Patent Description:
A radar transceiver is a device arranged for transmission and reception of radar signals in a radar frequency band. Radar transceivers are commonly used in vehicles for monitoring vehicle surroundings. Automatic Cruise Control (ACC) functions, Emergency Braking (EB) functions, Advanced Driver Assistance Systems (ADAS) and Autonomous Drive (AD) are some examples of applications where radar data represents an important source of information on which vehicle control may be based.

Vehicle radar transceivers are often arranged hidden behind vehicle body parts, such as a front or a rear vehicle bumper. This placement is often chosen due to aesthetic reasons, but there is also a need to protect the radar transceiver from mechanical impact, moisture and dirt.

A drawback associated with hiding transceivers behind vehicle body parts is that the radar transmission must penetrate the body part in order to monitor the vehicle surroundings. Some of the radar energy is often reflected back from the body part into the cavity behind the body part. This reflected radar energy may appear as a false target, and thus cause erroneous radar target detections.

Some work has been done towards improving the situation;
<CIT> discloses a vehicle bumper comprising a layered structure configured to reduce reflection.

<CIT> relates to vehicle body parts suitable for use with radar transceivers.

<CIT> discloses a vehicle obstacle detection device which comprises: a radar unit provided between a back surface of a bumper and a wheel and configured to detect an obstacle by transmitting a radio wave through the bumper; and a misdetection prevention member for preventing misdetection in the radar unit by suppressing the occurrence of an own-vehicle's wheel reaching wave which is a part of a transmission wave and which passes between a transmitter section of the radar unit and the back surface of the bumper and reaches the wheel of the own vehicle.

<CIT> discloses a radar system and method with reduced multipath effects include a first component of a radar sensor module on which at least one antenna element is formed, the at least one antenna element having a surface at which radar radiation is received or transmitted, the at least one antenna element having a radiation aperture. A second component in proximity to the antenna element such that a portion of the radar radiation impinges on the second component comprises an angled surface forming an angle with the surface of the antenna element. The angled surface of the second component comprises a texture such that when the portion of the radiation impinges on the angled surface, the amount of multipath signal propagating through the radiation aperture of the antenna element is reduced.

<CIT> discloses that An antenna device is mounted in a note PC and is used for communication between the note PC and the external of the note PC. The antenna device is provided with an antenna for wireless LAN for transmitting and receiving radio waves, and a cover. The cover is formed of a dielectric material for covering the antenna with a wall and a ceiling, and strengthens the directivity of radio wave communication on the wall side of the antenna device by a double layer structure of the ceiling that is thicker than the wall.

<CIT> discloses an antenna apparatus comprises an antenna (<NUM>), and a resin material (<NUM>) provided between the antenna (<NUM>) and a reflector (windshield (<NUM>)). The resin material (<NUM>) includes portions, and the thickness (or dielectric constant) of each portion of the resin material (<NUM>) is determined in accordance with a length of a straight line connecting a feeding point 1a of the antenna (<NUM>), each portion of the resin material (<NUM>), and the reflector (<NUM>). Therefore, a phase of a reflected wave can be easily adjusted, thereby improving a performance of the antenna. <CIT> discloses that A radar bracket for a vehicle includes a central portion configured to receive a radar module so that the radar module is exposed on a front side of the radar bracket, and a side wall encircling and extending laterally from the central portion and comprising a non-conductive material. At least of a portion of a backside of the side wall is covered by a radar absorbing material having a dielectric constant higher than a dielectric constant of the side wall. The at least a portion of the side wall has a thickness dw proportional to a quarter of the wavelength of a signal emitted by the radar module, and selected based on the dielectric constants of the side walls of the radar bracket and the radar absorbing material, such that a reflection at the interface between the side wall and the radar absorbing material is effectively cancelled out.

Another issue related to radar systems in vehicular applications is the overall system cost. It is desired to reduce cost of the overall vehicle, meaning that the cost of the radar system and its mounting on the vehicle should be kept at a minimum.

It is an object of the present disclosure to provide improved radar transceiver assemblies and installation techniques. This object is achieved by a side-shield for a radar transceiver according to claim <NUM> and a method for producing such a side-shield as set out in claim <NUM>. The side-shield comprises a non-uniform delay structure arranged over the side-shield, the non-uniform delay structure being configured to delay a radar signal propagating through the side-shield by a variable amount in dependence of a wavelength of the radar signal and in dependence of a location on the side-shield surface through which the radar signal propagates, thereby steering and/or diffusing the radar signal after propagation through the side-shield. Thus, any focused radar signal energy propagating though the side-shield is de-focused by the phase randomization. This alleviates problems with false detections incurred by reflections in vehicle body parts.

