Self velocity estimation using radar or lidar beam steering

Abstract

Methods, systems, computer-readable media, and apparatuses for radar or LIDAR measurements are presented. Some configurations include transmitting, via a transceiver, a first beam having a first frequency characteristic; computing a distance between the transmitter and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, where the second beam is directed such that an axis of the second beam intersects a ground plane; and computing a self-velocity of the transceiver based on information from at least one reflection of the second beam. Applications related to road vehicle (e.g., automobile) usage are described.

Description

TECHNICAL FIELD

[0001] Aspects of the disclosure relate to radar- or LIDAR-based sensors for powered ground vehicles. BACKGROUND

[0002] Radar signals - or generally electromagnetic signals - are often used to detect the presence of objects in the surrounding environment. For example, motor vehicles are sometimes equipped with a radar unit that transmits radar signals to detect corresponding signals reflected from another object, such as a nearby vehicle. It can be challenging to use such radar signals for speed estimation of the motor vehicle itself, i.e., the vehicle equipped with the radar unit. The speed of the vehicle equipped with the radar unit is also referred to as ego velocity. SUMMARY

[0003] A method for radar measurement according to a general configuration includes transmitting, via a transceiver, a first beam having a first frequency characteristic; computing a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is oriented such that an axis of the second beam intersects a ground plane; and computing an ego velocity of the transceiver based on information from at least one reflection of the second beam. A computer-readable storage medium including code that, when executed by at least one processor, causes the at least one processor to perform such a method is also disclosed.

[0004] An apparatus for radar measurement according to a general configuration includes a transceiver; and a processor communicatively coupled to the transceiver. The processor is configured to transmit, via the transceiver, a first beam having a first frequency characteristic; compute a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmit, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is oriented such that an axis of the second beam intersects a ground plane; and compute an ego velocity of the transceiver based on information from at least one reflection of the second beam. BRIEF DESCRIPTION OF DRAWINGS

[0005] Aspects of the disclosure are illustrated by way of example. In the drawings, like reference numbers indicate like elements.

[0006] Figure 1A A flowchart showing a method M100 for radar measurement according to a general configuration is shown.

[0007] Figure 1B A block diagram showing an apparatus A100 for radar measurement according to a general configuration is shown.

[0008] Figure 2A An example is shown of a range in which the transceiver can be located at the front and / or rear of the vehicle.

[0009] Figure 2B An example is shown of a transceiver located behind the bumper of the vehicle.

[0010] Figure 3A An example is shown of different elevation angles of the main lobe of a transmitted radar beam, ranging from about -45 degrees to about +45 degrees relative to the horizontal plane.

[0011] Figure 3B An example is shown of the transmitted beam direction of a radar sensor in a first mode of operation for object ranging and in a second mode of operation for ego speed estimation.

[0012] Figures 4A-4C An example is shown of the relationship between the ego speed magnitude and the radial component of the ego speed for different angles of incidence of a radar beam.

[0013] Figure 5A An example is shown of different azimuth angles of a received radar beam, ranging from about -45 degrees to about +45 degrees relative to the front axis.

[0014] Figure 5B An example is shown of obtaining measurements of a reflected beam at three different azimuth angles.

[0015] Figure 6A A block diagram is shown of an example of the transmitter part XC20A of the transceiver XC20.

[0016] Figure 6B A block diagram is shown of an example of the receiver part XC20B of the transceiver XC20.

[0017] Figures 7A-7C An example is shown of three different series of chirps of linear frequency modulation.

[0018] Figure 8A An example is shown of processing a received beam signal at intermediate frequency to obtain distance information.

[0019] Figure 8B An example is shown of processing a series of distance FFT vectors to obtain speed information.

[0020] Figure 9 An example is shown of the beam spot width of a road surface.

[0021] Figure 10 is a perspective view of an embodiment V20 of the vehicle V10.

[0022] Figure 11An example computer system 1100 in which one or more embodiments can be implemented is shown. DETAILED DESCRIPTION

[0023] One major task of vehicle automation is environment tracking, which includes object ranging, and can also include estimating the position and velocity of static and dynamic targets (obstacles, other vehicles, pedestrians, etc.) relative to the ego vehicle, i.e., the vehicle tracks the environment. The use of vehicle radars is becoming more and more common, and modern road vehicles (e.g., cars or passenger cars, trucks) are often equipped with one or more radar sensors for environment tracking. Typically, these radar sensors are used to measure the distance and relative velocity (by Doppler measurement) of static and dynamic targets (obstacles, other vehicles, pedestrians, etc.) around the ego vehicle. For example, a radar sensor can be used to detect the speed, distance, and / or direction of objects (e.g., other vehicles, cyclists, pedestrians, road features, or obstacles) near the vehicle. Such detection can be used to support features such as assisted driving (e.g., adaptive cruise control), collision avoidance (e.g., emergency braking assist), and / or autonomous driving.

[0024] Another major task of vehicle automation is ego localization, which estimates the position and velocity of the ego vehicle in a world reference frame. Sensors used for ego localization can include, for example, inertial measurement units (IMUs), global navigation satellite system (GNSS; e.g., global positioning system (GPS)) receivers, cameras (visible light and / or infrared), LIDAR sensors, wheel speed sensors, etc. Each of these sensor types can encounter problems in velocity estimation. Velocity measurements by wheel speed sensors (e.g., speedometers) can include errors due to tire diameter variations. Such variations arise from, for example, changes in wear, temperature, pressure, and / or vehicle load. Odometry sensors can be inaccurate, especially at low speeds, and can also be affected by drift and slippage. Visual sensors (e.g., cameras, LIDAR sensors) are susceptible to precipitation (e.g., rain, snow, fog) and strong light, and can not be usable in darkness. Relative measurements by IMUs (which can include one or more accelerometers, gyroscopes, and / or magnetometers) can be corrupted by bias, and require continuous correction, which is typically performed using GNSS receivers, which can be disabled when GNSS signals are not available.

[0025] One can desire a highly accurate ego speed estimate that is robust to precipitation and road conditions, and is immune to lighting conditions. The measurements of the vehicle radar sensor can also contain information about the ego vehicle's own speed, which can be used to solve the ego localization task to improve accuracy and robustness. Robustness is especially important because radar is a redundant sensor, which has a different failure mode than the sensors typically used for ego localization.

[0026] Unfortunately, there are several challenges associated with using Doppler measurements of the radar sensor directly for ego speed estimation. First, radar sensors are typically configured to optimize the performance of the environment tracking task. Specifically, this optimization includes a tradeoff between the maximum distance that can be unambiguously measured and the maximum Doppler velocity that can be unambiguously measured. A lower radar pulse repetition rate (also known as "pulse repetition frequency" (PRF)) increases the maximum distance, but decreases the maximum Doppler, and vice versa. The environment tracking task typically needs to support distances of up to at least 100 (one hundred) meters, and thus the maximum unambiguous Doppler measurement is typically configured to be very small: in one example, plus or minus 6 meters / second (approximately plus or minus 15 miles per hour (mph)). The resulting highly ambiguous Doppler measurements make the task of ego speed estimation challenging.

