattering matrices. Additionally, wet, dry, snow-covered, and ice-covered road surfaces have different scattering matrices. There are different scattering matrices for thermoplastic paint, regular road paint, and metallic road paint.

[0081] A typical FMCW radar sensor, such as the Texas Instruments AWR1843A0P, can provide object range by performing an FFT (fast Fourier transform) on the processed received signal to extract a beat frequency. The radar sensor can provide velocity by applying a second FFT to several sequential received signals (chirps with ramped transmitted frequencies) to detect phase changes from one chirp to the next. The radar sensor can determine direction using a third FFT on several received signals from different antennas via AoA. This results in a radar cube comprising range, velocity, and direction. Using smooth, metallic-painted lines 1445 as reflectors on the road surface 300, the radar signals are reflected back from the ground surface 300 at much higher amplitudes than the painted line 1445. The smooth, metallic-painted line 1445 reflects radar signals into space rather than back to the radar sensor. Accurate lateral distances to a radar sensor can be determined before and after the painted line width using a single FFT on the first frequency ramp, which is typically 10-250 microseconds, which is called a fast chirp in FMCW modulation. This fast chirp enables distance measurements over short time intervals, e.g., less than one millisecond. These short time intervals enable the radar sensor to capture short-length targets, such as pavement markers or signposts, at speeds exceeding 100 mph (~45 m / s). Typically, the lateral velocity measurement is small and near zero; therefore, a second FFT is not required. However, for more accurate distance measurements, a Zoom FFT can be performed near the selected target frequency from the first FFT. Also, the angle at which the minimum received signal occurs will be when the radar beam is over the painted50066 / 0601 Page 16 of 41line 1445. The processing software within or in conjunction with the radar sensor can use both techniques: One or more FFTs on the fast chirp for processing accurate lateral distance measurements to the road surface before and after the painted line width, and multiple FFTs on distance, velocity, and multiple receive antennas for detection of other objects surrounding the vehicle when the radar beam sweeps vertically along the side, e.g., blind-spot detection or for performing lane changing maneuvers and lane departure detection.

[0082] A 4D imaging radar from suppliers such as Arbe Robotics Ltd, Uhnder Inc., Vayyar Ltd., and Metawave Corporation, with semiconductor companies such as Texas Instruments, NXP, and Infineon providing imaging radar transceiver chips, can also be used to detect the painted line 1445 versus the road surface 300. 4D imaging radar is a sensor that maps the environment by adding elevation (height) to traditional radar's range, speed, and azimuth (horizontal angle), creating rich, image-like point clouds for object detection and classification. By scanning the painted line 1445 with a 4D imaging radar, the painted line can be located on the road surface, and its distance from the radar can be measured by an onboard vehicle's 4D imaging radar and used in a vehicle control system.

[0083] Terahertz radar (300-3000 GHz) with FMCW modulation, described, for example, in US Patent No. 12,105,181, operates similarly to millimeter-wave or RF (radio frequency) FMCW radar (30-300 GHz) and can detect the edge between the road surface 300 and the painted line 1445 with a higher degree of accuracy since the wavelength is from 1 mm to 0.1 mm. As shown in Figure 11, typical road surfaces may be easier to determine with higher frequencies.

[0084] Deep learning methods may be used to enhance the detection of painted lines 1445 among other objects on the roadway, thereby decreasing the likelihood that painted line 1445 is missed amid other radar clutter. Using Convolutional Neural Networks (CNNs) or Recurrent Neural Networks (RNNs), for example, on the radar cube or on range and other properties (e.g., polarization and magnitude), can improve distance measurements from the road surface and from desired reflectors or non-reflectors.50066 / 0601 Page 17 of 41

[0085] Phase-Modulated Continuous Wave (PMCW) radar, Orthogonal Frequency-Division Multiplexing (OFDM) radar, and other digital radar techniques can also determine the distance to the painted line 1445. Combinations of one or more of the above techniques can also be used. For example, an FMCW technique and a PMCW technique could be used in the same radar sensor to determine redundant distances to the reflector. Alternatively, two or more radar transceivers, with the same or different characteristics, could be used in combination at different distances.

[0086] The radar sensors can be any of the previously described types, e.g., FMCW, PMCW, OFDM, DCM, multiple-frequency radar, multiple-frequency phase radar, MIMO radar, UWB (Ultra-Wide Band) FMCW, UWB impulse radar, FSK (Frequency Shift Keying) radar, monopulse radar, 4D imaging radar, terahertz radar, or a combination of any of these types. The radar preferably operates at frequencies between 0.3 and 3000 GHz (300 MHz to 3 THz).

[0087] The radar beam transmitted by the radar transceiver preferably has a single or dominant lobe characterized by a beam direction and a beam shape. The beam direction is typically characterized by a vector along the center or centroid of the lobe. The radar transceiver is preferably positioned and pointed so that the beam direction is toward the painted line 1445 or the surface specialized reflector expected to be in place when the vehicle is centered in its lane. The beam shape may, for example, be Gaussian and characterized by a beam width, typically measured from half-power points on opposite sides of the beam center. The beam may be circularly symmetrical about the center direction vector or may be asymmetrical. The beam width is preferably narrow enough to distinguish the painted line 1445 edges from the road surface 300.

[0088] The beam shape and / or direction may be static or variable. Well-known beam shaping techniques can be applied to alter the beam dynamically or non-dynamically. For example, when the beam is generated by an antenna array, well-known electronic beam steering and beam shaping techniques (e.g., delay-and-sum, windowing, etc.) can be employed to electronically alter e.g., steer) the beam. For example, the beam can switch between a relatively narrow width aimed at a nominal painted line location and a relatively broader width aimed more upward for blind-spot detection.50066 / 0601 Page 18 of 41

[0089] Alternatively, or in addition, mechanical beam-shaping devices can be employed. For example, a radar lens can be used to alter a beam’s shape, including its width. If the radar transceiver is located within a vehicle light, the exterior light cover (or a suitable portion thereof) can be shaped and constructed from a suitable material to serve as a radar lens. As another example, a radar reflector (e.g., a horn or parabolic reflector) may also alter a beam’s shape and / or width.

