Slanted radome

Abstract

An exemplary embodiment relates to a tilted radome for protecting a radar unit. An exemplary radar system may include a radar unit including at least one antenna having a radiation pattern. The radar unit is configured to transmit radar signals based on the radiation pattern and to receive radar signals. The radar system further includes a radome positioned in a transmission direction of the radiation pattern. Specifically, the radome is aligned at an angle with respect to a plane of the at least one antenna such that reflections of the transmitted radar signal caused by the radome are directed toward at least one of a null in the radiation pattern and an absorbing component.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 16 / 532,655, filed August 6, 2019, which is hereby incorporated by reference in its entirety. [Background technology]

[0002] Radio detection and ranging systems ("radar systems") may be used to actively estimate distances to environmental features by emitting radio signals and detecting the returning reflected signals. The distance to radio-reflective features may be determined according to the time delay between transmission and reception. Radar systems may emit signals whose frequency changes over time, such as signals with a time-varying frequency ramp, to relate the difference in frequency between the emitted and reflected signals to a distance estimate. Some radar systems may also estimate the relative motion of a reflecting object based on the Doppler frequency shift of the received reflected signal.

[0003] Directional antennas may also be used to transmit and / or receive signals to associate each distance estimate with a bearing. More generally, directional antennas may be used to focus radiant energy on a given field of view of a target. Combining the measured distance and directional information allows for mapping of surrounding environmental features. Summary of the Invention

[0004] The present disclosure relates generally to radar systems and certain aspects of radomes designed to protect radar units within the radar systems.

[0005] Thus, a first embodiment describes a radar system. The radar system comprises a radar unit including at least one antenna having a radiation pattern. The radar unit is configured to (i) transmit a radar signal based on the radiation pattern and (ii) receive the radar signal. The radar system further comprises a radome located in a transmission direction of the radiation pattern. The radome is aligned at an angle with respect to a plane of the at least one antenna such that reflections of the transmitted radar signal caused by the radome are directed to at least one of (i) a null in the radiation pattern and (ii) an absorbing component.

[0006] A second embodiment describes a radar unit. The radar unit comprises a plurality of antennas having a radiation pattern. The plurality of antennas are configured to (i) transmit radar signals based on the radiation pattern and (ii) receive the radar signals. The radar unit further includes a radome located in a transmission direction of the radiation pattern. Furthermore, the radome is aligned at an angle with respect to a plane of the plurality of antennas such that reflections of the transmitted radar signals caused by the radome are directed to at least one of (i) a null in the radiation pattern and (ii) an absorbing component.

[0007] A third embodiment describes a method of operating a radar system. The method includes transmitting, using a radar unit including at least one antenna having a radiation pattern, a radar signal based on the radiation pattern. The radar system includes a radome located in a transmission direction of the radiation pattern. The radome is aligned at an angle with respect to a plane of the at least one antenna such that reflections of the transmitted radar signal caused by the radome are directed into at least one of (i) a null in the radiation pattern, and (ii) an absorbing component. The method further includes receiving, using the radar unit, one or more radar signals reflected to the radar unit by one or more surfaces in an environment of the radar system.

[0008] The fourth embodiment may include a system including various means for performing each of the operations of the first, second, and third embodiments.

[0009] These and other embodiments, aspects, advantages, and alternatives will become apparent to those skilled in the art upon reading the following detailed description, with appropriate reference to the accompanying drawings. Moreover, it should be understood that this summary and other descriptions and figures provided herein are intended to illustrate embodiments by way of example only, and thus, numerous variations are possible. For example, structural elements and process steps may be rearranged, combined, distributed, eliminated, or otherwise modified while still remaining within the scope of the claimed embodiments. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a functional block diagram illustrating a vehicle, according to one or more exemplary embodiments. [Figure 2A] 1 illustrates a side view of a vehicle in accordance with one or more exemplary embodiments. [Figure 2B] 1 illustrates a top view of a vehicle in accordance with one or more exemplary embodiments. [Figure 2C] 1 illustrates a front view of a vehicle in accordance with one or more exemplary embodiments. [Figure 2D] 1 illustrates a rear view of a vehicle in accordance with one or more exemplary embodiments. [Figure 2E] 1 illustrates additional views of a vehicle in accordance with one or more exemplary embodiments. [Diagram 3] 1 illustrates a layout diagram of a radar sector in accordance with one or more exemplary embodiments. [Figure 4A] 1 illustrates a basic radome of a radar unit in accordance with one or more exemplary embodiments. [Figure 4B] 1 illustrates another view of a basic radome of a radar unit in accordance with one or more exemplary embodiments. [Figure 5A]1 illustrates a tilted radome for a radar unit in accordance with one or more exemplary embodiments. [Figure 5B] 1 illustrates another view of a tilted radome for a radar unit in accordance with one or more exemplary embodiments. [Figure 6] 1 illustrates a method of operating a radar system in accordance with one or more exemplary embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like symbols typically identify like components unless otherwise stated in context. The exemplary embodiments described in the detailed description, figures, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are expressly contemplated herein.

[0012] A radar system uses one or more antennas to radiate (i.e., transmit) radar signals to measure aspects of the environment. Upon contact with a surface in the environment, the emitted radar signal scatters in multiple directions, some penetrating various surfaces and others reflecting off the surface back to one or more receiving antennas of the radar system. Once received by one or more receiving antennas, the radar reflections may be processed to generate two-dimensional (2D) and / or three-dimensional (3D) measurements of the environment. Specifically, these measurements may convey the position, orientation, and motion of nearby surfaces occupying the environment near the radar system.

[0013] Radar systems are increasingly being used to aid in vehicle navigation and safety because they can measure the distance and motion of nearby objects and other surfaces. In particular, measurements from vehicle radar systems can improve overall performance and safety during vehicle navigation. Vehicle radar systems can detect and identify the position, orientation, and motion of nearby vehicles. Radar measurements can also reveal information about other features of the vehicle's surrounding environment, such as road boundaries and road conditions (e.g., smooth or uneven surfaces), weather conditions (e.g., wet or snowy roads), traffic signs and signals, and pedestrians. In some examples, radar measurements are used to assist a driver in controlling the vehicle. For example, radar measurements can be used to generate a warning if the vehicle is too close to another vehicle or object. Radar measurements can also be used to develop control strategies for autonomous or semi-autonomous navigation of a vehicle.

[0014] Some vehicle radar systems are installed by mounting radar units at various external locations on the vehicle. For example, one or more radar units may be coupled to the vehicle at various locations, such as the vehicle's door mirrors, bumper, roof, front grille, doors, trunk, or side panels. Using external locations to mount and position the radar units allows for rapid installation of the radar system on a standard vehicle without requiring the vehicle to be redesigned or specially manufactured. Furthermore, the orientation and location of the radar unit may be easily adjusted when the unit is coupled to an external location on the vehicle. This may speed up the installation and calibration process. By using external locations on the vehicle, the radar unit may be able to capture measurements from an optimal location and orientation of the vehicle.