[0027] Second, only radar returns from static targets contain information about the ego speed. Returns from dynamic targets constitute outliers to the ego speed estimation task. It is challenging, if not impossible, to filter out these outlier measurements, especially in dense traffic.

[0028] Several illustrative configurations will now be described with reference to the following drawings. The following description is presented in connection with a particular configuration, which can implement one or more aspects of the disclosure. Other configurations, however, can employ each or none of the features described below, and some features described below can apply to a configuration other than the one presented herein. Furthermore, although the following description presents configurations as implemented in a particular environment, configurations can be implemented in any desired environment.

[0029] While the particular examples discussed herein primarily relate to passenger vehicles, it will be understood that the disclosed principles, methods, and apparatuses are more generally directed to powered road vehicles, including freight vehicles (e.g., trucks, tractor trailers), motorcycles, and public transit vehicles (e.g., buses), as well as other ground vehicles (including, for example, agricultural vehicles), and vehicles that use these principles in particular contexts and as disclosed herein.

[0030] Figure 1AA flowchart showing a method M100 for radar measurement according to a general configuration comprising tasks T10, T20, T30 and T40. Task T10 operates an apparatus to transmit a first beam having a first frequency characteristic via a transceiver. The apparatus can be, for example, a radar sensor. Based on information from at least one reflection of the first beam, task T20 computes a distance between the transceiver and a moving object. Task T30 transmits a second beam having a second frequency characteristic different from the first frequency characteristic via the transceiver, wherein the second beam is directed such that an axis of the second beam intersects the ground plane (e.g., a distance of no more than 10 meters from the transceiver). The first frequency characteristic and the second frequency characteristic can be, for example, pulse bandwidth, pulse duration, pulse repetition rate, or pulse shape. Based on information from at least one reflection of the second beam, task T40 computes a self-velocity of the transceiver.

[0031] In one example of the method M100, the apparatus is an environmental tracking radar sensor, and is also used to obtain information about the ego vehicle's own velocity, which can be used to solve the ego localization task with increased accuracy and robustness. The radar sensor alternates between two modes: a traditional object ranging mode and a self-velocity mode. During the object ranging mode, which can be implemented in a traditional way, the radar waveform is optimized for target detection. For example, the radar can be configured to maximize target detection (e.g., with a low PRF). During the self-velocity mode, the radar waveform is optimized for ego localization. For example, the radar can be configured to maximize the use of Doppler measurements for ego localization (e.g., with a high PRF). The system switches between the environmental sensing mode and the self-velocity mode several times per second (e.g., in the range of two, three, four, or five to one hundred, such as ten, twenty, or fifty). The frequency at which the two modes are alternated, as well as the duration of each mode, can be chosen so as to satisfy other system requirements (e.g., update rate and resolution).

[0032] The method M100 can also be implemented to include beam steering, such that the radar beam is steered differently in the two modes. During the object ranging mode, the radar beam can be directed away from the ground and towards surrounding targets. Whenever the radar is operating in the self-velocity mode, the radar beam can be steered such that its main lobe hits directly onto the ground in front of the ego vehicle. This region is in most cases free of any dynamic objects, and confusion with dynamic targets can be expected to be avoided. Thus, the radar echoes measured in the self-velocity mode are expected to come from static targets, and produce anomaly-free information about the ego velocity of the vehicle.

[0033] Figure 1BA block diagram of an apparatus A100 (e.g., a radar sensor) for radar measurement according to a general configuration is shown, which includes a processor P10 communicatively coupled to a transceiver XC10. The processor P10 (e.g., one or more processors, which can include one or more digital signal processors) is configured to transmit, via the transceiver XC10, a first beam having a first frequency characteristic; compute a distance between the transceiver XC10 and a moving object based on information from at least one reflection of the first beam; transmit, via the transceiver XC10, a second beam having a second frequency characteristic different from the first frequency characteristic, where the second beam is oriented such that an axis of the second beam intersects a ground plane; and compute a self-velocity of the transceiver XC10 based on information from at least one reflection of the second beam. For example, the processor P10 can be configured to execute computer-executable instructions that cause the processor to perform such actions. The first and second frequency characteristics can be, for example, a pulse bandwidth, a pulse duration, a pulse repetition rate, or a pulse shape. The apparatus A100 can be implemented such that the transceiver XC10 includes one or more antennas and performs front-end processing of the radar, and such that the processor P10 performs baseband processing of the radar. The apparatus A100 can be installed in a vehicle (e.g., a motor road vehicle) and can be part of a larger vehicle automation system. The transceiver XC10 can be implemented on one or more substrates, while the processor P10 can be implemented on the same substrate as at least a portion of the transceiver XC10 and / or on another substrate. For example, the processor P10 can include a microcontroller unit (MCU) and / or other logic on the same substrate and / or within the same housing as the transceiver XC10. Although the apparatus A100 can be implemented as a dedicated radar and / or LIDAR sensor, the apparatus A100 can also be implemented as a 5G (e.g., New Radio (NR)) and / or millimeter wave (mmWave) device for telecommunications that is also usable for radio frequency (radar) and / or LIDAR sensing. The processor P10 may, for example, be implemented as a 5G baseband processor.

[0034] A transceiver of a vehicle radar sensor emits pulses (e.g., “chirps”) and receives reflections of the pulses from external objects or “targets” (e.g., other vehicles, pedestrians, obstacles). Relative movement between the transceiver and a target can cause a phase drift of the transceiver’s echo signals from one pulse to the next. This drift (also called “Doppler shift”) is proportional to the speed (also called the radial component of the velocity) of the relative movement in the direction of the beam axis.

[0035] If the target's relative movement is neither towards nor away from the transceiver (e.g., directly through the transceiver's field of view), then the speed of the relative movement has little or no radial component. For this reason, to support self-velocity measurement, it can be desirable to position the transceiver XC10 to receive reflections from the road surface along at least a substantial portion of the vehicle's axis of movement (e.g., in a forward-facing direction or a rear-facing direction). Figure 2A Examples are shown in which the transceiver XC10 can be located in the range of the front and / or rear of a vehicle V10 (e.g., a passenger car), with several specific candidate locations indicated by dark circles. In a particular example, the transceiver XC10 is located in the center of the front of the vehicle (e.g., as indicated by the double circle in Figure 2A

[0036] The transceiver XC10 can be located in any location that provides a field of view suitable for environmental sensing (e.g., object ranging) as well as a field of view suitable for self-velocity measurement. For example, it can be desirable for the transceiver to be located behind the bumper of the vehicle (e.g., as shown in Figure 2B In this case, the bumper can be made of a material that is transparent to the beams (e.g., a resin or other plastic), or the transceiver can be mounted behind a window in the bumper that is covered by such a material. It can be desirable to mount the transceiver at a height from the road surface in the range of 30, 40, or 50 to 50, 60, 75, or 100 centimeters.