[0090] Range-based gating or filtering can be employed to ignore reflection signals from objects outside of the range of interest.

[0091] Figure 8 shows a schematic diagram of a radar sensor 4510 with multiple transmit / receive antennas. This embodiment can be used with an array of radar transceivers 1117. The radar processor 4260 starts a frequency synthesizer 4160 to provide a suitable FMCW signal, which may be amplified by power amplifier / phase shifters 4130 and transmitted to multiple transmit antennas set up in an array of paired antennas spaced vertically at a distance dant apart. In this embodiment, there is a gated power amplifier 4165 for each antenna pair, and the vehicle speed 8088 is provided to the radar processor 4260. The radar processor 4260 can determine which pair of antennas received the distance measurement from the road surface 300 and the painted line 1445. Once the edges of the painted line 1445 are determined relative to which radar antenna pair, the radar processor 4260 can anticipate which antenna pair and turn on the next gated power amplifier 4165 to transmit and receive signals from that pair. In this embodiment, each antenna pair can be switched on sequentially or switched on simultaneously to track the pained line 1445. In other embodiments, other sequences can be employed. This minimizes radar interference and reduces total transmitted power compared with transmitting power across all pairs simultaneously. The receive antennas may be part of a paired TX / RX antenna array 4309 and may receive return signals, which may be amplified by LNAs 4150. The received signals are mixed with the transmit signal via modulators 4180. The modulator 4180's output is filtered by the filter block 4190 to extract the beat frequency. The filtered signal is sampled by the A / D converter 4120 and sent to the radar processor 4260, which computes the measured distance, velocity, phase, and / or amplitude. The radar processor 4260 can control50066 / 0601 Page 19 of 41the frequency synthesizers 4160 to turn on various antennas sequentially to minimize interference between antenna pairs.Road Surface vs. Targeted Materials on the Road Surface

[0092] Figures 9A-9C show a transmitted radar signal 1119 reflecting off of different flat surfaces using a radar transceiver, e.g., 117 (not shown in this figure), aimed at an angle less than 90 degrees from the side of the vehicle, i.e., an oblique angle to the flat surfaces. Figure 9A shows that the surface 302 is smooth and metallic, and if the radar signal 1119 is transmitted at an angle to the flat surface 302, the radar signal is practically entirely or substantially reflected off in the opposite direction as the radar reflective signal 1120. No appreciable signal is returned to the radar transceiver 117, or the return reflection signal at the radar receiver 117 is noticeably lower so that it can be distinguished from a larger return reflection signal. In many of these embodiments, it is desirable to make the painted line 1445 as smooth and metallic as possible so that no detectable signal is returned to the radar transceiver. Figure 9B shows the surface 304 is somewhat smooth, but not metallic, and therefore, when the radar signal 1119 is transmitted at an oblique angle to the flat surface 304, the reflective signal 1120 off into the opposite direction is smaller. In this example, some of the transmitted radar signal 1119 will be reflected back to the radar transceiver. Figure 9C shows that the surface 306 is rough and has a higher dielectric constant than air. In this example, if the radar signal 1119 is transmitted at an oblique angle to the flat surface 306, a weak radar signal 1118 is reflected back to the radar transceiver. Worn asphalt has a surface similar to surface 306.

[0093] Figures 10A-10C show a transmitted radar signal 1119 reflecting off of different flat surfaces using a radar transceiver, e.g., 117 (not shown in these drawings), aimed directly down at the surfaces. Figure 10A shows that the surface 302 is smooth and metallic, and if the radar signal 1119 is transmitted directly towards the flat surface 302 (i.e., incident on the surface 120 at an approximately normal angle), the radar signal is reflected back to the radar transceiver as the radar reflective signal 1118. A significant amount of signal is returned to the radar transceiver. Figure 10B shows a surface 304 that is somewhat smooth, but not metallic, and therefore, when the radar signal 1119 is transmitted directly towards50066 / 0601 Page 20 of 41the flat surface 304, the reflected signal 1118 back to the radar transceiver is smaller in amplitude than in Figure 10A. Figure 10C shows that the surface 306 is rough and has a higher dielectric constant than air. In this example, if the radar signal 1119 is transmitted directly towards the flat surface 306, the radar signal 1118 that is reflected back to the radar transceiver is even smaller than the returned signal in Figure 10B.

[0094] Figure 11 shows a diagram of road-surface roughness versus the radar transceiver's incident angle for three frequencies: 80, 120, and 240 GHz. Also, the diagram illustrates the approximate roughness of the road surface for three types of roads: smooth concrete 332, smooth asphalt 334, and worn asphalt 336. For the three frequencies, all three road surfaces can be detected for incident angles below 70 degrees. For example, at an incident angle of 50 degrees, an 80 GHz radar sensor can distinguish among the three types of road surfaces, but at incident angles greater than 70 degrees, the same sensor may detect only smooth or worn asphalt. Another example: if the radar sensor operates at 240 GHz, the three surface types can be detected at incident angles up to 83 degrees. At higher frequencies, road surfaces are easier to detect. The incident angle is measured from a perpendicular to the ground. At a 0-degree incident angle, the radar sensor would be aimed directly at the ground. However, at an incident angle of 90 degrees, the radar sensor would be aimed parallel to the ground.