[0015] However, when coupled at these external locations on the vehicle, the radar unit may unfortunately encounter contact from road debris that may damage and degrade the performance of the radar system. For example, when the vehicle is navigating a route, debris (e.g., rocks, parts of the road) may be kicked up and directed at the radar unit by the vehicle and other nearby vehicles. This debris may damage the radar unit and affect the subsequent performance of the entire vehicle radar system. As such, repairing or replacing a damaged radar unit may be costly. Furthermore, it may not be safe to allow an autonomously operating vehicle to operate using a damaged radar unit.

[0016] Additionally, weather conditions may result in situations that may have undesirable effects on unprotected radar units coupled to external locations on the vehicle. Rain, hail, sleet, snow, and other weather conditions may unfortunately come into contact with the radar units and affect the performance and condition of each unit. Additionally, puddles and snow that accumulate on the roadway may be directed at the vehicle by nearby vehicles, similarly degrading the performance of the vehicle radar system. Thus, exposure to weather elements may cause the radar units to degrade and operate less optimally over time. Additionally, radar units coupled to external locations on the vehicle are also subject to undesirable contact from pedestrians, such as when the vehicle is parked and not in use.

[0017] To overcome these potential problems and other problems that may arise when locating a radar unit external to a vehicle, a radome may be used. A radome is a protective cover for a radar unit designed to protect and conceal the radar unit's components. A radar unit's radome may protect a portion or the entire radar unit, including the internal components. For example, the radome may be configured to couple to the radar unit such that a gap exists between the radome and the radar unit's antenna. In this manner, the radome may surround the radar unit's antenna and provide protection from undesirable environmental factors, such as debris and weather elements.

[0018] Ideally, a radome would not have any effect on the radar signals transmitted and received by the radar unit, however, in practice, a radome may have undesirable effects on the performance of the radar unit.

[0019] Because the radome is made of a material that can protect the radar unit, the radome may have a characteristic impedance that is different from the characteristic impedance of free space. This impedance difference, even if minimal, can still have an undesirable effect on the performance of the radar unit. In particular, the impedance mismatch between the radome and the air may result in a percentage of the transmitted signal's energy being reflected back toward one or more transmitting antennas when the radar unit is operating, rather than all of the transmitted signal's energy being propagated into the environment as intended. As a result, the energy may be trapped near the radar unit's antennas, resulting in interference that may be received by the radar unit's receiver, and may degrade overall performance by other similar means. In some cases, the radome may cause some transmitted signals to reflect one or more times in the space created between the radome and the radar unit before the signal traverses into the environment. These reflected radar signals, also called "ringing," may cause position-dependent phase errors that may further limit the phase stability of the channels of antenna arrays with a wide field of view. In some examples, ringing caused by the radar unit's radome may also limit the side lobe performance of the radar unit due to "ringing" signals that propagate away from the radar unit and appear to be transmitted by a location different than the antenna's actual location. Exemplary embodiments presented herein include a tilted radome designed and positioned to reduce undesirable effects that may result when using a radome to protect a radar unit. Like a basic radome, the tilted radome is located in the transmission direction of the radar unit's radiation pattern and serves to protect the radar unit. However, unlike a basic radome, the tilted radome may be aligned at an angle (rather than parallel) to the plane of the radar unit's antenna such that reflections of the transmitted signal caused by the tilted radome are directed in one or more desired directions (e.g., toward the void of the radiation pattern and absorbing components). For example, the tilted radome may be aligned at a 6 degree tilt to the antenna.Other angles are possible, among others. In this manner, the tilted radome can protect and conceal radar unit components with less impact on the performance of the radar unit compared to a conventional radome.

[0020] The tilted radome may be oriented at an angle relative to the radar unit to reflect the radar signal in a particular direction, such as toward a null in the radiation pattern of one or more antennas of the radar unit. A null may represent an angle in the radiation pattern where the radar unit does not receive the reflected signal well or at all. Thus, the degree to which the tilted radome is aligned relative to the radar unit's antennas may depend on the location of the null in the antenna's radiation pattern. By reflecting the radar signal toward the null of the radar unit, the effects of the reflected energy may be mitigated. In some examples, because the radiation pattern of the antenna array is a result of the antenna array's beamformer, the physical manifestation of the cancellation or mitigation may occur in the radar system's beamformer (e.g., processing unit).

[0021] In some examples, the radome may reflect electromagnetic energy toward a relatively low gain portion of the antenna's radiation pattern rather than toward a null. In function, when energy is reflected toward a low gain portion of the radiation pattern, the interference generated by the reflection may be small compared to the reflection of a signal received from a target object in the environment. Thus, when the term "null" is used in this disclosure, it may represent a true null. In some embodiments, the "null" may represent a portion of the radiation pattern that has low gain. For example, low gain may mean a gain that is -30 or -40 dB below the main lobe of the radiation pattern.

[0022] In some examples, the tilted radome may be aligned at different angles relative to the plane of the antenna to achieve the performance desired from the radar unit. For example, the tilted radome may be oriented at an angle that allows reflections of the radar signal caused by the tilted radome to be directed transversely toward the absorbing component. The absorbing component may include one or more waveguides configured to cause destructive interference. In some examples, the absorbing component may include a radio frequency (RF) absorbing material positioned against a null in the radiation pattern of the radar unit. In this manner, the RF absorbing material may absorb reflections of the transmitted radar signal caused by the tilted radome. Additional configurations of the tilted radome are described below.

[0023] The following detailed description may be used with an apparatus (e.g., a radar unit) having one or more antenna arrays. The one or more antenna arrays may take the form of single-input single-output single-input, multiple-output (SIMO), multiple-input single-output (MISO), multiple-input multiple-output (MIMO), and / or synthetic aperture radar (SAR) radar antenna architectures.

[0024] In some embodiments, an example radar antenna architecture may include multiple "dual open-ended waveguide" (DOEWG) antennas. The term "DOEWG" may refer herein to a vertical channel that separates into two portions in addition to a short section of a horizontal waveguide channel. Each of the two portions of the vertical channel may include an output port configured to radiate at least a portion of the electromagnetic waves that enter the radar unit. Additionally, in some examples, multiple DOEWG antennas may be arranged in one or more antenna arrays.

[0025] Some example radar systems may be configured to operate at W-band electromagnetic frequencies (e.g., 77 gigahertz (GHz)). The W-band may correspond to electromagnetic waves on the order of millimeters (e.g., 1 mm, 4 mm). Radar systems may use one or more antennas capable of focusing radiated energy into a tight beam to measure the environment with high accuracy. Such antennas may be compact (typically with a rectangular form factor), efficient (i.e., little of the 77 GHz energy is lost to heat within the antenna or reflected back to the transmitter electronics), low cost, and easy to manufacture (i.e., radar systems with these antennas can be mass produced).