[0037] The transceiver XC10 can be implemented to transmit at a frequency of approximately 77 GHz. For example, the transceiver XC10 can be implemented to emit beams in the range of approximately 76 to 81 GHz. At these frequencies, the wavelength of the beams is approximately 4 (four) millimeters. Additionally or alternatively, the transceiver XC10 can be configured to transmit at other frequency bands, such as a frequency band of approximately 24 GHz (wavelength of approximately 12.5 (twelve point five) millimeters), or a frequency band of a higher frequency range (such as one hundred GHz or higher). Because the road surface must have sufficient texture depth to provide a minimum required frictional property under both wet and dry conditions, it can be expected that any road surface will produce sufficient backscatter to support self-velocity at these beam frequencies.

[0038] The transceiver of a vehicle radar sensor can be configured to transmit a wide beam (also called a "fan beam") at an elevation angle that can vary over time. Figure 3A ​Examples are shown of different elevations, ranging from about -45 degrees to about +45 degrees relative to the horizontal. Such beams can have a width ranging from 60, 90, or 120 to 120, 150, or 180 degrees, and a height ranging from 5, 10, 20, or 25 to 25, 30, 35, or 45 degrees, for example, and either or both of the width and height can vary over time. Steering of the beam from one elevation to another can be performed in analog circuitry (e.g., by configuring a phased-array of transmitters) and / or digitally. Transceiver XC10 can also be configured to transmit more than one beam at a time.

[0039] Figure 3B Examples are shown of a first mode of operation, in which transceiver XC10 emits a beam for object ranging in a first direction at a first time, and a second mode of operation, in which transceiver XC10 emits a beam for self-velocity estimation in a second direction at a second time. The axis of the beam for self-velocity estimation intersects the ground plane on which the vehicle is located. In this example, the beam for object ranging is oriented at an elevation of zero degrees, while the beam for self-velocity estimation is oriented at an elevation of -45 degrees. In other examples, the beam for object ranging can be oriented at a lower elevation (e.g., for detection of objects in the roadway, for roadside detection, etc.) or a higher elevation (e.g., for detection of overpasses or other overhead objects, for estimation of the height of another vehicle, etc.).

[0040] It can be desirable for the beam for self-velocity estimation to have an elevation ranging from -three, four, five, or ten degrees to -ten, 20, 30, 40, 45, or 50 degrees. For example, it can be desirable for the beam for self-velocity estimation to be tilted downward enough that it cannot see vehicles that the ego vehicle can be tracking. At an elevation of -five degrees and a transceiver height of 50 centimeters, the beam center impinges on the ground about six meters from the transceiver. The elevation of the beam for self-velocity estimation can vary over time, e.g., according to information indicating the distance along the facing direction of the transceiver (e.g., forward or rearward) to the nearest vehicle. Such information can be obtained during an object ranging mode of the transceiver, from one or more other sensors of the vehicle, from communications of one or more other vehicles, and / or from communications of infrastructure entities.

[0041] As the elevation becomes more negative, the angle of incidence of the beam on the road surface increases. As the angle of incidence increases, the amount of backscatter (i.e., the intensity of the reflected beam) is expected to increase. The radial velocity component is expected to decrease as the angle of incidence increases, and can be computed as the product of the ego velocity and the cosine of the angle of incidence. Figures 4A-4C A relationship between the magnitude of the ego velocity and the radial component of the ego velocity is shown for different angles of incidence of a radar beam. In this example, the angle of incidence is measured relative to the road surface, and the radial component of the ego velocity is measured relative to the road surface. Figure 4AIn the example of FIG. 2, the angle of incidence is forty-five degrees, and the magnitude of the radial component of the ego velocity is smaller than the magnitude of the ego velocity by a factor of one-half the square root of two. Figure 4B The example of FIG. 2 shows that the magnitude of the radial component decreases as the angle of incidence increases (approaching zero when the angle of incidence approaches normal). Figure 4C The example of FIG. 2 shows that the magnitude of the radial component decreases as the angle of incidence increases (approaching zero when the angle of incidence approaches normal).

[0042] Vehicle radar sensors are often configured to receive reflected beams over a large azimuth angle, and can be configured to process the received signals to create multiple received beams having different respective widths and / or directions. Figure 5A An example is shown in which the different azimuth angles range from about -45 degrees to about +45 degrees relative to the front axle.

[0043] It can be desirable for the transceiver XC10 to receive information from multiple received beam points (e.g., from multiple different patches of the road surface) for making ego velocity estimates. For example, it can be desirable to estimate components of the ego velocity vector in more than one direction. Figure 5B An example is shown in which measurements of reflected beams are obtained for three different azimuth angles: one beam point at an azimuth angle of zero (e.g., a reflection from a patch of the road surface directly below), one beam point at a positive azimuth angle (e.g., a reflection from a patch of the road surface below and to the right), and one beam point at a negative azimuth angle (e.g., a reflection from a patch of the road surface below and to the left). It can be desirable, but not necessary, for the absolute azimuth angles of the left and right beams to be equal. It can be desirable for the absolute value of the azimuth angle to be in a range from, for example, two, three, four, or five degrees to five, ten, fifteen, 20, or 25 degrees, and the angle can be based on (e.g., limited by) the maximum turning angle of the vehicle.

[0044] The apparatus A100 can be implemented as an implementation P20 of a processor P10 and an implementation XC20 of a transceiver XC10. Figure 6A A block diagram is shown of an example including a transmitter portion XC20A of the transceiver XC20, Figure 6B A block diagram is shown of an example including a receiver portion XC20B of the transceiver XC20. In these particular examples, the transceiver XC20 is a frequency modulated continuous wave (FMCW) transceiver, and it includes a chirp generator CG 10 that provides pulsed signals to both the transmitter and receiver portions. The transmitter portion XC20A and the receiver portion XC20B can be implemented on the same substrate or on different substrates. In other examples, the transceiver XC10 can be implemented as part of a pulsed Doppler sensor or as part of a phase modulated continuous wave (PMC W) sensor.

[0045] Chirp generator CG 10 generates pulses as a series of chirps, the frequency of which varies as described in detail below. Transceiver XC 20 also includes a transmit array having n transmit antenna elements TA1, TA2,..., TAn, and a set of n transmit chains that shape the generated waveforms and drive the transmit array to produce a beam in a desired direction (e.g., elevation angle). Figure 6A In the example of FIG. 1, each of the n transmit chains includes a respective one of phase shifters PS 10-1, PS 10-2,..., PS 10-n that receives a corresponding phase shift value from processor P 20 and applies it to the generated waveforms. Processor P 20 computes the respective phase shift values based on parameter values such as the currently desired beam direction (e.g., depending on whether the sensor is in an environmental sensing mode or a self-velocity estimation mode) and the distance between adjacent transmit antenna elements TA1, TA2,..., TAn. Each of the n transmit chains also includes a respective one of power amplifiers PA1, PA2,..., PAn that drives the corresponding one of transmit antenna elements TA1, TA2,..., TAn with the phase-shifted waveforms. It should be understood that each transmit chain can also include one or more other elements (e.g., one or more filters, baluns, etc.). Transmit antenna elements TA1, TA2,..., TAn can be arranged in a linear (one-dimensional) array, a two-dimensional planar array, or other configuration. The waves produced by the antenna elements interfere constructively and coherently (according to the respective phase shifts) to produce a beam in the currently desired direction.