[0095] Figures 12A-12D illustrate the different materials used for painted line 1445. Figure 12A shows an embodiment in which the painted line 1445 is smooth and metallic. Current painted lines may require adding metallic compounds to the paint to achieve this embodiment. The radar transceiver (not shown in this figure) transmits signals 1119 towards the road surface 300 and the painted line 1445. The road surface 300, depending on the roughness, reflects signals 1118 back to the radar transceiver. The radar transceiver processes the signals to determine the distances prior to the painted line 1445. When the transmit signals 1119 hit the painted line 1145, the signals 1120 are reflected outward from the radar transceiver, and no signals are received, resulting in a null condition. If the radar signals 1119 are transmitted on the other side of the painted line 1145, then the road surface 300 would reflect signals 1118 back to the radar transceiver 117. Therefore, the lateral50066 / 0601 Page 21 of 41distances can be measured to both sides of the painted line 1445. Different line widths or multiple painted lines can indicate school zones, hospital zones, bike zones, speed zones, and other highway information.

[0096] Figure 12B shows an embodiment in which the painted line 1459 is smooth and has a dielectric material similar to, but higher than, that of air. Current painted road lines would be in this category. The radar transceiver (not shown in this figure) transmits signals 1119 towards the road surface 300 and the painted line 1459. The road surface 300, depending on the roughness, reflects signals 1118 back to the radar transceiver. The radar transceiver processes the signals to determine the distances prior to the painted line 1459. When the transmit signals 1119 strike the painted line 1459, most of the signals 1112 pass through the low-dielectric material and are reflected off the road surface beneath the painted line back to the radar transceiver as received signals 1118. Some of the transmitted signals 1119 would be reflected off the smooth, painted line 1459 and directed away from the radar transceiver as signal 1120. In this embodiment, the radar transceiver may require processing to determine the minimum received signal from the painted line 1459 relative to the received signal from the road surface 300, to determine the edge of the painted line surface, and then to determine the lateral distance prior to the painted line 1459.

[0097] Figure 12C shows an embodiment where the painted line 1457 is smooth and somewhat metallic. Thermoplastic painted road lines may fall into this category depending on the amount of titanium dioxide included in the thermoplastic mixture. Current thermoplastic paint contains a percentage of titanium dioxide, which is reflective at common radar frequencies. The radar transceiver (not shown in this figure) transmits signals 1119 towards the road surface 300 and the painted line 1457. The road surface 300, depending on the roughness, reflects signals 1118 back to the radar transceiver. The radar transceiver processes the signals to determine the distances prior to the painted line 1457. When the transmit signals 1119 hit the painted line 1157, the majority of signals would be reflected off the smooth painted line 1457 away from the radar transceiver as signal 1120. Some of the transmit signals 1119 hit the painted line 1157, and the signals 1122 go through the dielectric material and are reflected off the surface road underneath the painted line back to50066 / 0601 Page 22 of 41the radar transceiver as received signals 1118. The radar transceiver would process these signals in a manner similar to the transceiver in Figure 12A.

[0098] Figure 12D shows an embodiment in which the painted line 1453 is smooth and radar-absorbent. Current painted lines may need to be supplemented with radar-absorbent materials, such as ferrites, carbon compounds, and other composites, to make the material non-reflective. The radar transceiver (not shown in this figure) transmits signals 1119 towards the road surface 300 and the painted line 1453. The road surface 300, depending on the roughness, reflects signals 1118 back to the radar transceiver. The radar transceiver processes the signals to determine distances before and after the painted line 1445. When the transmit signals 1119 strike the painted line 1453, the signals 1122 are attenuated by the radar-absorbent material, and no reflected signals are returned to the radar transceiver, resulting in a null condition. The radar transceiver would process these signals similarly to the transceiver in Figure 12A.Road Surface vs. Pavement Markers

[0099] Figures 13A and 13B show typical pavement markers 445 that are currently used on today’s roads. The pavement marker 445 shown in Figure 13A is rectangular, but pavement markers come in many different shapes and sizes. The pavement marker 445 can be placed on top of a driving surface, in which case they are called raised pavement markers (RPMs), or they can be installed at or slightly below the driving surface level e.g., snowplowable markers), or below the roadway surface 300 in cut grooves, divots, or slots. The pavement markers 445 are typically installed along or in line with lane boundary lines, such as painted lines 305, 307, and 309 on the roadway 300, as shown in Figure 13B. The painted line 307 is typically a yellow center line, and the painted white lines 305 and 309 mark the sides of the road. The primary function of the pavement marker 445 is to reflect light so that vehicle headlights or sunlight are returned to the driver, enabling the driver to see the location of the road lines, especially in inclement weather. The pavement markers have a visible reflector 275 on one or more sides as shown in Figure 13A. Also, the raised pavement reflectors may act as a rumble guard when the vehicle crosses the roadway lines or pavement markers 445, since the markers 445 are typically 25 mm above the roadway surface and50066 / 0601 Page 23 of 41cause the vehicle tires to impact them. The raised pavement markers 445 have undergone numerous modifications over the years, with various visible reflective features, such as cat’s-eye reflectors, LED (light-emitting diode] lights, and LiDAR (light detection and ranging] reflection patterns. The pavement markers 445 are reflective to visible light and may or may not be reflective to radar radiation from radar transceivers, though they have traditionally not been purposefully designed for radar reflectivity. The pavement markers 445 are typically used on roadways, but also in parking lots, shipping yards, shipping docks, and other paved and non-paved areas.

[0100] The principles described herein can be applied to a pavement marker that has a highly reflective (at applicable radar frequencies] top surface 257. In that case, road surface 300 laterally near and far of the pavement marker 445 generates a relatively strong return reflection signal at the radar transceiver, whereas the top surface 257 of the pavement marker 445 generates a relatively weak or no return reflection signal at the radar transceiver.