[0026] Some example radar architectures may include multiple metal layers (e.g., aluminum plates) machined, aligned, and joined with a computer numerical control (CNC). For example, the metal layers may include a first half of an input waveguide channel, where the first half of a first waveguide channel includes an input port that may be configured to receive an electromagnetic wave (e.g., a W-band wave) into the first waveguide channel. The metal layers may also include a first half of a plurality of wave-splitting channels. The plurality of wave-splitting channels may include a network of channels that branch off from the input waveguide channel and may be configured to receive an electromagnetic wave from the input waveguide channel, split the electromagnetic wave into multiple portions of the electromagnetic wave (i.e., a power splitter), and propagate each portion of the electromagnetic wave to a respective wave-radiating channel of the plurality of wave-radiating channels. In some embodiments, the waveguide antenna elements and / or the waveguide output ports may be rectangular in shape. In alternative embodiments, the waveguide antenna elements and / or the waveguide output ports may be circular in shape. Other shapes are possible.

[0027] Based on the shape and material of the corresponding polarization correcting channels and waveguides, the distribution of propagating energy may vary at different locations, for example, within a radar unit. The shape and material of the polarization correcting channels and waveguides may define boundary conditions for the electromagnetic energy. The boundary conditions are known conditions for the electromagnetic energy at the ends of the polarization correcting channels and waveguides. For example, in a metallic waveguide, assuming that the polarization correcting channels and waveguide walls are nearly perfectly conductive (i.e., the waveguide walls can be approximated as perfect electric conductors - PECs), the boundary conditions stipulate that there is no electric field directed tangentially (i.e., in the plane of the waveguide walls) on any of the sides of the walls. Once the boundary conditions are known, Maxwell's equations can be used to determine how the electromagnetic energy propagates through the polarization correcting channels and waveguides.

[0028] Maxwell's equations can define several operating modes for a given polarization-modifying channel or waveguide. In each mode, there is one particular way that electromagnetic energy can propagate through the polarization-modifying channel or waveguide. Furthermore, each mode has an associated cutoff frequency. If the frequency of the electromagnetic energy is lower than the cutoff frequency, the mode is not supported in the polarization-modifying channel or waveguide. By appropriately selecting both (i) the dimensions and (ii) the operating frequency, electromagnetic energy can propagate through the polarization-modifying channels and waveguides in specific modes. The polarization-modifying channels and / or waveguides can be designed such that only one propagation mode is supported at the design frequency.

[0029] There are four main types of waveguide propagation modes: transverse electric (TE), transverse magnetic (TM), transverse electromagnetic (TEM), and hybrid. In TE modes, the electromagnetic energy has no electric field in the direction of propagation of the electromagnetic energy. In TM modes, the electromagnetic energy has no magnetic field in the direction of propagation of the electromagnetic energy. In TEM modes, the electromagnetic energy has no electric or magnetic field in the direction of propagation of the electromagnetic energy. In hybrid modes, the electromagnetic energy has some of both an electric field and a magnetic field in the direction of propagation of the electromagnetic energy.

[0030] The TE, TM, and TEM modes can be further specified using two suffixes corresponding to two directions perpendicular to the direction of propagation, such as the width and height directions. A non-zero suffix indicates the respective number of half-wavelengths of electromagnetic energy that are equal to the width and height of the respective polarization-modifying channel or waveguide (e.g., assuming a rectangular waveguide). However, a zero suffix indicates no change in the field with respect to that direction. For example, the TE 10 The mode indicates that the polarization-modifying channel or waveguide has a width of half a wavelength and no change in the electric field along its height. Typically, when the suffix number is equal to zero, the dimension of the waveguide in each direction is less than half a wavelength. In another example, the TE 21 The mode indicates that the waveguide is one wavelength (ie, two half wavelengths) wide and 1 / 2 wavelength high.

[0031] If the waveguide is operated in TE mode, the suffix also indicates the number of maximum electric fields along each direction of the waveguide. For example, TE 10 A mode indicates that the waveguide has a maximum electric field along its width and a maximum electric field of zero along its height. 21 The mode indicates that the waveguide has at most two electric fields in the width direction and at most one electric field in the height direction.

[0032] Additionally or alternatively, different radar units using different polarizations may prevent interference during operation of the radar system. For example, the radar system may be configured to interrogate (i.e., transmit and / or receive radar signals) in a direction perpendicular to the autonomous vehicle's direction of travel via SAR functionality. Thus, the radar system may be able to determine information about roadside objects as the vehicle passes. In some examples, this information may be two-dimensional (e.g., distances from the roadside of various objects). In other examples, this information may be three-dimensional (e.g., point clouds of various parts of detected objects). Thus, the vehicle may be able to "map" the sides of the road as it drives along the road, for example.

[0033] Some examples may involve using a radar unit having an antenna array arranged in a MIMO architecture. In particular, a filter may be determined by the radar unit having an antenna array arranged in a MIMO architecture to adjust the near-field measurement. The radar signals emitted by the transmitting antennas are mutually orthogonal and may be received by one or more corresponding receiving antennas. In that way, the radar system or associated signal processor may perform 2D SAR image formation together with a 3D matched filter to estimate the height of pixels of a 2D SAR map formed based on the processed radar signals.

[0034] If two autonomous vehicles use similar radar systems to interrogate the environment (e.g., using the SAR techniques described above), it may help to avoid interference for the autonomous vehicles to do so using different polarizations (e.g., orthogonal polarizations). Additionally, a single vehicle may operate two radar units with orthogonal polarizations to ensure that each radar unit does not interfere with the other radar unit.

[0035] Additionally, the configuration of the radar system may vary among the examples. For example, some radar systems may be comprised of radar units, each configured with one or more antenna arrays. An antenna array may include a set of multiple connected antennas that may function together as a single antenna to transmit or receive signals. By combining multiple radiating elements (i.e., antennas), the antenna array may improve the performance of the radar unit when compared to a radar unit that uses a non-array antenna. In particular, higher gain and narrower beams may be realized when a radar unit is equipped with one or more antenna arrays. As a result, a radar unit may be designed with antenna arrays in configurations that enable the radar unit to measure specific regions of the environment, such as target areas located at different ranges (distances) from the radar unit.

[0036] Radar units configured with antenna arrays may vary in overall configuration. For example, the number of arrays on the radar unit, the location of the array, the orientation of the array, and the size of the antenna array may vary between examples. Additionally, the quantity, location, alignment, and orientation of the radiating elements (antennas) within the array of the radar unit may also vary. As a result, the configuration of the radar unit may often depend on the performance desired for the radar unit. For example, the configuration of a radar unit designed to measure distances far from the radar unit (e.g., the far range of the radar unit) may be different compared to the configuration of a radar unit used to measure areas near the radar unit (e.g., the near field of the radar unit).