According to aspects, the non-uniform delay structure has a variable thickness measured along a normal vector of a surface of the side-shield and/or a non-uniform dielectric constant measured along the normal vector. Thus, the side-shield can be cost-effectively manufactured by, e.g., molding.

Further advantages are obtained by the dependent claims.

There are also disclosed herein radar transceivers, assembly methods, and vehicles associated with the above-mentioned advantages.

<FIG> shows a vehicle <NUM> equipped with a vehicle radar system <NUM>. The system <NUM> comprises a control unit <NUM> and at least one radar transceiver <NUM>.

The control unit <NUM> and the radar transceiver <NUM> may be comprised in a single physical unit or they may be distributed over more than one physical unit.

According to an example, the vehicle radar transceiver <NUM> is arranged for generating and transmitting radar signals in the form of frequency modulated continuous wave (FMCW) signals, sometimes also referred to as radar chirp signals, and to receive reflected radar signals <NUM>, where the transmitted signals have been reflected by an object <NUM>.

The present disclosure is not limited to FMCW radar waveforms. Rather, the disclosed concepts and techniques can be applied to many different radar waveforms. In particular, the techniques disclosed herein are applicable to Orthogonal Frequency Division Multiplex (OFDM) radar, and to Pulse Modulated Continuous Wave (PMCW) radar. One example of OFDM radar is the stepped OFDM radar waveform described in <CIT>.

The radar transceiver <NUM> is associated with a field of view <NUM>. In case the radar transceiver is a front radar, a boresight direction <NUM> of the radar often coincides with a center line of the field of view, where the boresight direction <NUM> here also coincides with a forward direction F of the vehicle <NUM>. In case the vehicle radar is instead configured as a side radar or a rearward facing radar, then the boresight direction may point in some other angle compared to the forward direction F of the vehicle <NUM>.

The radar transceiver <NUM> is mounted behind a body part of the vehicle <NUM>. This vehicle body part may be, e.g., a front bumper <NUM> or a rear bumper <NUM>. Reflections in a vehicle body part arranged in front of the radar transceiver may give rise to an increased noise floor and to false detections which are of course undesired. One such false detection <NUM> is indicated in <FIG>. The radar sensor and/or the control unit <NUM> cannot easily distinguish between a false detection <NUM> and a true target <NUM>. There may be a plurality of false targets <NUM> complicating radar signal processing.

Reflections in a body part such as a bumper <NUM>, <NUM> may give rise to unwanted radar side-lobes. Even though a vehicle radar typically has a narrow elevation beam-width, the effect of reflections in vehicle body parts may result in side-lobes at a non-zero elevation (or azimuth), such as pointing more towards the ground. These side-lobes may contribute to an increased level of clutter, which is undesired.

<FIG> schematically illustrates one cause for false detections. Here, the radar transceiver <NUM> is arranged behind a bumper <NUM> which reflects part of the transmitted radar energy <NUM> back into a cavity behind the bumper <NUM>. The reflected radar energy is incident on some reflective surface <NUM> on the vehicle <NUM> which returns the incident reflection. This return may at least in part end up back at the radar transceiver <NUM>. Thus, the radar transceiver receives signal energy which appears to have been reflected of a target, but which in reality is a false detection <NUM>. The reflected energy may arrive at the radar transceiver via a single reflection or via reflections in more than one vehicle part.

To reduce problems with false radar detections <NUM>, it is proposed herein to arrange a side-shield in vicinity of the radar transceiver <NUM>. The side-shield is configured to randomize a phase distribution of an electromagnetic wave propagating though the shield.

If the radar signal has been focused by the shape of a vehicle body part, such as a bumper, into a narrow sidelobe (somewhat similar to a satellite dish effect), then the transmission power density may be increased, e.g., 10dB higher than if the body part was flat. When this focused beam hits the side shield, if it is flat, the phase front will emerge on the far side of the side-shield medium substantially parallel to when it arrived and hence the focused beam will continue to stay focused. However, if the phase front of the radar signal <NUM> is randomized by propagation through a phase randomizing side-shield, then the beam is no long focused after side-shield penetration and the energy density (in terms of power per solid angle) is reduced. In other words, by randomizing the phase distribution of the radar signal, the radar signal is steered or diffused by the side-shield. This of course happens in both transmit and receive directions. Randomizing a phase distribution here means that the phase front across an outer <NUM>-dimensional surface of a radar side-shield has become randomized, which, e.g., removes any focusing effect that had been achieved by a vehicle body part like a bumper.