[0101] The pavement marker 445 may include a dihedral corner reflector at or near its lateral near side, such as described in Int'l Patent Appl. Publ. No. WO 2024 / 030302, the entire disclosure of which is incorporated herein by reference. As an oblique-incident radar beam is scanned laterally across such a pavement marker, the reflection back to the transceiver will be detectable on the road surface before the pavement marker, very strong at the near corner where the dihedral corner reflector is, and then weak or absent over the top of the pavement marker (assuming the top surface of the pavement marker is highly reflective].

[0102] The pavement marker 445 (and the other pavement markers described herein] may be affixed to any driving surface for any vehicle, including roadways such as one-way, bidirectional or multi-lane roads, highways, thoroughfares, lanes, avenues, boulevards, parkways, pathways, byways, streets, paths, trails, and the like, as well as on bridges, in tunnels, parking lots, parking structures, shipping yards, shipping docks, transportation depots, loading / unloading bays, warehouse lots or yards, etc., whether paved (e.g., asphalt, concrete, brick, stone] or unpaved. The pavement marker 445 (and the other pavement50066 / 0601 Page 24 of 41markers described herein] are preferably affixed to the surface so that the longitudinal axis of a dihedral corner reflector within the pavement marker 445 is generally parallel to the direction of vehicle travel and along one or both sides of the path of travel of the vehicle.

[0103] Figures 14A-14C and 15A-15C illustrate embodiments of pavement markers that may be mounted below the surface, such as in rumble strips, parallel-cut slots, or grooves. Figure 16A illustrates a front side view of a rumble strip 310, which is installed in a groove formed in the road surface 300 to produce a sound when a tire rides over the rumble strips to alert the driver. The radar transceiver 116 transmits a signal 1119 and receives a returned signal 1118 from the rumble strip 310. In this configuration, the side and bottom of the rumble strip form a dihedral corner reflector, which has higher reflectivity than a rough surface. However, if the radar transceiver 116’ is transmitting signals to the center of the rumble strip 310 with a lower incident angle, then there will be some returned signal 1118’ returned to the radar transceiver 116’. The majority of the transmitted signal will reflect off in the opposite direction of the radar transceiver as signal 1120. When a narrow beam antenna on the radar transceiver sweeps vertically across the rumble strip 310, a boundary is detected, and the distance is measured between the top of the road surface 300 and the side of the rumble strip 310.

[0104] Figure 15A shows a pavement marker 394 placed inside a rumble strip 310. Pavement marker 394 has a top, and the sides facing the radar transceiver 116 are metallic-like. In this embodiment, there will be almost no returned radar signal, and the majority of the transmitted signal will propagate in the opposite direction, as shown by signal 1120 when a narrow antenna beam is aimed at the top pavement marker 394. However, depending on the width of the pavement marker 394 to the width of the rumble strip 310, the boundaries are determined. If the widths are the same and the pavement fits tightly in rumble strip 310, then the boundaries will be the edges of rumble strip 310 where radar signals return from the road surface, but no radar signals return on top of pavement marker 394. If the pavement marker 394 width is much smaller than the rumble strip 310, then the boundaries will be the side 395 of the pavement marker 394.50066 / 0601 Page 25 of 41

[0105] Figure 14B shows a top view of rumble strips 310 along a roadway with a painted line 910. Figure 15B shows a top view of the pavement marker 394 installed in rumble strips 310 along a roadway with a painted line 910. Figure 14C shows the top view of slots 312 cut in the highway. Here, the radar transceiver 116 views the slots 312 for longer periods, thus allowing the onboard controller to determine the lateral position and / or the vehicle heading by taking multiple lateral distance measurements from the long slot 312. Figure 15C shows another embodiment in which the pavement marker 394 is installed in the slots 312 where existing pavement markers are installed, so that snow plows or other equipment will not tear them off the roadway surface.

[0106] Figure 16 shows a cut-away front view of an installed snow-plowable pavement marker 1290 and the radar transceiver 116. A snowplow rides on the top of sides 1206 and 1208, which are typically metal. An optical reflector 1275, which is typically made of plastic, is installed in the middle of the frame of the snow-plowable pavement marker 1290 so that drivers or vision sensors can see the marker 1290. The radar transceiver 116 transmits signals 1119 to the metal surface 1285 and receives signals 1118 back to a radar transceiver 116 from one side of the pavement marker 1290. The radar return signal 1118 is stronger for pavement marker 1295 than for the other raised pavement markers described earlier, because pavement marker 1295 is made of metal and some of its sides are at right angles. If the radar transceiver aims a narrow beam at the center of the pavement marker 1295 instead of the sides, the transmitted signal 1119’ reflects off the flat metallic reflector into the opposite direction as signal 1120. The boundaries can easily be determined as the metallic corner 1285. Snow-plowable markers 1290 may be mounted in a center or interior lane line to be viewed by radar sensors mounted on vehicles in two different lanes. The snow-plowable marker 1290 is usually mounted in an interior road line. When the snow plowable marker 1290 is covered with snow, it is not visible to the human eye, cameras, or lidar. However, the marker 1290 is visible to the radar transceiver 116 despite being covered with snow.50066 / 0601 Page 26 of 41Guidance and Control Systems with Downward Side-Looking Radar(s)

[0107] Figure 17A shows the radar transceiver 117 providing the lateral distance x to the boundaries of a continuous painted line or discrete pavement markers. No additional sensors are required to determine the lateral distance x from a continuous line. However, if discrete painted line segments or discrete pavement markers are used, additional sensors may be required. Figure 17B shows a block diagram of one embodiment for combining the radar transceiver 117 measurements, from road surface target materials, at about the same time with data from other sensors such as a vehicle speed sensor 8008, IMU 907 and a wheel angle sensor 8028 using a Kalman filter [e.g., Kalman filter, extended Kalman filter, unextended Kalman filter, discriminative Kalman filter, or adaptive Kalman filter) within a processor 830. The inputs to the processor 830 are the vehicle forward velocity from the vehicle speed sensor 8008, acceleration and yaw rate values from the IMU 907, the steering wheel angle from the wheel angle sensor 8028, and the radar distance measurements from the radar transceiver 116. The output of the processor 830 is the lateral distance x to the road surface target materials, e.g., pavement markers 445.