[0037] To further illustrate, in some examples, a radar unit may include the same number of transmit and receive antenna arrays (e.g., four arrays of transmit antennas and four arrays of receive antennas). In other examples, a radar unit may include a number of transmit antenna arrays that is different from the number of receive antenna arrays (e.g., six transmit antenna arrays and three receive antenna arrays). Additionally, some radar units may operate with parasitic arrays that can control the radar transmissions. Other example radar units may include one or more driven arrays with radiating elements connected to an energy source, which may have less overall energy loss when compared to a parasitic array.

[0038] The antennas on a radar unit may be arranged in one or more linear antenna arrays (i.e., the antennas in an array are aligned in a straight line). For example, a radar unit may include multiple linear antenna arrays arranged in a particular configuration (e.g., a parallel arrangement on the radar unit). In other examples, the antennas may also be arranged in planar arrays (i.e., antennas arranged in multiple parallel lines on a single plane). Additionally, some radar units may have antennas arranged in multiple planes resulting in a three-dimensional array.

[0039] A radar unit may also include multiple types of arrays (e.g., linear arrays in some parts and planar arrays in other parts). Thus, a radar unit configured with one or more antenna arrays can reduce the total number of radar units that a radar system may require to measure the surrounding environment. For example, a vehicle radar system may include a radar unit with an antenna array that can be used to measure specific areas in the environment as needed while the vehicle is navigating.

[0040] Some radar units may have different capabilities and operating characteristics. For example, one radar unit may be configured for long-range operation and another for short-range operation. A radar system may use a combination of various radar units to measure different regions of the environment. Therefore, it may be desirable for the signal processing of a short-range radar unit to be optimized for radar returns in the near field of the radar unit.

[0041] Referring now to the figures, FIG. 1 is a functional block diagram illustrating an exemplary vehicle 100. Vehicle 100 may represent a vehicle capable of operating fully or partially in an autonomous mode. More specifically, vehicle 100 may operate in an autonomous mode without (or with reduced human interaction) through receiving control instructions from a computing system (e.g., a vehicle control system). As part of operating in an autonomous mode, vehicle 100 may use sensors (e.g., sensor system 104) to detect and possibly identify objects in the surrounding environment to enable safe navigation. In some implementations, vehicle 100 may also include subsystems that enable a driver (or a remote operator) to control the operation of vehicle 100.

[0042] 1, vehicle 100 may include various subsystems, such as a propulsion system 102, a sensor system 104, a control system 106, one or more peripherals 108, a power source 110, a computer system 112, data storage 114, and a user interface 116. The subsystems and components of vehicle 100 may be interconnected in various ways (e.g., wired or wireless connections). In other examples, vehicle 100 may include more or fewer subsystems. Additionally, the functions of vehicle 100 described herein may be divided into further functional or physical components or combined into fewer functional or physical components within the implementation.

[0043] The propulsion system 102 may include one or more components operable to provide powered motion to the vehicle 100 and may include an engine / motor 118, an energy source 119, a transmission 120, and wheels / tires 121, among other possible components. For example, the engine / motor 118 may be configured to convert the energy source 119 into mechanical energy and may correspond to one or a combination of an internal combustion engine, one or more electric motors, a steam engine, or a Stirling engine, among other possible options. For example, in some implementations, the propulsion system 102 may include multiple types of engines and / or motors, such as gasoline engines and electric motors.

[0044] Energy source 119 represents an energy source that may fully or partially power one or more systems (e.g., engine / motor 118) of vehicle 100. For example, energy source 119 may correspond to gasoline, diesel, other petroleum-based fuels, propane, other compressed gas-based fuels, ethanol, solar panels, batteries, and / or other power sources. In some implementations, energy source 119 may include a combination of a fuel tank, a battery, a capacitor, and / or a flywheel.

[0045] The transmission 120 may transfer mechanical power from the engine / motor 118 to the wheels / tires 121 and / or other possible systems of the vehicle 100. Thus, the transmission 120 may include a gearbox, a clutch, a differential, and a drive shaft, among other possible components. The drive shaft may include an axle that connects to one or more wheels / tires 121.

[0046] The wheels / tires 121 of the vehicle 100 may have a variety of configurations within the exemplary implementation. For example, the vehicle 100 may exist in the form of a unicycle, a bicycle / motorcycle, a tricycle, or a four-wheeled car / truck, among other possible configurations. Thus, the wheels / tires 121 may be connected to the vehicle 100 in a variety of ways and may exist in different materials, such as metal and rubber.

[0047] The sensor system 104 may include various types of sensors, such as a global positioning system (GPS) 122, an inertial measurement unit (IMU) 124, one or more radar units 126, a laser range finder / LIDAR unit 128, a camera 130, a steering sensor 123, and a throttle / brake sensor 125, among other possible sensors. In some implementations, the sensor system 104 may also include sensors configured to monitor internal systems of the vehicle 100 (e.g., an O2 monitor, a fuel gauge, engine oil temperature, brake status).

[0048] The GPS 122 may include a transceiver operable to provide information regarding the position of the vehicle 100 relative to the Earth. The IMU 124 may have a configuration using one or more accelerometers and / or gyroscopes and may sense changes in the position and orientation of the vehicle 100 based on inertial acceleration. For example, the IMU 124 may detect the pitch and yaw of the vehicle 100 while the vehicle 100 is stationary or in motion.

[0049] The radar unit 126 may correspond to one or more systems configured to use radio signals (e.g., radar signals) to sense objects, including their speed and frontal orientation, in the local environment of the vehicle 100. Thus, the radar unit 126 may include one or more radar units with one or more antennas configured to transmit and receive radar signals as described above. In some implementations, the radar unit 126 may correspond to a mountable radar system configured to obtain measurements of the surrounding environment of the vehicle 100. For example, the radar unit 126 may include one or more radar units configured to couple to an underbody of the vehicle.

[0050] The laser rangefinder / LIDAR 128 may include one or more laser sources, a laser scanner, and one or more detectors, among other system components, and may operate in a coherent mode (e.g., using heterodyne detection) or a non-coherent detection mode. The camera 130 may include one or more devices (e.g., still or video cameras) configured to capture images of the environment of the vehicle 100.

[0051] The steering sensor 123 may sense the steering angle of the vehicle 100, which may include measuring the angle of the steering wheel or measuring an electrical signal representative of the angle of the steering wheel. In some implementations, the steering sensor 123 may measure the angle of the wheels of the vehicle 100, such as detecting the angle of the wheels relative to the forward axle of the vehicle 100. The steering sensor 123 may also be configured to measure a combination (or a subset) of the steering wheel angle, the electrical signal representative of the steering wheel angle, and the angles of the wheels of the vehicle 100.