<FIG> shows an example of a radar transceiver assembly <NUM> comprising this type of phase randomizing side-shield <NUM>. A radar side-shield <NUM> is normally arranged laterally with respect to a transmission direction of the radar transceiver <NUM>, i.e., extending out from the sides of the transceiver housing as schematically illustrated in <FIG>. The radar side shield extends in an extension plane, such as laterally out from the radar transceiver. However, the side-shield surface may be either planar or curved.

The side-shields <NUM> discussed herein all comprise a non-uniform delay structure arranged over the extension plane of the side-shield. The non-uniform delay structure is configured to delay a radar signal <NUM>, <NUM> propagating through the side-shield <NUM> by a variable amount in dependence of a wavelength of the radar signal and in dependence of a location on the side-shield through which location the radar signal propagates. This means that the structure is non-uniform in the sense that the phase of a signal component exiting the side-shield <NUM> depends on where, spatially, the signal component interacts with the side-shield. The effect of the side-shield is a randomization of a phase distribution of the radar signal <NUM> after propagation through the side-shield <NUM> as discussed above.

According to some aspects, the randomized phase distribution is a uniform phase distribution over some angular range, such as from <NUM> to π or <NUM> to <NUM>π.

The side-shield can be configured with a non-uniform delay structure to generate the phase randomization in some different ways. For instance, according to some aspects, the non-uniform delay structure has a non-uniform (variable) thickness measured along a normal vector V to the extension plane.

In general, the wavelength of a transmitted radar signal in vacuum, denoted λ<NUM>, is altered when the radar signal propagates through a material having a dielectric constant ε different from the vacuum permittivity ε<NUM> to <MAT>. This effect causes a phase shift of the radar signal when propagating through the material compared to the same radar signal propagating the same distance though vacuum. For example, if a radar signal with wavelength λ<NUM> in vacuum propagates through a material with thickness x and dielectric constant ε, the phase shift of the signal due to propagating through the material is approximately <MAT>.

The signal velocity is the speed at which a wave propagates. Signal velocity is usually equal to group velocity (the speed of a short "pulse" or of a wave-packet's middle or "envelope"). However, in a few special cases (e.g., media designed to amplify the front-most parts of a pulse and then attenuate the back section of the pulse), group velocity can exceed the speed of light in vacuum, while the signal velocity will still be less than or equal to the speed of light in vacuum.

In a transmission medium, signal velocity vs is the reciprocal of the square root of the capacitance-inductance product, where inductance and capacitance are typically expressed as per-unit length; <MAT> where εr is the relative permittivity of the medium, µr is the relative permeability of the medium, and c is the speed of light in vacuum. The approximation shown is used in many practical contexts because for most common materials µr ≈ <NUM>.

With reference to <FIG>, consider two components 220A, 220B of a propagating radar signal at a normal incidence angle. A first component 220A propagates a first distance x in air, having a first dielectric constant εA. A second component 220B also propagates the first distance x, where the second component 220B then first propagates a second distance y in air, having the first dielectric constant εA, and then propagates a third distance H that correspond to a height H of a protruding portion <NUM> made in a dielectric material having a second dielectric constant εB. The protruding portion <NUM> is for example made in a plastic material. According to some aspects, the second dielectric constant εB is between <NUM> and <NUM>, for example about <NUM>.

Since the first component 220A propagates the first distance x in air only, and the second component 220B propagates the first distance x partially in air and partially through the protruding portion <NUM>, the first component 220A and the second component 220B will have mutually different respective relative phases φ<NUM>, φ<NUM> after having propagated the first distance x.

These relative phases φ<NUM>, φ<NUM> of the two components 220A, 220B is <MAT> <MAT>.

In order to randomize φ<NUM> relative to φ<NUM> within an approximate range from <NUM> to π, the height H is preferably chosen in the range <NUM> to <MAT>. For an automotive radar operating around <NUM>, where the wavelength λ<NUM> in air is approximately <NUM>, the maximum height H then evaluates to approximately <NUM>.

Rays at other incidence angles than the normal angle will of course have a larger phase difference since the effective distance through the plastic cuboid-shaped protruding element will be longer.