[0108] In all embodiments, range-based gating, time-gating, amplitude gating, and other [e.g., Kalman) filtering can be employed to ignore reflection signals from objects that are not side targets of interest. There are several methods for gating or filtering the received signal to detect pavement markers 445 or other road surface target materials, e.g., painted lines 1445.

[0109] These techniques can have static range gating and amplitude threshold values, or the thresholds and ranges can be dynamic e.g., determined from previously collected radar data). The range, time, and amplitude can be updated with proper gates. Range gates are typically based on road width, lane widths, and lane count. Time gating between pavement markers can be based on marker spacing and vehicle speed, where the time interval is marker spacing divided by vehicle speed. The received signal strength (amplitude) gate can be based on the average received signal strength over previous [e.g., the last few) target passings, plus a pre-determined threshold value.50066 / 0601 Page 27 of 41

[0110] Figure 18 is a block diagram of a lateral guidance system 1850 that can warn the driver if the vehicle is leaving its lane with visual, audible, and / or haptic warnings. If the driver does not take corrective action, the system 1850 may automatically take steps to maintain the vehicle in its lane. This embodiment represents a Lane Departure Warning (LDW), Lane Keeping Assist (LKA / LKS), or Lane Centering Assist (LCA) system. The radar transceiver 116 transmits signals 1119 in the direction of the side target materials, e.g., painted line 1445, road surface 300, pavement marker 445, and receives signals 1118 reflected back from the road surface 300, but little from side target materials, e.g., painted line 1445. The distance dR from the boundary, which is between the side target materials, e.g., painted line 1445 and road surface 300, and the radar transceiver 116, is measured by the radar transceiver 116 using well-known radar techniques and provided to a lateral guidance controller 835, as shown in Figure 18. In addition to the radar input, the guidance controller 835 may have additional inputs from a vehicle speed sensor 8008, a steering wheel angle sensor 8028, the IMU 907, and a reference table 8282. The vehicle speed sensor 8008 provides the vehicle's forward velocity. The IMU 907 provides the vehicle body’s acceleration, angular rate, and, in some cases, body orientation, using a combination of an accelerometer, a gyroscope, and a magnetometer. If the vehicle 180 travels too close to or too far away from the side target, indicating a lane departure, the guidance controller 835 may transmit a sound signal to a speaker 824 (or plural speakers) to alert the driver of a lane departure and / or cause a display 826 to alert the driver of the lane departure visually and / or cause vibration or other haptic stimulation to the driver. If no driver response is detected, the controller 835 may control the steering mechanism 802 to control the wheels 804 to keep the vehicle in the lane. The guidance controller 830 may not generate an alert or take action if a turn signal 822 is turned on to signal a lane change or turn in the direction of the detected lane departure. Another embodiment similar to the system shown in Figure 18 can implement LCA. An LCA system controls the steering of vehicle 180 to keep the vehicle 180 in the lane without driver input via the steering mechanism 802 and wheels 804, but the system can be overridden by the driver.50066 / 0601 Page 28 of 41Sensors for Vehicle Location

[0111] Figure 19 shows a front view of radar transceiver 119 scanning side and road surface targets mounted at the front center of the vehicle, along with other sensors, e.g., GNSS (global navigation satellite system] 901, IMU 907, and vision sensor 903. In addition, radar transceivers 116 and 117 are mounted on the sides of the vehicle to view the surface targets. Figure 19 illustrates the mounting of a radar transceiver 119 in the center front of the vehicle 180 to view the road and roadside targets from two antennas viewing both directions (i.e., opposite lateral directions, right and left or driver-side and passenger-side]. In this embodiment, the radar transceiver 119 uses radar beams 1106-1107 to view the targets. Two advantages of this mounting scheme over mounting separate radar transceivers 116 and 117 on the front sides are that (1] having only one unit saves costs, and (2] the viewing distances allow the vehicle 180 to cross a road surface target while still tracking the target. In addition to a radar transceiver, other sensors on the vehicle 180 that provide more robustness to the guidance system are a GNSS 901, IMU 907, and vision sensors 903. The GNSS 901 receives signals from satellites 1901 to determine the vehicle’s location via triangulation.

[0112] For redundancy and / or higher reliability, the radar guidance techniques described herein can be combined with other guidance techniques based on other technologies. For example, the radar transceivers 116 and 117 can be integrated with other sensors such as, for example, a GNSS receiver 901, lidar sensor 902, vision sensor 903, forward-looking radar 904, IMU 907, an odometer 909, navigational database 8066, steering wheel angle sensor 8028, vehicle speed sensor 8008, or other location sensors 905, as shown in Figure 20. Figure 20 also shows that the navigational database 8066 can be updated wirelessly via the Internet 500. As another example, the processing of signals from a variety of sensors, including the radar sensors described herein, can be performed by a common processor or computer (which may have multiple processors]. Joint processing of the various sensor types can improve the performance of any single sensor type. For example, the output of an onboard processor 437, using one or more Kalman filters, can provide more reliable location information 914, steering information 912, and speed information 918.50066 / 0601 Page 29 of 41