[0052] The throttle / brake sensor 125 may detect the position of either the throttle position or the brake position of the vehicle 100. For example, the throttle / brake sensor 125 may measure the angle of both the accelerator pedal (throttle) and the brake pedal, or may measure an electrical signal that may represent, for example, the accelerator pedal (throttle) angle and / or the brake pedal angle. The throttle / brake sensor 125 may also measure the angle of the throttle body of the vehicle 100, which may include part of the physical mechanism that provides the modulation of the energy source 119 to the engine / motor 118 (e.g., a butterfly valve or a carburetor). In addition, the throttle / brake sensor 125 may measure the pressure of one or more brake pads on a rotor of the vehicle 100, or the angles of the accelerator pedal (throttle) and the brake pedal, an electrical signal representing the accelerator pedal (throttle) and the brake pedal angle, the throttle body angle, and a combination (or subset) of the pressure that at least one brake pad applies to a rotor of the vehicle 100. In other embodiments, the throttle / brake sensor 125 may be configured to measure pressure applied to a vehicle pedal, such as a throttle or brake pedal.

[0053] The control system 106 may include components configured to aid in navigating the vehicle 100, such as a steering unit 132, a throttle 134, a braking unit 136, a sensor fusion algorithm 138, a computer vision system 140, a navigation / pathfinding system 142, and an obstacle avoidance system 144. More specifically, the steering unit 132 may be operable to adjust the heading of the vehicle 100, and the throttle 134 may control the operating speed of the engine / motor 118 to control the acceleration of the vehicle 100. The braking unit 136 may decelerate the vehicle 100, which may include slowing the wheels / tires 121 using friction. In some embodiments, the braking unit 136 may convert the kinetic energy of the wheels / tires 121 into electrical current for subsequent use by a system or systems of the vehicle 100.

[0054] The sensor fusion algorithms 138 may include Kalman filters, Bayesian networks, or other algorithms that can process data from the sensor systems 104. In some implementations, the sensor fusion algorithms 138 may provide assessments based on the incoming sensor data, such as an assessment of individual objects and / or features, an assessment of a particular situation, and / or an assessment of potential effects within a given situation.

[0055] Computer vision system 140 may include hardware and software operable to process and analyze images in attempting to determine objects, environmental objects (e.g., stop signals, road boundaries, etc.), and obstacles. Thus, computer vision system 140 may use object recognition, Structure From Motion (SFM), video tracking, and other algorithms used in computer vision, for example, to recognize objects, map the environment, track objects, estimate the speed of objects, etc.

[0056] The navigation / routing system 142 may determine a driving route for the vehicle 100, which may include dynamically adjusting navigation during operation. Thus, the navigation / routing system 142 may use data from the sensor fusion algorithms 138, the GPS 122, and maps, among other sources, to navigate the vehicle 100. The obstacle avoidance system 144 may evaluate potential obstacles based on the sensor data and cause systems of the vehicle 100 to avoid or otherwise navigate the potential obstacles.

[0057] 1, the vehicle 100 may also include peripherals 108, such as a wireless communication system 146, a touchscreen 148, a microphone 150, and / or a speaker 152. The peripherals 108 may provide controls or other elements for a user to interact with a user interface 116. For example, the touchscreen 148 may provide information to a user of the vehicle 100. The user interface 116 may also accept input from a user via the touchscreen 148. The peripherals 108 may also enable the vehicle 100 to communicate with devices, such as devices of other vehicles.

[0058] The wireless communication system 146 may communicate with one or more devices directly or wirelessly through a communication network. For example, the wireless communication system 146 may use 3G cellular communications such as CDMA, EVDO, GSM / GPRS, or 4G cellular communications such as WiMAX or LTE. Alternatively, the wireless communication system 146 may communicate with a wireless local area network (WLAN) using WiFi or other possible connections. The wireless communication system 146 may also communicate directly with devices using, for example, infrared links, Bluetooth, or ZigBee. Other wireless protocols, such as various vehicle communication systems, are possible within the context of the present disclosure. For example, the wireless communication system 146 may include one or more dedicated short-range communication (DSRC) devices, which may include public and / or private data communications between vehicles and / or roadside gas stations.

[0059] The vehicle 100 may include a power source 110 for providing power to the components. The power source 110 may include a rechargeable lithium ion battery or a lead acid battery in some implementations. For example, the power source 110 may include one or more batteries configured to provide power. The vehicle 100 may also use other types of power sources. In one example implementation, the power source 110 and the energy source 119 may be integrated into a single energy source.

[0060] Vehicle 100 may also include a computer system 112 for performing operations such as those described herein. Thus, computer system 112 may include at least one processor 113 (which may include at least one microprocessor) operable to execute instructions 115 stored in a non-transitory computer-readable medium, such as data storage 114. In some implementations, computer system 112 may represent multiple computing devices that may function to provide distributed control of individual components or subsystems of vehicle 100.

[0061] In some implementations, data storage 114 may include instructions 115 (e.g., program logic) executable by processor 113 to perform various functions of vehicle 100, including those described above in connection with Figure 1. Data storage 114 may also include additional instructions, including instructions for transmitting data to, receiving data from, interacting with, and / or controlling one or more of propulsion system 102, sensor system 104, control system 106, and peripherals 108.

[0062] In addition to instructions 115, data storage 114 may store data such as road maps, route information, among other information. Such information may be used by vehicle 100 and computer system 112 during operation of vehicle 100 in autonomous, semi-autonomous, and / or manual modes.

[0063] Vehicle 100 may include a user interface 116 for providing information to or receiving input from a user of vehicle 100. User interface 116 may control or allow control of content and / or the layout of interactive images that may be displayed on touch screen 148. Additionally, user interface 116 may include one or more input / output devices in the set of peripherals 108, such as wireless communication system 146, touch screen 148, microphone 150, and speaker 152.

[0064] The computer system 112 may control functions of the vehicle 100 based on inputs received from various subsystems (e.g., the propulsion system 102, the sensor system 104, and the control system 106) as well as the user interface 116. For example, the computer system 112 may utilize inputs from the sensor system 104 to estimate outputs generated by the propulsion system 102 and the control system 106. Depending on the embodiment, the computer system 112 may be operable to monitor many aspects of the vehicle 100 and its subsystems. In some embodiments, the computer system 112 may disable some or all functions of the vehicle 100 based on signals received from the sensor system 104.

[0065] The components of vehicle 100 may be configured to interconnect and function with other components within or outside their respective systems. For example, in an exemplary embodiment, camera 130 may capture multiple images that may represent information about the state of the environment of vehicle 100 operating in an autonomous mode. The state of the environment may include parameters of the road on which the vehicle is operating. For example, computer vision system 140 may be able to recognize the slope (gradient) or other features based on multiple images of the road. Additionally, a combination of GPS 122 and features recognized by computer vision system 140 may be used along with map data stored in data storage 114 to determine certain road parameters. Additionally, radar unit 126 may also provide information about the vehicle's surroundings.

[0066] In other words, a combination of various sensors (which may be referred to as input indicator sensors and output indicator sensors) and computer system 112 may interact to provide an indication of an input provided to control the vehicle or an indication of the vehicle's surroundings.

[0067] In some embodiments, computer system 112 may make decisions regarding various objects based on data provided by systems other than a wireless system. For example, vehicle 100 may have lasers or other optical sensors configured to sense objects within the vehicle's field of view. Computer system 112 may use output from the various sensors to determine information regarding objects within the vehicle's field of view and may determine distance and direction information to the various objects. Computer system 112 may also determine whether an object is desirable or undesirable based on output from the various sensors.