[0046] Transceiver XC20 also includes a receive array having m receive antenna elements RAl, RA2,..., RAmbwhich receive the reflected pulses (chirps), and a set of m receive chains (where m can be greater than, less than, or equal to n). Receive antenna elements RAl, RA2,..., RAmbmay be arranged in a linear (one-dimensional) array, a two-dimensional planar array, or other configuration. In this example, each of the n transmit chains includes a respective one of low-noise amplifiers LNA1, LNA2,..., LNAmamplifying the corresponding received signal, a respective one of mixers MX1, MX2,..., MXm mixing the amplified signal with a waveform generated by chirp generator CG 10, a respective one of low-pass filters LPF10, LPF20,..., LPFmblocking high-frequency images of the corresponding mixed signal to pass a corresponding intermediate frequency (IF) signal, and a respective one of IF amplifiers IFA1, IFA2,..., IFAmIF. It should be understood that each receive chain can also include one or more other elements, such as one or more filters, baluns, etc. A respective one of analog-to-digital converters ADC10-1, 10-2,..., 10-mconverts the amplified IF signal from the corresponding receive chain to a digital IF signal provided to processor P20. In another example, transceiver XC20 performs additional processing (e.g., a fast Fourier transform or FFT) on the digital IF signal before providing the digital IF signal to processor P20.

[0047] In Figure 6B examples, processor P20 can be configured to perform a beamforming operation on the digital IF signals to produce one or more receive beams in a desired direction (e.g., a direction of a desired beam spot, as discussed above with reference to Figure 5B FIG. 3). For example, processor P20 can process the m digital IF signals to obtain a corresponding composite signal for each of one or more different directions of arrival (DOA), the composite signal representing a beam steered in that direction (e.g., left, center, and right beams as shown in Figure 5B FIG. 3). For each desired beam, and similar to transmit-side beam direction control, this beamforming typically includes applying different corresponding phase shift values to each digital IF signal.

[0048] In one example, the digital signal processor P20 calculates respective phase shift values based on parameter values such as the desired beam direction, the distance between adjacent receive antenna elements RA1, RA2,..., RAn, and so on, and sums the phase-shifted IF signals so that they constructively and coherently interfere (according to the respective phase shifts) to produce a beam in the desired direction. In other examples, different beamforming algorithms can be applied to produce one or more beam signals from the digital IF signals. In another example, the receive portion of the transceiver XC20 can be configured to perform beam steering in the RF domain upstream of the mixing (e.g., using a phase shifter array, and summing the phase-shifted signals to obtain a receive beam in the desired direction). For implementations of the transceiver XC20 that lack horizontal steering beam capability, it can be necessary to direct the beam downward for single-point measurements of the self-velocity estimate.

[0049] The chirp generator CG10 can be configured to produce the pulses as a series of linear frequency modulation (LFM) chirps. Figure 7A An example of a series of LFM chirps is shown, each chirp having a sawtooth shape characterized by a start frequency of f c , a bandwidth of B c , and a duration of T c . For a series of LFM chirps in sawtooth form, the IF bandwidth B IF is equal to the maximum frequency shift, which can be calculated according to the following expression, where c is the speed of light, the maximum distance R max , the chirp bandwidth B c , and the chirp duration T c :

[0050]

[0051] For an example of self-velocity, the chirp bandwidth is 5 (five) GHz, the chirp duration is 50 (fifty) microseconds, the distance from the transceiver to the road beam point is 70 (seventy) centimeters, and the IF bandwidth is approximately 0.5 (one-half) MHz. For an example of object ranging, the chirp bandwidth is 5 (five) GHz, the chirp duration is 50 (fifty) microseconds, the maximum required distance is 100 (one hundred) meters, and the IF bandwidth is approximately 33 (thirty-three) MHz. The maximum pulse repetition frequency (PRF) is equal to the inverse of the chirp duration; if a series of consecutive chirps is spaced apart, the PRF will be lower than this maximum value.

[0052] The chirp bandwidth can have a value in the range of, for example, one to ten GHz (e.g., one, two, 2.5, three, four, 4.5, or five GHz). The chirp duration can have a value in the range of, for example, one, two, four, or five microseconds to fifty or one hundred microseconds (e.g., ten, twenty, or thirty microseconds). It can be desirable to configure the apparatus A100 such that the chirp bandwidth for the object ranging mode is higher than the chirp bandwidth for the ego speed mode. Additionally or alternatively, it can be desirable to configure the apparatus A100 such that the chirp duration for the object ranging mode is longer than the chirp duration for the ego speed mode.

[0053] Figure 7B An example of a series of LFM chirps in the form of triangles is shown, in which the rise and fall times of the modulation are equal, Figure 7C An example of a series of LFM chirps in the form of triangles is shown, in which the rise and fall times of the modulation are not equal. Any of the chirp waveforms shown in Figure 7A , Figure 7B and Figure 7C may be modified such that one or more segments (e.g., the rise segment and / or the fall segment) of each chirp of the series is non-linear and / or stair-like. In one such example, a series of sinusoidal frequency modulated chirps is used. It can be desirable to configure the apparatus A100 such that the form of the chirps used for the object ranging mode is different from the form of the chirps used for the ego speed mode.

[0054] Figure 8A An example of processing the beam signals received at IF to obtain distance information is shown. For each echo chirp in the signal, the processor P10 or the transceiver XC10 can be configured to perform a Fast Fourier Transform (FFT) operation (also referred to as a “range FFT”) to obtain a corresponding FFT vector that indicates the distance of any object detected by the reflected chirp. In particular, each component of the range FFT vector represents a different value in the distance dimension.

[0055] Figure 8B An example of processing a series of range FFT vectors to obtain velocity information is shown. The processor P10 or the transceiver XC10 can be configured to perform a second FFT operation (also referred to as a “Doppler FFT”) on the series of range FFT vectors to obtain a two-dimensional array (also referred to as a “heat map”) that indicates the radial velocity of the detected objects. In particular, for each range component in the range FFT vector, the Doppler FFT performs an FFT operation on the series to obtain a corresponding velocity vector for that range component, where each component of the velocity vector represents a different value in the velocity dimension.