[0113] Figure 21 shows another embodiment in which multiple radar transceivers 117, along with IMUs 907, can be installed at several places on the leftside of the vehicle 180, and similarly, one or more radar transceivers 116, along with IMUs 907, can be installed on the right side of the vehicle 180. The radar transceivers 116 and 117 can be installed in side marker lights, headlights, fog lights, daytime running lights, or turn signals on the vehicle, or under covers or within enclosures for the same, for example, for minimum impact on the exterior design. The radar transceivers 116 and 117 can be mounted on or in a bumper [e.g., front bumper) of the vehicle 180. The radar transceivers 116 and 117 can be mounted behind the vehicle 180 body exterior [e.g., behind a body panel) made of radar-transparent material, typically plastic and / or fiberglass. In another embodiment, one or more radar transceivers 117 would see pavement markers 1284 or painted lines 1445 on the left, and one or more radar transceivers 116 would see pavement markers 284 and painted lines 2445 on the right. Also, a radar transceiver 119, along with an IMU 907, can be mounted in the center front of the vehicle 180 to provide coverage in both directions, the right and left sides of the vehicle 180, in view of pavement markers 284 and 1284. These additional radar transceivers 1117, 1017, 1116, 1016, and 1019 can provide redundancy, heading angle information, and more distance measurements to the same targets. Radar transceivers 117, 1117 and 1017 are on the leftside of the vehicle 180, radar transceivers 116, 1116, and 1016 are on the right side of the vehicle 180, and radar transceivers 119 and 1019 are in the front or rear, respectively, of the vehicle 180. There can be many other combinations of mounting one or more radar transceivers on the vehicle 180 to provide for more robust lateral guidance control.

[0114] The IMUs 907 around the vehicle 180 can be part of the radar transceivers 116, 117, and 119 or separate standalone units. A separate IMU is also shown in the center of the vehicle 180. The IMU 907 can provide a change in distance measurements from the last side target that the radar transceivers viewed. Therefore, when IMU information [i.e., inertial measurements) is fused with the radar transceiver information, a distance measurement between side targets, e.g., pavement markers 284 and 1284, can be continuously, quasi-continuously, or approximately continuously determined or determined at discrete points between side targets. As used herein, the phrase "inertial measurement” refers to any data50066 / 0601 Page 30 of 41that an IMU can produce. Examples of inertial measurements include acceleration, yaw rate, heading, and changes of the foregoing.Radar and Satellite Positioning

[0115] Figure 22 shows a block diagram of a processor 830 with inputs from radar transceiver 116 and 117, GNSS 901, IMU 907, wheel speed 8008, and steering wheel angle 8028. The radar transceivers 116 and 117 on the vehicle detects and determines the distance to the road surface target materials. A GNSS / route database 8006 can be created by storing the latitude and longitudinal information from the GNSS for each road surface target material as the vehicle traverses the road path. Using SLAM (simultaneous localization and mapping) techniques, the vehicle can be located using radar lateral measurement to a specific road surface target in the route database 8006 and the recorded GNSS coordinates from previously traversing the road path. Then, the difference between the actual GNSS readings and the database 8006 readings can be used to update the GNSS sensor 901 to provide a more accurate location as the vehicle passes the same road surface target.

[0116] The vehicle's position relative to the road surface target, both laterally (the radar-measured distance) and longitudinally (the minimum returned signal is received when the vehicle starts to pass or passes the known location of a discrete road surface target, e.g., a pavement marker or a dashed painted line), can be determined. The lateral distance between the road surface target and the vehicle is determined by radar sensors 116 and 117 on each vehicle, measuring the lateral distance to pavement marker 445 or painted line 1445 as each vehicle passes the marker or start / stop of painted line segments.

[0117] The route database 8006 can store the desired lateral distance between the vehicles in the center of each lane and the discrete road surface marker 445 and / or painted line 1145. The difference between the stored, desired lateral distance (which could be obtained, for example, by recording radar-measured distances when the vehicles are known to be in or near the center of the respective lanes) and the currently measured lateral distance is an offset distance of the vehicles versus the center of their respective lane. The50066 / 0601 Page 31 of 41database 8006 can store locations {e.g., GPS coordinates) of a vehicle in the center of the lane and / or the road surface targets. As the vehicles pass the pavement marker 445, the peak amplitude of the returned radar sensor signal indicates the longitudinal center of the pavement marker 445. The stored location of the road surface target (continuous painted line 1445 or discrete pavement marker 445) then determines the vehicle's current longitudinal location based on the peak radar signal return as the vehicle passes the discrete road surface target, e.g., pavement marker 445. Alternatively, the derivative of the return signal can be monitored, and a change in that derivative signal corresponds to the beginning of a pavement marker 445 or painted line 1445. In the above embodiment, the IMU 907 can be used between targets to continuously update the GNSS sensor 901. However, the painted line 1445 provides a continuous lateral position from the radar transceiver, and the IMU 907 may not be needed for lateral position updates. The longitudinal updates from painted line 1445 could be provided via IMU 907, vehicle speed 8008, and intersections between painted line 1445. The dashed lines can provide longitudinal updates since these short lines can be counted and recorded.

[0118] Figure 22 shows one embodiment with a GNSS / route database 8006, which is connected to the Internet 500 via a wireless module 8181, a GNSS sensor 901, an IMU sensor 907, radar sensors 116 and 117, a vehicle speed sensor 8008, a steering wheel angle sensor 8028, and a processor 830. The processor 830 matches the database information with the current sensor information to provide an accurate vehicle location in both x and y directions, where x is the lateral location within the lane, and y is the longitudinal location along the road. There are several different embodiments that provide vehicle location using the radar transceiver information:(1) Using a GNSS sensor with corrections {e.g., RTK (Real Time Kinematic) -GPS or PPP (Precise Point Positioning) corrections) for accurate location in view of the necessary satellites, and the IMU / radar acts as a backup to the GNSS.(2) GNSS without corrections for general vehicle location with the radar / IMU providing accurate location updates. The radar / IMU updates the GNSS sensor with accurate latitude and longitude information, providing the vehicle's location.50066 / 0601 Page 32 of 41(3) GNSS denied areas, e.g., tunnels, bridges, urban areas with tall buildings, mountainous areas, and dense forests. The radar / IMU provides accurate vehicle location both laterally and longitudinally.(4) Vision sensors provide vehicle lateral location via painted lane lines; the radar / IMU acts as a backup during inclement weather or when the vision sensor (not shown in Figure 22) gets blinded.(5) Lidar sensors (not shown in Figure 22) provide vehicle lateral location via painted lines and stored boundaries. The radar / IMU acts as a backup during inclement weather.