[0068] 1 illustrates various components of the vehicle 100, namely, the wireless communication system 146, the computer system 112, the data storage 114, and the user interface 116, as being integrated into the vehicle 100, one or more of these components may be mounted or associated separately from the vehicle 100. For example, the data storage 114 may exist partially or completely separate from the vehicle 100. Thus, the vehicle 100 may be provided in the form of device elements that may be located separately or together. The device elements that make up the vehicle 100 may be communicatively coupled together in a wired and / or wireless manner.

[0069] 2A, 2B, 2C, 2D, and 2E show various views of the physical configuration of vehicle 100. The various views are included to depict example sensor locations 202, 204, 206, 208, 210 on vehicle 100. In other examples, sensors may have various locations on vehicle 100. Although vehicle 100 is shown as a van in FIGS. 2A-2E, vehicle 100 may have other configurations within examples such as a truck, a car, a semi-trailer truck, a motorcycle, a bus, a shuttle, a golf cart, an off-road vehicle, a robotic device, or an agricultural vehicle, among other possible examples.

[0070] As noted above, vehicle 100 may include sensors coupled to various external locations, such as sensor locations 202-210. Vehicle sensors include one or more types of sensors, with each sensor configured to capture information from the surrounding environment or perform other operations (e.g., communication links, obtaining overall positioning information). For example, sensor locations 202-210 may serve as locations for any combination of one or more cameras, radars, LIDARs, range finders, wireless devices (e.g., Bluetooth and / or 802.11), and acoustic sensors, among other possible types of sensors.

[0071] When coupled at the example sensor locations 202-210 shown in Figures 2A-2E, a variety of mechanical fasteners may be used, including permanent or non-permanent fasteners. For example, bolts, screws, clips, latches, rivets, anchors, and other types of fasteners may be used. In some examples, the sensor may be coupled to the vehicle using an adhesive. In further examples, the sensor may be designed and constructed as part of a vehicle component (e.g., part of a vehicle mirror).

[0072] In some implementations, one or more sensors may be positioned at sensor locations 202-210 using a movable mount operable to adjust the orientation of one or more sensors. The movable mount may include a rotating platform that can rotate the sensor to obtain information from multiple directions around the vehicle 100. For example, a sensor located at sensor location 202 may use a movable mount that allows rotation and scanning within a particular range of angles and / or azimuth angles. Thus, the vehicle 100 may include a mechanical structure that allows one or more sensors to be mounted on the roof of the vehicle 100. Additionally, other mounting locations are possible within the scope of the examples.

[0073] FIG. 3 illustrates an example layout of a radar sector, according to one or more embodiments. As shown, each radar sector may have an angular width approximately equal to the scanning range of the radar unit. For example, a sector may divide an azimuth plane around the vehicle 100 into multiple sectors (e.g., 90 degree sectors, 120 degree sectors). In various different examples, scanning may be performed on the transmit side, the receive side, or both. For example, scanning on the transmit side may include repeatedly transmitting a radar signal in a predetermined direction and receiving the radar signal across the entire sector. In another example, scanning on the receive side may include transmitting a radar signal across the entire sector, receiving the radar signal across the entire sector, and performing digital beamforming on the received signal. In other examples, different forms of scanning may be used as well.

[0074] The exemplary radar sectors may be aligned with respect to the vehicle 100 using axes 302, 304. In some examples, each radar unit may be configured to scan one sector. Additionally, because each exemplary radar unit of FIG. 3 has a scan angle of approximately 90 degrees, each radar unit scans an area that may not overlap with the scan angles of other radar units. In other examples, the sectors may overlap.

[0075] To achieve a radar sector defined by the center point of the vehicle 100, each radar unit may be mounted at a 45 degree angle to the two axes of the vehicle 100. By mounting each radar unit at a 45 degree angle to the two axes of the vehicle 100, a 90 degree scan of the radar unit may scan from one vehicle axis to the other. For example, a radar unit mounted at a 45 degree angle to the axis of the sensor location 206 may be able to scan the left front and right front sectors (from the vertical axis 302 through the front of the vehicle 100 to the horizontal axis 304 through the side of the vehicle). To scan the right rear and left rear sectors, a radar unit may be mounted at the sensor location 204. The arrangement of the radar units shown in FIG. 3 is merely to illustrate one possible example.

[0076] In various other examples, the radar units may be located on or along (or within) other portions of the vehicle and / or may be coupled to the underbody of the vehicle 100. Additionally, the sectors may also be defined in other ways in various embodiments. For example, the sectors may be at a 45 degree angle relative to the vehicle. In this example, one radar unit faces forward, another faces rearward, and the other two face the sides of the vehicle.

[0077] In some examples, all radar units on a vehicle 100 may be configured with the same scan angle. The azimuth plane around the vehicle may equal a full 360 degrees. Thus, if each radar unit is configured with the same scan angle, the scan angle of the radar units will be approximately equal to 360 divided by the number of radar units on the vehicle. Thus, a full azimuth plane scan may require a vehicle 100 with one radar unit to have that radar unit capable of scanning over a full 360 degrees.

[0078] If the vehicle 100 has two radar units, each may scan approximately 180 degrees. For three radar units, each may be configured to scan 120 degrees. For four radar units, each may scan approximately 90 degrees, as shown in FIG. 3. Five radar units may be configured on the vehicle 100, each may be capable of scanning 72 degrees. Additionally, six radar units may be configured on the vehicle 100, each may be capable of scanning approximately 60 degrees. Other examples are possible.

[0079] In further examples, the number of radar units may be selected based on a number of criteria, such as ease of manufacturing the radar units, placement on the vehicle, or other criteria. For example, several radar units may be constructed in a sufficiently small planar structure. The planar radar units may be mountable in various locations on the vehicle. For example, the vehicle may have a dedicated radar housing mounted on top of the vehicle. The radar housing may contain various radar units. In other embodiments, the radar units may be located within the vehicle structure.

[0080] In some embodiments, it may be desirable to place the radar unit in a location where the object covering the radar unit (i.e., the radome) is at least partially transparent to the radar. For example, various plastics, polymers, and other materials may form part of the vehicle structure and cover the radar unit while allowing radar signals to pass through.

[0081] Additionally, in some embodiments, the radar units may be configured with different scan ranges for different radar units. In some embodiments, a particular radar unit with a wide scan angle may not be able to be placed in a suitable location on the vehicle. Thus, a smaller radar unit with a smaller scan angle may be placed in that location. However, other radar units may be able to have a larger scan angle. Thus, the total scan angles of the radar units may total 360 degrees (or more) to provide a full 360 degree azimuth scan. For example, a vehicle may have three radar units that each scan over 100 degrees, and a fourth radar unit that scans over 60 degrees. This may allow the radar units to scan the entire azimuth plane, but the angular size of the scan sectors may not be equal.