One example of a side-shield <NUM> having non-uniform thickness is a side-shield comprising a carrier structure <NUM> which tapers off in some direction, e.g., as a wedge-shaped side-shield illustrated in <FIG> that tapers from a thickness z mm to a thickness H+z mm. A radar signal component exiting the side-shield then has a phase in dependence of where it penetrated the side-shield since the thickness varies over the side-shield. Radar signal components penetrating the side-shield at the thickest end propagates through a material thickness of about H+z mm, while a radar signal component propagating through the thinnest end only experiences a side-shield thickness of about z mm. The wedge-shaped side-shield also bends the signal <NUM> to the left, i.e., the exiting radar signal <NUM> is not parallel to the incoming signal <NUM> due to the effects of diffraction by the side-shield. This is a beneficial effect of the wedge - to deviate the energy away from a reflecting surface if it were known that one were present.

<FIG> shows an example of a tapered radar side-shield which also comprises uneven surfaces <NUM> to further randomize the phase of a radar signal propagating though the side-shield.

According to the invention there is provided a side-shield having non-uniform delay structure is a side-shield comprising a carrier structure <NUM> and a plurality of protruding portions. Examples of different types of protruding portions <NUM>, <NUM>, <NUM>, <NUM> are schematically illustrated in <FIG> and <FIG>. Each protruding portion is configured to delay a radar signal <NUM>, <NUM> propagating through the side-shield <NUM> by a respective amount, in dependence of a wavelength of the radar signal. Due to the variable delay amounts, the radar signal will comprise components having different phases after propagation through the side-shield. In other words, making the side shield patterned rather than using a typical flat surface has the effect of randomizing the phase front that propagates beyond the side shield. This phase randomization diffuses the radar signal.

For example, adding pyramids or other protrusions to the inner and/or outer surface of the side-shield <NUM> will randomize the phases of the signal appearing on the outer surface, thus broadening and reducing the intensity of any side-lobes.

With reference to the examples shown in <FIG>, the plurality of protruding portions <NUM>, <NUM>, <NUM> are configured to randomize a phase distribution of the radar signal <NUM> after propagation through the side-shield <NUM>. This can be achieved, e.g., by configuring the protruding portions with different shapes and/or with materials having different dielectric constants. For instance, at least one of the protruding portions may be formed as a pyramid-shaped protruding portion <NUM>, exemplified in <FIG>. A pyramid-shaped protruding portion <NUM> will subject a radar signal to different propagation delays depending on where the radar signal propagates through the side-shield. The protruding portions may also be formed in other shapes, such as the cuboid-shaped protrusions <NUM> exemplified in <FIG>.

<FIG> shows pyramid-shaped protruding portions <NUM> on both sides of a carrier structure <NUM>. The pyramid-shaped protruding portions <NUM> on each side have a height of H/<NUM>, such that the total height of the pyramid-shaped protruding portions <NUM> is H.

This is applicable for all types of protruding portions, according to some aspects the protruding portions <NUM>, <NUM>, <NUM> may be arranged on one or both sides of the side-shield, i.e. they may be arranged on a first face of the side-shield and/or on a second face of the side-shield opposite to the first face.

The protruding portions may also be formed as polygon-shaped protruding portions. A blend of different shapes can be used to generate a desired phase randomization effect.

According to some aspects, as shown in <FIG>, the protruding portions <NUM>, <NUM>, <NUM> are supported by a carrier structure <NUM>. This is, however, optional as indicated with dashed lines for the carrier structure <NUM> in <FIG>. The carrier structure is not necessary if the protruding portions <NUM>, <NUM>, <NUM> form a coherent piece of material that is self-supporting.

If a carrier structure <NUM> is used, such a carrier structure can have a dielectric constant that is the same as, or differs from, a dielectric constant of the protruding portions <NUM>, <NUM>, <NUM>. The carrier structure <NUM> can also have any suitable shape, for example tapered as shown in <FIG>.

Combinations of different types of protruding portions <NUM>, <NUM>, <NUM> can according to some aspects be used.

According to some aspects, a protruding portion <NUM>, <NUM>, <NUM> is associated with a height in a range from <NUM> to H mm, measured in an extension direction of the protruding portion, from the carrier structure <NUM>. The height H can be determined in dependence of a radar transmission wavelength in vacuum λ<NUM> and a dielectric constant ε of a material in the protruding portion. For example, a height range from <NUM> to H mm can be determined as <MAT> mm, which gives a phase distribution from <NUM> radians to π radians. The height range can also be expanded to comprise heights in a range from <NUM> to H' mm where <MAT> mm, which gives a phase distribution from <NUM> radians to <NUM>π radians. The height range can also be selected somewhere in-between in order to generate phase randomization.

At least some of the side-shields disclosed herein can be cost-effectively manufactured by integrally forming the protruding portions and the carrier structure in a plastic material. , the radar side-shield <NUM> may be formed in a single piece by molding a plastic material, which is an advantage.