[0119] The GNSS sensors in these embodiments can use one or more satellite constellations. There are currently four global satellite navigation constellations: United States GPS, Russia's GLONASS, China's BeiDou, and the European Galileo. A GNSS sensor used with those systems can be with or without error corrections. A typical GNSS sensor without any error corrections can have an accuracy of around 1-7 m. There are many error correction services, such as Global Satellite-Based Augmentation Systems (SBAS), Regional SBAS including WAAS (US), EGNOS (EU), MSAS (Japan), GAGAN (India), and SDCM (Russia), GRAS, and the joint US Coast Guard, Canadian Coast Guard, Differential GPS (DGPS) service, and local GBAS typified by a single GPS reference station operating RTK-GPS corrections. There are also network (Internet) correction services via the above services. There are also continental and global correction services such as PPP. There are correction services that combine multiple schemes, such as PPP-RTK GNSS correction services. These correction services can provide vehicle location with an accuracy of 1 centimeter in real time.Guidance and Control Systems

[0120] Figure 23 is a block diagram of a guidance / navigation system 850 that warns the driver if the vehicle leaves its lane with visual 888, audible 824, and / or vibration warnings and also controls the vehicle’s lateral position via the block steering mechanism 802 and the steering wheels 804. This embodiment consists of the following sensors: GNSS 901 which is wirelessly connected to the Internet 500 to obtain GNSS correction, turn signal 822, wheel50066 / 0601 Page 33 of 41speed sensor 8008, IMU 907, radar transceiver 116, and vision sensor 903, which can be fused with the other sensors (e.g., GPS, IMU, radar, vehicle speed) and data in the route database 8006 which can be update wirelessly via the Internet 500 to provide a more robust system.

[0121] Figure 24 is a block diagram of a lateral guidance control system 960 that controls the vehicle's steering to keep it in its lane. This embodiment represents an autonomous lateral control system. The radar transceivers 116 and 1016, mounted on the front and rear of the vehicle, transmit signals toward the pavement markers or other target structures and receive signals reflected from those structures. The distances between the target structures and the radar transceivers 116 and 1016 are measured by the radar transceivers using well-known radar techniques and provided to the lateral guidance controller 8004 shown in Figure 24. The radar transceiver 116, mounted on the front of the vehicle, measures the distance dxi to a target structure. The radar transceiver 1016 measures the distance dx2 from a different target structure. The desired control distance de from the target structure is subtracted by the radar measured distance dxi to determine an error dERROR, which is input to the lateral guidance controller 8004. Vehicle speed 8008, location and radar characteristic database 8006, IMU 907, vision sensor 903, GPS sensor 901, and wheel angle 8028 may be sent to the lateral guidance controller 8004. There may be additional sensors, e.g., multiple IMUs, RTK-GPS, multiple vision cameras, laser radar, etc. (not shown) that can be used to augment the lateral control system 960. The guidance controller 8004 controls a steering mechanism 8020, which controls the wheel angle and, along with the vehicle dynamics 8040, the vehicle's lateral position in the lane relative to the pavement markers. Radar transceivers 116 and 1016 provide cross-track error (dERROR) and heading angle error based on the front and rear distance measurements to the markers. The lateral guidance controller system 960 can have many different embodiments of control algorithms for steering the vehicle along the pavement markers. Some embodiments are fuzzy control algorithms, PID (Proportional Integral Derivative) control algorithms, adaptive PID control algorithms, Stanley control algorithms, MPC (Model Predictive Control) control algorithms, neural network control algorithms, modified sliding mode control algorithms, multi-rate control algorithms, and LQR (Linear Quadratic Regulator) control algorithms.50066 / 0601 Page 34 of 41

[0122] The desired control distance de from the target structure maybe a predetermined value based on the assumed lane width, vehicle width, and the radar transceiver location on the vehicle. Alternatively, the desired control distance de from the target structure may depend on the vehicle's approximate location to account for different lane widths and / or different target structure 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 geographic location of the vehicle, such as determined, for example, by GPS, sufficient to determine which road or set of nearby roads the vehicle is traveling on. Additionally, the desired control distance de from the target structure may depend on the vehicle's direction of travel, which can be determined from compass sensors and / or GPS measurements, because lane widths and / or target structure locations may not be the same in different directions on the same road.

[0123] In another embodiment, the desired control distance de may be dynamically determined as the vehicle travels down the road by measuring distances to different, laterally displaced target structures. For example, the lane width can be indirectly measured by [a] measuring distance(s) to target structures marking an adjacent lane boundary on a given side of the vehicle, (b) measuring distance(s) to target structures marking the next lane boundary on the same side of the vehicle, (c) subtracting those measured distances to calculate the adjacent lane width, and assuming that the vehicle’s current lane width is the same.