[0056] Because the speed information in the heat map is typically indicated by the phase difference between the range FFT vectors, it can be desirable for the phase of the transmitted beam to remain consistent across the corresponding series of range FFT vectors. In practice, it can be desirable for the series of range FFT vectors to come from a series of consecutive echo chirps.

[0057] To support self speed measurement, it can be desirable to obtain samples of multiple echo beams from the same patch of road surface. The time to sample a patch of road surface depends on the patch size and the self speed, while the patch size depends on the angle of incidence and the beam width. Figure 9 An example is shown in which the transceiver XC10 is located fifty centimeters above the road surface, the angle of incidence of the beam is forty-five degrees, and the width of the received beam is twenty degrees. In this example, the width of the beam spot on the road surface is thirty-six centimeters. At a speed of seventy miles per hour (approximately thirty-one meters per second) on a highway, the vehicle V10 will travel this distance in approximately twelve milliseconds. In this time period, a radar transceiver operating at a PRF of 25 kHz (corresponding to a chirp duration of no more than 40 microseconds) will emit approximately three hundred chirps.

[0058] Doppler frequency aliasing can occur during self speed measurement when the radial velocity component of the self speed exceeds the following value:

[0059]

[0060] where PRF is the pulse repetition frequency, c is the speed of light, and f is the beam frequency. For an example in which the PRF is twenty-five kHz and the beam frequency is 77 GHz, this value is approximately fifty meters per second (approximately one hundred ten miles per hour). For a beam angle of incidence of forty-five degrees, this value corresponds to an explicit self speed range of approximately seventy meters per second (approximately one hundred sixty miles per hour). For cases in which Doppler frequency aliasing can be a concern for self speed estimation, the speed estimation of one or more other sensors (e.g., a speedometer) can be used to de-alias.

[0061] As described above, the processor P10 can be configured to cause the transceiver XC10 to switch between the object tracking mode and the self speed mode several times per second (e.g., in the range of two, three, four, or five to one hundred, such as ten, twenty, or fifty). The frequency at which the two modes are alternated, as well as the duration used for each mode, can be selected so that other system requirements (e.g., update rate and resolution) are met. The frequency at which the two modes are alternated can also vary over time to provide a highly dynamic approach. For example, the duty cycle in the two modes can change depending on whether increased environmental tracking or increased self speed estimation is needed at a particular time.

[0062] Coordination of the environmental tracking and self-speed sensing modes can also be performed between each vehicle equipped with an instance of the apparatus A100 and capable of communicating with each other. For example, for different vehicles traveling in a coordinated formation (e.g., a vehicle platoon), the duty cycle between the two modes can be different, with some vehicles (e.g., the lead vehicle) using a larger share of the time to perform environmental sensing (looking up and / or forward), while other vehicles (e.g., the followers) use a larger share of the time to perform speed sensing (looking down). Coordination between vehicles over time and / or frequency to reduce cross-interference is also possible; for example, beams oriented downward for self-speed measurement are less likely to cause interference.

[0063] In addition to self-speed measurement (e.g., estimation), information from the reflections of the received beams off of the road block can also be used to sense road conditions such as, for example, road noise estimation and / or detection of negative obstacles (e.g., potholes), instantaneous height variations (e.g., humps), uneven road surfaces, and / or one or more environmental conditions (e.g., wet road, black ice), and / or features (e.g., road surface roughness features). The apparatus A100 can be configured to process one or more of the received reflections using, for example, deep learning (e.g., trained neural networks) and / or classical algorithms to determine one or more such road conditions and / or features. Additionally or alternatively, such information can be used to support vehicle localization by detecting, for example, retro-reflectors or other lane markers (using, for example, deep learning (e.g., trained neural networks) and / or classical algorithms).

[0064] Although the apparatus A100 is described as a radar sensor, the principles disclosed herein can also be extended to embodiments where the apparatus A100 is a LIDAR sensor that supports beam steering (e.g., using metamaterials and / or MEMS-based mirrors) and Doppler measurements.

[0065] The apparatus A100 can be installed in a vehicle that includes one or more other sensors that can support vehicle automation. Figure 10is a perspective view of such an embodiment V20 of the vehicle V10. The vehicle V20 can include one or more cameras, such as a rearview mirror mounted camera 806, a front bumper mounted camera (not shown), side mirror mounted cameras (not shown), and a rear camera (not shown, but typically on the trunk, hatch, or rear bumper). The vehicle V20 can also have a lidar 804 for detecting objects and measuring distances to those objects; the lidar 804 is typically roof mounted, however, if multiple lidar units 804 are present, they can be oriented toward the front, rear, and sides around the vehicle. The vehicle V20 can have other various location related systems (such as a GNSS receiver (typically in a shark fin unit on the rear of the roof, as indicated), various wireless communication interfaces (such as WAN, WLAN, V2X; typically but not necessarily in the shark fin) 802, and SONAR 810 (if present, typically on both sides of the vehicle)). Various wheel sensors 812 and drivetrain sensors can also be present, such as tire pressure sensors, accelerometers, gyroscopes, and wheel rotation detection and / or counters. In embodiments, distance measurements and relative positions determined via various sensors such as LIDAR, radar, cameras, GNSS, and SONAR can be combined with car size and shape information and information about sensor locations to determine distances and relative positions between different vehicle surfaces, such that distances or vectors between sensors to another vehicle or between two different sensors (such as two GNSS receivers) are incrementally added to account for the location of the sensor on each vehicle. Thus, it can be desirable to modify the exact GNSS distance and vector between two GNSS receivers based on, for example, the relative positions of various car surfaces to the GNSS receivers. It should be appreciated that this list is not intended to be limiting, and Figure 10 intended to provide exemplary locations for various sensors in embodiments of vehicles including instances of the apparatus A100.

[0066] Figure 11 An example computer system 1100 is shown that can be utilized with and / or in conjunction with one or more electronic components of the apparatus A100 (e.g., the transceiver XC10, the processor P10). In certain embodiments, the computer system 1100 is deployed in a vehicle (e.g., the vehicle V10 or V20). It should be noted, Figure 11 is merely intended to provide a generalized illustration of various components, any or all of which can be utilized as appropriate. Hence, Figure 11 broadly illustrates how separate system elements can be implemented in a relatively

[0067] As Figure 11As depicted, computer system 1100 can include hardware elements that can be communicatively coupled via bus 1105 (or other wired and / or wireless communication means as appropriate). The hardware elements can include one or more processing units 1110, which can include without limitation one or more general-purpose processors, one or more special-purpose processors (such as digital signal processors (DSPs), graphics processing units (GPUs), application-specific integrated circuits (ASICs), and / or the like), and / or the like. Processing unit(s) 1110 can perform radar processing, including, for example, transmitting and receiving radar signals, applying DFTs, detecting interference from another radar source, and calculating distance and velocity of objects based on received radar signals. Processor P10 can be implemented in whole or in part within processing unit(s) 1110. For example, processor P10 can be implemented at least in part as an application processor, an infotainment processor, and / or an advanced driver assistance system (ADAS) processor.