[0082] 4A and 4B show a basic radome 400 for a radar unit, according to an example embodiment. Basic radome 402 represents an example radome configuration that provides protection to a radar unit (i.e., radar unit 404), but may also affect the performance of the radar unit.

[0083] As shown in FIGS. 4A and 4B , the basic radome 402 is coupled to the radar unit 404 such that a gap 406 is created between the basic radome 402 and the radar unit 404. More specifically, the basic radome 402 is aligned parallel to the plane of the antenna 508 of the radar unit 404. As a result, the basic radome 402 may have an undesirable effect on the performance of the radar unit 404. In particular, some radar signals (or portions of radar signals) transmitted by the antenna 508 may reflect off the basic radome 402 and remain within the gap 406. Other radar signals (or portions of radar signals) transmitted by the antenna 508 may ring within the gap 406 (i.e., bounce back and forth between the radar unit 404 and the inner surface of the basic radome 402). Thus, the radar signals that remain in the gap 406 and the energy from the reflection of the ringing radar signals may cause interference and degrade the performance of the radar unit 404. Thus, impedance differences caused by the underlying radome 402 can adversely affect the performance of the radar unit 404.

[0084] 5A and 5B show a tilted radome for a radar unit according to one or more example embodiments. Unlike the basic radome 402 shown in FIGS. 4A and 4B, tilted radome 502 represents an example radome with an angled configuration that may reduce the impact of tilted radome 502 on the performance of radar unit 500. The orientation (e.g., degree of angle) relative to radar unit 500 and the overall configuration of tilted radome 502 may vary between examples. Additional configurations are described below.

[0085] The tilted radome 502 may be used to provide protection to the radar unit 500. The radar unit 500 may correspond to any type of radar unit capable of measuring aspects of a nearby environment. For example, the radar unit 500 may be part of a vehicle radar system and may use the waveguide 504 and antenna 508 to transmit and receive radar signals into the environment. As such, the tilted radome 502 may be located in a transmission direction of a radiation pattern associated with the antenna 508 of the radar unit 500. Among other examples, the tilted radome 502 may be made from various types of materials such as fiberglass, PTFE coated cloth, plastic, and others. In some examples, the material may rely on fusion. For example, a non-metallic material with low dielectric value, low thermal expansion, and high environmental robustness (e.g., performing well in environmental conditions that a vehicle may encounter while operating) may be used.

[0086] The tilted radome 502 is shown aligned at an angle (e.g., 6 degrees) relative to the plane of the antenna 508 of the radar unit 500 such that reflections of the transmitted radar signal caused by the tilted radome 502 are directed toward a null in the radiation pattern associated with the antenna 508 and / or one or more absorbing components (e.g., absorbing components 510, 512). By angling the surface relative to the antenna 508 rather than a parallel surface (i.e., the basic radome 402 relative to the radar unit 404), the tilted radome 502 may provide protection and concealment of the components of the radar unit 500 to reduce any impact on the performance of the antenna 508. In some embodiments, the angle of the tilted radome 502 depends on the antenna pattern and therefore on the design of the antenna. The angle may also depend on the structural arrangement and / or characteristics of the waveguide 504.

[0087] In some examples, the tilted radome 502 may be tilted relative to the radar unit 500 (e.g., toward a null in the radiation pattern of the antenna 508 and an absorbing component 510, 512) to reflect the radar signal in one or more particular directions. The null may represent an angle in the radiation pattern where the radar unit 500 does not receive the reflected signal well or at all. Thus, by directing the radar signal reflected by the tilted radome 502 into one or more nulls in the radar unit 500, the tilted radome 502 may reduce or even eliminate any undesirable energy that may result from a radar signal ringing in space 506. In an additional example, a beamformer associated with the radar unit 500 may also cancel or contribute to canceling the undesirable energy. In another example, the tilted radome 502 may be further tilted relative to the plane of the antenna 508 such that the radar signal is reflected into the absorbing component rather than back to the antenna 508.

[0088] As shown in FIGS. 5A and 5B, the tilted radome 502 may be configured to direct energy toward one or more absorbing components, such as absorbing component 510 and absorbing component 512. Absorbing component 510 is shown disposed on a surface of the radar unit 500. Absorbing component 512 is shown as part of a waveguide 514. Waveguide 514 may be part of waveguide 504 or a physically separate waveguide. In some examples, the tilted radome 502 may include one or both of absorbing components 510 and 512. In other examples, the tilted radome 502 may include one or none of the absorbing components. Additionally, other absorbing components may be used.

[0089] 6 is a flowchart of an example method 600 for operating a radar system, according to one or more embodiments. Method 600 may include one or more operations, functions, or actions, such as illustrated by one or more of blocks 602 and 604, each of which may be performed by any of the systems illustrated in the figures above, among other possible systems.

[0090] Those skilled in the art will appreciate that the flowcharts described herein illustrate the functions and operations of certain implementations of the present disclosure. In this regard, each block of the flowchart may represent a module, segment, or portion of program code that includes one or more instructions executable by one or more processors to implement a particular logical function or step in a process. The program code may be stored in any type of computer-readable medium, such as a storage device including, for example, a disk or hard drive.

[0091] Additionally, each block may represent circuitry hardwired to perform specific logical functions within the process. As will be appreciated by those skilled in the art, alternative implementations are included within the scope of example implementations of the present application in which functions may be performed in different orders than those shown or described, including substantially concurrently or in reverse order, depending on the functionality involved.

[0092] Block 602 includes transmitting a radar signal based on the radiation pattern using a radar unit including at least one antenna having a radiation pattern. The radar system includes a radome located in a transmission direction of the radiation pattern. Further, the radome may be aligned at an angle with respect to a plane of the at least one antenna such that reflections of the transmitted radar signal caused by the radome are directed toward nulls and / or absorbing components of the radiation pattern.

[0093] The radome may be coupled to the radar unit such that a gap exists between the radome and the at least one antenna. As such, the radome may surround the at least one antenna. Furthermore, the degree of the angle may depend on the location of the null in the radiation pattern. In this manner, the radome may direct reflections caused by the radome toward the null in the radiation pattern and / or the absorbing component. For example, the radar unit may be configured such that the absorbing component is disposed on a top surface of the radar unit.

[0094] In some examples, the absorbing component is coupled to the waveguide. The absorbing component may include one or more waveguides configured to provide destructive interference. In some examples, the absorbing component may be coupled to the waveguide or a separate waveguide. Additionally, the absorbing component includes a radio frequency (RF) absorbing material disposed relative to a null in the radiation pattern. The RF absorbing material may be configured to absorb reflections of the transmitted radar signal.

[0095] In some examples, the radar unit may include multiple antennas arranged in a linear array. For example, the antennas may include one or more of a synthetic aperture radar (SAR) array, a multiple-input multiple-output (MIMO) transmit array, and a receiver array. The radar unit may also include antennas arranged in other configurations.