[0124] 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 equalize the two distances [e.g., using a zero difference between the right and left distances as the nominal setpoint) so that the vehicle is centered in its lane. Also, the desired control distance de may be offset from the true lane center for different vehicles so that the tire pattern does not wear out the pavement in the same area.50066 / 0601 Page 35 of 41CONCLUSION

[0125] The terms and descriptions used above are set forth by way of illustration and example only and are not meant as limitations. Those skilled in the art will recognize that many variations, enhancements, and modifications of the concepts described herein are possible without departing from the underlying principles of the invention. For example, skilled persons will appreciate that the subject matter of any sentence, paragraph, or drawing can be combined with the subject matter of some or all of the other sentences, paragraphs, or drawings, except where such combinations are mutually exclusive. The scope of the invention should therefore be determined only by the following claims, claims presented in a continuing patent application or a post-issuance proceeding, and equivalents to such claims.50066 / 0601 Page 36 of 41

Claims

CLAIMS1. An apparatus for determining a lateral position of a land vehicle on a pathway on which one or more discrete or continuous targets are distributed on a surface of the pathway in a direction of travel of the vehicle, the targets comprising material having different radar reflectivity than the surface of the pathway where no targets are present, the apparatus comprising:a radar sensor mounted to the vehicle and configured to transmit a radar signal having a beam pattern center aimed downward from the vehicle toward the surface of the pathway and sideways from the vehicle generally perpendicular to the direction of travel of the vehicle, the radar sensor being further configured to detect one or more reflections of the radar signal from the pathway and to detect a substantial absence of reflections of the radar signal from the at least one of said one or more discrete or continuous targets; and a processor operatively connected to the radar sensor and configured to determine a lateral position of the vehicle from said one or more targets.

2. An apparatus according to claim 1, wherein the radar sensor is selected from a group consisting of an FMCW radar sensor, a UWB radar sensor, a UWB impulse radar sensor, a monopulse radar sensor, and a multi-frequency radar sensor.

3. An apparatus according to claim 1, wherein the radar sensor is part of a 4D imaging radar system.

4. An apparatus according to claim 1, wherein the radar sensor operates in a terahertz frequency band.

5. An apparatus according to claim 1, wherein the radar sensor comprises a plurality of antennas.

6. An apparatus according to claim 1, wherein the continuous targets are selected from a group consisting of a painted line, a metallic painted line, a thermoplastic painted line, a50066 / 0601 Page 37 of 41metallic tape, a metallic strip, a metallic mesh, a radar-absorbent painted line, a radarabsorbent painted strip, and a frequency-selective surface.

7. An apparatus according to claim 1, wherein the discrete targets are selected from a group consisting of raised pavement markers, markers in slots, markers in grooves, bot dots, snow plowable markers, radar-absorbent raised pavement markers, short segments of painted line, short segments of a metallic painted line, short segments of a thermoplastic painted line, short segments of a metallic tape, short segments of a metallic strip, short segments of a metallic mesh, short segments of a radar-absorbent painted line, and short segments of a radar-absorbent painted strip.

8. An apparatus according to claim 1, wherein the pathway is one of a road, street, highway, lawn, field, open terrain, room in a building, manufacturing floor, parking lot, warehouse, or depot.

9. An apparatus according to claim 1, wherein a lateral position of a target is computed from a discontinuity between the target and the surface of the pathway based on different radar reflections received at the radar sensor, wherein the discontinuity represents an edge of the target.

10. An apparatus according to claim 1, wherein an incident angle of the radar signal from the radar sensor upon the target is less than 90 degrees.

11. A method for guiding or assisting in guiding a vehicle along a pathway having a surface and one or more targets on the surface, wherein said one or more targets have radar reflectivity characteristics different from the surface, the method comprising:directing radar waves from the vehicle downward and to a side of the vehicle; receiving reflections of the radar waves from the pathway;receiving either no detectable reflections of the radar waves from said one or more targets or reduced reflections of the radar waves from said one or more targets; and50066 / 0601 Page 38 of 41processing the reflections of the radar waves to determine distances between the vehicle and at least one of said one or more targets.

12. A method according to claim 11, wherein the radar waves are formed in a narrow beam, the method further comprising:sweeping the narrow beam laterally across a target.

13. A method according to claim 11, further comprising:controlling, based on the distances, steering of the vehicle so as to follow alongside the targets.

14. A method according to claim 11, wherein the radar waves are in a terahertz frequency band.

15. A method according to claim 11, wherein the directing step is performed with a plurality of antennas.

16. A method according to claim 11, wherein the receiving steps are performed with a plurality of antennas.

17. A method according to claim 11, wherein the targets are selected from a group consisting of a painted line, metallic painted lines, thermoplastic painted lines, metallic tapes, metallic strips, metallic meshes, radar-absorbent painted lines, radar-absorbent painted strips, pavement markers with lower radar-reflectivity than the surface of the pathway, frequency-selective surfaces, raised pavement markers, markers in slots, markers in grooves, bot dots, snow plowable markers, radar-absorbent raised pavement markers, short segments of painted line, short segments of a metallic painted line, short segments of a thermoplastic painted line, short segments of a metallic tape, short segments of a metallic strip, short segments of a metallic mesh, short segments of a radar-absorbent painted line, and short segments of a radar-absorbent painted strip.50066 / 0601 Page 39 of 4118. A method according to claim 11, wherein the pathway is one of a road, street, highway, lawn, field, open terrain, room in a building, manufacturing floor, parking lot, warehouse, or depot.

19. A method according to claim 11, wherein the targets are arranged along a line representing a boundary of the pathway or a lane within the pathway.

20. An apparatus for guiding a land vehicle along a pathway on which target material with different reflective signals than the pathway is distributed along the pathway in a direction of vehicle travel, the apparatus comprising:means for radiating downward and sideways from the vehicle, a radar transmit signal having a beam center aimed partially downward and sideways from the land vehicle toward one or more target materials and a surface of the pathway;means for detecting reduced reflections or an absence of detectable reflections from the target material;means for receiving reflections of the radar transmit signal as one or more received signals reflected from a surface of the pathway where no target material is present; and means for processing the received reflections to determine a position of the land vehicle relative to at least one edge of target material and the pathway.50066 / 0601 Page 40 of 41

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