Plastic materials may consist of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects. Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability. Plastics are typically organic polymers of high molecular mass and often contain other substances. They are usually synthetic, most commonly derived from petrochemicals.

Alternatively, or as a complement to molding the side-shield in a single piece, the protruding portions <NUM>, <NUM>, <NUM> can be attached to the carrier portion <NUM> by any of; an adhesive layer, a snap-fit mechanism, an interference fit mechanism, and/or by ultrasonic welding.

Thermoplastic olefin (TPO) or other plastic is a preferred material for manufacturing the radar side-shield. Radar absorbing plastics are available, however the properties can be different, it is more expensive, and can be more complicated to mold and weld.

A phase randomization of a radar signal propagating through the side-shield can also be obtained by adding chunks of material to the carrier structure <NUM>, where the added material is of a different dielectric constant compared to that of the carrier structure material.

<FIG> illustrates one such example radar side-shield where the non-uniform delay structure has a non-uniform dielectric constant along the normal vector V. This means that the dielectric constant experienced by an electromagnetic signal component propagating through the side-shield is different at different locations over the side shield <NUM>. The embedded portions <NUM> are associated with a dielectric constant ε different from a dielectric constant of the carrier structure <NUM>. The embedded portions <NUM> are preferably formed with different shapes to cause the phase randomization discussed above. It is also possible to add embedded portion which have been formed in different materials having different dielectric constants. According to some aspects, the non-uniform delay structure has a non-uniform dielectric constant along the normal vector V, but a uniform thickness. It is of course conceivable that the non-uniform delay structure according to <FIG> has a non-uniform thickness as well.

<FIG> schematically show a side view and a top view of a radar side-shield <NUM> where an irregular or piecewise linear trench <NUM> has been formed in the side-shield surface. This trench also has the effect of randomizing phase distribution.

The side-shield <NUM> can also be formed having an irregular or zig-zag shaped surface, as exemplified in the side-view shown in <FIG> shows a side view of a radar side-shield <NUM> with zig zag pattern on inner and outer surfaces. This has the advantage of a more constant material thickness for molding. Both top and bottom surfaces of the side-shield <NUM> take on the irregular shape in order to maintain a more constant thickness of material for ease of molding.

<FIG> schematically illustrates a radar transceiver assembly <NUM> where zig-zag trenches have been formed into the (normally flat) surface of the radar side-shield <NUM> that here is shown together with the radar transceiver <NUM>.

It may not be necessary to add the protruding portions to the entire side-shield. Thus, according to some aspects, the one or more protruding portions <NUM> are comprised within a part of a surface of the carrier structure <NUM>, as exemplified in <FIG> which shows an example radar transceiver assembly <NUM> comprising a radar transceiver <NUM> and a side-shield <NUM> according to the discussion above.

<FIG> is a flow chart illustrating methods. In particular, there is illustrated a method for producing a side-shield <NUM> for a radar transceiver <NUM>. The method comprises; configuring S1 a mold for molding a plastic element, wherein the mold is configured to form one or more protruding portions arranged protruding from a carrier structure <NUM> of the side-shield and/or an irregular trench in a surface of the side-shield, and producing S2 the side-shield <NUM> by forming a plastic material by the mold.

Claim 1:
A side-shield (<NUM>) for a radar transceiver (<NUM>), the side-shield (<NUM>) comprising a non-uniform delay structure arranged over the side-shield, the non-uniform delay structure being configured to delay a radar signal (<NUM>, <NUM>) propagating through the side-shield (<NUM>) by a variable amount in dependence of a wavelength of the radar signal and in dependence of a location on the side-shield surface through which the radar signal (<NUM>, <NUM>) propagates, thereby steering and/or diffusing the radar signal (<NUM>) after propagation through the side-shield (<NUM>), wherein the side-shield (<NUM>) is adapted to be arranged laterally with respect to a transmission direction of the radar transceiver (<NUM>), extending out from the sides of a transceiver housing and wherein the side-shield (<NUM>) further comprises a carrier structure (<NUM>) and a plurality of protruding portions (<NUM>, <NUM>, <NUM>, <NUM>) made in a dielectric material having a dielectric constant (EB), wherein each protruding portion is configured to delay a radar signal (<NUM>, <NUM>) propagating through the side-shield (<NUM>) by a respective and variable amount in dependence of a wavelength of the radar signal, thereby randomizing a phase distribution of the radar signal (<NUM>) after propagation through the side-shield (<NUM>).