[0096] Block 604 includes receiving, using the radar unit, one or more radar signals reflected to the radar unit by one or more surfaces in the radar system's environment. These reflections may enable the radar system to determine aspects of the environment, such as the position and movement of objects relative to the radar system. In some examples, the radar unit may include a receive array configured to receive radar signals reflected from the vehicle's environment.

[0097] Some examples of block 600 may further include transmitting a second radar signal based on the second radiation pattern using a second radar unit including at least one antenna having a second radiation pattern. The radar system may include a second radome located in a transmission direction of the second radiation pattern. In particular, the second radome is aligned at a second angle with respect to a plane of the at least one antenna such that reflections of the transmitted second radar signal caused by the second radome are directed toward at least one of the null and the second absorbing component of the second radiation pattern. The method may further include receiving, using the second radar unit, one or more radar signals reflected to the radar unit by one or more surfaces in an environment of the radar system.

[0098] In some examples, the radar system may further include an absorbing component coupled to the radar unit such that the absorbing component absorbs reflections of the transmitted radar signal. For example, the absorbing component may include one or more waveguides configured to cause destructive interference. The one or more waveguides may be part of the radar unit. In other examples, the absorbing component may include a radio frequency (RF) absorbing material positioned relative to a null in the radiation pattern. The RF absorbing material may be configured to absorb reflections of the transmitted radar signal.

[0099] In some examples, the radome may include one or more polarizing filters that may be constructed as part of the radome and configured to manipulate the polarization of the radar signal.

[0100] In some examples, the radar system may further include a second radar unit including at least one antenna having a second radiation pattern, the second radar unit configured to (i) transmit a second radar signal based on the second radiation pattern and (ii) receive the radar signal. The radar system may also include a second radome located in a transmission direction of the second radiation pattern. The second radome is aligned at a second angle with respect to a plane of the at least one antenna such that reflections of the transmitted second radar signal caused by the second radome are directed to a null in the second radiation pattern. Thus, the radar unit may be coupled to a first location of the vehicle, and the second radar unit may be coupled to a second location of the vehicle.

[0101] In some examples, the radar system may also include a processing unit. The processing unit may be configured to perform a beamforming process using one or more radar units. The processing unit may also be configured to perform beam steering. As such, the processing unit may be configured to mitigate reflections of the transmitted radar signal caused by the radome.

[0102] The above detailed description, with reference to the accompanying figures, describes various features and functions of the disclosed systems, devices, and methods. Various aspects and embodiments have been disclosed herein. While other aspects and embodiments will be apparent, the various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.

[0103] It should be understood that the arrangements described herein are for illustrative purposes only. Thus, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, devices, interfaces, functions, sequences, and groupings of functions, etc.) can be used instead, and that some elements may be omitted altogether depending on the desired results. Moreover, many of the described elements are functional entities that can be implemented as separate or distributed components, or in conjunction with other components, in any suitable combination and location.

Claims

1. 1. A radar system comprising: a radar unit including at least one antenna having a radiation pattern, the radar unit configured to: (i) transmit a radar signal based on the radiation pattern; and (ii) receive the radar signal; a radome located in a transmission direction of the radiation pattern, the radome being aligned at an angle not including 0 degrees with respect to the plane of at least one antenna such that reflections of the transmitted radar signal caused by the radome are directed towards an absorbing element disposed on a surface of the radar unit, the extent of the angle depending on the position of the absorbing element; Equipped with the radome is configured to be aligned at the angle relative to the plane based on a position of the absorbing component. Radar system.

2. 10. The radar system of claim 1, wherein the radome is coupled to the radar unit such that a gap exists between the radome and the at least one antenna.

3. The radar system of claim 2 , wherein the radome covers the at least one antenna.

4. the radar unit including at least one antenna having the radiation pattern, 10. The radar system of claim 1 comprising a plurality of antennas arranged in a linear array.

5. The radar system of claim 1 further comprising a receive array configured to receive radar signals reflected from an environment of the radar system.

6. 2. The radar system of claim 1, wherein the absorbing component comprises a radio frequency (RF) absorbing material disposed across a null in the radiation pattern, the RF absorbing material configured to absorb the reflections of the transmitted radar signal.

7. a second radar unit including at least one antenna having a second radiation pattern, the second radar unit configured to: (i) transmit a second radar signal based on the second radiation pattern; and (ii) receive a radar signal; 10. The radar system of claim 1, further comprising: a second radome located in a transmission direction of the second radiation pattern, the second radome aligned at a second angle with respect to a plane of the at least one antenna of the second radar unit such that reflections of the transmitted second radar signal caused by the second radome are directed into at least one of: (i) a null in the second radiation pattern; and (ii) a second absorbing component.

8. The radar system of claim 7 , wherein the radar unit is coupled to a first location on a vehicle and the second radar unit is coupled to a second location on the vehicle.

9. 10. The radar system of claim 8, further comprising a processing unit, the processing unit configured to perform a beamforming process using the radar unit and the second radar unit.

10. 10. The radar system of claim 9, wherein the processing unit is further configured to mitigate reflections of the transmitted radar signal caused by the radome.

11. A radar unit, a plurality of antennas having a radiation pattern, the plurality of antennas configured to: (i) transmit a radar signal based on the radiation pattern; and (ii) receive the radar signal; a radome located in a transmission direction of the radiation pattern, the radome being aligned at an angle not including 0 degrees with respect to a plane of the antennas such that reflections of the transmitted radar signal caused by the radome are directed towards an absorbing element disposed on a surface of the radar unit, the extent of the angle depending on the position of the absorbing element; the radome is configured to be aligned at the angle relative to the plane based on a position of the absorbing component. Radar unit.

12. The radar unit of claim 11 , wherein the radome includes one or more polarizing filters that manipulate the polarization of the radar signal.

13. 1. A method of operating a radar system, comprising: transmitting a radar signal based on the radiation pattern using a radar unit including at least one antenna having a radiation pattern, the radar system including a radome positioned in a transmission direction of the radiation pattern, the radome aligned at an angle, not including 0 degrees, with respect to a plane of the at least one antenna such that the radome is directed toward an absorbing component disposed on a surface of the radar unit, the magnitude of the angle depending on the position of the absorbing component; using the radar unit to receive one or more radar signals reflected to the radar unit by one or more surfaces in an environment of the radar system; the radome is configured to be aligned at the angle relative to the plane based on a position of the absorbing component. A method for operating a radar system.

14. transmitting, using a second radar unit including at least one antenna having a second radiation pattern, a second radar signal based on the second radiation pattern, the radar system including a second radome located in a transmission direction of the second radiation pattern, the second radome aligned at a second angle with respect to a plane of the at least one antenna of the second radar unit such that reflections of the transmitted second radar signal caused by the second radome are directed into at least one of (i) a null in the second radiation pattern, and (ii) a second absorbing component; and using the second radar unit to receive one or more radar signals reflected to the radar unit by one or more surfaces in the environment of the radar system.

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