[0068] Computer system 1100 can include one or more input devices 1115, which can comprise without limitation a touchscreen, a keyboard, a touchscreen, a camera, a microphone, and / or the like; and one or more output devices (not shown), which can comprise without limitation a display device, a speaker, and / or the like.

[0069] Computer system 1100 can also include wireless communication interface 1130, which can include without limitation a network card, an infrared communication device, a wireless communication device, and / or a chipset (such as a Bluetooth® device, an IEEE 802.11 device, a Wi-Fi® device, a WiMax® device, a ZigBee® device, and / or the like), and / or the like, which can enable computer system 1100 to communicate with external computer systems or electronic devices. Communication can be via one or more wireless communication antennas (not shown) that transmit and / or receive wireless signals.

[0070] Input device(s) 1115 can also include one or more sensors. Such sensors can include without limitation one or more instances of radar sensors (e.g., device A100 including transceiver XC10), inertial sensors (e.g., accelerometers and / or gyroscopes), cameras, magnetometers, altimeters, microphones, ultrasonic sensors, light sensors, and / or the like, some of which can be used to supplement and / or facilitate radar-related processing described herein.

[0071] Computer system 1100 can also include GNSS receiver 802, which can be operable to receive signals from one or more GNSS satellites using an antenna. These signals can be utilized to supplement and / or incorporate techniques described herein (e.g., deriving a shared time reference for aligning chirp sequences). In certain embodiments, GNSS signals can be used to determine a geographic location of computer system 1100, e.g., for vehicle navigation.

[0072] ​The computer system 1100 can also include and / or be in communication with a memory 1135. The memory 1135 can include, without limitation, local and / or network accessible storage, a disk drive, a drive array, an optical storage device, a solid-state storage device, such as a random access memory ("RAM"), and / or a read-only memory ("ROM"), which can be programmable, flash-updateable, and / or the like. Such storage devices can be configured to implement any appropriate data saves, including without limitation, various file systems, database structures, and / or the like. In certain embodiments, the memory 1135 can store a codebook including transmit waveform parameters.

[0073] The memory 1135 can include a non-transitory computer-readable medium that stores instructions executable by one or more processors (e.g., the processing unit 1110) of the computer system 1100. Such instructions can be saved as program code, e.g., an operating system 1140, device drivers, executable libraries, or other application programs 1145. The instructions saved in the memory 1135 can be configured to cause the processor to perform radar-related processing described herein. By way of example only, one or more processes of the method M100 discussed above with respect to Figure 1A may be implemented as code and / or instructions executable by the processing unit 1110. Then, in an aspect, such code and / or instructions can be used to configure and / or adapt a general purpose computer or other computing device (e.g., the processor P10 or P20) to perform one or more operations according to the techniques described herein.

[0074] Substantial variations can be made in accordance with specific requirements. For example, customized hardware might also be used, and / or particular elements might be implemented in hardware, software (including portable software, such as applets, etc.), or both. Further, connection to other computing devices such as network input / output devices can be employed.

[0075] Unless otherwise indicated herein, the term "signal" is used herein in its ordinary sense to indicate any of its ordinary meanings, including a state of a memory location (or set of memory locations) expressed on a cable, bus, or other transmission medium. Unless otherwise indicated herein, the term "generating" is used herein in its ordinary sense to indicate any of its ordinary meanings, such as computing or otherwise producing. Unless otherwise indicated herein, the term "computing" is used herein in its ordinary sense to indicate any of its ordinary meanings, such as calculating, evaluating, estimating, and / or selecting from a plurality of values. Unless otherwise indicated herein, the term "obtaining" is used herein in its ordinary sense to indicate any of its ordinary meanings, such as calculating, deriving, receiving (e.g., from an external device), and / or retrieving (e.g., from an array of memory elements). Unless otherwise indicated herein, the term "selecting" is used herein in its ordinary sense to indicate any of its ordinary meanings, such as identifying, indicating, applying, and / or using at least one of two or more sets, and less than all. Unless otherwise indicated herein, the term "determining" is used herein in its ordinary sense to indicate any of its ordinary meanings, such as deciding, establishing, concluding, calculating, selecting, and / or evaluating. The term "comprising" is used herein to mean that other elements can also be included (i.e., it is inclusive, not exclusive). The term "based on" is used herein to mean "based, at least in part, on" unless otherwise indicated herein (i.e., it is not exclusive, but rather, inclusive). Similarly, the term "in response to" is used herein to mean "in response, at least in part, to" unless otherwise indicated herein. The terms "at least one of," "one or more of," and "at least one of each of" are used herein to mean "one or more of each of," unless otherwise indicated herein. The terms "each of," "each of each of," and "each of A, B, and C" are used herein to mean "A and B and C," unless otherwise indicated herein.

[0076] Unless otherwise indicated herein, any disclosure of operation of a device having specific features is also expressly intended to disclose methods having the same features (and vice versa), and any disclosure of operation of a device according to a specific configuration is also expressly intended to disclose methods according to the same configuration (and vice versa). The term "configuration" can be used to refer to methods, devices, and / or systems, as the particular context indicates. The terms "method," "process," "procedure," and "technique" are generic and interchangeable, unless a particular context indicates otherwise. A "task" having multiple sub-tasks is also a method. The terms "device" and "apparatus" are also generic and interchangeable, unless a particular context indicates otherwise. The terms "element" and "module" are generally used to indicate a portion of a larger configuration. Unless otherwise indicated herein, the term "system" is used herein in its ordinary sense to indicate any of its ordinary meanings, including "a group of elements that interact to achieve a common purpose."

[0077] Unless originally introduced by a definite article, an ordinal word used to modify an element of a claim (e.g., "first," "second," "third," etc.) does not itself indicate any priority or order of that claim element relative to another element, but merely distinguishes that claim element from another claim element having the same name but using an ordinal word. Unless expressly limited by the context of their usage, each of the terms "plurality" and "a group" as used herein is used to indicate an integer quantity greater than one.

[0078] Various elements of embodiments of the apparatus or system disclosed herein can be embodied in any combination of hardware and software and / or firmware considered appropriate for the intended application. For example, such elements can be fabricated into electronic and / or optical devices, e.g., residing on the same chip or between two or more chips in a chipset. One example of such a device is an array of fixed or programmable logic elements (e.g., transistors or logic gates), any of which can be implemented as one or more such arrays. Any two or more, or even all, of these elements can be implemented within the same array or arrays, which can be implemented within one or more chips (e.g., within a chipset comprising two or more chips).

[0079] Processors or other means for processing disclosed herein can be fabricated into one or more electronic and / or optical devices, e.g., residing on the same chip or between two or more chips in a chipset. One example of such a device is an array of fixed or programmable logic elements (e.g., transistors or logic gates), any of which can be implemented as one or more such arrays. Such one or more arrays can be implemented within one or more chips (e.g., within a chipset comprising two or more chips). Examples of such arrays include arrays of fixed or programmable logic elements (e.g., microprocessors, embedded processors, IP cores, DSPs (digital signal processors), FPGAs (field-programmable gate arrays), ASSPs (application-specific standard products), and ASICs (application-specific integrated circuits)). Processors or other means for processing disclosed herein can also be embodied as one or more computers (e.g., machines including one or more arrays programmed to execute one or more sets or sequences of instructions) or other processors. Processors described herein can be used to execute tasks or execute other sets of instructions that are not directly related to the implementation of method M100 (e.g., tasks related to another operation of an apparatus or system in which the processor is embedded, or another method disclosed with reference to the operation of an apparatus or system described herein). It is possible for a portion of the method disclosed herein to be executed under the control of one or more other processors.

[0080] Each of the tasks of the methods disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. In a typical application of the implementations of the methods disclosed herein, an array of logic elements (e.g., logic gates) is configured to perform one, more than one, or even all of the various tasks of the method. One or more (possibly all) of the tasks can also be implemented as code (e.g., one or more sets of instructions), which can be embodied in a computer program product (e.g., one or more data storage media such as floppy disks, flash memories, or other nonvolatile storage, semiconductor memory chips, etc.), which can be read and / or executed by a machine (e.g., a computer) including an array of logic elements (e.g., a processor, microprocessor, microcontroller, or other finite state machine). The tasks of the implementations of the methods disclosed herein can also be performed by more than one such array or machine.

[0081] In one or more exemplary embodiments, the operations described herein can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the operations can be saved as one or more instructions or code on a computer-readable medium and transmitted over a computer network or through a computer program product. The term "computer-readable medium" includes both computer readable storage media and communication media. By way of example, and not limitation, computer readable storage media can include an array of storage elements (e.g., semiconductor memory (which can include without limitation dynamic or static RAM, ROM, EEPROM, and / or flash memory), or ferroelectric, resistive, ovonic, polymeric, or phase-change memories; CD-ROM or other optical disk storage; and / or magnetic disk storage or other magnetic storage devices) that are accessible by a computer. The storage elements can be configured to store instructions that implement the operations described herein. Communication media can include any medium that facilitates the transfer of computer program instructions or data between computing devices, including without limitation wired media (e.g., wired networks and direct-wired connections), and wireless media (e.g., wireless networks and Bluetooth® wireless technology). Additionally, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and / or microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and / or microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. TM ​

[0082] In one example, a non-transitory computer-readable storage medium includes code that, when executed by at least one processor, causes the at least one processor to perform the method of radar measurement described herein.

[0083] The preceding description is meant to be illustrative only and is not intended to limit the scope of the disclosure. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the teachings hereof. It is therefore understood that the scope of the disclosure is not to be limited to the specific examples set forth herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

[0084] In view of this description, embodiments can include different combinations of the features described. The following numbered clauses set forth examples of implementations.

[0085] Clause 1. An apparatus for radar measurement, the apparatus comprising: a transceiver; and a processor communicatively coupled to the transceiver and configured to: transmit, via the transceiver, a first beam having a first frequency characteristic; determine a distance between the apparatus and an object based on information from at least one reflection of the first beam; transmit, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is directed such that an axis of the second beam intersects a ground plane; and determine a self-velocity of the apparatus based on information from at least one reflection of the second beam.

[0086] Clause 2. The apparatus of clause 1, wherein the at least one reflection of the second beam is based on backscatter from a road surface.

[0087] Clause 3. The apparatus of clause 1 or 2, wherein transmitting the second beam comprises causing the transceiver to direct the second beam such that an axis of the second beam intersects the ground plane no more than ten meters from the transceiver.

[0088] Clause 4. The apparatus of any of clauses 1-3, wherein the processor is configured to cause operation of the transceiver to switch between transmitting the first beam and transmitting the second beam multiple times per second.

[0089] Clause 5. The apparatus of any of clauses 1-4, wherein the first beam comprises a first series of frequency-modulated pulses, and wherein the second beam comprises a second series of frequency-modulated pulses, wherein the first frequency characteristic is a characteristic of the first series of pulses, and wherein the second frequency characteristic is a characteristic of the second series of pulses.

[0090] Clause 6. The apparatus of clause 5, wherein the first frequency characteristic is a bandwidth of the pulses in the first series, wherein the second frequency characteristic is a bandwidth of the pulses in the second series, and wherein the first frequency characteristic is higher than the second frequency characteristic.

[0091] Clause 7. The apparatus of clause 5, wherein the first frequency characteristic is a duration of the pulses in the first series, and wherein the second frequency characteristic is a duration of the pulses in the second series, and wherein the first frequency characteristic is longer than the second frequency characteristic.

[0092] Clause 8. The apparatus of any of clauses 1-7, wherein the first frequency characteristic is a pulse repetition rate of the first beam, and wherein the second frequency characteristic is a pulse repetition rate of the second beam, and wherein the first frequency characteristic is lower than the second frequency characteristic.

[0093] Clause 9. The apparatus of any of clauses 1-8, wherein transmitting the first beam comprises causing the transceiver to direct the first beam such that an axis direction of the first beam is no lower than horizontal.

[0094] Clause 10. The apparatus of any of clauses 1-9, wherein the information from the at least one reflection of the second beam comprises information from each of a plurality of different patches of a road surface.

[0095] Clause 11. A radar measurement method, the method comprising: transmitting, via a transceiver, a first beam having a first frequency characteristic; determining a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is directed such that an axis of the second beam intersects a ground plane; and calculating a self-velocity of the transceiver based on information from at least one reflection of the second beam.

[0096] Clause 12. The method of clause 11, wherein the at least one reflection of the second beam is based on backscatter from a road surface.

[0097] Clause 13. The method of clause 11 or 12, wherein the transmitting the second beam comprises causing the transceiver to direct the second beam such that an axis of the second beam intersects the ground plane no more than ten meters from the transceiver.

[0098] Clause 14. The method of any of clauses 11-13, wherein the method comprises causing operation of the transceiver to switch between transmitting the first beam and transmitting the second beam multiple times per second.

[0099] Clause 15. The method of any of clauses 11-14, wherein the first beam comprises a first series of frequency modulated pulses, and wherein the second beam comprises a second series of frequency modulated pulses, and wherein the first frequency characteristic is a characteristic of the pulses of the first series, and wherein the second frequency characteristic is a characteristic of the pulses of the second series.

[0100] Clause 16. The method of clause 15, wherein the first frequency characteristic is a bandwidth of the pulses in the first series, and wherein the second frequency characteristic is a bandwidth of the pulses in the second series, and wherein the first frequency characteristic is higher than the second frequency characteristic.

[0101] Clause 17. The method of clause 15, wherein the first frequency characteristic is a duration of the pulses in the first series, and wherein the second frequency characteristic is a duration of the pulses in the second series, and wherein the first frequency characteristic is longer than the second frequency characteristic.

[0102] Clause 18. The method of any of clauses 11-17, wherein the first frequency characteristic is a pulse repetition rate of the first beam, and wherein the second frequency characteristic is a pulse repetition rate of the second beam, and wherein the first frequency characteristic is lower than the second frequency characteristic.

[0103] Clause 19. The method of any of clauses 11-18, wherein the transmitting the first beam comprises causing the transceiver to direct the first beam such that an axis direction of the first beam is no lower than horizontal.

[0104] Clause 20. The method of any of clauses 11-19, wherein the information from the at least one reflection of the second beam comprises information from each of a plurality of different patches of a road surface.

[0105] Clause 21. A non-transitory computer-readable storage medium comprising code, which, when executed by at least one processor, causes the at least one processor to perform a method of radar measurement, the method comprising: transmitting, via a transceiver, a first beam having a first frequency characteristic; calculating a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is directed such that an axis of the second beam intersects a ground plane; and calculating a self-velocity of the transceiver based on information from at least one reflection of the second beam.

[0106] Clause 22. The apparatus of clause 1, wherein the transmitting the second beam comprises varying an elevation angle of the second beam over time in accordance with information indicating a distance to a nearest vehicle along a facing direction of the transceiver.

[0107] Clause 23. The method of clause 11, wherein the transmitting the second beam comprises varying an elevation angle of the second beam over time in accordance with information indicating a distance to a nearest vehicle along a facing direction of the transceiver.

Claims

1. An apparatus for radar measurement, the apparatus comprising: a transceiver; and a processor communicatively coupled to the transceiver and configured to: transmit, via the transceiver, a first beam having a first frequency characteristic; determine a distance between the apparatus and an object based on information from at least one reflection of the first beam; transmit, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is oriented such that an axis of the second beam intersects a ground plane, wherein the first frequency characteristic is a pulse repetition rate of the first beam and the second frequency characteristic is a pulse repetition rate of the second beam, and wherein the first frequency characteristic is lower than the second frequency characteristic; and determine a self velocity of the apparatus based on information from at least one reflection of the second beam.

2. The apparatus of claim 1, wherein the at least one reflection of the second beam is based on backscatter from a road surface.

3. The apparatus of claim 1, wherein the transmitting the second beam comprises causing the transceiver to orient the second beam such that an axis of the second beam intersects the ground plane no more than ten meters from the transceiver.

4. The apparatus of claim 1, wherein the processor is configured to cause operation of the transceiver to switch between transmitting the first beam and transmitting the second beam multiple times per second.

5. The apparatus of claim 1, wherein the first beam comprises a first series of frequency modulated pulses, and wherein the second beam comprises a second series of frequency modulated pulses, and wherein the first beam has a first additional frequency characteristic, and wherein the second beam has a second additional frequency characteristic.

6. The apparatus of claim 5, wherein the first additional frequency characteristic is a bandwidth of pulses in the first series, and wherein the second additional frequency characteristic is a bandwidth of pulses in the second series, and wherein the first additional frequency characteristic is higher than the second additional frequency characteristic.

7. The apparatus of claim 5, wherein the first additional frequency characteristic is a duration of pulses in the first series, and wherein the second additional frequency characteristic is a duration of pulses in the second series, and wherein the first additional frequency characteristic is longer than the second additional frequency characteristic.

8. The apparatus of claim 1, wherein the transmitting the first beam comprises causing the transceiver to orient the first beam such that an axis of the first beam is no lower than horizontal.

9. The apparatus of claim 1, wherein the information from at least one reflection of the second beam comprises information from each of a plurality of different patches of a road surface.

10. The apparatus of claim 1, wherein transmitting the second beam comprises varying an elevation angle of the second beam over time in accordance with information indicative of a distance to a nearest vehicle along a facing direction of the transceiver.

11. A method of radar measurement, the method comprising: transmitting, via a transceiver, a first beam having a first frequency characteristic; determining a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is oriented such that an axis of the second beam intersects a ground plane, wherein the first frequency characteristic is a pulse repetition rate of the first beam and the second frequency characteristic is a pulse repetition rate of the second beam, and wherein the first frequency characteristic is lower than the second frequency characteristic; and computing a self velocity of the transceiver based on information from at least one reflection of the second beam.

12. The method of claim 11, wherein the at least one reflection of the second beam is based on backscatter from a road surface.

13. The method of claim 11, wherein transmitting the second beam includes causing the transceiver to orient the second beam such that an axis of the second beam intersects the ground plane no more than ten meters from the transceiver.

14. The method of claim 11, wherein the method includes causing operation of the transceiver to switch between transmitting the first beam and transmitting the second beam multiple times per second.

15. The method of claim 11, wherein the first beam includes a first series of frequency modulated pulses, and wherein the second beam includes a second series of frequency modulated pulses, and wherein the first beam has a first additional frequency characteristic, and wherein the second beam has a second additional frequency characteristic.

16. The method of claim 15, wherein the first additional frequency characteristic is a bandwidth of pulses in the first series, and wherein the second additional frequency characteristic is a bandwidth of pulses in the second series, and wherein the first additional frequency characteristic is higher than the second additional frequency characteristic.

17. The method of claim 15, wherein the first additional frequency characteristic is a duration of pulses in the first series, and wherein the second additional frequency characteristic is a duration of pulses in the second series, and wherein the first additional frequency characteristic is longer than the second additional frequency characteristic.

18. The method of claim 11, wherein transmitting the second beam includes varying an elevation angle of the second beam over time according to information indicative of a distance to a nearest vehicle along a facing direction of the transceiver.

19. The method of claim 11, wherein transmitting the first beam includes causing the transceiver to orient the first beam such that an axis direction of the first beam is no lower than horizontal.

20. The method of claim 11, wherein the information from at least one reflection of the second beam includes information from each of a plurality of different patches of a road surface.

21. A non-transitory computer-readable storage medium comprising code, which, when executed by at least one processor, causes the at least one processor to perform a method of radar measurement, the method comprising: transmitting, via a transceiver, a first beam having a first frequency characteristic; computing a distance between the transceiver and a moving object based on information from at least one reflection of the first beam; transmitting, via the transceiver, a second beam having a second frequency characteristic different from the first frequency characteristic, wherein the second beam is oriented such that an axis of the second beam intersects a ground plane, wherein the first frequency characteristic is a pulse repetition rate of the first beam and the second frequency characteristic is a pulse repetition rate of the second beam, and wherein the first frequency characteristic is lower than the second frequency characteristic; and computing a self velocity of the transceiver based on information from at least one reflection of the second beam.

22. An apparatus for radar measurements, the apparatus comprising means for performing the method of any one of claims 11-20.

23. A computer program product comprising computer readable instructions, which when executed by a processor, cause the processor to perform the method of any one of claims 11-20.

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